procedure for the design construction of distribution syste

GENERAL PEOPLE’S COMMITTEE OF ELECTRICITY, WATER AND GAS

NATURAL GAS TRANSMISSION & DISTRIBUTION COMPLIANCE

GPCOEWG/GAS/D/03

PROCEDURE & SPECIFICATION FOR THE DESIGN & CONSTRUCTION OF DISTRIBUTION SYSTEMS OPERATING AT LESS THAN 16 BAR

CONFIDENTIAL

Ref No.

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DOCUMENT AUTHORISATION SHEET

Document number: GPCOEWG/GAS/D/03

Document name: Procedure & Specification for the Design & Construction ofDistribution Systems Operating At Less Than 16 Bar

PREPARED BY:

Name: Phil Winnard

Position: Project Manager

Date: October 2007

CHECKED & AUTHORISED FOR ISSUE:

Name: Alan Lawless

Position: Director – Oil and Gas

Date: October 2007

RECEIVED AND AUTHORISED FOR DISTRIBUTION BY:

Name:

Position:

Date:

Amendment Record

Issue Issue Date Description of Changes

1 30/10/07

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DISCLAIMER

This document is not to be used as design handbook; it does not eliminate the need for a competent designer or for competent engineering judgement. All designs prepared by competent designers must be appraised and authorised for issue by a competent person or authority before any construction works are carried out in accordance with the design brief. The requirements of this specification are adequate for safety under conditions usually encountered in the gas industry. Requirements for all unusual conditions cannot be specifically provided for, nor are all details of engineering and construction prescribed; therefore activities involving the design, construction, operation, or maintenance of gas transmission or distribution systems should be undertaken using personnel having the experience and knowledge to make adequate provision for such unusual conditions and specific engineering and construction details.

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CONTENTS Page

1 DOCUMENT INTRODUCTION 10

1.1 Context 10 1.2 Purpose 10 1.3 Responsibility 10 1.4 General Requirements 10 1.5 Primary Design Codes 10

1.5.1 Distribution Mains 10 1.5.2 Services 10 1.5.3 Supplies To High Rise Multi Occupancy Buildings 10 1.5.4 Metering Installations 11 1.5.5 Industrial Meter Installations 11 1.5.6 Other Relevant Standards 11

1.6 Safety And The Environment 11 1.7 Statutory Requirements 11 1.8 Competency And Quality Assurance 12

2 DESIGN & CONSTRUCTION PROCESS 14

2.1 System Planning 15 2.2 Feasibility Study 16

2.2.1 Work Elements 17 2.2.2 Feasibility Study Report 18

2.3 Detail Design Report 21 2.3.1 Process Design 21 2.3.2 Pipeline Network Analysis 21 2.3.3 Selection Of Design Factors For Pipelines 22 2.3.4 Route Corridor Selection 22 2.3.5 Pipeline Drawings And Plans 22 2.3.6 Proximity Distances Based On Pressure, Pipe Diameter, Wall Thickness And

Material Grade 23 2.3.7 System Condition Monitoring And Control Requirements 23 2.3.8 Pipe Coating And Cathodic Protection 23 2.3.9 Pipe And Fitting Selection 24 2.3.10 Material Take Off 24 2.3.11 Special Crossing Details 24 2.3.12 Valve Facilities 25 2.3.13 Legal 25 2.3.14 Pressure Reduction Station Facilities 25 2.3.15 Civil Design 26 2.3.16 Mechanical Design 26 2.3.17 Electrical, Instrumentation And Telemetry 27 2.3.18 Welding, Inspection And Mechanical Testing Requirements 28 2.3.19 Swabbing, Gauging And Testing 28 2.3.20 Drying 29 2.3.21 Route Corridor 29

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2.3.22 Gas Services And Gas Risers To Multi Storey Buildings 30 3 HEALTH, SAFETY, EXCAVATION AND REINSTATEMENT 32

3.1 General Health And Safety Requirements 32 3.1.1 Information On The Laws Of The United Kingdom Governing Health And Safety32 3.1.2 Meeting Legal Safety Standards 42

3.2 List Of Useful References Specific To Health And Safety 57 3.2.1 UK Statutes And Regulations 57 3.2.2 Health And Safety Executive (HSE) Publications* 58

3.3 Competence Of Health And Safety Supervisors 59 3.4 Safety In Transportation Of Materials And Working In Excavations 60

3.4.1 Handling, Transport And Storage Of Steel Pipe, Bends And Fittings 60 3.5 Excavating And Reinstating Pipelines, Mains And Services 60

3.5.1 Excavating 61 3.5.2 Safety In Excavations 62 3.5.3 Back Filling And Reinstatement 72

4 DETAILED DESIGN SPECIFICATION 84

4.1 General Information 84 4.1.1 Competence And Training 84 4.1.2 Gas Safety 85

4.2 Gas Pipelines And Mains Design 91 4.2.1 Design Output 92 4.2.2 Project Appraisal 92 4.2.3 Route Selection - Mains 93 4.2.4 Special Crossings 95 4.2.5 Pipe And Fittings For Mains And (Services) 97 4.2.6 Minimum Proximity Distances Identification And Protection 99 4.2.7 Valves 101 4.2.8 Pipe Laying 104 4.2.9 Material Delivery / Storage / Handling 104 4.2.10 Techniques For Main Laying 105 4.2.11 Selecting The Route Of The Gas Main 107 4.2.12 Cathodic Protection 107 4.2.13 Coating And Wrapping 108 4.2.14 Jointing 108 4.2.15 Steel Pipe Jointing 112 4.2.16 Flow Stopping 113 4.2.17 Cut Out On Steel Mains 114 4.2.18 Cut Out On PE Mains 114 4.2.19 Anchorage 114 4.2.20 Pressure Reduction Stations 115 4.2.21 Metering 115 4.2.22 Pressure Testing 115 4.2.23 Commissioning 121 4.2.24 Pressurisation 127 4.2.25 De-Commissioning Pipelines And Mains 127 4.2.26 Records 130

4.3 Gas Services Design 131

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4.3.1 Gas In Flats And Other Multi-Dwelling Buildings 132 4.3.2 Gas Service Connections 133 4.3.3 Route Selection - Services 134 4.3.4 Depth Of Cover For Services 135 4.3.5 Width Of Trench 136 4.3.6 Pipe And Fittings For (Mains) And Services 136 4.3.7 Valves 139 4.3.8 Pressure Regulating Equipment (Mp Services) 142 4.3.9 Techniques For Service Laying 142 4.3.10 Labelling Of Gas Services 143 4.3.11 Service Entry Methods 144 4.3.12 Electrical Bonding 144 4.3.13 Meter Positioning 145 4.3.14 Meter Boxes 146 4.3.15 Timber Framed Buildings 146 4.3.16 Mobile Dwellings 146 4.3.17 Services Testing 147 4.3.18 Purging And Commissioning 147 4.3.19 Service Alteration 148 4.3.20 Service Cut Offs 149

4.4 Typical Mains And Service Configurations 150 4.4.1 Typical Distribution Systems 150 4.4.2 Diagrammatic Representation 154 4.4.3 Typical Gas Services Configurations 158

5 CONSTRUCTION MANAGEMENT 165 5.1.1 Work Elements 165 5.1.2 Competency Of Gas Distribution Operatives 165 5.1.3 Deliverables 169 5.1.4 Manuals And Drawings 169 5.1.5 Quality Management System 169 5.1.6 Safety Management System 169 5.1.7 Construction Method Statements 169 5.1.8 Environmental Management Plan 170 5.1.9 Project Risk Register 172 5.1.10 Access To Site 172 5.1.11 Audit 172 5.1.12 Construction Approvals Process 172 5.1.13 Collation Of Handover Documentation 176

6 APPENDICES 178

6.1 References 178 6.1.1 Igem Standards 178 6.1.2 Uk Gas Industry Standards 179 6.1.3 European & International Standards 180

6.2 Appendix 2 – Gas Industry Terms & Abbreviations 181

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List of Tables Table 1 - Protective clothing/equipment and their usage 44 Table 2 - Emergency situations and their immediate action/remedies 54 Table 2 (cont…) - Emergency situations and their immediate action/remedies 55 Table 2 (cont…) - Emergency situations and their immediate action/remedies 56 Table 3 – Natural Gas v Oxygen – Relationship and Effects 88 Table 4 - Minimum cover on mains and services 93 Table 5 – Pipeline Protection 100 Table 6 – Flange Dimensions 111 Table 7 – Minimum rider sizes – direct purging 123 Table 8 – Minimum rider sizes – indirect purging 125 Table 9 – Minimum quantities of inert gas 126 Table 10 - Purge velocities for decommissioning by direct purging 129 Table 11 – Minimum cover for service pipes 135 Table 12 - Service testing 147 Table 13 - Mains configuration advantages and disadvantages 153 List of Figures

Figure 1 - Design Process 15 Figure 2 - Typical warning notices 46 Figure 3 - Fitting of electrical continuity 57 Figure 4 - Recommended arrangement of mains in a 2 m footway including cable TV duct 75 Figure 5 - Close board timbering for unstable ground 75 Figure 6 - Sheet steel piling for unstable ground 76 Figure 7 - Stable ground pinchers 76 Figure 8 - Open timbering for moderately stable ground 77 Figure 9 - Use of pump in waterlogged ground conditions 78 Figure 10 - Stability check 79 Figure 11 - Stability check 80 Figure 12 - Layers in a trench reinstatement structure 81 Figure 13 – Road plate arrangement 81 Figure 14 - Off-take arrangement 102 Figure 15 - Mains configuration 1 154 Figure 16 - Mains configuration 2 155 Figure 17 - Mains configuration 3 156 Figure 18 - Mains configuration 3 157 Figure 19 – Single service configuration 1 158 Figure 20 – Single service configuration 2 159 Figure 21 – Single service configuration 3 160 Figure 22 – Multi occupancy configuration 1 161 Figure 23 – Multi occupancy configuration 2 162 Figure 24 – Multi occupancy configuration 3 163

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DEFINITIONS

Also see Appendix for common gas industry terms ‘must’ Indicates an essential requirement of the procedure

‘should’ Indicates the preferred method as described in the procedure, an alternative approach can be adopted, however the method used must be fully justified through a documented risk evaluation process.

Assets Mean the pipeline and any other installation or apparatus through which natural

gas is intended to flow, including block valves, a structure to be used solely for the support of a pipe, facilities to launch and receive Pigs, pressure reduction installations, cathodic protection system, odorisation plant, and, where requested, the metering installation and flow weighted average calorific value measuring equipment.

Responsible Engineer

Person representing the Authority/Owner/Operator of the system responsible for operating the gas supply system

Planning Engineer

Person representing the Authority/Owner/Operator of the system responsible for all planning activities relating to the system

Authorising Engineer

The Authorising Engineer shall be competent to approve written procedures and authorise work instructions and permits to work and documents for undertaking work on the gas system

The Authority Owner of the pipeline system

Competent body / person

Individual or organisation appointed by the authority to provide specialist support for damage assessment and repair

Project Manager

Person with overall responsibility of the construction project

Transmission pipeline

Pipeline operating at pressure greater than 16 bar

Distribution pipeline

Pipeline operating at a pressure between 4 and 16 bar

Distribution main

Pipe work normally laid below ground operating at pressures up to 4 bar

Distribution Service

Pipework connected to the distribution main and conveying gas to the gas consumers premises terminating at the consumers emergency control valve

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SECTION 1 DOCUMENT INTRODUCTION

SECTION 1

DOCUMENT INTRODUCTION

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1 DOCUMENT INTRODUCTION

1.1 Context

PB Power has been requested to prepare policies and procedures to ensure that the gas transmission and distribution system in Libya is operated, maintained and managed safely, securely and to international standards.

To ensure the appropriate standard of safety and reliability in construction, operation, and decommissioning it is essential that a system of design exists for assets associated with the distribution of natural gas.

This document applies to all aspects of design and construction of gas transmission assets, operating at below 16 barg. Disciplines covered include mechanical engineering, civil engineering, structural engineering, electrical, instrumentation, gas engineering, safety and environment.

1.2 Purpose

The purpose of this procedure is to ensure that distribution systems are designed to International standards and using best practice principles.

1.3 Responsibility

The Planning Manager is responsible for ensuring that this procedure is adhered to.

1.4 General Requirements

The design must incorporate all reasonably practicable measures to minimise the probability and consequences of failure.

1.5 Primary Design Codes

1.5.1 Distribution Mains

All new mains and modifications to existing mains shall be designed and constructed in accordance with the latest edition of IGE/TD/3, Distribution systems less than 16 bar.

1.5.2 Services

All new services shall be designed and constructed in accordance with the latest edition of IGE/TD/4, Services.

1.5.3 Supplies To High Rise Multi Occupancy Buildings

All new installations, and modifications to existing installations, shall be designed and constructed in accordance with IGE/G/5, Gas installations in flats and other multi-dwelling buildings.

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1.5.4 Metering Installations

All new installations, and modifications to existing installations, shall be designed and constructed in accordance with the following standards:

IGE/GM/6 - Standard diaphragm and RD meter installations. > 6 m3h-1 MOP ≤ 75 mbar

IGE/GM/5 Ed 2 - Electronic gas meter volume conversion systems

IGE/GM/7 Ed 2 - Electrical connections and hazardous area classification MOP ≤ 100 bar

1.5.5 Industrial Meter Installations


IGE/GM/8 Pt 1 - Meter installations I&C – Design. MOP ≤ 38 bar

IGE/GM/8 Pt 2 - Meter installations. I&C – Location and housing,

1.5.6 Other Relevant Standards

Other IGE specifications which are relevant to the design of transmission systems include:

IGE/TD/12 Ed 2 - Stress analysis

IGE/GL/5 Ed 2 - Managing new works, modifications and repairs

IGE/SR/25 - Hazardous area classifications

IGE/SR/26 - Horizontal directional drilling and impact moling

IGE/SR/28 - Trenchless techniques

IGER/SR/22 – Purging of fuel gases

1.6 Safety And The Environment

Development activities undertaken by the Authority can have an impact on the safety of the general public, Authority staff and contractors and can affect the local environment. The Authorities policy on Health Safety and the Environment shall be followed at all times to reduce this impact to a minimum.

1.7 Statutory Requirements

The Authority must comply with all relevant statutory requirements in designing the gas transmission system.

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1.8 Competency And Quality Assurance

The primary method of ensuring the design specification is consistently applied is by adoption and implementation of the IGE/GL/5 - Managing new works, modifications and repairs’. The Authority shall be responsible for management of the Design and Design Appraisal procedure.

Providers of design services shall comply with and be registered to ISO 9002 – Quality assurance standards.

The design process should follow the recommendations as detailed in BS 7000: Part 4: 1996 Design Management Systems, Guide to Managing Design in Construction.

Competency of designers should be demonstrated by a Safety and Technical Competence (STC) process.

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SECTION 2 DESIGN PROCESS

SECTION 2

DESIGN PROCESS

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2 DESIGN & CONSTRUCTION PROCESS

The design and construction process has been divided into four stages. The four stages are listed as follows:

1. System planning for the Authority gas distribution networks.

2. Feasibility Studies for Mains, Pipelines and Installations Operating at less than 16 Bar.

3. Detailed design of Pipelines, Mains, Services and Installations Operating at less than 16 Bar.

4. Management of construction activities.

The design and construction process includes a review and appraisal of each stage. This appraisal shall be carried out be a competent and independent organisation with extensive knowledge of the design technologies being reviewed. This will ensure that design and construction activities meet the requirements of the Authority procedures, standards and specifications.

Feasibility studies will normally be carried out on gas pipelines operating in the range 2 – 16 bar and gas installations with inlet pressures in the range 2 – 16 bar. Where the project involves large and more complex gas distribution mains and services schemes then the Authority may also commission a feasibility study in advance of detailed design and construction.

The design process is shown diagrammatically as follows:

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Figure 1 - Design Process

2.1 System Planning

The Authority shall undertake all activities associated with the future planning of gas supplies for Libya.

Network performance tools such as Graphics Based Network Analysis (GBNA) and Large Integrated Network Analysis System (LINAS should be used to provide comprehensive planning of the overall mains distribution system.

Typical activities undertaken by the system Planning Engineer include:

• Assessing the ability of an existing network to meet future demand condition.

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• Specify pressure settings for district regulators.

• Identify operational windows for work to be undertaken.

• Network validation by testing the network model against actual pressures experienced in the network - Recorded pressure measurements are taken at strategic points through the system & compared with the model pressure. Discrepancies are investigated and the model modified to more closely match reality.

• Design appraisal and review of feasibility studies and detail design proposal.

Reference shall be made to IGE/GL/1 ‘Planning distribution systems. MOP ≤ 16 bar’, for the planning of gas distribution systems.

2.2 Feasibility Study

The Authority shall provide a project brief for the organisation that is to carry out the feasibility study. The project brief will contain the following information:

• Gas flows.

• Inlet pressure(s) maximum and minimum.

• Outlet pressures(s) maximum and minimum.

• Basic system location drawing showing pipe diameters and pressures.

• Proposed commissioning date.

• Other projects that may affect the design.

Other constraints that should be included in the project brief are listed as follows:

• Arrangements for maintaining gas supplies.

• Time periods during which a particular construction process must be completed taking account of Network Outages for Connections.

• Previous project history in the geographical area.

• Intermediate route points that the pipeline has to connect with or be close to.

• Impact on, or creation of, a site that falls within any specific regulations.

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2.2.1 Work Elements

The Authority Project Manager will be responsible for producing the deliverables required by this procedure.

This feasibility study will enable informed and cost effective decisions to be taken based on engineering and environmental constraints.

The work elements of a feasibility study are as follows:

• Examine all identifiable options to meet the project objectives.

• Establish design alternatives.

• Identify possible sites for above ground installations such as pressure reduction and metering installations etc…

• Identify factors that may limit the scope of the project including potential risks to the overall project.

• Identification of possible connection points.

• Definition of an area of search to be considered for sites, mains and pipeline routes.

• Review of published information regarding the natural, physical and environment matters, and the identification of possible constraints which may affect the project.

• Identify environmental issues in order to prepare a basic Route Corridor Investigation.

• Production of a Route Corridor Investigation Report including constraints maps identifying the possible routing constraints and possible route corridor options for pipelines.

• Production of at least two costed options with a recommended solution.

• Production of a preliminary high-level outline project programme and expenditure phasing plan. This may include construction material lead times, land rights purchase and obtaining other consents.

• Production of basic Engineering Line Diagrams (ELDs) and outline General Arrangement (GA) drawings for the facilities/installations required.

• Consideration of the impact of any regulations that may affect the project.

• Ground conditions should be addressed in a Ground Risk Study in which the geotechnical impacts on each of the route corridor options should be identified, especially as ground conditions pose significant risk to the construction phase. The study should consider such aspects as geology, hydro-geology, ground conditions, mining subsidence, land slip, solution caverns, the presence of landfill sites and other forms of ground instability.

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2.2.2 Feasibility Study Report

The feasibility study report shall be representative of what took place during the design study. The report shall put emphasis on the decisions made, why they were made and by whom. The report shall outline the options considered and why, and identify the competency level for named personnel involved in the feasibility study including details of relevant qualifications, training and experience.

The report shall outline possible design options and explain the rationale behind them. Factors that may limit the scope of the project and evaluate any anticipated difficulties shall also be detailed.

The feasibility study report shall include, but not be limited to, the following:

Executive Summary

This section should be a brief summary of the need for the project the background to the project, a brief description of the pipeline route (if applicable), key site names and basic materials.

Pipeline Route

This section shall describe the proposed pipeline route corridor options identified including any environmental considerations including Route Corridor Investigation.

Design / Technical Information

Design or technical information relating to the options being considered shall be provided as follows:

• Basic description of process plant including proposed installation.

• Process criteria and design parameters for example, flow and pressure ranges (minimum and maximum), temperatures, flow meter accuracy, ramp up rates, etc…

• Mechanical design to address, for example, relevant legislative requirements, primary standards, specifications and codes of practice, design philosophy, site layout, design standards, location of possible pipeline connection points.

• Civil engineering requirements including basic description of foundations, earthworks, ground conditions, fencing etc…

• Materials, for example, outline details of pipe material grades and wall thickness recommended for the proposed pipeline, long lead time items that may restrict the programme, plant and equipment that is required for any installations etc…

• Confirmation of compatibility with the existing pipeline system and identification of factors that may affect future operation and maintenance.

• Any assumptions made in the feasibility study.

Safety Engineering

All legislative requirements that may impact on the project shall be addressed.

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Environmental Impact Assessment

An environmental impact assessment must be included in the feasibility study report.

Line Diagrams and Drawings

Engineering Line Diagrams (ELDs) and General Arrangement Drawings (GAs) shall be prepared for the installations, where appropriate, showing the relative size and position of pipework, plant and equipment. All drawings shall clearly show the relationship between new and existing plant, equipment and pipework, and identify any modifications necessary.

On pipeline projects this shall include outline details of connecting the start and finish points of the proposed pipeline into existing or future pressure systems or supply points and identify the land required.

Recommendations

The recommendation shall include the preferred option, further work and necessary actions to enable the scope of the Detailed Design for the project to proceed.

Outline Project Plan

An outline project plan (e.g. Gantt chart) shall be provided, showing details of all the major elements to project completion, typical lead times etc…, so the critical path of the project can be highlighted and addressed.

Route Corridor Investigation

For a pipeline the initial routing process will involve a desk top study to identify possible suitable routing options. Although the shortest route between 'A' and 'B' is normally the most economic, other criteria have to be considered which will affect possible routing options, such as centre of population, the location of environmental constraints etc. Careful routing of pipelines is the most effective means of ensuring protection of the environment, by avoiding sensitive areas wherever possible.

Generally, the alternative courses of action, choices for pipeline start and termination points, and different routing options, are considered during the feasibility study stage of the project.

Decisions on the range of alternatives to be considered will need to be taken with only a limited amount of information available, hence the process becomes iterative as more information becomes available. Environmental matters will influence the decision process and they will have to be balanced against issues such as engineering, technical, safety, economic and project programme.

Therefore early evaluation of the purpose of the project, the perceived need, possible alternatives and the assessment of a proposed project is important to identify the direction of the environmental assessment process.

The aim of pipeline routing is to locate the most cost effective option which satisfies the safety requirements, whilst minimising the impact on the environment and capital cost.

The issues typically considered as part of the Route Corridor Investigation study include, but are not limited to, the following:

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• Infrastructure, such as existing pipeline systems, roads, railways, airfields, watercourses etc…

• Main centres of population.

• Major geological features, such as mountains, upland areas, marshland etc…

• Nature conservation, including statutory and non-statutory designate sites.

• Landscape features, including designated and non-designated sites.

• Archaeology, including designated and non-designated sites.

• Land use: For example agriculture, mining areas, quarries, mineral extraction, recreational facilities etc…

• Topography, including an overview of the terrain within the area of search.

• Planning policies.

• Agriculture, including an overview of farming activities.

The route corridors are usually identified as a band of interest up to 1 kilometre in width having taken into account major constraints, such as conurbations, topography, scheduled sites, major road and rail crossings. The width of the route corridor(s) will depend on the complexity of the environment through which it passes. The corridor need not be a uniform width throughout and may alter in size due to constraints. One of the main objectives of the routing study is to determine route corridor options and show why some route corridors have not been considered or have been disregarded.

Possible route corridors are identified using the following criteria:

• The pipelines start and finish points.

• Any intermediate fixed points.

• Avoidance, as far as possible, of any significant environmental, archaeology, future developments and engineering features.

• Avoidance of potentially difficult construction areas.

• The shortest distance between the start and finish points, bearing in mind the above criteria and the implications on project costs.

• The requirements of the design code selected (e.g. IGE/TD/1 or IGE/TD/3 etc.) from the point of view of the minimum permissible building proximity distances between the pipeline and occupied buildings are detailed according to pipeline diameter, operating design parameters

It is desirable that the route corridors proposed should, as far as practicable, avoid running closely parallel to high density traffic routes, railways or overhead high voltage cables. The length of the route between the start and finish points should be kept to a practical minimum.

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2.3 Detail Design Report

The Detail Design Report shall be a comprehensive design package. The detailed design will consider and report upon the following parameters:

2.3.1 Process Design

• Upstream system details - overpressure protection system data.

• Gas Pressures - Max Incidental P, (Safe operating Limit), Max Operating P, and Min Operating P.

• Test pressures, type of tests and durations.

• Gas Temperatures - Max, Min and Operating case.

• Gas Flows - Max, Min and Operating case.

• Gas Velocities - Max, Min and Operating case.

• Dew-point requirements - water and hydrocarbon for steel systems.

2.3.2 Pipeline Network Analysis

• Methodology - transient, static, (based on Panhandle, Smooth pipe law, Other equation).

• Max operating pressure.

• Minimum operating pressure at source of supply.

• Maximum total flow rate.

• Flow profile details and or peak instant demands.

• Number of branch requirements.

• Flow profile or peak instant demand and each branch.

• Pipe diameter selection.

• Pipe material selection.

• System pressure losses.

• Velocities and ramp rates.

• Nodes and pressures.

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2.3.3 Selection Of Design Factors For Pipelines

• Route selection.

• Identification of band of interest.

• Selection of building proximity distance multiplier and section length (rolling circle or other method).

• Identification of populated buildings both existing and planned (Population density survey).

• Identification of special crossings, i.e. road, railway, river etc…

• Crossing methodology, open cut, trench-less.

• Area classification.

2.3.4 Route Corridor Selection

• Identification of route options.

• Identification of numbers and types of special crossings.

• Route corridor selection based on risk assessment.

2.3.5 Pipeline Drawings And Plans

• Engineering line diagram.

• Pipeline route plans 1:10,000 scale.


• Pipeline land owner / occupier details 1:2,500 scale.

• Pipeline special crossing 1:200 scale.

• Pipeline profile drawings 1:10,000 scale.

• Pipeline profile drawings 1:2500 scale.

• Pipeline service crossing drawings 1:2500 scale.

• Pipeline slab protection details.

• Pipeline CP ground bed and TR location details.

• Pipeline CP aerial and other marker post details.

• Trench profile details.

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• Pipeline test drawing.

• Trench-less crossing details.

• Pipeline welding bar chart drawings 1:2500 scale.

2.3.6 Proximity Distances Based On Pressure, Pipe Diameter, Wall Thickness And Material

Grade

• From normally occupied buildings.

• From roads.

• From railways.

• From areas of public gathering.

2.3.7 System Condition Monitoring And Control Requirements

• Cathodic protection requirement, specifications, data sheets.

• External / Internal protection (coating) requirement, specifications, data sheets.

2.3.8 Pipe Coating And Cathodic Protection

• External pipe coating, specification and testing requirements.

• Internal pipe coating, specification and testing requirements.

• Joint coating specification and testing requirements.

• Holiday test requirements.

• Soil resistivity report.

• Cathodic Protection system design specification and testing requirements.

• Electrical earth specification and testing requirements.

• Cathodic Protection test post locations, (ease of access /operator safety).

• Insulation joint specification and testing requirements and location.

• Field testing (CIPPS, current drain tests etc) specification and requirements.

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2.3.9 Pipe And Fitting Selection

• Design factor selection based on area classification.

• Pipe minimum wall thickness calculations.

• Selection of pipe steel material grade.

• Fracture toughness and ductility requirements.

• Pipe actual wall thickness and material grade.

• Pipe tally sheets.

• Pipe material certification.

• Fitting material certification – bends, tees, valves, flanges, reducers, “O”Lets, gaskets, bolts.

2.3.10 Material Take Off

• Standards, specifications, data sheets and Quantities of pipe, valves, fittings and other materials.

• QA / QC Inspection and material certification requirements.

• Pressure vessel requirements and certification (PD 5500 Asme 8, Form X etc).

• 3rd party inspection requirements.

2.3.11 Special Crossing Details

• High density traffic routes.

• Other traffic routes.

• Tracks.

• River crossings.

• Drain crossings.

• Ditch crossings.

• Rail crossings.

• Major utility and other crossings.

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2.3.12 Valve Facilities

• Valve layouts / ELD / P&ID.

• Pipe and material specifications and data sheets.

• Valve and actuator specifications and data sheets.

• Venting requirements.

• Stress analysis.

• Hazardous area assessment.

• Written scheme of examination.

2.3.13 Legal

• Land ownership, occupier and tenant details.

• Wayleave schedule.

• Land purchase requirements.

• Land owner / occupier pre entry requirements.

• Tennant pre entry requirements.

• Compensation register.

2.3.14 Pressure Reduction Station Facilities

• Pressure or Volumetric control requirement.

• Isolations requirements, valve and actuator types.

• Filter requirement, filtration level, differential, venting.

• Metering requirement, accuracy, type, flow computer interfaces.

• Gas chromatography and gas quality measurement.

• Field instrumentation requirements.

• Shutdown/isolation requirements.

• Boilers and heat exchanger system, frequency response and control requirements.

• Regulators / control valve stream requirements.

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• Hazardous area assessment.

• Pressure systems.

• Written scheme of examination.

2.3.15 Civil Design

• Detail civil design.

• Concrete, steelwork, aggregate, and finishing specifications and data sheets.

• Site selection.

• Topographical / Bathymetric studies.

• Geotechnical assessment.

• Geophysical assessment.

• Hydro-graphic assessment.

• Support design.

• Slab base design details.

• Detail structural design buildings / pits.

• Fencing design.

• Site drainage design.

• River / rail / road / crossing arrangement.

• Marker post details.

• Settlement analysis / displacements in stress analysis report.

• Housings for gas equipment indicating ventilation and explosion relief design calculations.

2.3.16 Mechanical Design

• Detail mechanical design report.

• Pipe, fitting, valve and equipment specifications and data sheets.

• Support design.

• Material take off.

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• Testing schedule.

• Engineering line diagram.

• P & ID.

• General arrangement drawings for Block Valve sites.

• Weld record sheets.

• General arrangements for Above Ground Installation (AGI) works.

• Mechanical details for AGI works.

• Mechanical section details.

• MTO for AGI works.

• Testing for AGI works.

• Fabrication record drawings.

• Mechanical support details.

• Pipeline safety evaluation.

• Emergency response procedures.

• Operational procedures.

2.3.17 Electrical, Instrumentation And Telemetry

• Detail electrical design specifications and data sheets.

• Detail instrumentation design specifications and data sheets.

• Detail telemetry design specifications and data sheets.

• Detail metering design specifications and data sheets.

• Gas chromatography design specifications and data sheets.

• Detail hazardous area design.

• Wiring loop drawings.

• Block diagrams.

• P&IDs.

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• Earthing drawings.

• Cable layouts.

• Fire and gas detection systems.

• Cable calculations.

• Power supply requirements including UPS.

• Power consumption calculations.

2.3.18 Welding, Inspection And Mechanical Testing Requirements

• Welding specification.

• Welding procedure requirements.

• Welder procedural qualification requirements, register and approvals.

• Mechanical destructive test requirements.

• NDT - Radiography inspection requirement.

• NDT - Ultrasonic inspection and MPI inspection requirement.

2.3.19 Swabbing, Gauging And Testing

• Pre test audit report.

• Swabbing pig run details and certification.

• Magnetic pig run details and certification.

• Brush pig run details and certification.

• Gauge pig run details – gauge plate thickness and diameter and certification.

• Test limits drawing.

• Testing procedure.

• Testing equipment calibration certification including pumps, gauges, hoses, test ends etc…

• Test pressure, duration and % smys at test pressure.

• Pressure volume plot including hold points and entrained air by volume calculation.

• Test pass / fail criteria and certification.

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• Test pressure and temperature recorder charts / data logger printout.

• Test pack to match each test section.

2.3.20 Drying

• Hydrocarbon and water dew-point requirements.

• Drying procedure.

• Instrument and equipment calibration certification.

• Soak test report, (Vacuum test only).

• Dryness report.

2.3.21 Route Corridor




• Pipeline special sections 1:500 scale.

• Pipeline profile drawings 1:10,000 scale.

• Pipeline As built profile drawings 1:2500 scale.

• Pipeline welding bar chart drawings 1:2500 scale.

• Pipeline service crossing As built drawings 1:2500 scale.

• Pipeline special crossings 1:100 scale.

• Pipeline protection details.

• Trench profile details.

• Trenchless crossing details.

• Land and easement agreements.

• Land Owner wayleave agreement.

• Tennant wayleave agreements.

• Land purchase.

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• Wayleave payments.

• Crop loss compensation.

2.3.22 Gas Services And Gas Risers To Multi Storey Buildings

• Riser pipe sizes, valve types and locations, construction proposals and materials.

• Lateral off take sizes, lengths, valve type(s) and locations, construction proposals and materials.

• Arrangements for mitigating effects of expansion and contraction.

• Nodes (annotated to relate to flow calculations).

• Bare metal protection proposals.

• Detailed incoming mains design proposals.

• Cathodic protection proposals.

• Riser supports both at riser base and vertically.

• Architects scaled drawings for all floors in all building types. Drawings to show as required:

• Proposed meter locations.

• Riser and lateral routes.

• Riser and lateral duct design including expected fire rating, access panels and proposed panel fire sealing.

• Riser and lateral duct ventilation design, size, sizing calculations and location ventilation ducts (high & low level).

• Penetration sealing proposals, between floors and into properties (material and application process).

• When meters are to be located within meter room(s) ventilation calculations, ventilation design details and electrical hazardous area analysis.

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SECTION 3 HEALTH, SAFETY, EXCAVATION AND REINSTATEMENT

SECTION 3

HEALTH, SAFETY, EXCAVATION AND REINSTATEMENT

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3 HEALTH, SAFETY, EXCAVATION AND REINSTATEMENT

This Section provides relevant information on safety matters relating to the design and construction of gas transmission systems. The following safety aspects are addressed:

• General health and safety requirements.

• Competence of health and safety supervisors.

• Safety in transportation of materials, excavations and reinstatement.

3.1 General Health And Safety Requirements

To ensure that all work carried out in a safe manner, it is necessary for employees to know about the occupational safety laws which affect them. This Section provides a resume of the Safety Laws which are in place in the United Kingdom and provides an effective framework for ensuring work is undertaken safely in Libya.

3.1.1 Information On The Laws Of The United Kingdom Governing Health And Safety

3.1.1.1 The Health And Safety At Work, Etc. Act, 1974

Everyone has a responsibility for safety and safe working. The Health and Safety at Work, etc. Act 1974 (HASWA) requires everyone to ensure, so far as is reasonably practicable, the health and safety of themselves and others who may be affected by what they do or fail to do.

As an employee each person has a duty to:

a) Everyone who may work with you, including casual workers, part-timers, trainees and contractors or sub-contractors;

b) Anyone who visits your job or site (e.g. customers or contractors);

c) Anyone who may be affected by your work (i.e. the public and others).

HASWA 1974 applies to all work activities, and everyone at work at whatever level (e.g. employee, supervisor, manager, Chairman and Chief Executive) has certain responsibilities under HASWA 1974.

3.1.1.2 Principal Regulations Affecting Gas Operations

The Gas Safety Regulations 1972

The Gas Safety Regulations 1972 as amended by the Gas Safety (Installation and Use) Regulations 1994 detail statutory requirements regarding the installation of service pipes, service governors, internal supply pipes, meters and appliances.

Guidance on these Regulations is given in Health and Safety Executive booklet L56.

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3.1.1.3 The Regulations Provide For:

a) the use of sleeves when pipes pass through walls;

b) the fitting of control valves on specified sizes and types of service;

c) the prevention of damage to buildings;

d) precautions against corrosion, etc…

3.1.1.4 The Important Requirements Relating To Engineering Operations Are:

a) That satisfactory material is used.

b) That services and fittings must be verified as gas-tight following installation.

c) That services and fittings must be purged of air following installation.

d) That a service must be disconnected where the meter has been removed for a period exceeding 12 months.

e) That competent workman are employed to carry out the work.

It is a statutory requirement that all gas installers are registered. It is the responsibility of the employer and the duty of the employee to ensure compliance with the requirements of the Regulations regarding the laying of gas services.

Management of Health and Safety at Work Regulations 1992

The Management of Health and Safety at Work Regulations 1992 ('the Management Regulations') set out broad general duties which apply to almost all work activities in Great Britain and offshore. They are aimed mainly at improving health and safety management and can be seen as a way of making more explicit what is required of employees under HASWA 1974. Their main provisions are designed to encourage a more systematic and better organized approach to dealing with health and safety.

The Regulations will require employers to:

a) Assess the risks to the health and safety of employees and of anyone else who may be affected by their work activity. This is so that the necessary preventive and protective measures can be identified. Employers with five or more employees have to record the significant findings of the assessment. (The same threshold is already used in HASWA 1974. Employers with five or more employees have to prepare a written health and safety policy);

b) Make arrangements for putting into practice the health and safety measures that follow from a risk assessment. They will have to cover planning, organization, control, monitoring and review, in other words, the management of health and safety. Again, employers with five or more employees will have to record their arrangements;

c) Provide appropriate health surveillance for employees where the risk assessments show it to be necessary.

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d) Appoint competent people (either from inside their organization or from outside) to help to devise and apply the measures needed to comply with their duties under health and safety law;

e) Set up emergency procedures;

f) Provide employees with information they can understand about health and safety matters;

g) Co-operate with other employees sharing their work site;

h) Make sure that employees have adequate health and safety training and are capable enough at their jobs to avoid risks; and

i) Provide temporary workers with some particular health and safety information to meet special needs.

The Regulations also:

a) Place duties on employees to follow health and safety instructions and report danger.

b) Extend the current law which requires you to consult employees' safety representatives and provide facilities for them.

These general duties lie side-by-side with the more specific ones in other health and safety regulations, although that does not mean doing things twice. For example, a risk assessment made to comply with the COSHH Regulations does not need to be repeated for the same hazardous substances to comply with the Management Regulations. A specific duty will normally take the place of a general one that duplicates it.

The HSE Approved Code of Practice (unreferenced) shall be complied with.

Provision and Use of Work Equipment Regulations 1992

The Provision and Use of Work Equipment Regulations 1992 are designed to pull together and tidy up the laws governing equipment used at work. Instead of piecemeal legislation covering particular kinds of equipment in different industries they:

a) Place general duties on employers.

b) List minimum requirements for work equipment to deal with selected hazards whatever the industry.

'Work equipment' is broadly defined to include everything from a hand tool, through machines of all kinds, to a complete plant such as a refinery. 'Use' includes starting, stopping, repairing, modifying, installing, dismantling, programming, setting, transporting, maintaining, servicing and cleaning.

The general duties require employers to:

a) Make sure that the equipment is suitable for the use that will be made of it.

b) Take into account the working conditions and hazards in the workplace when selecting equipment.

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c) Ensure equipment is used only for operations for which, and under conditions for which it is suitable.

d) Ensure that equipment is maintained in an efficient state, in efficient working order and in good repair.

e) Give adequate information, instruction and training.

f) Provide equipment that conforms to EC product safety directives.

Specific requirements cover:

a) Work equipment parts and substances at high or at very low temperatures.

b) Protection against specified hazards, i.e. falling/ejected articles and substances, rupture/disintegration of work equipment parts, equipment catching fire or overheating, unintended or premature discharge of articles and substances, explosion.

c) Work equipment parts and substances at high or very low temperatures.

d) Control systems and control devices.

e) Isolation of equipment from sources of energy.

f) Stability of equipment.

g) Lighting.

h) Maintenance operations.

i) Warnings and markings.

Manual Handling Operations Regulations 1992

The incorrect handling of loads causes large numbers of injuries and can result in pain, time off work and sometimes permanent disablement. The Manual Handling Operations Regulations 1992 apply to any manual handling operations which may cause injury at work. Those operations are identified by the risk assessment carried out under the Management of Health and Safety at Work Regulations 1992. They include not only the lifting of loads, but also lowering, pushing, pulling, carrying or moving them, whether by hand or other bodily force.

Employers have to take the following three key steps:

a) Avoid hazardous manual handling operations where reasonably practicable. Consider whether the load must be moved at all, and, if it must, whether it can be moved mechanically, (i.e. by fork-lift truck).

b) Assess adequately any hazardous operations that cannot be avoided. An ergonomic assessment should look at more than just the weight of the load. Employers should consider:

1. The shape and size of the load.

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2. The way the task is carried out (e.g. the handler’s posture).

3. The working environment (e.g. is it cramped or hot?).

4. The individual's capability, (i.e. unusual strength required).

Unless the assessment is very simple, a written record of it will be needed. The general guidance will include some simple guidelines to help assessment.

c) Reduce the risk of injury as far as is reasonably practicable. A good assessment will not only show whether there is a problem, but will also point to where the problem lies. That is the starting point for your improvements. For example, if the load is bulky or heavy it may be possible to use mechanical handling aids or break down the load. If handlers have to adopt an awkward posture it may be possible to re-arrange the task. Additional training may be required.

The regulations are supported by general guidance in HSE Publication L23, which includes some numerical guidelines which help to identify the more serious risks which deserve a more detailed assessment. More detailed guidance may be developed for individual industries where there are special needs.

HSE Guidance document L23 shall be complied with.

Workplace (Health, Safety and Welfare) Regulations 1992

The Workplace (Health, Safety and Welfare) Regulations 1992 cover many aspects of health, safety and welfare in the workplace. Some of them are not explicitly mentioned in the current law though they are implied in the general duties of HASWA 1974. The Regulations apply to all places of work except:

a) Means of transport.

b) Construction sites.

c) Sites where extraction of mineral resources or exploration for them is carried out.

Workplaces on agricultural or forestry land away from main buildings are also exempt from most requirements. Only the requirements on toilets, washing facilities and drinking water apply. The Regulations set general requirements in four broad areas, as follows:

a) Working environment

The following working environment requirements are covered by the Regulations:

1. Temperature in indoor workplaces.

2. Ventilation.

3. Lighting, including emergency lighting.

4. Room dimensions and space.

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5. Suitability of workstations and seating.

b) Safety

The following safety requirements are covered by the Regulations:

1. Safe passage of pedestrians and vehicles, (e.g. traffic routes must be wide enough and marked where necessary, and there must be enough of them).

2. Windows and skylights (safe opening, closing and cleaning).

3. Transparent and translucent door and partitions (use of safety material and marking).

4. Doors, gates and escalators (safety devices).

5. Floors (construction and maintenance, obstructions and slipping and tripping hazards).

6. Falling a distance and into dangerous substances.

7. Falling objects.

c) Facilities

The following facilities requirements are covered by the Regulations:

1. Toilets.

2. Washing, eating and changing facilities.

3. Clothing storage.

4. Drinking water.

5. Rest area (and arrangements to protect people from the discomfort of tobacco smoke).

6. Rest facilities for pregnant women and nursing mothers.

d) Housekeeping

The following housekeeping requirements are covered by the Regulations:

1. Maintenance of workplace, equipment and facilities.

2. Cleanliness.

3. Removal of waste materials.

Employers will have to make sure that any workplace within their control complies with the Regulations. Other people connected with the workplace (such as the owner of a building which is

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leased to one or more employers or self-employed people) also have to make sure that the requirements falling within their control are satisfied.

HSE Approved Code of Practice L24 shall be complied with.

Personal Protective Equipment at Work Regulations 1992

The Personal Protective Equipment (PPE) at Work Regulations 1992 set out in legislation sound principles for selecting, providing, maintaining and using PPE.

PPE is defined as all equipment designed to be worn or held to protect against a risk to health or safety. This includes most types of protective clothing and equipment such as eye, foot and head protection, safety harnesses, life jackets and high visibility clothing. There are some exceptions (e.g. ordinary working clothes and uniforms (including clothing provided inlet for food hygiene), PPE for road transport (e.g. crash helmets) and sports equipment).

PPE should be relied upon only as a last resort. But where risks are not adequately controlled by other means employers now have a duty to ensure that suitable PPE is provided, free of charge, for employees exposed to these risks. The Regulations say what is meant by 'suitable' PPE, a key point in making sure that it effectively protects the wearer. PPE will only be suitable if it is appropriate for the risks and the working conditions, takes account of worker's needs and fits properly, gives adequate protection, and is compatible with any other item of PPE worn with them.

Employers also have duties to:

a) Asses the risks and PPE they intend to issue to ensure that it is suitable.

b) Maintain, clean and replace PPE.

c) Provide storage for PPE when it is not being used.

d) Give training, information and instruction to employees on the use of PPE and how to look after it.

New PPE is also subject to a separate EC Directive on design, certification and testing. PPE complying with this directive will be marked by the manufacturer with a 'CE' mark. This directive is to be implemented in the UK by Regulations made by the Department of Trade and Industry (to be called the PPE (Safety) Regulations).

HSE Guidance documents L25 shall be complied with.

Health and Safety (Display Screen Equipment) Regulations 1992

Work with display screen equipment is not generally high risk, but it can lead to muscular and other physical problems, eye fatigue and mental stress. Problems of this kind can be overcome by good ergonomic design of equipment, furniture, the working environment and the tasks performed.

The Regulations will apply to display screens where there is a 'user', that is, an employee who habitually uses the display screen equipment as a significant part of normal work. Employers will also have some duties toward the self-employed using display screen equipment in their undertakings. The Regulations cover equipment used for the display of text, numbers and graphics regardless of the display process used. There are some specified exclusions though, such as systems on board a

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means of transport, systems mainly for public use, portable systems not in prolonged use, cash registers and window typewriters.

Employers now have duties to:

a) Assess display screen equipment workstations and reduce risks which are discovered.

b) Make sure that workstations satisfy minimum requirements which are set for the display screen itself, keyboard, desk and chair, working environment and task design and software.

c) Plan display screen equipment work so that there are breaks or changes of activity.

d) Provide information and training for display screen equipment users.

Display screen equipment users are now entitled to appropriate eye and eyesight tests by an optician or doctor and to special spectacles if they are needed and normal ones cannot be used. It is now the employer's responsibility to provide tests, and special spectacles if needed.

HSE Guidance document L26 shall be complied with.

The Construction Regulations

The Construction Regulations comprise a number of different Regulations as follows:

a) General provisions -specify the requirements for safe working conditions handling and stacking of material, supervision of work, and welfare facilities.

b) Working places -provide details on fencing and work on roofs, ladders, scaffolds, and platforms.

c) Lifting appliances -specify the design and construction requirements for lifting appliances together with details of chains, ropes, slings and winches. They also set down the training needed for the operators of lifting appliances, and equipment inspection procedures.

d) Excavations and earthworks -contain information relating to deep excavations, timbering, fencing, inspections and examinations.

Abrasive Wheels Regulations 1970

The Abrasive Wheels Regulations 1970 were formulated to ensure safe use of grinding and cutting machines using abrasive wheels, discs, etc. Among other topics covered, there is a requirement to ensure that only trained and competent persons are permitted to change or mount abrasive wheels and/or discs.

Control of Asbestos at Work Regulations

The use of asbestos is controlled by the Control of Asbestos at Work Regulations 1987, as amended by the Control of Asbestos at Work (Amendment) Regulations 1992.

If there is any doubt about whether material contains asbestos or not, arrangements shall be made for a sample to be taken for analysis. If the presence of asbestos is confirmed, the working method given in Safety Information Note 4/90 shall be followed.

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NOTE -Asbestos boards and cement sheets encountered on customers' premises are often painted or otherwise treated, making recognition even more difficult.

Any large quantities of asbestos-related materials shall be reported to the Safety Adviser.

Control of Substances Hazardous to Health Regulations 1988

The Control of Substances Hazardous to Health (COSHH) Regulations 1988 require all work involving substances hazardous to health to be fully and sufficiently assessed and all necessary precautions communicated to persons involved in the work.

Naturally occurring radioactive materials come within the scope of the COSHH Regulations 1988.

Electricity at Work Regulations 1989

The Electricity at Work Regulations 1989 impose requirements in relation to:

a) Carrying out work on or near electrical systems, including underground cables.

b) Inspection and maintenance of portable electrical equipment.

Generally, low voltage or 110 V equipment should be used wherever possible.

HSE document HS(G)85 shall be complied with.

Noise at Work Regulations 1989 and Construction (Head Protection) Regulations 1990

General

The Noise at Work Regulations 1989 and Construction (Head Protection) Regulations 1990 have been introduced to ensure that employees are provided with adequate job/process assessments, training and personal protection in respect of some basic hazards that may be present on any work site.

There is also a necessity to consider others who may be working nearby.

Most of the equipment in use during normal operations can produce dangerous noise levels: such equipment will normally incorporate a warning label stating that hearing protection must be worn whilst the equipment is in operation.

In such cases, hearing protection (ear muffs) must be worn at all times, not just by the operator of the equipment, but by all personnel in the immediate vicinity. This is a legal requirement - the Noise at Work Regulations 1989 refers.

As a general guide as to the necessity for wearing ear protection, if you have to shout at a distance of 1 m or less to make yourself heard, hearing protection (ear muffs) shall be worn. If you are at all unsure about the need for personal ear protection, consult the Health, Safety and Environment (H, S & E) Department.

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Construction (Head Protection) Regulations 1990

The Construction (Head Protection) Regulations 1990 require that persons at work and exposed to risk of head injury must wear an approved head protector (safety helmet), generally known in the trade as a 'hard hat'. Typical situations where head protection should be worn include the following:

a) Working with or near cranes.

b) Working in excavations, pits, chambers greater than 1.2 m deep.

c) Areas of restricted headroom.

d) On or near scaffolding.

e) On or near buildings where work is taking place overhead.

f) On any site where the person in charge makes rules requiring the wearing of head protection.

Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 1985

General

There are two major parts of the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations (RIDDOR) 1985. These are detailed in 5.3.14.2 and 5.3.14.3. Guidance is given in HS(G)23 and HSE 24.

Accident Reporting

Accidents at work which result in an injury and absence from work for more than three consecutive days (excluding the day of the accident but including any days that would not have been working days) must be reported to the Health and Safety Executive (HSE), on their official form (F 2508) within seven days.

Similarly, an accident at work which results in death or a prescribed major injury, or the casualty being detained in hospital, must be reported to the HSE by the quickest practicable means, but within 24 h.

3.1.1.5 Dangerous Occurrences Reporting

There is a list of seventeen prescribed 'dangerous occurrences' which must be reported to the HSE by the quickest practicable means, but within 24 h, and within seven days in writing on Form F 2508.

The Radioactive Substances Act 1960

All sources of a type and strength in the Third Schedule of the Radioactive Substances Act 1960 have to be registered, the location specified and authority obtained for their disposal. If such a source is portable, a log shall be kept of its use and locations.

The Public Information for Radiological Emergency Regulations 1992 empowers Fire and Civil Defence authorities to require information to be supplied for use in the event of a radiation emergency.

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NOTE - Naturally occurring radioactive materials come within the scope of the COSHH Regulations 1988.

The Ionising Radiations Regulations 1985

The Ionising Radiations Regulations 1985 are made under the HASWA 1974 and apply wherever the Act or Regulations made under the Act are in force. They cover the notification and records, basic principles of protection, radiological and medical surveillance, organization of work and monitoring.

They also cover radiography and other processes and specify in an attached schedule the maximum permissible radiation doses.

Further guidance on the use of radioactive sources is given in the publication Radiation Safety Site Radiography prepared by the Oil and Chemical Plant Constructors' Association.

Carriage of Dangerous Substances Regulations (various)

Dangerous substances must be packaged and labelled in compliance with the Classification, Packaging and Labelling of Dangerous Substances Regulations 1984.

Carriage of dangerous substances must be in accordance with the Road Traffic (Carriage of Dangerous Substances in Packages etc.) Regulations 1992 or the Road Traffic (Carriage of Dangerous Substances in Road Tankers and Tank Containers) Regulations 1992, as appropriate.

Guidance is available on application to the H, S & E Department.

3.1.2 Meeting Legal Safety Standards

3.1.2.1 Competence

All persons engaged in the design, construction, commissioning, operating, maintenance and alteration of mains, services and related plant shall be competent to carry out such work. This may be achieved by an appropriate combination of education, training and practical experience.

3.1.2.2 A General Guide To Working Safely

The following represents a general guide to safe working. Certain items are directed particularly to those employees who have a responsibility for others. Basically you should ensure:

a) that you are familiar with the Health, Safety and Environment Statement, The H S & E Requirements Manual

b) that your staff are trained and aware of any hazards at their place of work;

c) that your staff know where to find First Aid and fire-fighting equipment, and especially are aware of its limitations and method of use;

d) that adequate supervision is available at all reasonable times, particularly for younger or less experienced members of staff;

e) that safety rules are observed at all times and, where required, protective equipment is used;

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f) that safety devices, where provided, are properly adjusted and maintained;

g) that machinery and equipment is frequently inspected to ensure it is properly maintained and safe to use;

h) that any defects in equipment are promptly reported and rectified;

i) that good standards of housekeeping are maintained;

j) that you regularly review working practices to improve Health and Safety aspects at your place of work.

If there is any doubt, advice should be sought from your Safety Adviser.

3.1.2.3 Protective Clothing And Equipment

Specification

All protective clothing and equipment must, where appropriate, comply with the relevant British Standards(s) and/or regulations and Certificates of Approval currently in force.

All protective clothing and equipment shall have the approval of the relevant Safety Adviser. If the introduction of new protective clothing or equipment is proposed (or a variation in use of existing protective clothing or equipment), the Responsible Engineer shall seek the advice of the Safety Adviser before introduction.

Provision

The majority of protective clothing and equipment is provided for employees on a personal issue basis in compliance with statutory regulations (e.g. head protection, ear defenders, safety footwear).

Some protective clothing and equipment may be provided on loan, as and when required, at the discretion of the Responsible Engineer (e.g. full fire protection suits, chemical and waterproof clothing). However, in either case, it is essential that adequate supplies of all items are stocked at local depots, such that they are immediately available for issue. Suitable arrangements shall be made for access out-of-hours.

Where equipment is issued in compliance with Statutory Regulations, it is essential that replacement items are issued with the minimum of delay.

Inspection and maintenance

The Responsible Engineer shall ensure that proper inspections are carried out on protective clothing and equipment for which he is responsible within the timescale required by Statutory Regulations.

The Responsible Engineer shall ensure that adequate records are kept of all inspections, and any subsequent maintenance carried out or replacements issued.

Practical guidance on the use of protective clothing and equipment

Protective clothing and equipment should be worn whenever necessary. Table 1 gives detail of these and the hazardous environment for which they are particularly suitable.

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Item(s) Area(s) of Protection Possible environmental hazard(s)

Safety Helmet Head and neck a) Impact from falling or flying objects b) Chemical drips or splashes c) Adverse climate or temperature NOTE - Some safety helmets incorporate, or can be fitted with, specially designed facial, respiratory or hearing protection.

Scarves Neck During welding operations.

Flash Hoods Neck and face Where a fire risk is high.

Goggles; face screens; face visors

Eyes a) Chemical or metal splash. b) Airborne dust. c) Projectiles. d) Gas or vapour.

Ear muffs Hearing a) Impact noise. b) High intensity noise (even for short exposure). c) Pitch (high and low frequencies).

Gloves; gauntlets Hands and arms a) Abrasion. b) Temperature extremes. c) Cuts and punctures. d) Impact. e) Chemical spillage. f) Electric shock or burns. g) Skin infection. h) Vibration.

Safety boots and Wellingtons (incorporating Transco approved steel toe caps)

Feet and ankles a) Damp or wet (sometimes frozen) areas. b) Slippery (possibly due to oil or chemical spillage) areas. c) Cuts and punctures. d) Falling objects. e) Heavy pressures. f) Metal splash. g) Abrasion.

Disposable respirators; half masks or full-face mask respirators fitted with filtering cartridge or canister; powered respirators blowing filtered air to mask, visor, helmet or hood; fresh air hose equipment; self-contained and fresh air type breathing apparatus

Respiratory Tracts a) Toxic and harmful dusts. b) Gases and vapours. NOTE - The correct type of respirator filter must be used, as each type is effective for only a limited range of substances. Cartridges and canisters have a limited life. Where there is a shortage of oxygen, or any danger of losing consciousness from fumes, etc., use only breathing apparatus of the correct type. It should also be noted that correctly worn breathing apparatus face masks not only provide excellent protection against asphyxiation, but also against flesh burns and inhalation of hot gases.

Overalls All-over protection For live gas operations, only overalls which have been ‘Proban’ treated or similar should be worn - these give excellent protection against flame.

Table 1 - Protective clothing/equipment and their usage

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The use of protection, additional to that given in Table 1, against possible ignition of natural gas should be largely dependent on the amount of gas likely to be present and the means of egress from the work area.

The Responsible Engineer, when deciding on the use of full fire protective clothing for the safety of employees involved on live gas operations, shall take account of the following:

a) The amount of gas present or likely to be present.

b) The ease and speed of safe evacuation should an incident occur.

Recommended standards for fire protective clothing are:

a) fire suits

b) flash hoods

c) gloves

all manufactured from heavy duty 'Proban' treated cotton, or Nomex III or Bristol type.

Fire suits should be of the boiler suit design, close fitting at the wrists and ankles with a heavy duty zip under a protective flap.

Face and respiratory protection will ideally be provided by breathing apparatus appropriate for the situation and must always be worn in conjunction with the fire protection clothing.

Any person working in or near the highway or visiting such works, must wear the appropriate high visibility clothing.

3.1.2.4 Safe Use Of Substances

The main item of legislation is the COSHH Regulations 1988 which covers virtually all substances hazardous to health. Only asbestos, lead and materials producing ionizing radiations, which have their own legislation, are omitted.

The following basic principles of occupational hygiene are embodied in the COSHH Regulations 1988:

a) Assessing the risk to health arising from work and what precautions are needed.

b) Introducing appropriate measures to prevent or control the risk.

c) Ensuring that control measures are used and that equipment is properly maintained and procedures observed.

d) Where necessary, monitoring the exposure of employees and carrying out an appropriate form of surveillance of their health.

e) Informing, instructing and training employees about the risks and the precautions to be taken.

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It is essential that only substances on an approved list are purchased. Any new substances shall be cleared by the Safety Advisor and an assessment carried out as necessary.

3.1.2.5 Fire Precautions

Fire prevention

The formation of a flammable mixture in gas engineering operations may only be avoided by reducing to a minimum the amount of uncontrolled gas discharged into the atmosphere.

Accordingly, full use should be made of any equipment and working methods designed for 'no gas' working.

During all engineering operations where escaping gas could be present, regular checks should be made with approved gas detection instruments, to safeguard anyone affected by the work activities.

Suitable notices shall be displayed to warn and instruct persons affected as follows.

Figure 2 - Typical warning notices

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Good ventilation of all working areas during an engineering operation is necessary to help prevent the build-up of gas concentrations in the atmosphere.

Any natural ventilation available should be taken advantage of by ensuring, as far as possible, that the flow of air in working areas is not restricted (e.g. governor kiosks doors are fully opened from front and rear).

Natural ventilation may not be sufficient to control the concentrations of gas in air, such as accumulations of gas in a trench or confined space. In these circumstances consideration should be given to clearing the accumulation by the use of a suitable air mover. It is essential that the air mover is not a potential source of ignition. It may be driven by compressed air, hydraulic power or approved electric motor (see 12.1.3.4 regarding certified and non-certified electrical equipment). It shall be made of electrically conducting materials and it shall have a means of earthing which must prevent a build-up of static electricity.

Impact between steel tools such as hammers and chisels can cause a spark. Sparks can also easily be produced by steel tools such as forks, picks, shovels and points striking flints, rock, stones and concrete, etc.

It is possible that such sparks could ignite a gas-air mixture.

With all tools, the use of water will reduce the likelihood of sparks occurring. In the presence of leaking gas, water should be poured on the ground before any potentially spark producing tool is used.

When pipe is being broken out with a hammer, consideration shall be given to purging the pipe thoroughly. Both pipe and hammer shall be wetted in areas where impact or friction is likely to take place. This may be achieved by wetting the pipe with a wet cloth. (The cloth may also reduce the likelihood of the hammer bouncing off and broken pieces of main being ejected into the air).

Equipment on site employing a naked flame shall be placed at least 5 m from any possible source of escaping gas, and preferably upwind. If the equipment has to be placed downwind, this distance should be increased.

In certain circumstances the Responsible Engineer may need to specify that equipment is placed further away from the work and additional atmospheric monitoring adjacent to the equipment is necessary (e.g. where gas in atmosphere may be present over a wide area from an open-ended main as a result of impact damage in a third party excavation or a medium pressure escape).

There shall be no smoking on any site where live gas working is to be/is being carried out.

Suitable warning signs and barriers shall be erected to prevent any unauthorized entry into areas where gas is being, or will be, discharged into the atmosphere.

Unless specified otherwise by the Responsible Engineer, all electrical equipment which is likely to be used in a gas-air mixture shall preferably bear the following explosion protection symbol:

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Non-certified equipment used on site shall be suitably located to avoid any possible source of ignition, but in any case not less than 5 m from any possible source of escaping gas. The ignition system on a petrol engine is electrical and shall be taken into account when siting equipment.

Immovable and non-certified electrical equipment such as street lighting, illuminated traffic signs or traffic light switching equipment can be sources of ignition. In the event of a gas escape, the Responsible Engineer shall, if necessary, contact the people responsible for the equipment, so that appropriate action may be taken to make the situation safe.

Metal gas pipework acts as a carrier for stray electric currents. These currents can cause sparking during cut outs and disconnection operations on both mains and services.

Temporary continuity bonds shall be installed before any connection or disconnection work. They shall be positioned so that they are not disturbed during the progress of the work (see Appendix B).

Static electricity is generated by rubbing contact. Materials normally considered to be electrically insulating, such as polyethylene, become charged most readily. The ignition of a gas-air mixture can result if an object charged with static electricity is allowed to discharge to earth from a point.

Dusty gas passing through a main at high velocities can generate large static charges. The charges can be retained on the dust particles and also on the pipe wall if the pipe is plastics or insulated from earth.

If an operative is insulated from earth by rubber boots and has to insert a plug in a metallic main, the plug and operative can become charged from dust in the gas stream coming from the hole. When the plug is brought close enough to the pipe, the charge collected on the plug and operative may be discharged to the pipe causing a spark that can ignite the gas.

In this situation the operative and the plug shall be earthed. This can be done by resting the plug on the metal pipe preferably 350 mm away from the hole and sliding it along the surface of the pipe to the hole.

High velocity discharges of gas from pipes in mains shall be avoided whenever possible. Pipes used for venting gas shall be adequately earthed.

Sufficient static charge to cause a spark that can ignite gas can be built up on plastics pipe by handling and cleaning.

When there is a risk of escaping gas, the pipe shall be covered with a cloth dampened with clean water and in good contact with earth. This allows the static charge to be discharged safely to earth.

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Sufficient static charge to cause a spark that will ignite gas can be built up on plastics pipe by both application and removal of stretch wrap and shrink wrap film.

Plastics film should not be applied or removed in areas where potentially flammable or explosive vapour/air mixtures can exist.

The flow of dusty gas will generate static charge on the internal surface of plastics pipe. Although polyethylene is generally considered a non-conducting substance, the static charge can be conducted through the pipe wall to create high potentials on the outside surface.

A damp cloth draped over the pipe and making contact with earth will safely drain the charge and prevent it building up to dangerous levels.

Plastics pipes should not be used as vent pipes.

To avoid the possibility of causing an ignition by static sparks, operatives shall not take off or put on any clothing where gas is escaping or venting.

Care shall be taken to avoid striking electric cables when excavating and barholing. See A Code of Practice for Barholing.

Whenever possible, electric cables should be isolated, particularly when embedded in concrete.

The position of electric cables should be established from drawings whenever possible. A cable locator shall be used prior to and during excavating or barholing. Reference should be made to HSE publication HS(G)47.

Incidents have been reported of dust glowing red and smoking in sections of pipe cut out from mains near to old gas works. This dust is pyrophoric and can ignite a gas-air mixture. If a dust from a gas main begins to heat up, it should be cooled down with water.

Pyrophoric dust is rarely encountered, but all operatives should be aware of its existence.

When it is necessary to weld on to or adjacent to live gas plant, or to carry out other hot work, the operation shall only be undertaken in accordance with a written routine procedure or a valid Permit to Work.

The storage and use of other flammable substances (e.g. petrol, fuel oil, liquefied petroleum gas) may give rise to similar hazards as escaping gas if vapour-air mixtures are allowed to accumulate.

Fire prevention measures to be taken when dealing with these substances are generally the same as when dealing with gas.

Vapours produced by these substances are usually heavier than air and will not dissipate as easily as gas. Good low and high level ventilation is essential in storage areas to ensure that any vapours are adequately removed.

All flammable substances should only be stored in approved, appropriately marked containers. Minimum quantities only, consistent with effective usage should be stored on site and these in secure storage.

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Fire protection

In the event of a fire, the protective clothing and equipment worn by an operative should give sufficient protection to allow time to escape from the incident without injury.

During all engineering operations where there is a risk of escaping gas, appropriate protective clothing and equipment shall be worn including for hands, head, neck, face and respiratory system as necessary.

As a minimum during all live gas operations, operatives shall wear full body protection made from flame retardant materials together with suitable hand protection.

Where conditions require, the Responsible Engineer must also consider the issue and use of additional protection in the form of full fire protection suits together with head and neck protection.

The Responsible Engineer, when deciding on the use of full fire protective clothing for the safety of employees involved on live gas operations, shall take account of the following:

a) The amount of gas present or likely to be present.

b) The ease and speed of evacuation should an incident occur.

Face and respiratory protection will ideally be provided by breathing apparatus appropriate for the situation.

It shall always be worn in situations where the Responsible Engineer has specified the use of full fire protective clothing. It shall be worn whenever working in an excavation where the activity is likely to give rise to a release of gas, or whenever gas readings in the breathing zone are 20% LEL or above.

Additionally, it shall be worn whenever gas readings taken in the atmosphere are equal to or greater than 20% gas in air (GIA).

Where Breathing apparatus is required to be used there shall be 2 persons trained in its use present on site and a second fully operational breathing apparatus set is available (for use by the second person should the need arise).

Breathing apparatus shall be prepared and available for immediate use, easily accessible and alongside any excavation containing exposed gas mains or services.

During all live gas operations, suitable and sufficient fire extinguishers should be available on site.

At every site where work is being carried out, and where there is the risk of the release of gas, at least two fire extinguishers shall be conveniently placed for immediate use in an emergency.

Fire extinguishers should be of the dry powder type with a capacity of at least 9 kg.

Every fire extinguisher should be thoroughly examined at least every twelve months by a competent person.

Each week fire extinguishers should be inspected for external impact damage and replaced if necessary. At the same time fire extinguishers should be inverted to prevent compaction of the powder.

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Whenever a fire extinguisher has been primed (whether it has been used or not), arrangements shall be made to replace it without undue delay. All the remaining dry powder shall he disposed of before refilling and the hose and trigger equipment cleared of any remaining powder.

It is essential that there is always a means of rapid escape from areas of work in case of fire. Depending on the circumstances, more than one escape route may need to be provided. Special precautions are necessary in the case of deep excavations.

In areas where escape would otherwise be difficult, sloping ramps or run-outs should be provided if possible. Where this is not possible because of site conditions, securely fixed ladders shall be provided, extending at least 1 m above the level of the excavation or other stepping-off point.

Where an excavation is deeper than 2 m, lifelines shall be provided. They shall be placed ready for use or worn as the conditions warrant. In this circumstance it is essential that adequate numbers of personnel are immediately available on site to effect a rescue by lifeline.

Fire fighting

If escaping gas catches fire, it is necessary to decide which is the greater hazard; the fire or the escaping gas if the fire is extinguished. If the escaping gas would be of the greater hazard, it is essential that the fire is allowed to burn under close attention until all materials required for sealing the escape are available or until the gas supply is turned off.

If the fire is allowed to burn, the Fire Brigade shall be called.

The Responsible Engineer shall attend the site. Representatives from other affected utilities shall be asked to attend also.

It is essential that the Fire Brigade are requested to work closely with the Responsible Engineer and are asked not to extinguish the fire until it is safe to do so. In some cases it may be necessary to cool the surrounding area and exposed pipes.

When it is decided to extinguish a fire, one of the following methods may be used:

a) If the fire is not too large, it may be extinguished by directing dry powder from a fire extinguisher into its base.

b) The gas supply may be cut off. In some cases valves may be available, but in many cases it will be necessary to isolate the main either side of the fire. The size of the fire should be reduced by partially shutting off the supply. The fire should then be extinguished with a dry powder fire extinguisher and the gas supply immediately shut off completely.

All appropriate engineers and operatives must be trained in basic fire fighting techniques. Practical refresher training should be given at appropriate intervals.

3.1.2.6 Infectious Diseases Affecting Farm Livestock

In the event of an outbreak of an infectious disease such as foot-and-mouth disease an 'infected area' is imposed covering a minimum radius of 10 miles around the infected premises. This area usually remains in force for 21 days. Wide publicity is given when outbreaks of disease occur, and the extent of the 'infected area' can be obtained from the local police station.

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Emergency work may continue, but if such work is necessary on land within five miles of an outbreak, the Veterinary Officer in charge of the local Control Centre should be informed. The address and telephone number of the Control Centre is given wide publicity locally, and details of the extent of the 'infected area' will also be available from the Control Centre.

NOTE - Employees who own or attend farm livestock are excluded from working on premises where disease exists.

Routine work within two miles of the infected premises should be stopped until the 'infected area' restrictions are lifted.

In the area extending from two miles to five miles from the infected farm, work should be postponed for seven days after the outbreak, and then continued only if the occupier of the land on which the work is to be carried out agrees.

On land over five miles from the outbreak to the boundary of the 'infected area' work may continue as normal.

When work is being undertaken on any farm land within an 'infected area', all boots, equipment and the outside of vehicles, particularly the wheels and wheel arches, should be cleaned and disinfected with a disinfectant approved for use against the infectious disease.

3.1.2.7 First Aid Advice

All sites should have at least one First Aid box placed at a convenient point and clearly marked with a white cross ( ) on a green background. Small, travelling First Aid kits should be provided to personnel working alone, or in small groups, away from the main site.

You may or may not be a qualified First Aider and, if you are not, it would be irresponsible on your part to assume that you are. However, in the event of an accident involving a colleague, you may be the only other person present and therefore represent that colleague's only hope between life and death (e.g. could you stand by and let your colleague bleed to death whilst waiting for a qualified First Aider to save your colleagues life?).

The advice given in subsequent clauses is intended to provide a few commonsense things to do should you find yourself in a circumstance similar to that described above. However, such advice given herein should not be construed as a substitute for proper First Aid training, especially in the areas of artificial resuscitation and cardiac arrest where a course of practical instruction should be undertaken.

Fist aid boxes and kits

First Aid boxes and kits are provided for use in an emergency. Do not misuse the contents; it is not much help if an accident occurs resulting in injury to a colleague and you find that someone has taken and not replaced the essential bandages, sterile dressings, safety pins, etc.

Vehicles should contain a First Aid kit. This kit should be kept in the space provided or other prominent position so that whoever is using the vehicle can locate it easily when required.

If a First Aid kit or any of its contents are badly damaged, the kit should be returned to for replacement.

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Accident reporting

Every accident shall be reported to a responsible person. Details of any injury, and the treatment (if any) given, shall be entered in the on-site Accident Book as soon as possible after the accident.

In the event of an accident causing injury to personnel, the following course of action should be taken:

a) Get help: that does not mean that you should leave the casualty whilst you go in search of a telephone. Call out (or shout) to attract the attention of passers-by or other persons in the vicinity.

b) Take immediate action: do what you can to protect the casualty from further danger or injury. Attempt to stop any bleeding and, if you know how and the need is evident, give artificial resuscitation. You are not the doctor and might not be a qualified First Aider, so limit your aid to the more obvious, commonsense actions until expert help arrives.

c) Comfort the casualty: keep the casualty warm and dry and above all reassure him/her that help is on the way. Anyone who has been involved in an accident will know how good it feels to know that someone is at hand to take care of you.

Situations likely to require basic first aid

Some of the emergency situations likely to be encountered on and the immediate action/remedies are given in Table 2.

However, where medical attention is not readily available, especially in the following circumstances:

a) hazardous substance in the eyes;

b) hazardous substance swallowed;

c) inhalation of a vapour, powder or gas;

d) serious skin burns;

e) bleeding wounds,

The casualty shall be referred to a hospital with the minimum of delay

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Emergency situation

Immediate action/remedy

Electric shock a) b) c)

Do not touch the casualty. Break the electrical contact by: 1) switching off at the mains, or 2) removing the plug from its socket-outlet, or 3) wrenching the cable free. Seek medical attention.

Cuts and bruises a) b) c) d) e)

If practicable, wash your hands before dealing with the casualty. Temporarily protect the wound with a sterile swab (or clean handkerchief) and clean the skin around the wound, wiping away, not towards, the wound and dab it gently to dry. If bleeding is continuous, apply direct pressure to stem the flow of blood and, if possible, raise the injury to reduce the flow of blood. Dress the wound. A small cut can be dressed with a plaster or small bandage; in the case of a larger wound apply a sterile dressing or a clean pad and bandage firmly. Seek medical attention.

Burns and scalds a) b) c) d) e) f)

If practicable, wash your hands before dealing with the casualty. Relieve the pain and minimize the shock. Place the injured part under slow running cold water, or immerse it in a container of cold water. NOTE -If cold water is not readily available, any cold, harmless, fluid (e.g. milk, beer, wine, cold tea) will do. Do not apply an adhesive dressing or any lotions, ointments, fats or oils to the injury Do not break blisters, loose skin, or otherwise interfere with the injured part Seek medical attention.

Hazardous substances (Swallowing)

a) b) c)

If the casualty is conscious, give him/her two or three cups full of water to drink; do not attempt to make the casualty sick. Get the casualty to the Accident and Emergency Department of a hospital without delay. If details of the hazardous substance are known and the casualty is unconscious, advise the medical team accordingly.

Hazardous substances (Inhalation)

a) b) c)

If attempting a rescue, ensure you will not be affected. Remove the casualty to fresh air; keep him/her warm and at rest. Seek medical attention.

Table 2 - Emergency situations and their immediate action/remedies

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Carbon monoxide (CO) poisoning a)

Remove the casualty into the fresh air as quickly as possible and seek medical attention

b)

Assess the situation and ensure that you do not carry out any action, which may cause you also to become a casualty.

c)

In any case of doubt, breathing apparatus must be worn in attempting a rescue. However, it should be noted that breathing apparatus should not be used by personnel who have not received proper training in its use.

d)

Loosen or remove anything pressing on or constricting the casualty’s neck, waist or chest. If the casualty has false teeth, remove them to a safe place as they may cause the casualty to choke.

e) If breathing has stopped altogether, apply artificial resuscitation. The most important factor is to endeavour to ensure that breathing continues.

f)

If the casualty is conscious and breathing is regular, keep the casualty warm and lay him/her in the recovery position (see below).

g) When the casualty and his/her breathing become stronger, do not allow him/her to move about or exert himself/herself in any way. This applies to anyone who has been even slightly gassed. Under no circumstances shall the casualty be allowed to walk.

h)

Keep the casualty under constant observation and, in the absence of a doctor, the casualty must be taken, still under observation, to the Accident and Emergency Department of a hospital. If, during the journey, the casualty’s heart or breathing stops, artificial resuscitation must be applied. On arrival at the hospital advise the hospital staff of the type of poisoning.

i) Never attempt to give an unconscious casualty anything to drink - it may choke him/her. Above all, never administer alcohol as this will worsen the circumstances

j) Never attempt to make the casualty vomit.

Table 2 (cont…) - Emergency situations and their immediate action/remedies

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Emergency situation

Immediate action/remedy

Accidents involving cylinder gases (Inhalation)

a) b) c) d)

Having ensured there is no personal risk, immediately remove the casualty to an uncontaminated area. If the casualty has stopped breathing, check that his/her airways (e.g. remove his/her false teeth if fitted) are not obstructed and that a pulse is present. If trained, start immediate artificial resuscitation. Seek medical attention.

Accidents involving cylinder gases (Burns)

a) b) c)

Wash the contaminated area thoroughly in cold water for at least 10 min. Apply a clean dressing or cloth (e.g. handkerchief) to the burn. Seek expert medical attention, i.e. on site medical centre or local hospital.

Accidents involving cylinder gases (Eye contact)

a) b)

If practicable, wash the eye out with cold running water or, preferably, a proprietary eye wash solution. Refer the casualty to a hospital.

Eye injuries. a) b) c) d) e)

Eye injuries shall be regarded very serious. An eye can be cut or bruised from a direct blow or by fragments of grit, metal or glass. Eye injuries can be very painful and, if the eye is inflamed or bloodshot, the casualties vision may be seriously impaired As the only person at hand, your aim should be to protect the casualty’s eye(s) from further damage, i.e.: Ask the casualty to, if possible, close the injured eye. Cover the injured eye with an eye pad or sterile dressing. Hold this in place with a bandage or sticky tape Advise the casualty to keep his/her other eye as still as possible. If necessary apply a blindfold but, before resorting to this form of action, reassure the casualty beforehand. On no account attempt to remove a foreign body from an eye - leave this to someone who knows what they are doing. Seek expert medical assistance as soon as possible.

Table 2 (cont…) - Emergency situations and their immediate action/remedies

3.1.2.8 Fitting and Removing Temporary Electrical Continuity Bonds

1. Temporary electrical continuity bonds shall be installed before any connection or disconnection work is carried out on a main or service. Electrical continuity bonds shall be positioned such that they will not be disturbed during the progress of the work.

2. Having determined the positions on the main and/or service where the electrical continuity bonds are to be connected, remove any pipe wrapping, paint or other protective coating and thoroughly clean the area using a wire brush.

3. The electrical continuity bonds shall be of adequate length, and the end fittings shall be clean, securely connected to the wire or braid and in good working order.

4. The electrical continuity bonds shall be attached to the main or service pipe as shown in Figure 3 ensuring that good 'electrical' contact is made.

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5. The electrical continuity bonds shall be removed from the main or service pipe only when all connection or disconnection work is completed and after ensuring that the area is 'gas free'.

Figure 3 - Fitting of electrical continuity

3.2 List Of Useful References Specific To Health And Safety

3.2.1 UK Statutes And Regulations

Abrasive Wheels Regulations 1970

Classification, Packaging and Labelling of Dangerous Substances Regulations 1984 Construction (General Provisions) Regulations 1961

Construction (Head Protection) Regulations 1990

Construction (Lifting Operations) Regulations 1966

Construction (Working Places) Regulations 1966

Control of Asbestos at Work Regulations 1987

Control of Asbestos at Work (Amendment) Regulations 1992

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Control of Substances Hazardous to Health (COSHH) Regulations 1988

Electricity at Work Regulations 1989

Factories Act 1961

Gas Safety (Installation and Use) Regulations 1994

Gas Safety Regulations 1972

Health and Safety at Work etc. Act (HASWA) 1974

Health and Safety (Display Screen Equipment) Regulations 1992

Health and Safety (First Aid) Regulations 1981

Ionising Radiations Regulations 1999

Management of Health and Safety Regulations 1992

Manual Handling Operations Regulations 1992

Noise at Work Regulations 1989

Offices, Shops and Railways Premises Act 1963

Personal Protective Equipment at Work Regulations 1992

Provision and Use of Work Equipment Regulations 1992

Public Information for Radiological Emergency Regulations 1992

Reporting of Injuries, Diseases and Dangerous Occurrences Regulations (RIDDOR) 1985

Road Traffic (Carriage of Dangerous Substances in Packages etc.) Regulations

Road Traffic (Carriage of Dangerous Substances in Road Tankers and Tank Containers) Regulations 1992

Third Schedule of the Radioactive Substances Act 1960

3.2.2 Health And Safety Executive (HSE) Publications*

* Publications in the L (legal) series explain or interpret legislation. They will gradually supersede existing publications in the HSC COPS series (Approved Codes of Practice) and the HSE HS(R) Series.

EH36 Work with asbestos cement EH55 -The control of exposure to fumes from welding, brazing and similar processes

GS6 Avoidance of danger from overhead electric lines

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GS7 Accidents to children on construction sites

HS(G)23 A guide to the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 1985

HS(G)47 Avoiding danger from underground services

HS(G)85 Electricity as Work. Safe Working Practices

HSE 24 Reporting under RIDDOR

L21 Management of health and safety at work. Approved code of practice

L22 Provision and Use of Work Equipment Regulations 1992. Guidance on Regulations

L23 Manual Handling Operations Regulations

L24 Workplace (Health, Safety and Welfare) Regulations 1992. Approved Code of Practice and Guidance

L25 Personal Protective Equipment at Work Regulations 1992. Guidance on Regulations

L56 Safety in the Installation and Use of Gas Systems and Appliances. Gas Safety (Installation and Use) Regulations 1994.

PM5 Automatically controlled steam and hot water boilers

PM30 Suspended access equipment

PM32 Safe use of portable electrical equipment

PM42 Excavators used as cranes

PM54 Lifting gear hazards

3.3 Competence Of Health And Safety Supervisors

All construction work shall be overseen by a competent Health and Safety supervisor. The person appointed shall meet the following criteria:

a) A seasoned HSE professional with significant experience of major hazard operations in a continuous process industry.

b) Trained to degree level, will be a member of a relevant professional body e.g. UK Nebosh Certificate or Diploma and be able to demonstrate a substantial track record in a similar role within the oil and gas sector.

c) Will possess leadership and managerial skills.

d) Will have experience in dealing with environmental issues.

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e) Broad knowledge of principle health, safety and environmental legislation requirements.

f) Ensure that suitable HSE management arrangements are in place to deliver performance standards.

g) Alignment of Project HSE Plans with Company/Organisation Plans.

h) Implementation of HSE Management Systems.

i) Supervision, co-ordination and monitoring of HSE performance including identification, communication and monitoring KPI’s.

j) Identification and co-ordination of worksite HSE resources.

k) Incorporation of Organisation and Industry ‘lessons learned’ into project planning.

l) Maintenance of HSE visibility throughout life of project.

m) HSE presence and input at key project stages/meetings.

n) Application of Risk Management processes.

o) Management of Risk Registers.

p) Chairmanship and facilitation of HAZID and HAZOP processes.

q) Liaison with all engineering functions contributing to a project.

r) Control of internal and external audit schedules including those of subcontractors.

s) Monitoring of subcontractor acceptance criteria and contract performance.

t) Incident investigation.

u) Root cause identification and information dissemination.

3.4 Safety In Transportation Of Materials And Working In Excavations

3.4.1 Handling, Transport And Storage Of Steel Pipe, Bends And Fittings

For information on the handling, transport and storage of PE pipes and fittings reference shall be made to IGE/TD/3 Edition 4 Supplement 1.

3.5 Excavating And Reinstating Pipelines, Mains And Services

All persons engaged in the design, construction, commissioning, operating, maintenance and alteration of mains, services and related plant shall be competent to carry out such work. This may be achieved by an appropriate combination of education, training and practical experience.

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3.5.1 Excavating

For all projects reference shall be made to Libyan Environmental Legislation and the relevance of Lows (Low 15). Archaeological permission shall be obtained from the relevant local authority.

On projects in the public highway the Responsible Engineer shall walk the route with the team leader or contractor's representative and a representative of the Highways Authority. Any obvious defects in the surface of the road or path (e.g. broken flags, building defects) should be noted and confirmed in writing to the appropriate authority.

Where the works involve land in private ownership, a joint inspection to agree and note any existing defects in the surfaces along the proposed route shall be made by the owner and/or tenants together with representatives of the contractor and Transco.

Once the approximate route has been determined, a detailed survey shall be undertaken to establish the most suitable line on which to lay. During this survey, the position of surface boxes, marker posts and recent excavations shall be noted.

When laying across infilled sites, the line of the trench shall be surveyed and investigated for the presence of obstructions or permanent hard spots, so that they may, whenever possible, be avoided.

Due regard shall be paid to:

a) Future access and maintenance:

b) Interference with traffic;

c) Inconvenience to the public.

The location of all obstructions and underground plant should be recorded and, where necessary, clearly marked before construction plant is allowed to enter the area.

Where it is necessary to lay pipes in close proximity to buildings or other structures, any structural defects shall be noted and either agreed with the owners of the property or, alternatively, photographed.

Where reliance is placed on photographic evidence, it is essential to establish that such evidence was obtained prior to the commencement of the works.

The Engineer or Engineer's representative shall ensure that each team leader or contractor shall be supplied with all available relevant drawings or information describing the position, size and capacity/rating of any current carrying cable, for:

a) Planned work; up-to-date information should be obtained on the position of cables before excavation begins and a hard copy made available on site.

b) Emergency and urgent works; if not readily available on site, relevant information should be obtained as soon as possible after work starts.

For planned work, drawings giving the cable location should be attached to job instruction cards. Alternatively, teams may be provided with microfiche plans.

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The team leader or Contractor shall exercise great care in order that existing underground plant is not damaged. Cable and pipe locators shall be used to confirm the position of existing cables and other metallic underground plant. Reference should be made to HSE Guidance Note HS(G) 47 for precautions to be observed.

A clearance of not less than 250 mm should, wherever possible, be kept between gas mains and fittings and the known position of other Utilities plant, irrespective of whether it is running over, alongside or under the plant. If the gas pipe crosses other Utilities' plant, this clearance may be reduced if there is further external protection to either the gas pipe or other Utilities' plant.

Prior to the commencement of the works, agreement shall be reached with the Highway Authorities and such other persons as may be concerned with the programme of work, methods of construction, access ways, traffic control, alternative reinstatement specifications, and any road signs.

It is an offence to remove or obliterate any lawfully placed permanent traffic signs. The responsible highway authority should be consulted where there is a need to remove or severely restrict viewing access of any such signs, in order that they can make the necessary alternative arrangements. They should also be advised of the completion of the works so that the signs may be properly replaced.

Special care shall be taken to avoid damage to pressure regulating and gas storage facilities and their associated control systems.

Where excavations are to be made within 10 m of the perimeter of a pressure reduction station, governor installation the team leader shall be advised of suitable precautions and, where necessary, be given the assistance of a person competent to exercise control of the plant.

The Engineer shall ensure that the team is made aware of the accurate position of inlet and outlet mains and by-passes, and of any impulse pipes or other associated plant. The Engineer may require the continuous presence of a Responsible Engineer who will ensure that adequate precautions are taken so as to safeguard gas supplies.

3.5.2 Safety In Excavations

Trenches and excavations can, in some situations, be regarded as confined spaces. Before entering any confined space a suitable and sufficient risk assessment must be carried out and advice must be sought as to whether a Permit to Work or written procedure is required, as appropriate.

An approved trench support system should be used in excavations at depths of 1.2m or above (measured from the bottom of the excavation). Where a trench support system is not used an alternative safe system of work must be determined e.g. sloping the sides of the trench by at least 45° from the vertical. The risk assessment must be recorded (written or electronic) with details of the specified controls as agreed with a supervisor or line manager.

A permit to work must be issued for all excavations where any type of trench support system is used. The permit will be valid for a period of seven days with a new permit being issued by a Responsible Engineer following completion of each weekly inspection.

The trench support system must be installed by trained and competent persons (i.e. operatives with sufficient training and experience of excavation work.

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Work in excavations less than 1.2m deep may also be dangerous, and it may be necessary to provide support. Risks are greater when bending or kneeling in excavations. If there is any doubt, seek advice from a Responsible Engineer or Safety Supervisor.

Extra care must be taken:

a) During wet or icy weather.

b) When opening ground in the vicinity of previous excavations.

c) Where there are variations in the nature of the soil (e.g. pockets of sand).

d) Where a crane or other mechanical plant is employed in close proximity to the excavation.

e) Where prolonged pumping in waterlogged ground has been carried out.

The ground conditions will determine the method of support e.g. in moderately stable ground the open poling board method may be employed, whilst in loose ground close-boarded timbering, sheet piling or a similar approved method would be required. Staging must be provided if the excavation is deeper than 2 m. Examples of trench supports are given in figures 5 - 8 inclusive.

3.5.2.1 Inspection Of Excavations

All excavations must be inspected each day, before work begins, by a trained (i.e. someone with sufficient training and experience of excavation work. An inspector must pay specific attention to:

a) The stability of the ground.

b) Changes in ground conditions.

c) Adequacy of supports.

d) Undue loading to trench edges.

e) Clear working space.

f) Adequate means of entry and exit.

g) Provision of suitable protection to prevent persons falling into the excavation.

h) Maintenance of all signing, lighting and guarding of the works.

The excavation must also be inspected after any event likely to have affected its strength or stability e.g. heavy rain, freezing or thawing, and after accidental fall of rock, earth or any other material. A written report must be prepared for all inspections carried out in these circumstances.

For excavations where a trench support system is in place a Responsible Engineer must undertake the weekly inspection. The following information must be recorded on the permit to work at the start of the job and in all subsequent permits after each weekly inspection:

a) Name and address of person on whose behalf the inspection was carried out.

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b) Location of the workplace.

c) Description of the workplace.

d) Date and time of inspection.

e) Details of any factor identified that could pose a health and safety risk.

f) Details of any action taken.

g) Details of further action considered necessary.

h) Name and position of person making the report.

All deficiencies noted in the inspection must be made good; any remedial or other works necessary must be carried out as soon as possible and, in any intervening period, no other works must be carried out in the excavation. Where this is the case, or where any other change to the excavation or the site are apparent the new permit to work must be detail all remedial action, additional risks and requirements for additional action.

3.5.2.2 Vehicles And Plant

Vehicles and plant shall not be brought alongside excavations unless it is essential and the team leader has approved the operation. No person shall be under a suspended load.

Special care is necessary when vehicles, plant or equipment, etc., are brought into the vicinity of overhead power lines. The Responsible Engineer should be consulted regarding precautions to be taken to prevent accidents involving overhead power lines. Reference should be made to the HSE Guidance Note GS6.

Vibrating and impact machinery shall be kept well clear of trench sides.

3.5.2.3 Live Gas Working

When live gas working is being carried out and tunnelling or undercutting is unavoidable, consideration should be given to preventing the possibility of gas pockets being formed.

3.5.2.4 Entry And Exit

Adequate means of entry and exit shall be provided for all excavations. Ladders or other assistance shall be provided where entry or exit would otherwise be difficult. Lifelines shall be provided and placed ready for use where any excavation is deeper than 2 m, and shall be worn when trench conditions warrant such action.

Special precautions are necessary in the case of deep excavations or those having restricted entry or exit. Consideration shall be given to the possibility of asphyxiation of personnel working in such conditions.

3.5.2.5 High Visibility Clothing

For their own safety it is important that all personnel working on or near a highway be readily visible to all road users. To achieve this, high visibility garments shall be worn.

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High visibility garments must comply with BS 6629, Appendix G. Class A standard jackets/coats shall be used on 'high speed' road conditions, with Class B waistcoats/tabards as a minimum requirement for all other situations.

3.5.2.6 Overhead Lines

Personnel working in the vicinity of overhead lines and underground services must undertake the works in accordance with HSE Guidance Notes GS6 and/or HS(G)47 as appropriate.

Where cables are embedded in concrete, a route should be selected for the new pipe, either by means of tunnelling or diversion, which does not disturb the cable or concrete.

If a new route is not possible, and it is necessary to break out or disturb the concrete, the electricity supplier (or cable owner) should be consulted first. No further work shall be carried out until the electricity supplier (or cable owner) agrees an alternative safe method of work or isolates the cable.

3.5.2.7 Waterlogged Ground

Where waterlogged ground conditions are encountered and water removing equipment is required, it is usually satisfactory to pump from sumps within the excavation (see Figure 9).

Where in-trench pumps are used for prolonged periods, particularly in ground of a sandy or silty nature, it may be necessary to install suitable filters behind sump linings to prevent loss of ground which could affect stability. Similar filters may be necessary along the trench sides in extreme conditions. Trench sumps shall not be excavated to such a depth that they present a hazard.

Alternative water removing methods shall be considered in any of the following circumstances:

a) Where it is proposed to excavate through running sand or water-bearing peat.

b) Where pumping from trench sumps is inadequate to keep trenches free from water.

c) Where deep excavations have to be made in waterlogged ground.

d) Where excavations are to be present for a considerable period of time in waterlogged ground.

Alternative measures include sumps external to the excavation, well points, electro-osmosis and consolidation by freezing or by chemical process.

Where it is anticipated that such measures will be needed, the advice of a suitability qualified engineer experienced in such works shall be sought.

3.5.2.8 Corrosive Ground

Where excavations are to be made in corrosive ground (i.e. ground with a resistivity of less than 2000 O cm) in order to lay steel pipe or other ferrous materials, or where any pipe is to be laid through chemically polluted soil, provision shall be made for bringing to site a supply of suitable non-corrosive material for the pipe bed and surrounding backfill.

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3.5.2.9 Made-Up Ground

Trenching in conditions in which hard spots may be expected should be avoided as far as possible. Care should be taken to eliminate hard spots which would place unacceptable bending stresses on pipes. Where there is reason to believe that hard spots exist, probing to a depth of 300 mm below the pipe bed should be carried out to identify a suitable route.

Where serious problems are foreseen, the advice of a civil engineer should be sought as to the most appropriate remedial action.

3.5.2.10 Excavation Near To Walls

When excavating trenches parallel to a wall, the stability of the wall, and hence the ability to work safely in its vicinity, shall be ensured.

Excavation work should not proceed if the wall is leaning, cracked or showing any signs of instability.

The stability of the wall should be checked whenever:

e) the edge of a service trench is within 0.5 m of the wall;

f) the edge of a mains trench is within 1 in of the wall, or

g) the main is larger than 200 mm nominal diameter, or

h) the main or service is to be laid at a depth greater than normal.

Stability check

1) With reference to Figure 10, measure S and calculate H.

If S is greater than H the trench may be excavated. Otherwise:

- either move the trench so that S is greater than H, or

- trial hole as detailed below.

2) With reference to Figure 11, dig a trial hole to determine depth of foundations or base of wall, taking care to avoid undercutting any foundation or base.

Measure W and calculate X.

If W is greater than X, the trench may be excavated. Otherwise:

- either reduce the depth of the trench, or

- provide suitable supports appropriate to the type of structure, soil characteristics and depth of trench.

3.5.2.11 Excavation Near To Tree Roots

Every effort should be made to minimize damage to tree roots during excavations.

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3.5.2.12 Trial Holes

Where necessary, trial holes shall be opened in advance of trench excavations to prove the proposed route. Trial holes should be excavated to a depth of 250 mm below the proposed trench bed to ensure that utility plant proximity distances are maintained. These excavations shall be adequately signed and barriered to ensure the safety of the public and employees.

3.5.2.13 Gradients and Levels

The Engineer or Engineer's representative should consider whether there is a requirement to lay the main to a fall and the need to provide water or liquid removal facilities. This consideration should be based on the risk or possibility of water or liquids entering the system, possibly from interconnected systems.

3.5.2.14 Checking For Depth Of Cover

Once the line and approximate fall of the proposed main has been determined on the surface, excavation of a sufficient (determined by the material dimensions) length of trench in advance of pipelaying should be carried out to ensure that the required depth of cover can be maintained.

For crossings at railways, canals, rivers, etc..., the requirements of the Authority concerned shall be followed.

3.5.2.15 Trench Delineation

Trench edges at the surface should, where possible, be cut and/or delineated by approved saw cutting methods and equipment.

3.5.2.16 Depth Of Trench

The trench shall be cut to give a solid, even bed to the correct depth.

Where mains are laid under verges, the depth of cover shall be measured from the kerb level or surface level, whichever is the lower, having due regard to the likelihood of regrading.

If the correct depth is exceeded, the bottom of the trench shall be backfilled to the correct level with selected and suitable material.

Where obstructions are encountered it may be necessary to lay a main at depths of cover greater than those stated below.

Where mains are to be laid across rock, made-up or irregular ground, the trench should be excavated to 75 mm below the required depth and backfilled with a suitable non-corrosive material to form the pipe bed.

3.5.2.17 Depth Of Cover

The normal minimum depth of cover for mains in roads shall be 750 mm and, in footpaths and verges, 600 mm. For mains laid in agricultural or cross country locations the depth shall be not less than 1.1 m.

It may be necessary to select a greater depth of cover after taking into account the following:

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a) Traffic loading.

b) The design of the trench.

c) The pipe material, dimensions and laying technique.

d) Corrosion control.

e) The reduction in the strength of the pipe caused by connections.

f) Known obstructions.

Where practicable, mains laid in close proximity to road junctions should be at a depth of not less than 750 mm to overcome the future likelihood of having to lower mains affected by road junction improvements.

Where the normal depth of cover in roads of 750 mm cannot be met, the depth of cover may be reduced to 650 mm cover for all mains, at the discretion of the Engineer. If a further reduction is deemed necessary, expert advice shall be sought.

For mains in footpaths and verges the minimum depth of cover (600 mm) may be reduced at the Engineer's discretion. However, additional protection using concrete slabs or steel plates should be installed.

The maximum depth of cover shall be:

a) Ductile iron pipe - 2.4m

b) Electric resistance welded (ERW) steel pipe - 4.3m

c) PE pipe (SDR11 and 17, up to 500 mm diameter) - 6.0m

3.5.2.18 Width of Trench

Trench widths shall be kept to a minimum and should not be greater than the nominal size of the main plus 30 mm. This recommendation is based on the requirement to ensure that the minimum trench width should equal the pipe outside diameter plus four times the maximum finefill particle size.

Maximum trench widths shall typically be nominal size of main plus 250 mm.

An allowance should also be made for any necessary trench shuttering. For trenches deeper than 1.2 m, the trench width may be increased.

Trench widths should also allow for safe access and for the use of necessary tools and equipment in the trench.

3.5.2.19 Underground Plant

When mechanical excavators (or machine powered surface breakers) are to be used, it is essential that the integrity of all underground plant is maintained through location and exposure by hand digging in advance of the machine.

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For mains operating at pressures in excess of 2 bar, mechanical excavation shall not be permitted within 3 m and the use of hand held power tools shall not be permitted within 500 mm, of the previously exposed position, unless approved by the Responsible Engineer.

For mains operating below 2 bar, mechanical excavation and hand held power tools shall not be permitted within 500 mm, unless approved by the Responsible Engineer.

When mechanical excavators are to be used in the vicinity of gas pipelines operating above 7 bar or in the vicinity of Third Party plant, the owner shall be consulted for the proximity distance to be applied.

To ensure the safer use of any mechanical excavator, consideration should be given to the use of a banksman.

Should any damage be caused to underground plant, it shall be reported to the Engineer or Engineer's representative as soon as possible.

3.5.2.20 Excavated Material

Excavated material shall normally be placed along the side of the trench.

Care shall be taken to prevent the weight of excavated material contributing to excess loading and collapse of the trench side.

To provide adequate working space and to avoid the danger of debris falling into the trench, sufficient space (preferably 600 mm to 1.2 m, but not less than 300 mm) shall be left between the trench and excavated material.

If the material is to be placed in a gutter, suitable channels or covered drainage pipes shall be left for surface water drainage. Where conditions permit, consideration should be given to placing the excavated soil so as to form an additional barrier against traffic. In all cases, excavated material shall be placed so as to cause least nuisance and inconvenience to traffic.

Where the excavated material is to be re-used, the surface materials shall be kept separate from the sub-soil, so that suitable layers may be replaced in the proper order during reinstatement. This is particularly important when pipelaying in agricultural land.

If the excavated material is to be re-used, it should be protected against adverse wet weather conditions or excessive drying out and consideration should be given to covering the excavated material in order to maintain the moisture content.

3.5.2.21 Preparation of the Bed

The bottom of the trench shall be prepared to provide a bed for the pipe. The bed should be levelled and suitably compacted so as to provide a firm support under the pipe and should be free of hardspots or sharp stones which are potentially damaging to PE pipe or the protective coating on other pipe materials.

Where the trench excavation crosses poor ground conditions, i.e. rock or irregular consistency, then the trench should be excavated to 75 mm below the required depth and replaced.

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3.5.2.22 Considerations for Excavations Close to Gas Mains

The Responsible Engineer shall determine the line of the main or service, paying due regard to the locations of existing gas plant and other Utilities' plant and shall indicate this on the line of proposed excavation works.

After the location of adjacent plant has been established by hand excavation, consideration may be given by the Responsible Engineer to the use of mechanical excavators. A minimum of 500 mm should be maintained between the excavator and plant wherever possible, this distance may be reduced at the discretion of the Responsible Engineer.

When giving advice regarding the use of mechanical excavation equipment, consideration should be given to the hazards which may be caused if the plant becomes damaged.

Where major excavation works are being carried out adjacent to pipelines, full specification for the works covering the method of construction, type of support system, timing of support, backfill materials and their methods of placement should be obtained from the initiating party. If considered necessary, arrangements should be made to continually or regularly monitor the site works to ensure that the agreed specification is adhered to.

The following factors should be recognised as those likely to give rise to damage:

a) The nature of the soil, which can be such that it is difficult to excavate without causing substantial movement.

b) Ground water and methods of lowering the ground water table which, if carried out carelessly, increase the risk.

NOTE - Information on factors a) and b) can be obtained from borehole records and/or the site investigation works from the initiating party.

c) Depth and width of excavation and its relationship to the affected main.

d) Temporary supports to the excavation. Inadequate design or careless workmanship increases the risk, as does the failure to remove supports in stages during backfill. The vertical sides of excavations greater than 1.2 m deep should be supported. Trenches less than 1.2 m deep in mobile soils should also be supported.

e) Backfill material and its consolidation, particularly the failure to compact in stages.

f) The time during which the side of the excavation is not fully supported. This can occur during excavation and during backfill, if the supports are not installed and removed in stages.

g) Loads imposed on the sides of the excavation by plant and stored spoil/backfill materials.

h) Increased impact forces from traffic due to irregularities in the restored surface.

i) Lack of uniformity in standards of reinstatement causing local differences in ground movement.

j) Continuing very cold weather.

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k) Previous ground movement leaving the main in an already stressed state.

3.5.2.23 Temporary Bridging of Excavations

It may be necessary to bridge excavations temporarily (e.g. to provide access to premises, or to make the full carriageway available when work in roads subject to considerable traffic is closed down at night, at weekends or during peak traffic periods).

NOTE - When bridging footways for pedestrian access, materials other than those normally used for road plates may be used at the Responsible Engineer's discretion, i.e. suitable purpose-built wooden/composite structures.

When road plates are used the following precautions shall apply:

a) The trench sides shall be stable or suitably supported.

b) No persons shall work under a roadplate (unless traffic is halted).

c) The plate should be of sufficient length to be firmly supported for at least 600 mm on each side of the trench and of a width sufficient to provide a distance of at least 250 mm from the wheels of vehicles to the edge of the plate.

d) The thickness of the plate should be sufficient to support the range of traffic encountered (If further advice is deemed necessary, expert advice should be sought).

e) Ramps should be formed of a suitable material where the roadplate is proud of the road surface.

f) When the site is not attended, or when subject to frequent use by heavy vehicles, consideration should be given to securing the roadplate(s) by pinning or sinking into the roadway.

g) Appropriate ramp warning signs shall be displayed.

All road plates on unmanned sites should be submitted to visual inspection on a regular basis.

3.5.2.24 Excavation for Services

Excavation for services shall be carried out employing the general principles laid down for mains. Wherever possible, services shall be laid in a straight line between the main and the service entry position.

Services larger than 63 mm nominal diameter should be laid as mains.

The normal depth of cover in private property shall be 375 mm with, wherever possible, an even gradient towards the main. Where it is necessary to lay at less than 375 mm cover, the approval of the Responsible Engineer should be sought as protective measures may be necessary.

The requirements for public roadways shall be applied where pipes in private property are subjected to surface loading comparable with normal roadways (e.g. factories, hospitals).

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The normal minimum depth of cover in public roadways shall be 450 mm. However, the depth of cover shall be increased to ensure that there is 75 mm of fine fill between the bottom of the road foundation and the top of the service pipe, or other precautionary measures should be taken (e.g. sleeving).

Services in proximity to road junctions should be laid at 450 mm minimum depth or at a depth sufficient to provide 75 mm of fine fill between the top of the service and the bottom of the adjacent road structure.

The trench width shall be kept to a minimum and should not exceed 300 mm.

The trench shall be excavated to the correct depth and the service pipe fully supported throughout its length on firm ground, free from stones or projecting rock. Wherever possible, the trench bed should have a continuous downward gradient towards the main.

3.5.3 Back Filling And Reinstatement

Prior to placing fine fill reinstatement materials around the pipe, all coating and wrapping shall be completed, where applicable. Care shall be taken not to damage any coating or wrapping during the reinstatement procedure.

If necessary (mandatory in the case of PE pipe) the subsoil shall be clean, moist and free from sharp stones greater than 18 mm in size, to prevent damage. Certain soils can be riddled to remove sharp stones and produce a fine backfill material. If this is not possible it will be necessary to import suitable material. Cementitious materials shall not be used as finefill material around the pipe. The fine material should be packed firmly around the pipe or fittings to give a minimum compacted thickness of 75 mm.

When placing fine fill around pipelines and mains, particularly those greater than 250 mm nominal size, or where the side gap between the wall of the excavation and the main is greater than 75 mm, special care should be taken to ensure firm compaction of the fine fill especially around the lower half of the pipe. This provides good side support, prevents ovality in the main, and gives adequate support to the reinstatement structure (see Figure 12).

When undertaking insertion work using PE pipes of wall thickness less than SDR 17, care should be taken when backfilling at unsupported tie-in or launch receive pits. Fine backfill should be used that is well compacted around the pipe to provide adequate support. Consideration may be given to the use of a structured backfill material such as foam concrete in this instance.

3.5.3.1 Backfill, Sub-Base and Roadbase

The required thickness of the backfill, sub-base and roadbase layers (as shown in Figure 12) will depend on the type of carriageway or footway, etc., in which the reinstatement is carried out.

Where reinstatement is carried out to a permanent standard, the following guidelines shall apply:

a) Excavated materials may be suitable for re-use at backfill level or a suitable granular or cementitious material may be imported.

b) Sub-base may be imported granular or cementitious materials or re-used excavated pavement materials, if suitable.

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c) Roadbase materials will always be imported. They may be unbound granular materials, cementitious materials or bitumen/asphalt bound materials.

When foamed concrete is used for reinstatement purposes, adequate safety measures shall be employed to ensure that members of the public and employees are prevented from becoming trapped in an uncured layer. These safety measures may include some form of heavy duty mesh or plastic sheeting fixed over any open excavation containing foamed concrete.

All unbound materials at backfill, sub-base or roadbase levels shall be placed in layers within the trench and firmly compacted using approved mechanical compaction equipment.

3.5.3.2 Re-Use Of Excavated Material

Excavated material may be suitable for re-use as backfill material provided that the material is moist, does not contain any particles larger than 75 mm and is not uniformly graded i.e. is not single-sized.

The following materials shall not be used for backfill under any circumstances:

a) Organic materials including spoil from swamps, marshes or bogs.

b) Perishable materials including peat, logs and vegetable matter.

c) Corrosive or combustible materials including coal or coke dust, clinker and ashes.

d) Hazardous materials including chemically polluted spoil.

e) Frozen or partly frozen materials (may be satisfactory when wholly thawed).

f) Materials with high plasticity; typically certain clays or silts or mixtures thereof.

Excavated pavement materials may be suitable for re-use at sub-base level provided that the material is moist, well graded, does not contain any particles larger than 75 mm and is not contaminated with materials.

3.5.3.3 Reinstatement

Reinstatement shall be carried out to the standard prescribed Local Authority specification.

The surface of all interim reinstatements shall be laid in accordance with the Local Authority specification and shall be maintained in that condition during the period before that reinstatement is made permanent.

A 75 mm minimum cushioning layer of consolidated clay/soil/sand should be left between the top of the pipe, or of the service tee if applicable, and the base of the road foundation. This distance may be reduced at the Responsible Engineer's discretion provided compliance with the Local Authority specification can be achieved.

The reinstatement of the surface layers of a flexible carriageway or footway, etc., will require the use of bitumen/asphalt bound material. The type of material will be prescribed in the Local Authority specification.

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Reinstatement of rigid carriageways and footways, modular footways and other paved surfaces shall be carried out in accordance with the Local Authority specification.

All surplus materials shall be removed from the site on completion of works.

3.5.3.4 Reference Diagrams Used In This Section

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Figure 4 - Recommended arrangement of mains in a 2 m footway including cable TV duct

Figure 5 - Close board timbering for unstable ground

NOTE - If steel sheet piling is driven into the ground the lower walings and struts may be omitted.

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Figure 6 - Sheet steel piling for unstable ground

Figure 7 - Stable ground pinchers

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Figure 8 - Open timbering for moderately stable ground

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Figure 9 - Use of pump in waterlogged ground conditions

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Figure 10 - Stability check

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Figure 11 - Stability check

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Figure 12 - Layers in a trench reinstatement structure

Figure 13 – Road plate arrangement

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3.5.3.5 Weekly Inspection Pro-Forma

Construction (Health, Safety and Welfare) Regulations 1996

INSPECTION REPORT

Report of results of every inspection made in pursuance of regulation 29(1)

1) Name and address of person for whom inspection was carried out.

2) Site address.

3) Date and Time of inspection.

4) Location and description of workplace (including any plant, equipment or materials) inspected.

5) Matters which give rise to any health and safety risks.

6) Can work be carried out safely? Y/N.

7) If not, name of person informed.

8) Details of any other action taken as a result of matters identified in 5 above.

9) Details of any further action considered necessary.

10) Name and position of person making the report.

11) Date report handed over.

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SECTION 4 DETAILED DESIGN SPECIFICATION

SECTION 4

DETAILED DESIGN SPECIFICATION

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4 DETAILED DESIGN SPECIFICATION

This Section provides relevant information for the detailed design of gas distribution systems including main and service laying.

Pipelines are defined as bulk feeder systems operating at pressures greater than 4 bar and below 16 bar.

Mains are defined as pipes supply more than two consumers operating at pressures up to and including 4 bar.

Services are defined as pipes supplying up to 2 consumers. Service pipes are described as pipes between the distribution main and the outlet of the first emergency control valve downstream from the distribution main.

This document covers construction design, construction planning, construction, connection, testing, commissioning and decommissioning of pipes used for the distribution of natural gas.

The end of the distribution system is defined as the outlet of the emergency control valve. The emergency control valve is used by the gas consumer to close of the gas supply to the installation pipe-work in the event of an emergency.

Before undertaking the design or construction of gas services the minimum ventilation requirements of any appliances to be installed within a building must be considered.

4.1 General Information

4.1.1 Competence And Training

Technical competence is established through training, assessment, knowledge and experience for a particular role. A job title is not in itself a measure of competence.

Records of training of operatives must be maintained by the Authority to include:

• The competency level of the individual.

• Date Operative commenced work on gas systems.

• Authority registration number.

• Gas Network Safety Passport qualification (GNSP) which sets out the basic gas safety needs for persons employed on gas related activities.

The Authority will establish a competency framework for all persons employed on gas systems.

An example of a competency framework based on UK systems is detailed as follows:

4.1.1.1 Basic Requirements:

A fundamental requirement is to demonstrate that the personnel employed to design and construct the gas assets are competent to do so. Therefore sufficient current, valid, credible and authenticated

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documentary evidence shall be provided to satisfy the authority that the individuals designing, installing and administering the process are competent. This may be a combination of qualifications, training, experience, aptitude and fitness for the job.

Design Engineers.

Persons engaged on the design of gas infrastructure should be able to provide evidence of both competence and knowledge and understanding of the design phase. This may be achieved by an appropriate combination of education, training and practical experience relating to the design activity undertaken. Formal qualifications shall include Chartered or Incorporated Engineer through a professional body such as The Institution of Gas Engineers and Managers.

Construction Engineers

A Gas Networks Operations qualifications structure should be in place to ensure persons employed on the construction of the gas network or competent to carry out the activities they have been delegated to undertake.

4.1.2 Gas Safety

4.1.2.1 Reports of Gas Escapes

If at any time a person becomes aware of or suspects there is a gas escape or other emergency any person employed by the Authority or its contractors must record:

• Address / location of the gas emergency

• Name, address and telephone number of the person reporting the gas escape

• Where is the smell most noticeable?

• When the smell was first noticed?

• Is the gas turned off at the meter?

• If YES, can you smell gas?

• Is there a smell of gas outside?

• Are the neighbours affected?

• Are there any special circumstances / access details?

Advise the gas consumer to:

• Turn off the gas at the meter, unless the meter is located in a cellar or basement – in which case, advise them not to enter the cellar / basement.

• Extinguish all naked flames – do not smoke or strike matches.

• Turn off all gas appliances and do not use until they are checked by the engineer.

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• Do not operate any electrical appliances or turn any switches on/off.

• Open doors and windows to ventilate the property.

• Inform the consumer that immediate access will be required.

• If there is a smell in the cellar or basement, you must advise the consumer/s to evacuate the building.

Pass details of the report to the Emergency Authority for action.

4.1.2.2 Personal Protective Equipment

The minimum requirement for PPE equipment for all personnel engaged on distribution work include reflective jackets, safety clothing and foot-wear and other task specific equipment must be deployed and used at all times.

Operatives involved in gas operations must wear gloves and flame retardant overalls along with all other relevant protective clothing.

4.1.2.3 Working In A Gaseous Atmosphere

A live gas operation is one where gas is not physically controlled by a closed valve or physical disconnection. These operations can range from routine minor live gas operations, such as changing a meter control valve to failure of a main due to third party interference. It is possible to further sub-divide live gas operations into controlled and uncontrolled.

Controlled Releases of gas

Examples of controlled releases of gas are listed as follows

• Venting during gas purging operations etc…

• Connection of new/replacement mains and services.

• Commissioning and decommissioning.

• Flow-stopping.

• Under pressure drilling.

For the above tasks the element of the live gas operation is controlled by a technique or procedure, which eliminates the release of gas wherever practical or to such an extent that the release is so small and controlled that it does not constitute a risk. Where gas is released, it will be vented to a position away from the working or public area.

Uncontrolled release of gas

Examples of uncontrolled releases of gas are listed as follows:

• Cutting off a steel service pipe.

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• Plugging steel long radius bends or long screw service connections to mains.

The amount of gas present during each of these tasks will vary as will the exposure time/duration of individual working on each task. The concentration levels of gas will be dependant on a number of factors such as pressure, diameter of the pipe/service connection to main, what natural ventilation is available, etc…

However, there can still remain an uncontrolled release of gas and control measures must to be adopted which reduces the risk of exposure to the absolute minimum.

4.1.2.4 Risks Of Working With Natural Gas

The risks associated with working with natural gas are the occurrence of fire/explosion or oxygen deficiency, which can cause asphyxiation at high concentrations or cause narcotic effects, headaches, dizziness or nausea at lower concentrations.

The explosive range of natural gas is between 5%-15% gas in air.

Asphyxiation caused by natural gas deprives the brain of oxygen, causing confusion and irrational behaviour. The brain can last without oxygen, under good conditions, for about 4 minutes before definite damage appears. Once asphyxiation commences judgement is markedly affected and it becomes very difficult for individuals to make sensible decisions, such as getting out of a trench and putting on breathing apparatus. Sudden collapse can be followed within minutes by permanent brain damage and death.

If escaping gas ignites and is inhaled, serious and lasting damage can be caused to the lungs.

Whilst losing consciousness or being asphyxiated is an uncommon occurrence, operatives must be mindful of how quickly the environment they breathe can change due to a sudden or constant release of natural gas, especially in a confined space such as an excavation.

Breathing apparatus will offer respiratory protection and limited face protection when working in a gaseous atmosphere.

From the table it can be seen that the initial risk is that of being burnt from the ignition of a flammable gas/air mixture, with asphyxiation occurring once you have passed through the explosive range of natural gas. However, the dispersion of gas will always result in the explosive range being present somewhere in the gas cloud and therefore the risk of being engulfed within an ignited gas cloud is always present if you work in an atmosphere above the lower explosive limit (L.E.L.).

PPM LEL % GIA % OXYGEN % EFFECTS 500 1% 0.05 NORMAL

1000 2% 0.1 NORMAL 1500 3% 0.15 NORMAL 2000 4% 0.2 NORMAL 2500 5% 0.25 NORMAL 3000 6% 0.3 NORMAL 3500 7% 0.35 NORMAL 4000 8% 0.4 NORMAL 4500 9% 0.45 NORMAL

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5000 10% 0.5 20.9 NORMAL 10000 20% 1.0 20.8 NORMAL 15000 30% 1.5 20.7 NORMAL 20000 40% 2 20.6 NORMAL 25000 50% 2.5 20.5 NORMAL

60% 3.0 20.4 NORMAL 70% 3.5 20.3 NORMAL 80% 4.0 20.2 NORMAL 90% 4.5 20.1 NORMAL 100% 5.0 20.0 NORMAL LOWER LIMIT 6.0 19.7 NORMAL EXPLOSIVE 7.0 19.5 NORMAL EXPLOSIVE 8.0 19.3 NORMAL EXPLOSIVE 9.0 19.1 NORMAL EXPLOSIVE 10.0 18.9 NORMAL EXPLOSIVE 15.0 17.9 NORMAL UPPER LIMIT 20.0 16.8 SUFFERING 25.0 15.8 SUFFERING 30.0 14.7 SUFFERING 35.0 13.7 SUFFERING 40.0 12.6 DANGER 45.0 11.6 DANGER 50.0 10.6 DANGER 55.0 9.5 DANGER 60.0 8.4 DANGER 65.0 7.4 DANGER 70.0 6.3 DANGER 75.0 5.3 FATAL 80.0 4.2 FATAL 85.0 3.2 FATAL 90.0 2.1 FATAL 95.0 1.1 FATAL 100.0 0 FATAL

Assumed 21 % Oxygen and 79% other in air

Table 3 – Natural Gas v Oxygen – Relationship and Effects

4.1.2.5 Warning Notices

Suitable warning signs and barriers must be erected to prevent any unauthorised entry into areas where gas is, or will be discharged into the atmosphere. These notices must be displayed at appropriate distances to warn and instruct persons affected of the hazard and to ensure that there will be no smoking on any site where live gas working is to be/is being carried out.

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4.1.2.6 Ventilation of Working Area

Ventilation of the working area should be so that the flow of air in the working area is not restricted.

4.1.2.7 Elimination Of Sources Of Ignition

The following is a list of sources of ignition which should be eliminated from the working area:

• Electric cables

• Electric equipment

• Plant location instruments

• Tools

• Naked flames

• Stray electric currents

• Static electricity from

• Personnel

• Plastic pipes

• General – through rubbing contact

• Dusty gas

• Hot works

• Pyrophoric dust

Impact between steel tools such as hammers and chisels can cause sparks, which can ignite a gas-air mixture. Sparks can also be easily produced when the steel tools (e.g. forks, picks shovels and points) strike flints, rock, stones, concrete, etc. ‘Spark reducing’ tools may be used, but they do not provide a guaranteed spark –free operation.

With all tools the use of water will reduce the likelihood of sparks occurring.

4.1.2.8 Fire Protection

In the event of a fire, the protective clothing and equipment worn by an operative should give sufficient protection to allow time to escape from the incident without injury.

At least two 9 kg dry powder fire extinguishers must be placed in a convenient position next to the location of operations and within easy reach of the operatives on site for immediate use in an emergency.

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The fire extinguisher must be inspected for external damage, maintenance date and replaced if necessary.

The fire extinguishers must be turned upside down to prevent compaction of the powder as part of the initial checks.

Wherever a fire extinguisher has been primed, whether or not it has been used, arrangements must be made to replace it immediately.

4.1.2.9 Breathing Apparatus

Always check the atmosphere for gas before entering the excavation and continue to monitor during and on completion of work. Some non routine operations may require atmospheric checks to be recorded. Safe and unaided egress to a firm and clear position must be made available.

Breathing apparatus must be assembled and ready for use when any work is to be undertaken on live gas mains or services in excavations or other such confined spaces as follows:

• As specified within a permit to work.

• Drilling of gas mains.

• Connections.

• Flow stopping.

• For excavation more than 1.2m deep.

Breathing Apparatus must be worn under the following conditions to safeguard persons from asphyxiation or internal damage to lungs:

• If gas in the breathing zone is above 20% LEL and continues at that level following ventilation.

• When an oxygen reduced atmosphere is present.

4.1.2.10 Electrical Safety

A Voltstick is a device for detecting the presence of an AC voltage. When an AC voltage above 50v AC is detected a red indicator in the plastic tip illuminates. The Voltstick must be used in the following situations:

• Cutting off a service

• Disconnecting meters

• Any metallic mains connections work

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4.1.2.11 Working in the Highway

All operatives and staff working in the Highway must be suitably qualified and have sufficient signs, lights and barriers to enable work to be undertaken safely.

4.1.2.12 Identification of Exposed Plant

Underground plant must be identified before any work is undertaken. The following must be borne in mind:

• Any black service must be assumed to be a live electricity cable.

• Iron and steel water pipes and gas pipes will look very similar. If uncovered they must be treated as a gas pipe.

• Continuously welded steel pipe must be treated as containing a hazardous or high-pressure gas or liquid.

• Other pipelines e.g. Oil, gas pipelines, chemical etc. may be present.

4.2 Gas Pipelines And Mains Design

Construction design and planning includes: route selection; lay technique; materials specifications for mains. The specification for services is contained in Section 3.3 however certain information contained in this Section is also relevant to the laying of gas services.

The following pressure tiers have been designated:

• Low Pressure (LP) - Pressure not exceeding 75 mbar

• Medium Pressure (MP) - Pressure > 75 mbar but not exceeding 2 bar

• Intermediate Pressure (MP) - Pressure > 2 bar but not exceeding 7 bar

• High Pressure (HP) – Pressure > 7 bar

Pipelines operating at pressure above 4 bar may be located in cross country routes to ensure the minimum proximity distance to occupied buildings is achieved.

Mains operating at pressures below 4 bar should be located within a service strip or public roadway to ensure unrestricted access for maintenance and installation purposes. PE pipe shall be used unless the pipe encroaches within the defined proximity distance, special crossing, locations of shallow cover and other situations determined by a risk assessment. Where steel is to be used as part of a PE system, the designer shall identify this on the project drawing.

The design shall ensure that the minimum mains design pressure at the system extremity remains above 21mbar at the design flow rate and 23mbar at the normal flow rate.

New mains should have a minimum diameter of 63 mm. This is so that temporary bypasses can be installed in the event of flow stopping.

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4.2.1 Design Output

The designer shall provide as a minimum the following information:

• Relevant Pressure Tier – LP, MP, IP

• Characteristics of new pipe

• Effective Diameter

• Material

• Grade of material (PE80, PE100, Profuse)

• SDR

• Grade of steel

• Proposed length of main to be laid

• Fittings; –

• Special requirements – connections and terminations

• In line or branch

• UPT or cut-out

• Cap-end or flanged

• Valves - Full bore or Other

• Grade of welds

• Expected main laying technique to be used – Open cut or no dig technique

• Operating window - within year and within day

• Pressure test requirements – Pneumatic or Hydrostatic

• Fittings installed - Welded or electro-fused

• Type of purging – direct, indirect, slug

4.2.2 Project Appraisal

For system operating at pressures greater than 2 bar a design appraisal shall be carried out in accordance with the recommendations made in IGE/GL/5.

The stages of the appraisal process shall include:

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• Initiation stage – carried out by the initiating design engineer.

• Design Appraisal stage – Appraised by registered independent appraiser, competent in the appropriate work area.

• Approval and Installation stage – approved by the Authority.

• Records completion stage.

Application of the procedure will ensure that material specifications are fit for purpose, that Safe Operating Limits are specified, that a suitable pressure system schematic is provided and that the system maintenance regime is initiated.

4.2.3 Route Selection - Mains

For relatively simple main laying schemes, e.g. single diameter, 355 mm diameter and below of 100 m length, it is likely that a route will be chosen from area plans, with attention being taken to avoid, if possible, locations having, for example, electricity sub-stations, culverts or bridge crossings and heavily trafficked routes. Where these cannot be avoided, additional information may be needed at an early stage.

For more complex schemes, a more thorough route planning exercise shall take place. Site visits will take place and information will be gathered on other utilities plant and third party pipelines. Consultation with other parties, consumers and others affected by the scheme should be made. If necessary, these will be supplemented by trial holing to find a route and determine ground conditions. Dependent on the proposed main laying technique to be use trial holes must reflect the recommended minimum main laying depths, as shown in Table 4 or depths increased as appropriate.

Pipe Location Depth of Cover (mm) Mains in open ground 1100

Mains in traffic highways 750 Mains in pedestrian walkways 600

Services in traffic highways 450 Services in pedestrian walkways 450

Services within residential boundaries 375

Table 4 - Minimum cover on mains and services

Trial holes should be carried out at strategic locations e.g. proposed connection points, road crossings, and approaches to bridges and along the proposed route in the highway.

Factors, which may affect the future safety of the pipe, include:

• Inconvenience to public or highway users.

• Roads with special engineering difficulties.

• Physical obstructions: typical examples are waterways, railways and major roadways, structures from below ground foundations, bridges, tunnels and trees;

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• Public buildings, schools hospitals.

• The location and age of other underground plant: in particular, indications of settlement of trenches should be investigated.

• The route should be selected so as to avoid areas of possible future settlement which may be caused by deep trenches for sewers or other plant laid by open cut method which can give rise to unstable ground.

• Areas already congested with underground plant that will not allow sufficient clearance for flow stopping equipment or repair techniques.

• Location of overhead plant.

• Proximity distances between the potential line of the main and existing buildings or unventilated voids See Reference IGE/TD/3 – Section 5.8 -Table 5 for building proximity distances for PE and steel mains.

• Traffic loading from vehicles.

• The presence of traffic factors such as bus lanes, pedestrian crossings, school, hospital or fire station entrances and exits, for which special provision may have to be made in planning the work.

• Topology of site – Where hydrostatic testing is required water inlet and outlet discharge points must be identified.

• Known flood plains or areas which may become prone to flooding.

• The presence of above ground structures: these may become unstable as a result of construction work close by.

• Areas of known or suspected aggressive ground conditions.

• Landfill sites.

• Areas liable to subsidence or landslip.

• For long lengths of steel pipelines an adequate electrical supply for cathodic protection (CP); for short lengths anodes should be installed.

• Existences of protected wildlife.

• Where special reinstatement of the surface is needed.

• Presence of rock. A suitable fine fill material should be imported.

• If the subsoil is waterlogged, expensive de-watering equipment will be required for construction and subsequent alteration or repair will be difficult.

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• The existence of street furniture: typical examples are traffic control kiosks, telephone kiosks, lamp columns, and traffic signs.

• Areas of sand, gravel or flood risk, (where anti-dewatering devices may be deployed).

• Trees and tree roots: damage to trees or their roots may have an environmental impact.

• Contaminated ground.

• For steel systems the following should be avoided:

• Close proximity to existing CP systems, particularly ground bed locations.

• Installations near DC tracking systems with high voltage direct current.

• Long parallel runs to high voltage (HV) overhead electrical cables.

Where the recommended depths cannot be achieved on of the following shall be adopted:

• The route to be reselected; to ensure recommended depths are maintained.

• Change in material to steel pipe.

• Use of a steel/concrete carrier pipe.

• Additional protection over the pipe for shallow depths, e.g. use of concrete slabs, steel plates or reinforced marker tape.

The result of the risk assessment must be recorded within the project documentation and ‘as laid’ drawing marked up accordingly indicating the protective measures taken, e.g. depth.

4.2.4 Special Crossings

A detailed design proposal must be prepared and consultation with relevant authorities shall take place where the following is encountered. These situations are also applicable to gas services;

• Rail Crossings

• Water Crossings

• Major Highway Crossings

• Environmentally Sensitive Areas

Buried crossings are preferred to overhead and bridge crossings. Wherever possible the use of ducts or sleeving should be avoided for such crossings. Auger boring, thrust boring and horizontal directional drilling can be employed.

If it is necessary to design and construct an overhead crossing then the following factors must be taken into account:

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• Safety of personnel and members of the public during construction.

• Design of the access platforms to enable construction of the crossing.

• Method of jointing to be employed.

• The crossing must be designed to withstand the stresses and environmental conditions imposed on the pipe, carrier system and supports.

• It must be environmentally acceptable.

• It must be high enough to avoid damage from both vehicular traffic and river traffic etc…

• There must be barriers to prevent unauthorised access to the crossing.

• Provision of isolation valves.

• Anchorage requirements.

• The effectiveness of cathodic protection either side of the crossing must be safeguarded.

• Weight of the pipeline.

• Temperature effect - expansion and contraction on the pipe.

• Protection from lightning strikes.

• The entire structure must be accessible for maintenance.

• Exposed PE pipe must not be installed above ground.

• The provision of marker posts.

• Possible means of crossing bridges include:

• Burial in the road deck which relies on sufficient depth of road construction.

• Insertion through an existing buried pipe.

• Insertion through an existing above ground pipe, thermal expansion and contraction must be allowed for.

• Laying in a dedicated service duct.

Where laying a pipeline, main or service under a ditch, a depth of cover (below the true bed of the ditch) of not less than 1.1 metres must be maintained. This will minimise the risk of interference damage when cleaning of the ditch is carried out. In addition concrete slabs or concrete filled bags should be placed 300mm above the crown of the pipe. Marker posts must then be installed on both sides of the ditch to indicate its presence.

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4.2.5 Pipe And Fittings For Mains And (Services)

Pipe shall be constructed from one of the following materials:

• PE 80 polyethylene


• Steel line pipe

The choice of material is dependent upon the desired Maximum Operating Pressure (MOP), environmental factors, laying technique and safety factors, such as proximity to buildings and susceptibility to damage, or above ground for special crossings such as bridges.

PE pipe and fittings shall be manufactured to an appropriate standard such as UK standard:

GIS/PL 2-1 Technical specification for polyethylene pipes and fittings for natural gas and suitable manufactured gas Part 1 - General & PE compounds for use in PE pipes and fittings.

GIS/PL2 Part 2 Technical specification for polyethylene pipes and fittings for natural gas and suitable manufactured gas Part 2 - Pipes for use at pressures up to 5.5 bar

GIS/PL2 Part 4 Technical specification for polyethylene pipes and fittings for natural gas and suitable manufactured gas. Part 4 - Fusion fittings with integral heating element(s)

GIS/PL2 Part 8 Technical specification for polyethylene pipes and fittings for natural gas and suitable manufactured gas Part 8 - Pipes for use at pressures up to 7 bar

GIS/PL3 Technical specification for Self Anchoring Mechanical Fittings for Polyethylene Pipe for Natural Gas and Suitable Manufactured Gas

GIS/F9: Part 1 Specification for Metric and Imperial Carbon and Stainless Steel Single Ferrule Compression Fittings for Tubes. Part 1 - General Requirements.

GIS/F9: Part 2 Specification for Metric and Imperial Carbon and Stainless Steel Compression Fittings for Tubes. Part 2 - Evaluation Procedure

4.2.5.1 PE 80 Pipe Uses

PE 80 is supplied in a number of standard dimension ratios and is commonly referred to as MDPE. The different SDRs and their pressure limitations can be found in IGE/TD/3 – Section 5.6 – Table 4. It should be noted that due to ongoing development in materials and SDR’s manufacturers recommendations must be consulted to ensure the latest specification is applied.

Service pipes are supplied in SDR 11, with the exception of 16mm diameter and 20mm diameter, which are supplied in SDR 7 and 9 respectively.

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There are two types of colour coded PE 100 pipe, orange and multi layer - (Profuse) yellow with brown stripes. Multi layer pipe was introduced in 2003 as an alternative pipe for diameters from 250mm upwards and excludes close fit pipe diameters. The different SDRs and their pressure limitations can be found in IGE/TD/3 – Section 5.6 – Table 4. It should be noted that due to ongoing development in materials and SDR’s manufacturers recommendations must be consulted to ensure the latest specification is applied.

4.2.5.3 Multi-Layer Pipe (Profuse)

This utilises PE100 SDR 21 pipe to provide a system, which maximises capacity via the thinner wall, provides greater flexibility than SDR 11 PE 100 and permits a higher maximum operating pressure than PE 80. The pipe diameters range from 250mm to 630mm operating at pressures up to 2 bar. The peel off polypropylene skin provides a surface which requires no scraping prior to jointing, thus saving considerable time and improving joint quality. The contrast between the pipe colour of the skin and the core pipe provides clear evidence of any surface damage, occurring during delivery, storage, handling and during the pipe laying process. The brown strip on the skin of the pipe identifies the pipe as a multi-layer.

4.2.5.4 Orange PE100 (HDPE)

This material has significant strength and crack resistance advantages over PE 80. It can be used for both direct burial and insertion applications. Manufactured in SDR 11, it is used for systems operating between 2 and 7bar, and is orange in colour.

Note: Further information on maximum operating pressures with respect to the ambient temperature range, refer to manufacturers’ recommendations.

4.2.5.5 Electrofusion Fittings For PE Mains And Services

Fusion fittings with integral heating elements are fused to polyethylene (PE) pipes using electrical energy supplied to a heating element integral with the fitting. The energy is supplied via a control box, which operates for a selected time depending upon the fitting type and size.

Fittings are classified as class B (suitable for use at operating pressures not exceeding 5.5 bar) or class C (suitable for use at operating pressures not exceeding 7 bar). It is essential that the pipe be supported to prevent it being moved during the heating, fusion and cooling phases. Long pipes should be supported to avoid misalignment due to sagging.

Pressure testing must not be carried out until the complete system has cooled down to ambient temperature. Each fitting is marked as follows:

• Size (i.e. outside diameter) and SDR

• Fusion time(s)

• Cooling time

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4.2.5.6 Steel Pipe

Steel pipe is available in a variety of wall thickness, and is used in systems where polyethylene is not suitable. These include:

• Building proximity

• Pressure range

• Exposed locations

• Special crossings

Steel pipe for use at below 7bar must comply with BS1387 and API 5L.

For information on grades of steel pipe and minimum wall thickness refer to IGE/TD/3 – Section 5.6 – Table 1 and Table 2.

Whenever steel service pipes are laid, they must be protected by suitable wrapping and the application of sacrificial anodes.

Steel pipe shall be manufactured to an appropriate standard such as UK standard:

GIS/L2 Technical specification for steel pipe 15mm to 450mm inclusive nominal size for service at pressures up to 7 bar (Supplementary and amending specification to BS 3601) + Amendment no.1 (September 1994)

4.2.5.7 Jointing Of Steel Pipe

For threaded joints, taper-to-taper, or taper (male) to parallel (female) threads may be used. Pipe threads must comply with BS 21. All such threaded joints must be assembled using an approved jointing material.

Threaded joints should not be used on main and service laying working where operating pressures exceed 2bar.

The welding of pipes in nominal sizes up to 50 mm must be carried out using fillet welding in conjunction with fittings to BS 3799. Pipes and fittings in nominal sizes above 50 mm must be butt welded, using full penetration welding.

4.2.6 Minimum Proximity Distances Identification And Protection

The permissible proximities to normally occupied buildings vary depending upon construction material and operating pressure.

See Reference IGE/TD/3 – Section 5.8 -Table 5 for building proximity distances for PE and steel mains.

To facilitate repair, maintenance or extensions to the mains system a minimum clearance of 250mm should be maintained between gas pipes, fittings and the known positions of other utilities’ plant.

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This distance is for plant running in parallel. For plant crossing the main this distance, may be reduced, as long as protection is provided in the form of concrete tiles, concrete sleeves or heavy-duty marker tape.

There are a number of protective measures available which may be used for PE/steel pipes. Some measures will only provide a warning that a pipe is present whilst others provide a protective barrier. Their advantages and disadvantages are summarised in Table 5 as follows

Warnings Protective Measures Advantages Disadvantages Warning marker tape Easy to install and can be used

in conjunction with other protections measures

Only used as a warning does not provide protection to the pipe

Marker posts Easy to install and used as above ground identification of a pipeline route


Detectable – tracer wire – marker tape

Provides identification for persons using detecting equipment


Barriers Protective Measures Advantages Disadvantages

Concrete/PE slabs or tiles above the pipeline

Provides protection and identification when used with warning tape

Use over short lengths

Concrete or steel sleeving Provides protection and identification when used with warning tape

Installation problems, CP requirement and provides track for any escaping gas

High tensile netting / mesh Provides protection and identification when used with warning tape, does not affect drainage

Use over short lengths, can be penetrated by excavators

Increased depth of cover Reduces frequency of interference damage

No warning of presence of pipe. Increases installation cost

Ducting – perforated (small diameter service application)

Used on new build construction works utilising pre installed service ducting

Offers limited protection

Table 5 – Pipeline Protection

Where concrete tiles or concrete sleeves are used marker tape should be placed above the tile/sleeve for future identification purposes and the ‘as-laid’ drawing marked accordingly.

If there is a need to protect other underground services, contact should be made direct to the appropriate utility company. Further guidance can be found in HSG 47 ‘Avoiding danger from underground services’ published by the UK Health and Safety Executive.

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When open cut techniques are employed, suitable marker tape with an appropriately marked legend must be laid above mains of all sizes and all services, to minimise the risk of interference damage. This should be placed at a convenient depth between the backfill and sub-base layers in road or footpath constructions, or 250 mm above the crown of the main in open ground.

When laying PE 100, SDR 11 pipe for use at pressures up to 7bar, the use of marker tape incorporating a single insulated tracing wire should be installed. This will enable the position of the main to be determined using a cable locator during pre-excavation surveys, and provide a visual indication of the presence of a buried main during excavation.

For additional protection, in the public highway, a yellow 3.5 mm thick PE strip, of width not less than the diameter of the PE100, SDR 11 pipe, should be installed 75 mm above the crown of the main.

Marker posts should be installed to provide access to tracer wires and to indicate branches, changes in direction of the main and location of valves. In the case of cross-country pipelines the installation of aerial markers should be installed. Reference to IGE/TD/1 Edition 4 should be made for information on marker posts.

Reference should also be made to IGE/TD/3 Section 5.9 Figure 3 for additional information on protection measures.

4.2.7 Valves

Valves should be installed on new connections to the existing network or to maintain or safeguard supplies during maintenance or for management of a supply emergency.

For MOPs exceeding 2.0bar, valves must be of steel construction.

Plastic bodied valves may be installed on pipe diameters up to and including 180mm at a pressure up to and including 2bar. Plastic bodied valves must not be used as a construction valve.

Valves shall be manufactured to an appropriate standard such as UK standard:

GIS/V7 Part 2 Specification for Distribution Valves - Part 2 plastic bodied valves of sizes up to 180mm suitable for operation at pressures not exceeding 5.5 Bar

GIS/V7 Part 1 Technical specification for distribution valves Part 1 - Metal-bodied line valves for use at pressures up to 16 bar and construction valves for use at pressures up to 7 bar

Valves on services are installed for the purpose of emergency control valves, service isolation valves, tamper proof valves, additional emergency control valves and excess flow valves.

The following additional information is relevant to the installation of valves:

• For main > 180 mm/150 mm rider/purge diameter = 63mm (2” steel).

• For main > 180 mm/150 mm rider/purge diameter = 32mm (1” Steel).

• Pressure points diameter = 32mm (1” steel).

• Pressure points should be constructed from PE for pressures < 4 bar.

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• Valve body vent sealed with plugged valve. Not normally piped to surface.

• No levers or wheels are to be left on valves below ground.

• The top of the valve spindle extension or pressure / rider points should terminate 100mm below the underside of the surface box lid.

4.2.7.1 Strategic Valves

Strategic valves should be installed in pipelines having MOP exceeding 2bar.

The following situations are typical of strategic valves:

• Where there is more than one valve between off takes on any section of main, unless the main is two-way fed.

• On the outlet of off takes.

• Either side of major road crossings or rivers.

Typically maximum spacing of strategic valves in urban areas is 800 metres.

Typically maximum spacing of strategic valves in rural areas is 1500 metres.

For pipelines subject to hydrostatic pressure testing the valve must be full bore to allow the passage of a pigging device.

For off- take valves a valve must be installed on the valve supplying the off-take and valves must also be installed either side of the off-take. Pressure points must be installed either side of each valve.

Figure 14 - Off-take arrangement

Strategic valves must be of double block and bleed construction. The valve spindle must be extended to a surface box. Pressure points and rider/purge vent points must also be installed and extended to surface boxes.

Slide valves must not be used as strategic valves or as a method of retaining gas in a pipeline. In such cases the pipeline must be physically capped.

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4.2.7.2 Construction Valves

Construction valves are used solely for the purpose of aiding the process of connecting systems, i.e. under pressure tee connections. For low pressure mains, where the tee outlet does not exceed 300 mm (12 in.) diameter, a slide valve of the self-sealing type may be used. For low pressure mains above 300 mm (12 in.) tee outlet diameter and all medium and intermediate pressure tees a double block and bleed valve must be installed. Where a double block and bleed valve is to be used as a strategic valve, pressure and riser points must be installed, otherwise the valve must be buried and its control mechanism should not be accessible from the surface.

4.2.7.3 Valve Records

Strategic, construction and service valves must be identified as follows:

• Valve number - unique number to that Network.

• Marker Plate - marker plate must have the diameter, valve number, pressure and distance, which are attached to a marker post or wall.

• Valve covers/marker disc - the valve cover should be marked “gas”. Alternatively a marker disc should be fitted over the valve spindle.

A record card/sketch must be prepared for each valve on which the following information should be recorded:

• Unique valve number

• Dimensional sketch of the valve location

• GIS Map reference

• Address of the site

• Size and safe operating limit

• Make and type of valve

• Open or closed valve

• Date fitted

• Details of pressure and rider points fitted

• Number of turns and direction of rotation

• Function of valve

• Maintenance history

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4.2.8 Pipe Laying

Care must be taken to place pipes so as to cause the minimum possible interference with, or obstruction to, traffic, pedestrians or other plant/structures. Pipes must be wedged to prevent accidental movement and where necessary, barricades must be erected and warning signs and lamps positioned. Before pipes are positioned in the trench, pipe bores must be checked to ensure that they are free from obstructions and debris. Care must be taken during pipe laying and jointing that pipe bores are kept clean.

When pipe laying is in progress, pipe ends must be temporarily capped, e.g., using an expanding stopper, dust cap or sealed to prevent ingress of foreign bodies during construction work.

The use of rollers should be used to prevent pipe coating damage. On steel pipelines the use of pull through should be used to clear the pipe. Pipes must be lowered into the trench using approved equipment and during lowering operations no person must be allowed to stand underneath the suspended pipe.

PE gas pipe must not be used as a duct for another gas pipe or any other utility.

PE pipes should not be installed in locations where the temperature of the ground surrounding the pipe exceeds 200C. Jointing tents must be used when the air temperature is below – 50C or above 400C.

All pipes and fittings must be inspected for cuts, deep scratches or other damage before use. PE pipe can sustain damage on site of up to 10% (including circumferential gouge and longitudinal scores etc) of the pipe wall thickness and still perform satisfactorily over its design life. A depth gauge must be used to determine the depth of any gauge. Damaged pipe exceeding these criteria must not be used.

IP PE mains must be internally de-beaded to facilitate pigging following hydrostatic testing.

4.2.9 Material Delivery / Storage / Handling

For most main laying projects, it will be necessary to provide a suitable area for storage. Care must be taken that the chosen location is:

• Easily accessible for delivery and transportation of materials.

• Level, to enable safe stacking.

• Sited to cause the minimum interference with or obstruction to traffic and pedestrians.

• Suitably barriered off and capable of being secured.

• Protected from Direct Sunlight.

Stacks of pipes must be no more than 2 metres high for steel, no more than eight layers high for PE up to (and including) 125mm diameter and for larger diameters pipe must not be stored greater than four layers high. Pipe coils 63mm and above must not be stacked more than 2 coils high.

When offloading pipes from the delivery vehicle, mechanical handling of pipes should only take place, using slings for PE pipes or slings/chains for steel pipe but only slings for PE, which have been inspected and are covered by appropriate certification, confirming suitability for use. Chains must not

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be used on coated steel pipe. Under no circumstances must pipes or fittings be dropped from vehicles.

When offloading, no one must stand beneath the load.

Upon delivery, pipes and fittings must be checked for any obvious damage and if necessary marked, to facilitate return to the supplier.

Reference should be made to IGE/TD/1 supplement 1, Handling, transport and storage of steel pipe, bends and fittings and IGE/TD/3 supplement 1, Handling, transport and storage of PE pipe and fittings.

Coil trailers should be used to dispense coiled pipe. Correct sequences for cutting of coils’ security bands must be adopted. Only sufficient bands should be cut to provide the required length of pipe. For coils of 125mm diameter or greater provision must be made for at least three operatives on site.

Particular care should be taken, before lifting coils into and out of trailers to avoid overhead cables.

4.2.10 Techniques For Main Laying

There are three solutions to Main laying these are as follows:

• Displacement

• Open cut

• Open trench

4.2.10.1 Displacement

Types of displacement techniques are described as follows:

4.2.10.2 Impact Moling

Impact Moling, using either unguided or directionally guided machines can be employed to lay pipes up to and including 180mm PE. Unguided moles have limited use and require significant prior investigation to avoid damage to adjacent buried plant.

4.2.10.3 Horizontal Directional Drilling (Hdd)

Horizontal directional drilling is a steerable system for the installation of pipes, in which usually a fluid (Bentonite) filled pilot bore is drilled and enlarged by back reaming to the size required and through which is drawn back the new pipe

HDD shall not be used in the following situations:

• Inside or within 10m of the boundaries of Above Ground Installations and Pressure Reduction Sites.

• Within 10m of the known location of a pipeline.

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• Within 10m of oil cooled electric cables and electric stations/sub-stations where their underground plant exits.

• Within streets that contain basements.

• Multi-occupied buildings/premises where cellars, basements, personnel or service corridors/tunnels protrude from the building line, e.g. hospitals, schools, office blocks, cinemas, theatres, shopping malls/buildings, high rise flats, Ministry establishments, etc…

• Within the boundary of airports and docks.

• Within areas of special scientific/environmental interest or containing known wildlife habitats.

• Contaminated sites where PE material may degrade once laid.

• Landfill sites.

• Known areas of underground mines, voids, cavities, natural caverns which are close to the surface.

A detailed safety plan must be produced at the project planning stage, covering the following areas:

• Information on all buried services/structures along the proposed route including details from their owners of their requirements for the avoidance of damage and precautions to be observed.

• Details of any special engineering difficulties, e.g. road/rail/water crossings, industrial plants.

• Information from the relevant authority/owner must be sought.

• Identification of ground conditions.

• Suitability of launch and receive sites.

• Developments which may have altered ground levels.

4.2.10.4 Mole Ploughing

Mole ploughing is carried out on cross country pipe laying and it enables long lengths of pipe to be buried very effectively in agricultural land without the need for top soil stripping.

Disadvantages of the technique are the possible destruction of land drains and substantial ground heave, which will require rectification.

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4.2.10.5 Open Cut

By mechanical excavator

For general work in the highway, excavators provide a reasonable level of productivity. Mini excavators are available to carry out work in confined spaces, where a full size machine cannot be used.

Hand Excavation

Hand excavation must be used for trial holing in areas of known buried plant and for excavation in close proximity to plant.

Mechanical trencher (chain trencher / rock wheel) etc.

Mechanical trenchers can provide extremely high levels of productivity, but the route must be very carefully chosen to avoid damage to underground plant.

Open Trench

Where the excavation work is undertaken by a third party and the trench left open to allow the pipe to be laid.

4.2.11 Selecting The Route Of The Gas Main

Prior to any excavation taking place, the route of the main should be walked and a visual record (either photographic or video evidence) made of any damage to roads or structures and any other potential on site complications e.g. mature trees, crossings, etc. Where existing damage is identified the extent of the damage should be notified to the owners in advance of work.

Information on utility plant, third party pipelines and other buried structures must be collated and located on site as necessary. Precautions must be taken to avoid damage to overhead plant by vehicles or mechanical excavators.

When planning to excavate parallel or in close proximity to adjacent boundary walls, a stability check must be made.

4.2.12 Cathodic Protection

Cathodic protection must be applied to buried steel pipelines to provide protection from corrosion. In order that protection can be satisfactorily achieved the pipe must have a very high quality coating and the pipeline system must be electrically isolated from above ground installations and pipelines of other materials. Either impressed current or sacrificial anode cathodic protection should be used.

4.2.12.1 Impressed Current Cathodic Protection Systems

For impressed current, an electric current is applied, which makes the pipe more negative than the surrounding ground. Impressed current is, more suitable for protecting long lengths of cross-country pipelines, where danger of electrical interaction with other buried metallic structures is low.

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4.2.12.2 Sacrificial Anode Cathodic Protection Systems

Sacrificial anodes are generally used in populated areas, where they provide corrosion resistance over short distances, and are unlikely to interact with other plant.

In order to provide the required corrosion protection, the pipe to soil potential, with respect to a copper/copper sulphate reference electrode, should be –0.85 volts (-0.95 volts in the presence of sulphate reducing bacteria in the soil).

On completion of the pipeline, the cathodic protection system should be validated to ensure that the pipeline is adequately protected over its total length.

4.2.13 Coating And Wrapping

To ensure satisfactory protection of steel pipes and fittings high performance coatings should be applied in addition to cathodic protection.

Tapes must be applied to all bare sections of pipe to give a 55% overlap in all cases. Particular attention must be given to fittings, such as valves, flanged joints, service tees and other items where tapes need to be moulding to the profile of the fitting during application.

Where metallic fittings are connected to polyethylene pipes, they should be wrapped to prevent corrosion. Bolts on fittings, such as under pressure tees may be anodic to the rest of the fitting or to the parent main and, hence, these must also be wrapped to prevent corrosion.

Site wrappings must not affect the integrity of the PE system e.g. the petrochemical properties of ‘denso’ wrapping has a long term degrading effect on PE pipe.

Wrapping of joints and fittings must not be undertaken until after a successful pressure test(s).

4.2.14 Jointing

When carrying out pipe jointing if the air temperature is below -5°C or above 40°C precautions must be taken to bring the air temperature within limits.

Pipes made from dissimilar polymers should only be joined by electrofusion joints. Where electrofusion couplings are used to connect sections of thin walled pipe (e.g. SDR 26), steel inserts must be fitted to prevent pipe wall collapse during the fusion operation.

Pipes must be supported using proprietary clamps which allow the pipe to move back and forward within the butt fusion machine and remain still when using electrofusion, during the heating, fusion and cooling phases.

Electrofusion is the recommended option of jointing mains up to and including 90mm diameter. Above this diameter butt-fusion should be used.

PE mains must not have any unrestrained mechanical joints during pressure testing.

4.2.14.1 Electrofusion Jointing

Restraining clamps must be used when using electrofusion fittings and for larger diameter mains the use of re rounding clamps must be used to remove the ovality from the pipe.

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Should the fusion process be interrupted the joint must be discarded or cut out and a new fitting used. Re-heating of the fitting must not be carried out.

The following checks should be made:

• That the fusion indicators have risen and that no melted material or wire has exuded from the ends of the fitting

• That the pipe has not moved during fusion cycle

• That the area around the joint is clean and there is evidence of scraping

When using multi layer pipe the outer skin must be removed creating a uniform circumferential peel, to allow the electrofusion joint to take place.

4.2.14.2 Butt Fusion Jointing

Fully automatic butt fusion machines must be used. All machines should have the facility for printing records or electronically downloading the data from the jointing process. The use of aluminium cleaners or scouring powders is permitted for cleaning excessive deposits on the heater plate. For the first joint of the day or when changing the pipe diameter, the fusion cycle must be aborted to ensure that the heater plate is clean. The cycle must then be restarted.

All external weld beads must be removed with an approved tool and inspected. (IGE/TD/3 Section 6.8.3.4. - 7 and Appendix 7)

Removed beads must be kept for inspection and must be numbered with its corresponding joint number.

A bead gauge must be used to confirm the bead width is within the specified size range.

Where the bead inspection identifies a faulty joint, or where indications show that an electrofusion joint has failed, the joint must be cut out and the jointing operation repeated. The reason for the joint failure must be investigated to determine the mode of failure. Common failures include:

• Equipment Failure

• Fitting Failure

• Human Failure

It may be necessary to cut out adjacent joints and test them.

4.2.14.3 Mechanical and Flanged Joints for Use on PE Mains

Mechanical joints are generally used for the transition between a PE system and metallic systems. Flanged joints i.e. ‘pecat’ adaptors can be used at valve interfaces as well as connections on to steel.

4.2.14.4 Flanged Joints

Pipework must be fabricated so that mating flanges are aligned and abutted squarely. The type of flanges to be used must be to PN16 specification for operating pressures up to 7 bar. For operating

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pressures above 7 bar refer to specification for flanges detailed in the appropriate design code IGE/TD/1, Steel Pipelines for High Pressure Gas Transmission or; BS 8010 Codes of practice for steel pipelines or; ASME 31.8 Gas Transmission and Distribution Piping systems. In the case of PE flanges the sealing faces must be protected against damage prior to assembly.

Bolts should be tightened in the correct sequence and a sufficient number of circuits undertaken to ensure that the specified bolt torques are. It must be noted on flanged joints using elastomeric gaskets some relaxation of the gasket will be experienced.

The jointing sequence is detailed as follows:

• Use only 3mm thick, one piece, 80 hardness Nitrile rubber gaskets to EN681-1 and to suit flange rating.

• Hold the gasket in correct position on clean flange face until flanges meet.

• Use only undamaged rust free bolts, nuts and washers.

• Lubricate bolt threads and all mating surfaces of nuts, washers and flanges using an automotive grade of oil or grease.

• Tighten the bolts in sequence until full torque is achieved.

• Check and, if necessary, re-tighten bolts immediately before pressure testing.

Nominal

size

(mm)

No of Bolts

Bolt Diameter

(mm)

Bolt length

(mm)

Sealing torque

(Nm)

Hole Diameter

(mm)

Hole PCD

(mm)

80 8 M16 65 70 19 160

100 8 M16 65 75 19 180

150 8 M20 70 115 23 240

200 12 M20 70 110 23 295

250 12 M24 85 155 28 355

300 12 M24 85 165 28 410

350 16 M24 85 160 28 470

400 16 M27 100 200 31 525

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450 20 M27 100 195 31 585

500 20 M30 110 240 34 650

600 20 M33 120 305 37 770

700 24 M33 130 350 37 840

800 24 M36 140 475 41 1050

900 28 M36 140 475 41 1050

1000 28 M39 160 605 44 1170

1200 32 M45 180 810 50 1390

1400 36 M45 180 915 50 1590

1600 40 M52 200 1180 57 1820

1800 44 M52 220 57 2020

Table 6 – Flange Dimensions

Bolts should be Mild Steel Grade 4.6 (BS 4190).

Gasket Materials should be:

Grade G – Nitrile (NBR) BS2494: 1990 Type G (silver colour)

Grade C – Epichlorhydrin (white with “ECO” superimposed)

Grade O - Fluoroelastomer (blue colour) – Spiral Wound Gaskets

Gaskets should be stored in a cool dark place in black polyethylene sacks which exclude light, especially ultraviolet. Store away from sunlight, electrical discharges and sparking electric motors.

Storage temperature should be below 20 deg. C. Always store gaskets in an unstressed condition – never hang on hooks, nails, handrails, etc. even for a short time.

Gaskets should be lubricated prior to fitting. Failure to apply lubricant can cause gasket creep under load. This may cause bolt torques to drop, thus necessitating re-tightening.

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4.2.14.5 Screwed Joints

Screwed joints must only be used on steel pipe up to and including 50mm dia and a maximum pressure of 2 bar. Other joints must be either welded or flanged.

4.2.14.6 Insulation Joints

The transition from steel to other metallic mains and to non-cathodically protected steel mains is undertaken using an insulating joint. Insulation joints shall be manufactured to an appropriate standard such as UK standard:

GIS/E17 Part 2 Technical specification for insulation joints Part 2 - Joints operating at pressures not greater than 7 bar

4.2.14.7 Welded Saddles Tees To Steel Mains

For welded saddles to steel mains a welding procedures must be prepared.

Following removal of the coating and cleaning of the steel main, ultrasonic and magnetic particle examination should be carried out to confirm satisfactory wall thickness and freedom from flaws in the area where the fitting is to be located.

If the wall thickness is found to be less than 4mm, connections must be made using mechanical fittings where practicable and be limited to maximum operating pressures of less than 2 bar. Any service tees or pressure points must be fitted using a saddle or split collar. These fittings must be checked to ensure that they are approved for the maximum operating pressure of the main.

On mains greater than 2 bar where the wall thickness is found to be less than 4mm an alternative position for the connection must be found.

4.2.14.8 Fused Saddles to Polyethylene Mains

A branch saddle is electrofused to the main and tested prior to drilling. In the event of a test failure, the saddle must be abandoned, cut off as near to the main as possible and a new fitting electrofused more than 250mm away. The drilling must be carried out through a valve attached to the branch saddle.

4.2.15 Steel Pipe Jointing

The design for the welding of steel pipe must address the following criteria:

• Welding specification

• Welding procedure

• Welder procedural qualification requirements, register and approvals

• Mechanical destructive test requirements

• NDT - Radiography inspection requirement

• NDT - Ultrasonic inspection and MPI inspection requirement

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Welding shall be carried out to an appropriate standard such as BS 2971 Arc welding of carbon steel pipework.

Full penetration butt-welding is used for jointing of steel pipes. Saddles and fittings must be fillet welded. When pipes are to be jointed by welding, the welding operation must, whenever possible, be carried out above ground, barriers and screens erected to protect members of the public and those not involved in the welding operation from arc flashes. The maximum length of pipes, which can be welded in this manner, will depend on road traffic conditions and the nature and frequency Where ‘in ground’ welds are required, additional localised excavation will be required at the joint positions. Sufficient ground must be excavated to permit the welder to gain access to the full joint circumference.

Welding of joints must not be carried out when prevailing weather conditions are such that the quality of the weld could be impaired, unless adequate weather protection is used. Pipes and fittings should not be welded when they are at a temperature below 00C, pre-heating of pipe and fittings will be required in these conditions.

The minimum level of inspection should be as follows:

Standard girth weld – 100% visual examination and 10% radiography.

Fillet welds – 100% visual examination- 100% radiography – 100% magnetic particle examination.

Fittings shall be manufactured to an appropriate standard such as UK standard:

GIS/F7 Technical specification for steel welding pipe fittings 15mm to 450mm inclusive nominal size for operating pressures not greater than 7 bar.

4.2.16 Flow Stopping

The following precautions need to be observed. These are listed below.

• The requirements of Safe Control of Operations must be followed.

• IGE/GL5 approval is required for connections to mains operating at pressures above 2 bar.

• A correctly sized bypass determined by Network Analysis must be installed around every section of pipe to be cut or connected unless its omission can be specifically justified.

• A low resistance electrical continuity bond must be fitted across all sections of ferrous pipe to be cut or connected. Vent pipes must be included in cross bonding or earthed. When non-metallic gas pipes are encountered cloths soaked in water must be wrapped around the position of the remaining pipe ends and draped down to the ground to form a low resistance electrical path to earth.

• Where impressed current cathodic systems are installed the system should be isolated.

• Pressure gauges and/or recorders must be installed either side of the operation.

Flow stopping equipment shall only be used when other means of mains isolation e.g. valve closure, cannot be achieved.

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For PE 80 mains over 500 mm diameter, no squeeze off is currently available; flow stopping must be achieved by closing a line valve.

For PE 100 SDR 11 mains squeeze-off must only be used for pipe sizes up to and including 315 mm. For pipe sizes 250 mm and 315 mm, a stainless steel wrap around clamp must be subsequently fitted the squeeze-off position to remove hoop stress from the PE100 pipe wall.

On completion of a squeeze-off operation, the pipe must be re-rounded and a tape marked ‘Squeeze-off applied’ affixed to the pipe. The same squeeze-off position must not be used again and at least six pipe diameters distance must be allowed between squeeze-off positions on the same pipe.

The minimum distance between squeeze off bars or beams is calculated as a percentage of twice the minimum wall thickness.

For 250mm pipe the limit is 80% of twice the minimum wall thickness.

For 315mm – 400mm pipe the limit is 90% of twice the minimum wall thickness.

Refer to manufacturers instructions for detailed information on the positioning and application of squeeze offs.

4.2.17 Cut Out On Steel Mains

A welding procedure should be prepared for any work is undertaken on steel mains.

Pipe may be cut using rotating wheel cutters, mechanical rotary cutters, flame cutters or hacksaws. Flame cutters must not be used on mains, which have contained gas, or in a gaseous or potentially gaseous atmosphere.

When welding to a stopped main is unavoidable, a constant bleed of inert gas must be maintained and the distance between the stopper and the ignition source maximised as far as is practically possible.

4.2.18 Cut Out On PE Mains

Having excavated around the main at the cut out position, the main should be thoroughly cleaned and examined for damage.

The cut out should be made, after earthing the pipe either side of the cut, using a damp cloth around the main and touching the ground.

4.2.19 Anchorage

Anchorage is required to prevent movement of pipe work and/or fittings that could cause a joint to be disturbed or a fitting to be displaced. Anchorage is not normally required for all welded steel or fusion jointed polyethylene (PE) pipelines. However, when these systems are connected to new or existing pipe work by flexible compression joints, temporary thrust restraints and permanent anchor blocks must be used.

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4.2.20 Pressure Reduction Stations

Between the boundary of each pressure tier a pressure reduction station shall be installed. For the design of pressure reduction stations reference shall be made to IGE/ TD/13 Pressure regulating installations for transmission and distribution systems. Pressure regulating modules shall be purchased to an appropriate standard such as UK standard:

GIS/E34 Specification For The Procurement Of Pressure Regulating Modules With Inlet Pressures Above 75 Mbar But Not Exceeding 7 Bar For Regulators With Design Flow Rates Greater Than 6 m3/hr

4.2.21 Metering


IGE/GM/6 - Standard diaphragm and RD meter installations. > 6 m3h-1 MOP ≤ 75 mbar

IGE/GM/5 Ed 2 - Electronic gas meter volume conversion systems

IGE/GM/7 Ed 2 - Electrical connections and hazardous area classification MOP ≤ 100 bar

IGE/GM/8 Pt 1 - Meter installations I&C – Design. MOP ≤ 38 bar

IGE/GM/8 Pt 2 - Meter installations. I&C – Location and housing,

4.2.22 Pressure Testing

All new mains must be pressure tested. Any part of the supply system, which is diverted, altered or renewed, must be pressure tested. Joints, which cannot be included in such a pressure test, must be tested at operating pressure using an approved leak detection fluid.

A pneumatic pressure test must be applied to mains operating at less than 2 bar.

For mains operating at more than 2 bar a preliminary pneumatic pressure test at 350 mbar must be applied prior to a hydrostatic test being carried out - followed by a pneumatic pressure test.

For PE mains that have been subjected to a hydrostatic pressure test, a relaxation period of 3 hours at atmospheric pressure must be allowed for creep to relax before commencing pressurisation for a pneumatic pressure test.

Where PE pipe is subjected to a pressure test, the pressure will drop initially owing to creep (see Appendix 4 – Creep Effects – Table 12 IGE/TD/3) of the pipe wall. This is not normally an issue during less than 75 mbar operating pressure mains testing, or for mains with small test volumes where the stabilisation period allows the majority of the creep to occur. However, for pneumatic pressure tests on greater than 75 mbar operating pressure mains, the effects of creep must be taken into account prior to commencing the actual pressure test.

Steel mains must not have any unrestrained mechanical joints during pressure testing.

IGE/TD/3 – Section 7 provides guidance on selection of the appropriate test specification for pneumatic and hydrostatic tests.

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For IP mains it is advisable to raise the pressure in stages (i.e. 1bar, 4bar 7bar) to allow any tie-in joints to be progressively tested, using leak detection fluid.

For LP and MP systems, the effect of plant and equipment failure must be taken into consideration when pneumatic pressure testing. If the consequences of failure during the pressure test are high, a hydrostatic test should be performed using the appropriate test pressure. The hydrostatic test should be conducted prior to a pneumatic test.

The same, calibrated, test instrument must be used for the initial, intermediate (if any) and final pressure readings. The test instrument used on pressure tests between 2 and 10.5 bar must have an absolute accuracy of 3 mbar (for an instrument with a range 0-10.5 bar the accuracy required will be 0.0285%) or greater and have a resolution of 0.1mbar.

Mobile telephones, radios, etc. should not be operated in the vicinity of digital test instruments, as the pressure indications may become erratic.

For all pneumatic pressure tests of longer than 2 hours duration, gauge pressure readings must be corrected for barometric pressure. Barometric pressure readings should preferably be taken at the test site or alternatively at a point within 15 km of the site. Test instruments providing absolute pressure readings should be used where available to remove the need to apply correction. Absolute pressure measurements include atmospheric pressure.

For IP mains (i.e. operating above 2 bar), a hydrostatic pressure test must be applied followed by a pneumatic pressure test.

Where PE pipe is subjected to a pressure test, the pressure drops initially owing to creep of the pipe wall. For pneumatic pressure tests on MP & IP mains, the effects of creep should be considered. An extra pressure drop allowance for creep during the test period may be added to the 3 mbar allowable drop.

Where the pipework system under test contains flanged or (threaded joints only below 2 bar), pressure testing must be undertaken prior to wrapping the joints.

The full number of appropriate studs or bolts provided for blanking flanges must always be used. Any studs or bolts with worn or damaged threads must be replaced.

Pressure relief valves of adequate size, set at the appropriate setting (10% above maximum test pressure), sealed and marked with the set pressure and within the calibration date, must be installed in the test supply line to prevent the test pressure from being exceeded (testing of low-pressure services with a water gauge fulfils this purpose.). Pressure relief valves must be fitted during pressurisation or during any subsequent pressurization of the pipe work, but may be removed for the test period.

Interchangeable pressure test components (used in applications above 2 bar) such as blank flanges, pressure gauges, safety valves, temperature gauges and flexible connections should be the subject of an annual examination by the Competent Person. Pressure test components should be properly stored, and labelled and registered to assist correct selection and use for the purpose intended. Their issue must be recorded.

A Permit to Work must be raised for the pressure testing of all Intermediate Pressure mains with a diameter greater than 2” (63mm). A site-specific risk assessment must determine the requirement to

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issue a Permit to Work for the pressure testing of MP mains, taking cognisance of volume, location and any other circumstance.

Non Routine written procedures must be prepared for the testing of all Intermediate Pressure mains and services with a diameter greater 2” (63mm). A Routine Operation written procedure must be prepared for the testing of Intermediate Pressure services with a diameter of 2” (63mm) or less. A site specific risk assessment should determine the requirement to prepare a Non Routine Operation written procedure for the testing of MP mains and services with a diameter greater than 2” (63mm), taking cognisance of volume, location and any other circumstance. In circumstances where a Non Routine Operation is not used, a Routine Operation written procedure should be prepared.

Written procedures must include a method statement detailing as a minimum:

• The test pressure, the test duration and testing medium to be used

• Where the testing medium supply line is to be attached to the plant to be tested

• The position and specification of safety valves, pressure gauges and other test components

• The status of isolation valves and valve movement sequence

• Details of the designated test area and minimum safe distances

4.2.22.1 Safety Precautions

All employees engaged on any work associated with testing should be are aware of the possible consequences of pipe or test fitting failure under pressure test conditions. The site specific risk assessment must be completed to include the test procedure, and consideration must be given to how and where pressure tests ends and test equipment are located, so as to minimise hazards resulting from a potential pipe or test fitting failure. Warning of the hazards associated with the energy stored within a pipe under test and, in particular, the energy stored within a pipe containing both water and air, must be given to personnel.

There is a risk of injury from particles of dirt and high velocity jets at the time of pressure testing. Personal protection equipment (PPE), including eye protection must be worn by all persons required to work within the test area.

All new welded steel and fused PE systems must not incorporate flexible joints whilst pneumatic or hydrostatic pressure testing is being carried out. Such joints are permitted for connection purposes on LP or MP systems only

To reduce the risk of failure, flexible air inlet pipes and their connections should be visually examined prior to use to ensure they are fit for their intended purpose. They must be secured and anchored by a secondary restraining device (e.g. whip-check or similar) to prevent movement as a precaution in the event of failure.

The Site Engineer must ensure that all precautions are taken:

• Before pressurisation

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• During pressurisation

• During de-pressurisation and before dismantling of equipment

• After de-pressurisation and during dismantling of equipment

The impact of noise generated during pressurising and de-pressurising must be minimised by the controlled introduction and release of air.

For mains operating at MP or higher, notices warning that pressure testing is in progress must be prominently displayed where the main is exposed and accessible to the public and viewed from all access points.

Before pressurisation commences, a final visual check should be made that the test section is secure for pressurising. The introduction and release of air must be carried out whilst all personnel are outside the trench.

Whilst the pressure is being raised, no un-authorised person must enter the designated test area or interfere with the pipe work.

Throughout the duration of the test, particularly in the case of MP and IP mains, the system should be examined at intervals to ensure that all anchorages are secure and that no hazard exists. It may be appropriate, in some cases, to maintain a presence on site at all times to minimise the impact of failure. A site-specific risk assessment should determine whether or not this is necessary. This will depend on factors such as location, pressure and diameter.

Mains must not be subjected to any form of shock loading or work of any description whilst a pressure test is ongoing.

4.2.22.2 Pneumatic Pressure Testing

The pneumatic pressure test is a leakage test that demonstrates the soundness of a main, requiring the system under test to be pressurised with air. The application of this test, which simulates the system operating at its maximum operating pressure under gas conditions, will allow all detectable leakage to be identified.

The maximum permitted leakage rate is 0.0028m3/h of natural gas at the maximum operating pressure. This is irrespective of material, size, operating pressure or length. Any leakage in excess of this rate should be detectable, if occurring at one point.

Note: Physically isolated means; the main to be tested must not be connected to the existing systems. Closed valves must not be used as end caps. All valves must be tested in the open position. Valves fitted at the extremity must be securely blanked using a correctly designed blank flange. The insertion of a correctly designed spade at a flange acts as a physical isolation.

The main must be tested at the pressures and durations calculated in accordance with IGE/TD/3 – Section 7

Immediately upon satisfactory completion of any sectional tests, the whole of the main must be subjected to a pneumatic soundness test at maximum working pressure (in stages of 1bar, 4bar and 7bar for an IP system) held while the interconnecting joints between sections are proved with leak detection fluid. Any pipe-work or fittings used in connecting sections must be pre-tested to the

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appropriate pressure test specification. If pre-testing of all the fittings used in the connection is not possible, spades must be fitted between the last joint (s) and a pressure test to the appropriate pressure for ten minutes should be conducted, this will act as a strength test. On satisfactory passing the strength test all joints must be tested using leak detection fluid.

Following the satisfactory completion of the final tests, the main must be purged and the tie-in joints tested under maximum operating conditions with leak detection fluid.

Following the completion of final tests, where hydrostatic tests have bee undertaken drying operations must be carried out before commissioning.

Sections of tested main should be left at a reduced pressure (350 mbar maximum) until commissioning is undertaken. Details of the partial pressurisation should be indicated on the pressure test certificate. A recorder should be used to indicate the condition of the pipe during this period.

The pipe must be checked before commissioning to ensure that the positive pressure has been maintained. Before any further work is carried out on the pipe, the pressure must be reduced to atmospheric pressure.

Consideration should be given to insulating the pressure test instrument and hose to avoid the effect of localised temperature variation. When testing mains, the standpipes should be located at all extremities of the new main and incorporate a relief valve set to lift at a pressure 10% above the specified test pressure.

Test instruments must be fitted so that they can be read and operated without entering the trench or standing in line with the end of the main.

Closed valves must not be used as end caps. All valves must be tested in the open position. Where a valve is fitted at the extremities of the main under test, the valve must be securely blanked and anchored against movement.

The Project Engineer must be in attendance at the commencement of pressurisation and during the pressurisation period, to ensure that the necessary safety requirements are met, and the time of commencing pressurisation must be recorded on the test certificate.

Where creep allowances are to be applied to PE mains tests, it is important that the exact conditioning time is established by recording the time of commencing pressurisation and the time at which the first test reading is taken. Conditioning time includes the effects of the 2 h stabilisation period referred to above. Alternatively, the APT procedure (see Specialist Techniques Chapter) may be used to log and diagnose the entire test.

Air must be introduced under controlled conditions into the main until the appropriate test pressure is reached. Care must be taken not to over pressurise the pipework. A single or twin tool compressor (80 cfm to 100 cfm) will be adequate for pressurising the majority of pipe systems. Where larger capacity compressors are used, the stabilisation or conditioning time must still be adhered to.

No work must be carried out on a main under test other than any necessary leakage testing or operation of the valves on the test standpipe.

Before the start of the test period, the temperature of the air in the main should be allowed to stabilise before the test period is commenced.

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For metallic mains and low-pressure PE mains, this will normally occur within 2 hours, and will be indicated by a stable pressure reading.

For MP/IP PE mains, the effects of creep must be taken into account and the conditioning period allowed.

All exposed mechanical joints must be tested for leakage upon initial pressurisation with an approved leak detection fluid.

Following the period of the temperature stabilisation, the initial pressure reading must be taken. For PE mains at MP/IP (where the effect of creep is being considered) the first test reading must be taken at the end of the conditioning period.

A further pressure reading must be taken at the end of the test period. Where a long duration pressure test period (i.e. over 24 h) is to be undertaken, intermediate pressure readings must be taken so that the test may be assessed and aborted at an early stage if there is an indication that the test will ultimately fail.

When the test has been completed to the satisfaction of a competent person, the air pressure must be released through suitable vents. One vent point must be situated at each extremity of the system and depressurised in a controlled manner until the whole of the main is at atmospheric pressure. Appropriate PPE, including ear protection, must be worn.

The Project Engineer must confirm, by checking the gauges installed at all extremities, that the pressure within the whole of the main has been reduced to atmospheric. The Project Engineer must record this information on the test certificate before authorising further construction work to proceed.

Where a pressure loss greater than the total allowance has occurred, having accounted for any variation in barometric pressure and the effects of creep in a PE system, investigations must be carried out to find the source of leakage. All connections, plugs and external fittings must be re-examined for possible leakages by leak detection fluid. In the event of discovering leaks, they may be repaired with appropriate tools without excessive force but the pressure should be reduced in order to minimise hazards resulting from a potential pipe or fitting failure.

Where no obvious cause can be attributed to a pressure test failure and the test conditions have not altered the test may be undertaken, using the final or an intermediate test reading as the starting point for the new test period. In the case of pressure tests on MP/IP PE mains, the revised creep allowance should be established following calculation of the new conditioning time.

Where an MP/IP PE main is to be retested following de-pressurisation, it must remain at atmospheric pressure for a minimum of three hours prior to re-pressurisation, to allow creep from the original test to relax. Where a test has failed, further investigations using tracing techniques as detailed below should be carried out.

The tracing methods available are as follows:

Halogen detector (this methods method involves specialist mains equipment): A small quantity of sulphur hexafluoride (SF6) must be inserted into the main at the point and time of introduction of air for testing, and a check made to ensure permeation along the length of the main. When handling SF6 care must be taken to avoid contact with skin and inhalation of fumes. The pneumatic pressure in the main must then be raised to the appropriate test pressure and the atmosphere at the bar holes

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sampled with an approved halogen detector which gives an audible warning when SF6 is present at the bar holes.

The main may be divided into sections, each being tested separately, and the section failing the test must be further subdivided until the location of the leakage is determined.

4.2.22.3 Hydrostatic Pressure Testing

HPT is a specialist technique and must be referred to an appropriate expert.

4.2.23 Commissioning

For commissioning reference shall be made to IGE/SR/22 Purging of fuel Gases

To ensure the safe commissioning of gas mains, it is essential when purging that certain velocity rates are maintained. This will ensure that a sharp interface exists between gas and air / inert gas. If the velocity is too low, it is possible that there will be a layering of gases, with that having the lowest density, remaining at the top of the main rather than being swept out. This situation could result in an explosive mixture developing.

Direct purging is the preferred option for commissioning or de-commissioning mains. If the criteria for direct purging cannot be achieved (i.e. correct velocity), then indirect purging should be used. Wherever possible, complete displacement is preferred, using an inert gas. However large volume purges will often necessitate the use of air/inert gas slugs. Indirect and slug purging is classified as a specialist technique and specialist operatives will be required to carry it out.

Care must be taken to avoid the interruption of purging operations, which can result in gas and air becoming mixed, potentially resulting in explosive mixtures.

For all purging operations there are a number of general factors to be taken into account. These include:

• Purging operations must be carried out in accordance with an authorized written procedure as stipulated in the requirements of GPCOEWG/GAS/OP/03 – Safe Control of Operations.

• When preparing a written procedure, which involves a purging operation.

• Pipelines and mains that have been hydrostatically pressure tested must be thoroughly dried before commissioning.

• Riders should be constructed from metallic tube, approved flexible steel pipes/hoses or polyethylene (PE). An on-site risk assessment, which identifies the potential impact on the rider of mechanical damage, interference or fire hazard, should be used to determine rider construction.

• Commissioning of mains must not be undertaken by the removal of inflatable stoppers, or by the use of an ejector.

• A continuity bond must be maintained across separated metallic pipes.

• Plastic pipes to be cut or separated must be earthed to prevent static build up.

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• Fire extinguishers must be available and positioned for use.

• Dividing the length of the main by the proposed purge velocity should provide an assessment of the purge duration.

• Once a purge has started, it should continue without interruption until complete.

• When planning any commissioning operations, it is important to ensure that an adequate supply of natural gas is available to provide the required flow rate, without reducing the local network pressure below minimum requirements. Further advice can be sought from Network Analysis

• For all commissioning operations, a system of communication must be organised and tested for personnel operating the riders and vents

• For major purging operations, it may be necessary to inform the Gas Control Centre, the local authority environmental officers, the Civil Aviation Authority (CAA), the local Police, Fire Brigade, local residents and any other affected parties, as identified within the written procedure and on-site risk assessment, to discuss noise, smell and flammability.

• During a purging operation should the pressure in the source main fall below the specified minimum pressure stated in the NRO/RO the purging operation must stop immediately, the gas in the new main vented and the reason for the drop in pressure investigated.

4.2.23.1 Direct Purging

When direct purging, low-pressure PE mains not greater than 180 mm diameter the main may be isolated by a single faced valve or squeeze off. Checks must be undertaken to confirm that the isolation is sound.

Mains of greater pressure and diameter must be isolated from the parent main by a double block and bleed system. This system may be a valve with a double block and bleed facility or, alternatively, a double squeeze-off system with an intermediate vent.

The minimum rider and vent sizes required to prevent stratification, are shown in Table 7. For mains operating at pressures greater than 2bar, purge velocities should not exceed 20 m/s.

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Minimum rider and vent diameters Nominal pipe diameter

(mm) 21 mb 30 mb 75 mb 350 mb 2 bar

0-150 32 32 32 32 32

150-200 63 63 63 32 32

200-250 63 63 63 63 63

250-300 90 90 63 63 63

300-450 90 90 90 63 63

450-600 180 180 125 90 63

600-900 180 180 180 125 90

900-1200 250 250 250 180 90

Table 7 – Minimum rider sizes – direct purging

Purging riders must meet the following criteria:

• Maximum length of rider – 10m

• No more than six bends should be used in the rider

• Valves must be full bore

• Rider connections to the pipeline or main should be full bore. (It is recommended that saddles are used to connect the pipeline or main, not service tees).

Vent pipes should be fitted at the far end of the main to be purged and should be manned whilst venting.

Vent pipes for pipelines and mains must:

• Discharge vertically into the open air not less than 2.5 m above ground level.

• Be sited where possible not less than 5 m downwind of possible sources of ignition.

• Be sited where vented gas is unlikely to drift into buildings.

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• Be firmly supported.

• Be metallic.

• Include a full bore control valve and a sample test point.

• Not include a flame trap.

• Be adequately earthed if connected to a PE pipeline or main.

Where the minimum velocity given in the above table cannot be achieved, the mains must be commissioned using indirect purging methods.

When direct purging it is permissible to purge without riders in the following circumstances:

• Sections of LP and MP mains, up to and including 2”/63mm diameter, may be commissioned by the controlled release of a squeeze-off or by the controlled opening of a valve or service tee.

• With agreement of the Project Engineer, sections of pipelines and mains above 2”/63mm diameter may be commissioned, using direct purging only, by the controlled release of a squeeze-off, if the release of the squeeze-off can be controlled to a position corresponding to the required rider size for achieving the minimum purge velocity.

• At the discretion of the Project Engineer sections of mains above 2”/63mm diameter up to and including 10”/250 mm diameter, may be commissioned by the controlled opening of a valve, using direct purging only (A slide valve is not permissible). Care must be taken not to damage the seals of the valves.

Commissioning of branched systems can be carried out simultaneously or sequentially. When carrying out simultaneous purging, riders and vents must be sized to take account of the combined diameters, through which gas is flowing.

Short stubs, whose length is less than eight diameters, are not classed as branches and will automatically be purged by natural convection.

Any loops must be isolated by valves or stopping off equipment and then treated as branches.

For branched systems, when simultaneously purging, it is necessary to calculate mains diameters equivalent to the sum of the cross-sectional areas of all the pipes being purged, and to check effective sizes of riders and vents, to ensure that minimum velocities are maintained.

4.2.23.2 Indirect Purging (Complete Displacement)

Indirect purging, using an inert gas, is employed where the minimum velocity for direct purging cannot be met. It is a specialist activity, requiring operatives, specifically trained for the task.

A purging operation involving the use of nitrogen must be carried out as a non-routine procedure, in accordance with a Safe Control of Operations procedure.

When indirect purging, the pipeline or main to be commissioned must be physically isolated from the parent main. Alternatively, it may be isolated by an approved flow stop technique provided that the

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nitrogen injection pressure is limited to less than the pressure in the live main and the minimum velocity can be achieved.

At all times during indirect purging, a velocity of not less than 0.6 m/s must be maintained with riders and vents sized in accordance with Table 8 as follows:

Minimum rider and vent diameters Nominal pipe diameter

(mm) 21 mb 30 mb 75 mb 350 mb 2 bar

0-150 32 32 32 32 32

150-200 63 63 63 32 32

200-250 63 63 63 63 32

250-300 90 90 63 63 32

300-450 90 90 90 63 63

450-600 125 125 90 90 63

600-900 180 180 125 90 63

900-1200 180 180 180 125 125

Table 8 – Minimum rider sizes – indirect purging

The volume of inert gas and gas required to ensure complete displacement is shown in Table 9 as follows. The minimum volumes stated in the table include a safety factor of approximately 50% above the actual main volume.

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Pipe diameter (mm) Minimum quantity of inert gas per 100m length (m3)

100 1.3 180 3.0 200 5.0 250 8.0 315 12.0 400 20.0 450 25.0 600 45.0 750 70.0 900 100 1050 135 1200 175

Table 9 – Minimum quantities of inert gas

Inert gas for purging mains not greater than 315 mm diameter is normally supplied from one or more cylinders or a bank of nitrogen cylinders. The capacity of a typical 1.5 m long cylinder is usually 7.7 m3. The maximum flow rate from a cylinder or bank is typically 1 m3/min. The nitrogen facility must be able to deliver the minimum flow rate.

Example:

When purging a 300mm main, a flow rate of 2.6m3/min. is required, therefore three nitrogen cylinders, each with their own high capacity regulators, will be required, discharging simultaneously.

(All cylinders must be carefully checked to confirm that the contents are nitrogen. For nitrogen, the colour of the cylinder will be FRENCH GREY with a BLACK band at the top).

Where large quantities of inert gas are required for mains greater than 315 mm diameter, the use of an inert gas generator, which produces a mixture of carbon dioxide, water vapour and nitrogen should be used. Competent personnel must operate the generator. Alternatively, a tanker of liquid nitrogen and vaporizers can be used.

4.2.23.3 Indirect Purging (Slug Purging)

For mains having lengths greater than 250 metres, slug purging may be used as a substitute for complete displacement, for economic reasons. This is a specialist activity.

The slug volume of inert gas must be not less than 10% of the pipe volume.

Each branch must be isolated and purged individually simultaneous purging of branches by slug purging is not permitted.

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4.2.24 Pressurisation

After purging to gas the mains must be slowly pressurised so that the pressure in the supply main does not fall below the minimum allowable. The final connections that were not included in the test and any exposed sections must be checked as pressure increases, to ensure that there is no leakage.

For MP and IP mains this is done in incremental stages of pressure to identify leakages at an early stage.

4.2.25 De-Commissioning Pipelines And Mains

Prior to de-commissioning a medium or intermediate pressure system, every effort must be made to reduce gas venting, by passing gas in a controlled manner into a system operating at a lower pressure.

Before decommissioning low pressures mains for insertion or abandonment decay tests must be carried out.

Purges may be undertaken using a compressor to expel gas out of a vent, or an ejector utilised (for direct purging only) to draw the gas out of the main and draw air in through an open hole.

The main to be de-commissioned must be isolated from the parent main by physical isolation if a compressor is used to undertake the gas purge. Alternatively, an approved stopping off method may be used provided the purge pressure is limited to 1/3 of the pressure in the live main, and the minimum purge velocity can be achieved.

A double block and bleed valve will be required if an ejector is used to draw the gas out of the main. For low-pressure mains not greater than 180 mm diameter, isolation may be undertaken using a single faced valve or a single squeeze off, ensuring the isolation is sound.

4.2.25.1 Decay Tests

Prior to cutting off a main for abandonment or insertion, decay tests must be undertaken to ensure that:

• There are no consumers still connected to the section being abandoned.

• There is an adequate supply to the main beyond the section to be abandoned.

• There is no unknown back feed.

Tests must be undertaken at times when a significant quantity of gas could be expected to be consumed.

Essentially decay testing involves the isolation of the main in question, and the monitoring of pressures within that section. A significant pressure drop in the section to be abandoned could indicate the presence of gas consumers still connected or that gas supplies to the downstream system are insufficient. If pressures are found to be stable during the monitoring period, the isolated system should be vented and then monitored to identify any pressure increase. Such an increase indicates the presence of a back feed, which must be found and disconnected. In both cases further

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work must be carried out to determine the cause of the fall or rise. This may involve any of the following:

• Re-survey the site for unknown loads.

• Flame Ionisation survey to determine possible gas leakage.

• Section the pipeline.

• Insertion of a camera.

• Check existing plans.

• Pressure management of the system.

4.2.25.2 Decommissioning By Direct Purging

Direct purging of mains may be undertaken using either compressors or an ejector.

To prevent stratification vent sizes must be those given in the Table 7. In order to achieve the purge velocity, minimum air inlet holes and vent diameters together with the minimum size of compressor must be as shown. Multiple holes may be drilled to achieve the same inlet hole cross-sectional area, e.g. 2 x 2 in. diameter holes = 1 x 3 in. diameter hole.

A compressor may be used to purge mains up to 10 in. diameter. Above this, an ejector must be used; the 150 mm ejector will purge pipelines or mains not greater than 600 mm diameter. The 250 mm ejector is required for pipelines greater than 600 mm diameter.

Direct purging of branched systems may be effected simultaneously or sequentially, sequential purging is preferred. If branches are purged simultaneously, the rider and vents must be sized for a pipe diameter equivalent to the sum of the cross-sectional areas of all the pipes being de-commissioned.

When an ejector is used, the vent holes must all be the size of the vent hole in the largest diameter pipe. The ejector must be fitted to the end of the largest pipe and the branches purged in descending order of size.

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Pipe size (mm)

Min purge velocity

m/s

Typical purge velocity

m/s

Minimum air inlet hole in

pipe

(mm)

0-150 0.6 1.5 32

150-200 0.7 1.4 63

200-250 0.8 1.2 63

250-315 0.9 1.1 63

315-400 1.0 1.5 75

400-450 1.0 2.0 100

450-500 1.1 2.0 125

500-600 1.2 2.0 150

600-750 1.5 1.6 150

750 - 900 1.5 2.0 200

900-1050 1.7 1.8 200

1050-1200 1.7 1.8 300

Table 10 - Purge velocities for decommissioning by direct purging

A single tool compressors deliver 1.9m3/min to 2.8m3/min (70ft3/min to 100ft3/min) Two tool compressors deliver 3.9m3/min (140ft3/min).

4.2.25.3 Decommissioning By Indirect Purging

Where minimum purge velocities cannot be met, indirect purging should be carried out, Riders, vents and inert gas facilities must be sized to achieve a minimum velocity of 0.6 metres per second.

Pipelines or mains with branches may be indirectly decommissioned by complete displacement either simultaneously, or sequentially, starting with the largest diameter branch. If branches are purged simultaneously, the rider and vents must be sized for a pipe diameter equivalent to the sum of the cross-sectional areas of all the pipes being de-commissioned.

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4.2.25.4 Slug Purging

If a slug purge is used (for mains lengths in excess of 250 metres), a minimum slug volume of inert gas of not less than 10% of pipe volume must be used.

Each branch must be isolated and purged individually; simultaneous purging of branches by slug purging is not permitted.

4.2.26 Records

The following attributes must always be recorded:

• Position

• Depth

• Diameter

• Material

• Pressure

• Lay method

• Pipe Object number

• Crossing Pipes/Connections

• Location, diameter and material of sleeves

All as laid mains shall be recorded on a drawing of 1:500 scale.

Adequate information should be provided to allow the location of the position of the service connection to the parent main. This point should be located using at least two dimensions.

In addition the depth of the connection must be indicated, together with a confirmation of the size and material of the parent main.

The attributes listed above will be retained in a graphical records system.

4.2.26.1 Retention Of Other Records

These include the following:

• Pressure test certificates.

• Records of pressure tests for mains designed to operate at pressures greater than 2 bar must be retained for the life of the system, whilst those for mains operating at 2 bar or lower need to be retained for a minimum of two years.

• Butt fusion printouts.

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4.3 Gas Services Design

A gas service is defined as pipework connected to the distribution main and conveying gas to the gas consumers premises terminating at the customers emergency control valve (ECV). All subsequent downstream pipework conveying gas to appliances is defined as installation pipework.

A service shall be installed at right angles to the main to assist future identification, and terminate at a meter location as close to the connecting main as practical to minimise service length.

All above ground pipework should be in steel pipe to avoid degradation due to high ambient temperatures.

Service terminations can be any of the following;

• In an external meter box or purpose built compartment on the front or within 2m of the front face building.

• In an internal position, sited on the internal face of an external wall terminating no more than 2m from the external face (maximum service operating pressure 75 mbar).

The maximum pressure drop for a service pipe is 2mbar providing a minimum pressure at the downstream side of the ECV of 19mbar.

Service design must be carried out using the approved software tool.

The following factors must be taken into account when planning to install a service:

• Diameter and material of the service?

• Is it possible to insert within the existing service or duct?

• Is it possible to “mole” the service?

• Volume of gas required?

• Design minimum pressure at strategic points on line of main?

• Is the design flow rate available from the mains system?

• Is it necessary to use a default flow rate (3scmh / 32kWh)?

• Will additional capacity be required in future?

• Length of service pipe?

• Pressure requirements?

• Is there adequate pressure in the mains system?

• Is the service subject to an elevated pressure? A service operating above 75mbar must not be installed internally to the premise.

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• Does the premises encroach upon the minimum proximity distances of the main and can the pipe material be altered to meet the minimum requirements?

• Allow minimum distance from windows, vents, other openings and electrical apparatus for MP service governor.

• Are there any special requirements to be met - 24hr access etc?

A service should be constructed from a single piece of pipe with the minimum number of joints possible. However, it may be necessary to install composite services comprising pipes of different diameters in order to minimise the installation costs. Manifold Connections must not be installed.

The bore of the connection should be the same as that of the pipe immediately downstream of it.

Any proposed connection must only be installed using a standard, equivalent size, connection fitting specifically designed for the purpose.

4.3.1 Gas In Flats And Other Multi-Dwelling Buildings

For the design methodology for gas installations to supply flats and other multi dwelling buildings reference shall be made to IGE/G/5.

Note: under section IGE/G/5 – (section 4.1.3).

Medium and High Rise buildings whose design renders them liable to progressive collapse shall not be supplied with gas unless a written assurance is obtained from the owners that the building has been satisfactorily strengthened.

The steps to be followed for the design of gas connections to flats and multi occupancy buildings are as follows:

• Selection of suitable meter position (IGE/G/5 – section 5) in increasing risk level these are

• External single box

• External Bank

• Dedicated Common Meter Room

• Internal to each flat

• Selection of Entry of Network pipelines (IGE/G/5 – Section6) in increasing risk levels

• Above ground entry

• Below ground entry

• Selection of Network Risers and Laterals.( IGE/G/5 – Section 7)

• External Steel Risers

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• Internal Steel risers

Reference shall be made to IGE/G/5 for the following information:

• Provision of Ventilation IGE/G/5 – Section 5 & 7)

• Meter Installations ( IGE/G/5 Section 5.4)

• Internal Risers ( IGE/G/5 Section 7.3)

• Provision and location of Isolation Valves (IGE/G/5 – Section 9 also see Section 3.4 Figures 1 -6)

The design of gas services to flats building should be undertaken in full consultation between the designer, the Gas Authority, the Architect and the Developer.

Provision shall be made for expansion joints to ensure that service risers are not stressed due to the expansion and contraction of above ground pipework. The designer shall ensure that the specified expansion joints will tolerate daily ambient pressure cycling of – 5 to + 50 0 C for the lifetime of the service pipe.

4.3.2 Gas Service Connections

Gas service connections should be carried out in accordance with IGE/TD3 and IGE/TD/4.

Connection designs should take account of pressure loss across the connection components.

All connections must be made under controlled gas conditions and be carried out in accordance with approved written procedures supplemented as necessary by permits to work, risk assessments and method statements.

Under pressure tees fitted to mains must incorporate a construction valve in the connection.

The bore of the pipe must not be restricted through use of reduced diameter fittings or branch drilling.

Any proposed connection must only be installed using a standard, equivalent size, connection fitting specifically designed for the purpose.

Where a top tee connection is to be used account must be taken of the pressure losses across the tee.

The diameter of the downstream pipe should be no greater than the nominal diameter of the connection tee.

For connections to steel pipes the wall thickness should be established by ultrasonic testing, or similar approved method and a minimum wall thickness of 4mm established before direct drilling may be used. Where this is not possible the connection should be made using a full encirclement fitting.

For connections to PE mains one of the following methods should be used:

• Top outlet service tee / Branch saddle

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• Cut out and insert tee

• Straight connection to cap end

• Straight connection to valve

4.3.3 Route Selection - Services

Prior to any excavation taking place, the route of the service should be walked and a visual record (either photographic or video evidence) made of any damage to roads or structures and any other potential sources of claims for compensation. Where existing damage is identified, the extent of the damage should be agreed with owners in advance of work.

Utility plant information should be collated, located with a cable and pipe locator, identified and its position marked on the road surface. Precautions should be taken to avoid damage to overhead plant by vehicles or mechanical excavators.

When planning to excavate parallel to adjacent boundary walls, a stability check needs to be made in order to ensure safe working in the vicinity of the wall.

Excavation work should not proceed if the wall is leaning, cracked or showing any signs of instability.

The stability of the wall should be checked whenever:

• The edge of a service trench is within 0.5 m of the wall.

• The edge of a mains trench is within 1 m of the wall.

• The main is larger than 200 mm nominal diameter.

• The main or service is to be laid at a depth greater than normal.

Factors which must be taken into account when deciding the route of the service include:

• Avoidance of unventilated voids. - Service pipes must not be installed within a cavity, a cavity wall or in the space between the floor and the ceiling below, unless it is to pass through the wall or floor from one side to the other and take the shortest practical route and be enclosed in a gas tight sleeve.

• Avoidance of damage to foundations and other parts of premises. A service must not be installed under the foundation of a building, the base of a load bearing wall or a floating raft foundation. The service must not be installed in such a way such as to impair the structural integrity of the building or the fire resistance of the structure of the building.

• Meter locations.

• Where the building construction involves a concrete raft, and there is not the recommended depth of cover between the raft and the proposed finished ground level (375 mm), the developer must provide a slot or vertical channel in the raft to allow safe installation of the gas pipe.

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• A service installed above ground must be properly supported to ensure that no undue risk of accidental damage to the pipework.

• Is there a known vandalism problem in the local area - use of a below ground entry fitting (bend) and steel riser.

• MP services must not be installed within residential premises.

Reference should be made to IGE/UP/8 Gas Installations for caravans, holiday homes, residential park homes and permanently moored boats for further information on installation requirements in temporary buildings.

IGE/UP/7 Gas Installations in Timber Frame Buildings should be consulted for detailed information on installations in timber frame buildings.

4.3.4 Depth Of Cover For Services

Table 11 details the minimum recommended depth of cover for services up to and including 63mm.

The minimum recommended depth of cover in private property is 375 mm. The laying of the pipe should be laid with a slight gradient towards the main.

Pipe Location Depth of Cover (mm) Services in traffic highways 450

Services in pedestrian walkways 450 Services within residential boundaries 375

Table 11 – Minimum cover for service pipes

The normal minimum depth of cover in highways should be 450 mm. However, the depth of cover should be increased to ensure that there is 75 mm of fine fill between the bottom of the road foundation and the top of the service pipe.

The trench must be excavated to the correct depth and the service pipe fully supported throughout its length on firm ground, free from stones or projecting rock. Wherever possible, the trench bed should have a continuous downward gradient towards the main.

Because of their proximity to road junctions, mains may be laid at 750 mm minimum depth under footpaths. Services at these locations should be laid at a minimum of 450 mm depth, sufficient to provide 75 mm of fine fill between the top of the service and the bottom of the adjacent road structure.

Where it is necessary to lay at less than 375 mm cover, protective measures to prevent damage must be installed such as the additional protection of sleeving, concrete marker tiles or a change in material.

Where the recommended depths cannot be achieved on of the following shall be adopted:

• The route to be reselected; to ensure recommended depths are maintained.

• Change in material to steel pipe.

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• Use of a steel/concrete carrier pipe.

• Additional protection over the pipe for shallow depths, e.g. use of concrete slabs, steel plates or reinforced marker tape.

The result of the risk assessment must be recorded within the project documentation and ‘as laid’ drawing marked up accordingly indicating the protective measures taken, e.g. depth.

4.3.5 Width Of Trench

The trench width should be kept to a minimum and should not exceed 300 mm.

4.3.6 Pipe And Fittings For (Mains) And Services

Pipe shall be constructed from one of the following materials:



• Steel line pipe to BS1387

The choice of material is dependent upon the desired Maximum Operating Pressure (MOP), environmental factors, laying technique and safety factors, such as proximity to buildings and susceptibility to damage, or above ground for special crossings such as bridges.


PE 80 is supplied in a number of standard dimension ratios and is commonly referred to as MDPE. The different SDRs and their pressure limitations can be found in IGE/TD/3 – Section 5.6 – Table 4. It should be noted that due to ongoing development in materials and SDR’s manufacturers recommendations must be consulted to ensure the latest specification is applied.

Service pipes are supplied in SDR 11, with the exception of 16mm diameter and 20mm diameter, which are supplied in SDR 7 and 9 respectively.


There are two types of colour coded PE 100 pipe, orange and multi layer - (Profuse) yellow with brown stripes. Multi layer pipe was introduced in 2003 as an alternative pipe for diameters from 250mm upwards and excludes close fit pipe diameters. The different SDRs and their pressure limitations can be found in IGE/TD/3 – Section 5.6 – Table 4. It should be noted that due to ongoing development in materials and SDR’s manufacturers recommendations must be consulted to ensure the latest specification is applied.

4.3.6.3 Multi-Layer Pipe (Profuse)

This utilises PE100 SDR 21 pipe to provide a system, which maximises capacity via the thinner wall, provides greater flexibility than SDR 11 PE 100 and permits a higher maximum operating pressure than PE 80. The pipe diameters range from 250mm to 630mm operating at pressures up to 2 bar. The peel off polypropylene skin provides a surface which requires no scraping prior to jointing, thus saving considerable time and improving joint quality. The contrast between the pipe colour of the skin and

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the core pipe provides clear evidence of any surface damage, occurring during delivery, storage, handling and during the pipe laying process. The brown strip on the skin of the pipe identifies the pipe as a multi-layer.

4.3.6.4 Orange PE100 (HDPE)

This material has significant strength and crack resistance advantages over PE 80. It can be used for both direct burial and insertion applications. Manufactured in SDR 11, it is used for systems operating between 2 and 7bar, and is orange in colour.

Note: Further information on maximum operating pressures with respect to the ambient temperature range, refer to manufacturers’ recommendations.

4.3.6.5 Electrofusion Jointing For PE (Mains) And Services

Fusion fittings with integral heating elements are fused to polyethylene (PE) pipes using electrical energy supplied to a heating element integral with the fitting. The energy is supplied via a control box, which operates for a selected time depending upon the fitting type and size.

Fittings are classified as class B (suitable for use at operating pressures not exceeding 5.5 bar) or class C (suitable for use at operating pressures not exceeding 7 bar). It is essential that the pipe be supported to prevent it being moved during the heating, fusion and cooling phases. Long pipes should be supported to avoid misalignment due to sagging.

Each fitting is marked as follows:

• Size (i.e. outside diameter) and SDR

• Fusion time(s)

• Cooling time

Precautions should be taken when carrying out pipe jointing when the air temperature is below -5°C or above 40°C. These include the use of temporary tenting to prevent the electrofusion process from being affected.

Pipes must be supported using proprietary clamps, which allow fitting to remain aligned and still when electrofusion, during the heating, fusion and cooling phases. The fittings should always be stored in their plastics bags until ready for use on site. All pipes and fittings should be inspected for cuts, deep scratches or other damage before use. Where damage is found to be greater than 10% of the SDR, the fittings or pipe must not be used.

Care should be taken not to handle or contaminate the surface of the fitting containing the heating coil. Prior to carrying out any Electrofusion the gas in the atmosphere around the electrofusion process must be confirmed to be less than 20% LEL. Should the reading be greater than 20% LEL, the process must not start until readings are brought down to a safe level.

Joints must be made only with dry pipe and fittings. Pipe ends should be cut square using suitable tooling and any burrs removed. A fusion surface which has been cleaned by scraping should not be touched. Electrofusion joints need not be protected by an anti-shear sleeve. Pressure testing must not be carried out until the complete system has cooled down to ambient temperature.

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Multi layer pipe comprises a core of PE 100 material, which is clad with an external peelable skin. The reason for producing a multi-layered pipe in this format is to improve the quality of jointing by achieving a consistent surface quality for the top tee installation procedure for electrofusion purposes. Instead of scraping the pipe, a skin is peeled off the outside of the pipe to reveal a pipe surface, which can be welded onto without any further preparation.

Multi layer pipe will range from 250mm to 400mm.

Checks to ensure joint quality should include the following:

• That the fusion indicators have risen and that no melted material or wire has extruded from the ends of the fitting.

• That the pipe has not moved during welding.

• That the area around the joint is clean and there is evidence of scraping.

• Protection from weather conditions i.e. protective tents.

• When using multi layer pipe the outer skin must have been removed to allow the electrofusion joint to take place.

PE tapping tees must not be positioned within:

• 3 x diameter (parent PE main) of any squeeze off/previously squeezed off points.

• 250 mm of any joint on the PE main.

• 100 mm of another tapping tee.

If the pressure test shows a failure of the tapping tee or coupler on the spigot, cut off the stack to prevent it from any future use.

Should the power fail during the fusion process, DO NOT attempt to re-heat the fitting. The tapping tee must be cut off at the stack.

Select a new position for the new tapping tee, minimum of 100 mm from the failed tee.

Where a joint has failed the reason for the joint failure must be investigated to determine the mode of failure. Common failures include:

• Equipment Failure

• Fitting Failure

• Human Failure

For steel mains up to 3 ‘’ in diameter a full encirclement fitting must be used for the service connection.

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On completion of pipe construction work, all sections of steel pipe and fittings that do not have a factory applied protective coating must be protected with an approved anti-corrosion tape or other coating, after satisfactory completion of the appropriate pressure test.

Anti corrosive tapes should be applied to all bare sections of pipe to give a 55% overlap in all cases. Particular attention should be given to fittings, such as valves, flanged joints, service tees and other items where tapes require moulding to the profile of the fitting during application.

All screwed and mechanical joints must be tested prior to wrapping.

For sizes up to and including 63 mm, anti-shear sleeves must be installed whenever a PE/steel transition is made.

Electrofusion joints need not be protected by an anti-shear sleeve, but the outlet pipework should be adequately supported so as to resist loading of the joint.

All service pipes must be laid so as to ensure that they are not left in tension.

Pressure testing must not be carried out until the complete system has cooled down to ambient temperature.

4.3.6.6 Jointing Of Steel Pipe

For threaded joints, taper-to-taper, or taper (male) to parallel (female) threads may be used. Pipe threads must comply with BS 21. All such threaded joints must be assembled using an approved jointing material.

Threaded joints should not be used on main and service laying working where operating pressures exceed 2bar.

The welding of pipes in nominal sizes up to 50 mm must be carried out using fillet welding in conjunction with fittings to BS 3799, Class 300. Pipes and fittings in nominal sizes above 50 mm must be butt welded, using full penetration welding.

See Section on mains for relevant specifications.

4.3.7 Valves

Valves should be installed on new connections to the existing network or to maintain or safeguard supplies during maintenance or for management of a supply emergency.

For MOPs exceeding 2.0bar, valves must be of steel construction.

Plastic bodied valves may be installed on pipe diameters up to and including 180mm at a pressure up to and including 2bar. Plastic bodied valves must not be used as a construction valve.

Valves on services are installed for the purpose of emergency control valves, service isolation valves, tamper proof valves, additional emergency control valves and excess flow valves.

See Section on mains for relevant specifications.

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4.3.7.1 Service Isolation Valves

Service isolation valves must be fitted in the following circumstances:

• Low pressure services 50 mm / 63 mm diameter and above.

• Multi-occupancy buildings (Schools, Hospitals, High Rise).

• Places of public assembly (Cinemas, Public Houses, Shops etc).

• Supplies to industrial and commercial properties.

• Services supplying multiple primary meters in the same premise.

• Medium pressure (MP): operating pressures greater than 75 mbar where no SEFV is fitted.

• Where a service excess flow valve cannot be fitted a service valve must be installed.

• Wherever the property being supplied has the service entering below ground terminating in a cellar or other locations deemed as a confined space.

Means of external isolation of service pipes should be incorporated in all services entering premises above ground.

PE valves shall be used in preference to metallic valves for below ground installation.

For all above ground installations metallic valves must be used.

Pressure testing must not be undertaken against a closed valve.

Service valves must be installed in an accessible position as near as possible to the property boundary and clearly indicated with a surface cover marked G or GAS.

Service valves must be left in the ‘open’ position after purging.

Service isolation valves 63 mm and below do not require pressure or rider points fitted either side.

The service valve should be installed in the service as close as possible to the boundary of the premises and must be installed with an approved surface box fitted flush with the ground surface.

Service valve covers should have a concrete surround or purpose made plastic chamber and installed over the centre line of the valve.

When a service valve has been closed for any reason then, if the service is not to be immediately re-commissioned, the service should be disconnected at the meter and securely capped off at Emergency control valve. The ECV must be left in the closed position. Open ends on the meter installation pipe work should be securely capped.

4.3.7.2 Emergency Control Valves (Ecv)

An Emergency Control Valve is for shutting off the supply of gas in an emergency to be operated by the gas consumer.

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If the emergency control valve is lever operated, the lever should be so attached that the downward movement turns the valve to the OFF position.

Where a meter is not to be immediately connected or re-connected at the time a service is laid, then, immediately following the testing and purging of the service, the emergency control valve must be securely capped and sealed with the valve left in the closed position.

The Emergency Control Valve should be clearly labelled.

The specification of the Emergency Control Valve should be compatible with the maximum operating pressure and maximum incidental pressure of the associated network.

The outlet of the Emergency Control Valve defines the interface between the gas network and the gas supply meter installation.

The outlet of the Emergency Control Valve should be either of flanged or threaded connection.

MP ECVs must not be installed internally as they do not meet fire resistance standards for use inside a building.

MP ECV’s must not be used for low pressure services.

4.3.7.3 Service Excess Flow Valves (Sefv)

All new and replacement medium pressure services must have a SEFV fitted into the service pipe, normally at its junction with the main. The SEFV is designed to reduce the volume of gas released should damage occur where the service is cut or severed. It will automatically restore the gas supply when the damaged section of pipe has been repaired.

The maximum pressure drop across an SEFV is 8 mbar and this should be taken into account in the design of mains and service systems. When considering integrated MP systems all services should be designed using the pressure drop associated with the highest MOP.

SEFV’s should not be installed dual services.

4.3.7.4 Valve Records

Service valves must be identified as follows:

• Valve number - unique number to that Network.

• Marker Plate - marker plate must have the diameter, valve number, pressure and distance, which are attached to a marker post or wall.

• Valve covers/marker disc - the valve cover should be marked “gas”. Alternatively a marker disc should be fitted over the valve spindle.

A record card/sketch must be made out on which the following information is included:

• Unique valve number

• Dimensional sketch of the valve location

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• GIS Survey map reference

• Address of the site

• Size and safe operating limit

• Make and type of valve

• Open or closed valve

• Date fitted

• Details of pressure and rider points fitted

• Number of turns and direction of rotation

• Function of valve

• Maintenance history

4.3.8 Pressure Regulating Equipment (Mp Services)

There are two categories of Pressure Regulating equipment:

Single Stage regulator installation for: – Inlet pressures between 75 mbar and 2bar. Connected to a gas service having a MOP pressure not exceeding 2bar and a Lower Operating Pressure (LOP) not less than 75 mbar.

Two Stage regulator installation for: – Inlet pressures between 350 mbar and 2bar. Connected to a gas service having a MOP pressure not exceeding 2bar and a LOP not less than 75 mbar.

All boundary MP service regulators must be sited a minimum distance of 3 metres from inhabited property.

4.3.9 Techniques For Service Laying

Types of service laying techniques are listed as follows:

• Service pipe ducting

• Open trench prepared by others

• Soil displacement technique

• Open cut trench technique

4.3.9.1 Services In Ducting

Ducting used for the gas services must be perforated. Prior to installing the new service, a check of the proposed, finished ground level must be carried out to ensure that the service meets with the recommended minimum depths of cover required. Warning tape must be placed a minimum of 75mm

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over the crown of the duct. .A pre-laid service duct may be used for PE service pipe laid external to buildings.

The service ducting specification is BS 4962 ‘Specification for plastic pipes and fittings for use as sub soil field drains’; The ducting must be overlaid with gas caution tape for identification. The duct must be of the perforated type to allow for any potential gas ingress to disperse and not track to a nearby property.

Installation Requirements

• Service pipe ducting must be yellow in colour and Gas marker tape applied a minimum of 75mm above the duct over its entire length to avoid interference damage to gas pipes.

• PE gas or water pipe must not be used as a duct.

• The ducting should wherever possible be laid perpendicular in a straight line any bends should not exceed the permitted radii.

• For ease of insertion, the internal diameter of the duct must be sufficient to allow insertion of the PE pipe with out damage.

• The external ducting must terminate adjacent to the service entry point, allowing a minimum 1 metre of pre-excavated ground to assemble entry fittings.

• The mains connection excavation must be left open with sufficient ducting to receive the service pipe.

• A check must be made to ensure that the proposed finish levels to allow the ducting and PE service are correct at the correct depths.

• The ducting must be laid on a prepared bed or soft ground and the first 75mm backfilled with imported fine fill.

Ensure that the PE pipe does not exceed the minimum bend radius for PE pipe. The minimum bend radius equals 15x diameter of the PE pipe.

4.3.9.2 Soil Displacement Technique

See Mainlaying section

4.3.9.3 Open Cut Services

The technique can be used to lay a full service from main to property or for part of the route as circumstances dictate. Long distance sections of open cut should normally be avoided in favour of alternative techniques.

4.3.10 Labelling Of Gas Services

On completion of installation of the service the emergency control valve must be fitted, capped and sealed with the label completed and be secured to the emergency control valve or as near as practical upstream of it using a cable tie of sufficient length to allow a person to be able to read the information on the label.

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4.3.11 Service Entry Methods

For information on service entries and typical meter locations reference should be made to IGE/TD/4 – Section 5 and IGE/G/5 and also later in this specification.

Polyethylene (PE) services must not enter occupied premises if the operating pressure exceeds 75 mbar.

Service entries must not be laid in unventilated voids.

PE services must not enter any premises, including integral and attached garages, unless enclosed in a metallic pipe that is either gas tight or where the annular space is filled with an approved material.

A service must not be installed under the footing of the building, under the base of a load-bearing wall or under a floating raft.

Where the building construction involves a concrete raft, and there is not the recommended depth of cover between the concrete raft and proposed finished ground level (375 mm), a slot or vertical channel in the raft should be provided to allow safe installation of the gas pipe.

All buried parts of service pipes should be of PE material. The only exceptions being:

• Where, for reasons of pressure & temperature, steel pipe is used.

• Where, due to existing ducts or the exceptional circumstances of a particular case, another material is more appropriate.

In all cases, corrosion protection must be applied to all metallic pipes in accordance with Chapter B of the Work Procedures.

Where a service pipe is installed through any wall or through any floor of solid construction the service pipe must be enclosed in a sleeve. Mechanical pipe joints must not be installed within the sleeve.

There must be no joints installed in a carrier pipe inside a building.

4.3.12 Electrical Bonding

Equipotential electrical bonding should comply with BS 7671. For domestic premises, rated at 100A or less the main equipotential bond conductor must be copper with a minimum cross-sectional area of 10mm2 and green/yellow PVC insulation, construction reference 6491X. The requirements for industrial and commercial premises with electrical supplies greater than 100A single phase are given in BS 7671.

Electrical insulation joints serve to prevent the flow of stray electrical current from installation pipe work through metallic pipe work which may result in corrosion of metal pipe work.

Metallic gas services must be electrically insulated from the meter installation pipe work in premises. For all services, the optimum position of the electrical insulation joint is above ground level as close as possible to the entry point to the premises. Electrical insulation joints for services larger than 32 mm nominal size should be installed in this position.

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Electrical insulation joints may alternatively be fitted directly upstream of the ECV. However, where exposed metallic pipe work exists between the entry point to the premises and the insulation joint, the pipe work and fittings should be wrapped to provide adequate insulation of this section of pipe work.

Where the service is of all PE construction, and the PE is above ground, an electrical insulation joint is not required.

Where services are constructed from PE, terminating with a steel tail into the premises, and where part of the steel tail is buried, electrical insulation is required.

New metallic services off metallic mains should also be insulated at the main to service connections unless the service is to be protected by the corrosion protection system applied to the main.

4.3.13 Meter Positioning

The preference should be given to the installation of external meter boxes either on or within 2 metres within the face of the building. Where an internal meter position is to be used the service should terminate on an internal face of the external wall within 2m of entry into the building.

The locations listed below must not be used for the siting of the meter position.

• In close proximity to any source of heat, or where it may be subjected to extremes of temperature.

• Where food is stored.

• Where it might be liable to mechanical damage.

• Where it might cause an obstruction.

• In bathrooms.

• Where it might be affected by a corrosive atmosphere or liquid.

• Where readily combustible material is stored.

• Meters must not be installed into any lockable meter housing unless the consumer has been provided with a suitably labelled key for the lock.

• A meter and its ancillary controls must not be installed on or under a stairway, in a common hallway, passageway or any other part of the building which provides the sole means of escape in the event of fire.

An above ground entry using a service house entry can be used where fitting a meter box is not practical.

The annulus between the inserted house entry tee and the wall must be sealed, externally and internally.

The position of the entry fitting and riser must be selected to avoid ventilation bricks, flue outlets and other external building features.

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Any above ground service pipe entry must be retained by the use of pipe clips at a maximum of 1 metre intervals.

Where a service is to terminate in the basement/cellar then a service isolation valve (SIV) must be fitted external to the property.

4.3.14 Meter Boxes

Meter boxes must not be located directly above drains, air bricks, manholes, under appliance flues or where access / egress may be restricted in the event of an emergency e.g. narrow foot walks.

Surface mounted or semi concealed meter boxes must never be installed on public footpaths or highways where damage from pedestrians or vehicles can occur.

The meter box must be fitted onto an external wall and must not bridge the damp proof course (DPC).

Medium pressure regulators must not be installed in recessed meter box.

In timber-framed properties, the sleeve must end flush with the inner plaster finish, and all pipes must be sealed with mastic or plaster to prevent air movement into the inner leaf framework.

All sides of the box must be fully bedded into mortar to hold it into the wall with the outer frame flush with the outer brickwork.

The spigot supplied will pass completely through wall up to 278 mm thickness and can easily be trimmed to length during installation of the internal pipe work.

Under no circumstances must any other holes be made in the box for gas pipe work or electrical cross bonding cables.

For secure installation, the box or boxes must be built into the outer leaf as the building progresses. Nails or spikes must not under any circumstances be used to locate the box.

Medium pressure (MP) services to premises must be installed in surface mounted or semi concealed type meter boxes.

4.3.15 Timber Framed Buildings

The installation of gas services to this type of structure offer varying constraints when the special features of their construction are considered. Further guidance on the design and construction can be found in IGE/UP/7.

4.3.16 Mobile Dwellings

For mobile dwellings, the meter position must be installed externally to the dwelling, in either a standard meter box or purpose built meter housing with adequate ventilation. Where purpose built housing must be provided, the total amount of ventilation should be equal to 3% of the floor area of the housing.

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4.3.17 Services Testing

A pneumatic pressure test must be applied to all LP and MP services.

The same, calibrated, test equipment must be used for the initial, intermediate (if any) and the final pressure readings. The test instrument used on pressure tests between 2 and 10.5 bar must have an accuracy of 3 mbar (for an instrument with a range 0-10.5 bar must the accuracy required will be 0.0285%) or greater resolution of 0.1 mbar.

Precautions should be taken to ensure mobile telephones; radios etc are not used near the instrument, as pressure indications may become erratic.

Creep and barometric pressure need not be considered on LP and MP service tests, as these factors are negligible over a short duration test and small volumes of pipe work. Temperature however, could have a small factor in the accuracy of the test, all testing equipment and pipe should be protected from direct sunlight.

Where the pipe work system under test contains flanged or threaded joints, pressure testing must be undertaken prior to wrapping the joints.

Type of system

Working pressure

mbar

Test pressure

mbar

Type of test gauge Permissible

pressure drop

Duration (Minutes)

Service 75 100

Water manometer or

electronic device

0 5

Service 2000 3 000 Electronic device

0 5

Encirclement fitting

75 350 Electronic device

0 5

Encirclement fitting

2000 3000 Electronic device

0 5

Table 12 - Service testing

4.3.18 Purging And Commissioning

After completion of a successful pressure test the service will be directly purged by complete displacement of air by natural gas.

During all purging operations the following must be followed:

• A continuity bond must be maintained across separated metallic pipes.

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• There must be no smoking or naked lights or other sources of ignition present, and NO SMOKING signs should be displayed.

• Precautions against static electricity in plastics pipes and hoses must be observed.

• All operational personnel should wear full personal protective equipment including ear protection devices.

• The purge should start immediately after testing.

• Exclude all ignition sources within 5 m of any gas release.

• Fire extinguishers must be available and positioned for use.

• Care must be exercised when venting/purging large volumes of gas in built-up areas.

• Once a purge has commenced it should continue without interruption until complete.

• When planning any commissioning operations, it is important to ensure that an adequate supply of natural gas is available to provide the required flow rate without reducing the local network pressure below minimum requirements.

• For all purging operations, a system of communication should be organised and tested for personnel involved in the control of the purge. This system must be intrinsically safe or positioned outside the 5m exclusion zone.

• Two successive tests confirm 90% gas in air (GIA) at the outlet of the purge hose using a Gascoseeker or:

• When the service has been purged with natural gas for one second for each metre length of service pipe not greater than 32 mm diameter, and four seconds for each metre length for a 63 mm diameter service.

• A pre-fabricated flexible purge hose, 32mm fitted with a flame trap is used for all service purging operations.

4.3.19 Service Alteration

When diverting or altering a gas service pipe the following should be considered:

• Check adjacent residences to ensure that it is not part of a dual service.

• If a dual service is found this should be re-laid as two individual services.

• All sections of below ground steel services must be replaced in PE.

• When a service is to be cut off for any alteration work, it must be cut at least 2m from the building line ensuring that adjacent vents and any other openings have been temporary isolated or closed. Any other potential sources of ignition should be identified and isolated where possible i.e. extinguish pilot lights on balanced flue appliances, extractor fans, etc...

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• If a service alteration is downstream of an above ground entry tee, with an integral stopper, the integral stopper should be used as a means of isolation. This can be determined by a ‘let by’ test using a pressure gauge connected to the outlet of the Emergency Control Valve (ECV) to confirm that the entry tee is not passing gas.

• The correct squeeze off distances must be maintained between fittings or joints.

• When undertaking an alteration on an MP service it must be isolated at the service isolation valve, or the mains connection, or mains connection, or a suitable point for single squeeze off up to and including 32 mm and a double squeeze off for 63 mm diameter. If the squeeze off equipment fails to stop the flow of gas an additional squeeze off must be used.

• Wherever possible services should be laid perpendicular between the service entry point of the building and connection to existing pipe work.

• Compression fittings must not be used for reconnection of services within 2m of a property.

• Prior to leaving the site, adjacent buildings must be checked to ensure that supplies have not been affected by the work undertaken.

• If the new section of service pipe to be laid increases the length of the existing service pipe then the total service length pressure drop should be calculated to ensure that the correct pressure is maintained at the ECV. Table D3 Pressure Loss over given length and diameter.

4.3.20 Service Cut Offs

All disconnections must be made under controlled gas conditions wherever possible and be carried out in accordance with any necessary approved written procedures supplemented by associated permits to work, risk assessments and method statements. Breathing apparatus and fire extinguishers must be placed adjacent to the working area of the activity being undertaken and available for immediate use.

Where service pipes are to be disconnected under uncontrolled conditions, breathing apparatus must be worn and fire extinguishers placed adjacent to the working area for immediate use. The use of additional protective equipment must be used including fire suits, lifting equipment, guard lines etc…

Medium pressure service connections that do not contain a means of controlled isolation should be reduced in operating pressure to a safe level before the service cut off is undertaken.

Before and after cutting off the service, check adjacent properties for a dual service i.e. a visual inspection on the service entry positions, pipe location equipment, asking the consumer/s.

Service pipes should be disconnected at the mains connection, to avoid future leakage and potential interference damage.

Only approved mains sealing plugs must be used (taper plugs and reducers are not permitted).

There must be a physical break on the line of the service pipe from the main to the premises to break any potential gas path. All exposed pipe ends must be capped with an appropriate fitting.

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The service must be cut off at a minimum distance of 2m from the property to avoid any gas ingress into the property.

The purpose of a temporary continuity bond is to protect the operative and ensure that an ignition source will not be created by an electrical discharge across a temporary gap in pipework.

A TCB must be fitted before any part of a metallic main, service meter or other plant is connected, disconnected or cut and when installing an insulation joint. Continuity bonds should not be fitted such that it bridges an insulation joint.

TCBs must be fitted so that they will not be disturbed during the progress of the work and must not be removed until the work has been completed. Bonds must not be removed until the connection or disconnection work has been completed, and must be fitted or removed in a gas-free area only.

TCBs should be constructed from fully insulated wire having at least 10 mm2 cross-sectional area. Clamps should be to BS 951 or approved equal. Ensure that the TCB is the correct type for the task to be undertaken.

4.3.20.1 Meter Removal

Before de-commissioning a service pipe, any meters connected to that service should be disconnected, removed and open installation pipework capped using an appropriate fitting prior to starting the decommissioning. The meter should be placed in a well ventilated area until it can be re-fitted. If the meter is not to be re-fitted it should be capped and returned to the depot.

Prior to starting work the meter installation must be checked with a voltstick and a temporary continuity bond fitted.

4.3.20.2 Abandoned Service Pipes

Where a service is to be abandoned, the ends should be capped and sealed.

After disconnecting the service from the gas main, the service riser should be removed and both ends of the service sealed and capped. Any existing entry points in the floor or wall must be sealed as appropriate.

Where the existing standpipe cannot be removed without damaging the fabric of the building, the standpipe should be left capped and the service information label must be attached to the redundant service pipe with the ‘Disconnected Service’ details completed.

4.4 Typical Mains And Service Configurations

4.4.1 Typical Distribution Systems

The following section describes typical distribution system configurations and provides information to aid the selection of the most appropriate configuration for a given location.

A selection Table is included at the end to factors for and against any option.

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4.4.1.1 Configuration Option 1

An off-take will be taken from the Transmission system which will be regulated to a maximum of 16 Bar and a Minimum of 7 Bar. One or more primary feeder pipelines will be run to operate at a maximum Pressure between 7 Bar & 16 Bar.

Pressure reduction stations will be installed at selected points off this primary supply pipeline to reduce the pressure to a maximum of 4 Bar. From this Pressure Reduction Station supply mains will be run to operate at a maximum pressure of 4 Bar.

Individual Large Loads (Industrial or Commercial Users) will be supplied directly at 4 Bar with a suitable pressure regulator installed locally.

Individual residences in suitable locations will also be supplied directly at 4 Bar with Meter / Regulator sets close to but outside the residence.

Further Pressure Reduction Stations may be installed if need to supply at 75 mbar directly to premises with a Governed Meter outside the residence or in a suitable internal location where proximity distances dictate.

This option will be best suited to more heavily Industrialised areas with small areas of residences.


An off-take will be taken from the Transmission system which will be regulated to a maximum of 16 Bar and a minimum of 7 Bar. One or more primary supply pipelines will be run to operate at a maximum Pressure of between 7 Bar & 16 Bar.

Pressure reduction stations will be installed at selected points off this primary supply pipeline to reduce the pressure to a maximum of 2 Bar. From this Pressure Reduction Station, supply mains will be run to operate at a maximum pressure of 2 Bar.

Individual Large Loads (Industrial or Commercial Users) will be supplied directly at 2 Bar with a suitable pressure regulator installed locally.


Further Pressure Reduction Stations may be installed if need to supply at 75 mbar directly to premises with a governed meter outside the residence or in a suitable internal location.

This option will be best suited to areas of Commercial / Light Industrial activity with more densely populated areas of residences.


An off-take will be taken from the Transmission system which will be regulated to a maximum of 16 Bar and a Minimum of 7 Bar. One or more primary feeder Pipelines will be run to operate at a maximum Pressure between 7 Bar & 16 Bar.

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Pressure reduction stations will be installed at selected points off this primary supply main to reduce the pressure to a maximum of 4 Bar. From this Pressure Reduction Station supply mains will be run to operate at a maximum pressure of 4 Bar. These will be interconnected to form a ring system.

Individual Large Loads (Commercial Users) will be supplied directly at 4 Bar with a suitable pressure regulator installed locally.


Further Pressure Reduction Stations may be installed if need to supply at 75 mbar directly to premises with a governed meter outside the residence or in a suitable internal location.

This option will be best suited to areas with many residences and flats and some commercial developments.


An off-take will be taken from the Transmission system which will be regulated to a maximum of 16 Bar and a minimum of 7 Bar. One or more primary feeder pipelines will be run to operate at a maximum Pressure between 7 Bar & 16 Bar.

Pressure reduction stations will be installed at selected points off this primary supply pipeline to reduce the pressure to a maximum of 2 Bar. From this Pressure Reduction Station Area supply mains will be run to operate at a maximum pressure of 2 Bar. These will be interconnected to form a ring system.

Individual Larger Loads (Commercial Users) will be supplied directly at 2 Bar with a suitable pressure regulator installed locally.


Further Pressure Reduction Stations may be installed if need to supply at 75 mbar directly to premises with a Governed Meter outside the residence or in a suitable internal location.

This option will be best suited to areas with densely populated residences and flats and some Commercial development.

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4.4.1.5 Configuration Advantages And Disadvantages

Design Configuration

Type of area most likely to suit this example For Against

Example 1 Heavily Industrialised Area with small areas of Residences

Higher Pressures enable smaller diameter pipes to be used

There may be possible problems with proximity of buildings

Example 2 Areas of Commercial / Light Industrial activity with larger areas of Residences

Lower Pressure allows closer proximity of Buildings

May need to use larger pipe sizes.

Example 3 Many residences and flats with areas of Commercial Activity

Higher Pressures enable smaller diameter pipes to be used

There may be possible problems with proximity of buildings

Example 4 Very many residences and flats with small areas of Commercial Activity

Lower pressures allow closer proximity to buildings

Likely to need to use larger pipe sizes.

Table 13 - Mains configuration advantages and disadvantages

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4.4.2 Diagrammatic Representation

Configuration 1

Design Configuration 1City GatePressureRegulator

Area System PressureRegulator

(Reduce to 4 bar

Primary Supply Pipeline7 to 16 bar

Area Network Main - 4barpressure 4 bar supply to Medium /Large

single Load

4 bar supply to Medium /Large single Load

4 bar supply to Medium /Largesingle Load

Supply to small CityLocal Network Regulator4 Bar reduced to 75mbar


SingleResidencesfed directfrom 4Bar



Local Network Mains75 mbar


LocalNetworkMains

75 mbar

Figure 15 - Mains configuration 1

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Configuration 2

Design Configuration 2

City GatePressureRegulator


(Reduce to 2 bar)


Area Network Main - 2 barpressure 2bar supply to Medium /Large

single Load

2bar supply to Medium /Large single Load

2bar supply to Medium /Largesingle Load

Supply to small CityLocal Network Regulator2Bar reduced to 75mbar


SingleResidencesfed directfrom 2 Bar

Supply to small CityLocal Network Regulator2Bar reduced to 75mbar




LocalNetworkMains

75 mbar


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Configuration 3


4 barcommercial

supply

4 barcommercial

supply

4Bar to75 MBarRegulator

Local 75 MBarNetwork

4 bar to75 mbar

RegulatorLocal 75 mbar

Network

4 bar services to individualResidences.

4 bar to75 mbar

Regulator

Local 75 mbarNetwork




(Reduce to 4 bar)


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Configuration 4


2 barcommercial

supply

2 Barcommercial

supply

2 Bar to75 MBar

Regulator

Local LP Network

2 bar to75 mbar

RegulatorLocal 75 mbar

Network

2 bar services to individualResidences.

2 bar to75 mbar

Regulator

Local 75 mbarNetwork




(Reduce to 2 Bar)


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4.4.3 Typical Gas Services Configurations

4.4.3.1 Single Occupancy Residence

Example 1

Single service run at 2 or 4 bar with meter governor unit external to property

Single Occupancy GasServices

Example 1

2 / 4 barmain

2 / 4 barservice

Meter & Regulator setin external housing

Property

Figure 19 – Single service configuration 1

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Example 2

Single Low pressure service with meter external or internal to property


Example 2

75 MBarmain

75 MBarservice

Meter in externalhousing

Property


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Example 3

Dual Low pressure service split in public with meter external or internal to property


Example 3

75 MbarMain

75 MBarService

Meter in external orinternal housing

Property1

Property275 Mbar

Service

Back of public highway


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4.4.3.2 Multiple Occupancy Residences (Flats)

Example 1

Single service run at 2 or 4 bar, feeding bank of meter governor sets external to property. With meter outlets run to individual properties

Multi Occupancy Gas Services Example 1

2 / 4 barmain

2 / 4 barservice

Bank of Meter /Governors

Property

Individual MeterOutlets

Floor 4

Floor 1

Floor 2

Floor 3

Figure 22 – Multi occupancy configuration 1

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Example 2

Single service run at 75 MBar feeding meter external to property with outlet run to individual property.


75 MBarmain

75 MBarservice

Bank of Meters

Property

Individual MeterOutlets

Floor 4

Floor 1

Floor 2

Floor 3


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Example 3

Single service run at 75 mbar pressure feeding riser to several meter positions internal to property


LP main

LP service

Riser with Lateralssupplying meters

internal to property

Property

Floor 4

Floor 1

Floor 2

Floor 3


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SECTION 5 CONSTRUCTION MANAGEMENT

SECTION 5

CONSTRUCTION MANAGEMENT

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5 CONSTRUCTION MANAGEMENT

5.1.1 Work Elements

The work elements associated with the construction process are listed as follows:

• Issue of government and non-government notices.

• Quality management system, including audit plans, and environmental management plan.

• Implementation of the safety management systems for construction.

• Selection of competent contractors and suppliers.

• Procurement of materials, plant and equipment to the required specification.

• Vendor certification.

• Construction method statements.

• On site inspection, supervision and audit.

• Carrying out health, safety and environmental audits.

• Installation, construction, inspection, examination, testing and commissioning of pipeline. Installations, mains and services.

• Pipeline, mains and services reinstatement.

• Access to site and access to all project records.

5.1.2 Competency Of Gas Distribution Operatives

Operatives undertaking work on gas systems shall be appropriately qualified to undertake the activities on which they are employed. Examples of competency modules in the UK are listed as follows:

GNO101 Assist in locating and avoiding supply apparatus and sub-structures

GNO102 Working under supervision excavate holes and trenches in ground and pavement structures

GNO103 Assist in preparing for re-instatement of excavation and pavement surfaces

GNO104 Working under supervision, contribute to an efficient and effective work environment

GNO105 Working under supervision, contribute to Health, Safety and Environment in the workplace

GNO106 Working under supervision, operate powered tools and equipment for routine and predictable requirements during gas network operations

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GNO107 Working under supervision, join materials by manually controlled thermal processes

GNO108 Working under supervision, assemble components to meet specifications

Optional Units-Select one unit from the two options

GNO109 Assist in preparing resources and segregating the area for highways works

GNO110 Assist in preparing resources and segregating the area for site works

5.1.2.1 Mandatory Units Service Laying

GNO201S Locate and avoid supply apparatus and sub-structures during gas network operations (service laying)

GNO202S Excavate holes and trenches in ground and pavement structures to access the gas network (service laying)

GNO203S Re-instate excavation and pavement surfaces after gas network operations (service laying)

GNO204S Contribute to an efficient and effective work environment during gas network operations (service laying)

GNO205S Contribute to Health, Safety and Environment in the workplace during gas network (service laying)

GNO206S Operate powered tools and equipment during gas network operations (service laying)

GNO212S Install engineering products or assets (service laying)

GNO213S Replace assembly or sub-assembly components (service laying)

GNO214S Conduct specified testing of engineering products or assets (service laying)

Optional Units Service laying

Section A: Select a minimum of one unit from section A

GNO209S Prepare resources and segregate the area for highways works during gas network operations (service laying)

GNO210S Prepare resources and segregate the area for site works during gas network operations (service laying)

Section B: Select a minimum of one unit from section B

GNO207S Join materials by manually controlled thermal processes (service laying)

GNO211S Join materials by machine controlled thermal processes (service laying)

Section C: Select a minimum of two units from section C t

GNO208S Control allocated resources to achieve requirements (service laying)

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GNO215S Prepare work areas and materials for engineering activities (service laying)

GNO216S Restore components to operational condition by repair (service laying)

GNO217S Contribute to the organisation of work activities (service laying)

GNO218S Contribute to effective working relationships (service laying)

5.1.2.2 Mandatory Units-Main Laying

GNO201M Locate and avoid supply apparatus and sub-structures during gas network operations (Main laying)

GNO202M Excavate holes and trenches in ground and pavement structures to access the gas network (Main laying)

GNO203M Re-instate excavation and pavement surfaces after gas network operations (Main laying)

GNO204M Contribute to an efficient and effective work environment during gas network operations (Main laying)

GNO205M Contribute to Health, Safety and Environment in the workplace during gas network operations (Main laying)

GNO206M Operate powered tools and equipment during gas network operations (Main laying)

GNO212M Install engineering products or assets (Main laying)

GNO213M Replace assembly or sub-assembly components (Main laying)

GNO214M Conduct specified testing of engineering products or assets (Main laying)

Optional Units-Main laying


GNO209M Prepare resources and segregate the area for highways works during gas network operations (Main laying)

GNO210M Prepare resources and segregate the area for site works during gas network operations (Main laying)


GNO211M Join materials by machine-controlled thermal processes (Main laying)

Section C: Select a minimum of two units from section C

GNO208M Control allocated resources to achieve requirements (Main laying)

GNO215M Prepare work areas and materials for engineering activities (Main laying)

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GNO216M Restore components to operational condition by repairs (Main laying)

GNO217M Contribute to the organisation of work activities (Main laying)

GNO218M Contribute to effective working relationships (Main laying)

5.1.2.3 Mandatory Units-Craft

GNO301 Locate and avoid supply apparatus and sub-structures in diverse situations

GNO302 Excavate holes and trenches in ground and pavement structures in diverse situations

GNO303 Re-instate excavation and pavement surfaces in diverse situations

GNO304 Contribute to an efficient and effective work environment in diverse situations

GNO305 Contribute to Health, Safety and Environment in the workplace in diverse situations

GNO306 Operate powered tools and equipment for routine and predictable requirements in diverse situations

GNO308 Control allocated resources to achieve requirements in diverse situations

GNO312 Install engineering products or assets in diverse situations

GNO313 Replace assembly or sub-assembly components in diverse situations

GNO314 Conduct specified testing of engineering products or assets in diverse situations

GNO315 Prepare work areas and materials for engineering activities in diverse situations

GNO319 Analyse and interpret the results of engineering tests in diverse situations

Optional Units Craft


GNO309 Prepare resources and segregate the area for highways works in diverse situations

GNO310 Prepare resources and segregate the area for site works in diverse situations


GNO307 Join materials by manually-controlled thermal processes in diverse situations

GNO311 Join materials by machine-controlled thermal processes in diverse situations

Section C: Select a minimum of three units from section C

GNO316 Restore components to operational condition by repairs in diverse situations

GNO317 Contribute to the organization of work activities in diverse situations

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GNO318 Contribute to effective working relationships in diverse situations

GNO320 Determine technical requirements to achieve objectives in diverse situations

GNO321 Determine resource requirements to achieve objectives in diverse situations

5.1.3 Deliverables

The Construction process shall fulfil the following deliverables:

5.1.4 Manuals And Drawings

Reports, as laid drawings, and manuals shall be provided by the construction contractor.

5.1.5 Quality Management System

The Authority Project Manager shall manage construction activities through an approved quality management system which should ensure that construction is completed in accordance with the design.

Prior to the commencement of construction, the Authority Project Manager shall be required to make a submission in the form of a project specific quality management system, to address the following, as a minimum. It is anticipated that any quality system would mirror the relevant parts of BS EN ISO 9001 or other appropriate standards and provide assurance that project requirements are met.

The Project Manager shall provide details of how monitoring, audit and appraisal shall be carried of the following:

• Construction

• Installation

• Testing and certification

• Contractor selection (work scope, criteria, methodology)

5.1.6 Safety Management System

An effective and comprehensive safety management system is essential for good health and safety performance during construction. Refer to Health and Safety Executive (HSE) guidebook ‘Successful Health and Safety Management’ for the requirements of the safety management system. Construction method statements are an essential part of the safety management system.

5.1.7 Construction Method Statements

The Project Manager shall review method statements for all construction activities.

Construction Method Statements shall include, but not be limited to, the following:

• Location (and protection) of third services.

• Land drainage (pre and post construction).

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• Top soil stripping.

• Materials delivery, handling and storage.

• Pipe bending.

• Welding.

• Radiography and NDT.

• Pipe jointing.

• Trench excavation (or non dig (trenchless) techniques).

• Narrow trenching.

• Pipe laying.

• Special crossings (e.g. railways, roads, watercourses, third party services).

• Sleeves.

• Valve installations.

• Tie-ins and connections.

• Pipe corrosion protection coating (internal and external), including coating surveys (Close Interval Potential Survey).

• Wrapping.

• Backfill and reinstatement processes.

• Pigging.

• Testing and commissioning.

5.1.8 Environmental Management Plan

The Project Manager shall create an Environmental Management Plan identifying all potential environmental impacts (direct and indirect) and mitigation measures identified for the construction works, reference the method statements to be utilised for each area and define the responsibilities.

The plan shall meet the requirements of ISO 14001 and shall enable the Project Manager to prepare a schedule of environmental audits carried out to the EMP, work activities and environment record keeping.

The purpose of the EMP is:

• To provide a mechanism for ensuring that measures to mitigate potentially adverse environmental impacts are implemented.

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• To ensure that standards of good construction practice are adopted throughout the construction of the pipeline or installation.

• To provide a framework for mitigating impacts that may be unforeseen or unidentified until construction is underway.

• To provide assurance that environmental performance will be met.

• To provide a framework for compliance auditing and inspection to enable the Authority to be assured that its aims for environmental performance is being met.

A pre-tender EMP consists of a set of generic environmental requirements with which prospective Contractors will have to demonstrate how they will comply as part of the Invitation To Tender (ITT).

The EMP is further developed to reflect any consents and conditions, and again once the Contractor has been appointed. At this stage, the Contractor's Method Statements are incorporated into the EMP, after having been approved. As more information becomes available through further environmental surveys, it will be passed on to the prospective Contractors through the tendering process.

Each source of emission (e.g. liquid effluent, solid waste, etc…) should be discussed in detail, possible impacts considered (e.g. water and ground pollution) and mitigation measures proposed to include:

• Identification of legislation, standards, specifications and codes of practice relating to environmental activities associated with construction.

• Method statements.

• Identification of a programme of audits.

• Management of:

• Excavations (for potential environmental impact).

• Environmental incident reporting.

• Pollution control.

• Waste management.

• Trees and hedges.

• Watercourse discharges and pumping operation.

• Hydrostatic testing.

• Reinstatement.

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5.1.9 Project Risk Register

A project risk register should identify risks associated with the construction process, particularly with the safety, integrity and quality of the assets, with impact on the environment and with respect to operation and maintenance. The risk register should identify and categorise the risks, assess the impact and identify the mitigation actions and plans to be used.

5.1.10 Access To Site

The Project Manager shall arrange access to site in accordance with the Authority safe control of operations procedures.

5.1.11 Audit

Prior to construction commencement, an audit of the project quality management system shall be carried out to ensure that the minimum technical standards in relation to asset integrity, operation and maintenance are maintained.

The Project Manager shall carry out audits of the following construction activities:

• Welding and non-destructive testing (NDT) processes

• Materials traceability

• Construction works

• Testing

• Commissioning

• Corrosion Protection

• Reinstatement

5.1.12 Construction Approvals Process

The Contractor shall submit to the Authority for approval the following documentation at each stage of the construction process.

5.1.12.1 Technical Procedural Health and Safety

• Health and safety plan

• Construction risk assessment

• Construction method statements

5.1.12.2 Specific Method Statements

• Signing and guarding excavations and traffic management

• Safe working in vicinity of buried plant

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• Excavating procedures

• Laying of PE mains

• Laying PE Services

• Moling

• Electrofusion of PE pipe

• Butt fusion of PE pipe

• Testing of PE joints and fittings

• Laying steel pipe up to 7 barg pressure

• Non routine operations procedure

• Purging and commissioning of mains and services

• Pressure testing of mains and services

• Installation of gas equipment e.g. pressure reduction equipment

• Preparation of as-laid drawings

• Managing gas escapes and incidents

• Environmental assessments

• Welding steel pipe up to 7 barg pressure

• IGE/GL/ 5 Process

• Waste Management

5.1.12.3 Construction Works

• Pipe laying methodology

• Pipe and material handling, inspection, storing, quarantine and requisitioning

• Special Crossing methodology, open cut, trench-less

• Route corridor report

• Right of Way preparation, access and working areas set out, signed and fenced proposals

• Pre entry arrangements including material storage, site offices and working strip definition

• Land boundary furniture removal proposals

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• Pre construction land reinstatement proposals

• Trial hole proposals

• Ditching survey audit report

• Fine fill backfill, warning tape, impact protection installation and inspection report

• Special crossing installation and coating loss test report

• Sub soil reinstatement and drainage installation and inspection report

• Top soiling and marker post (CP aerial and line marker) installation report

• Final reinstatement report

• As built drawings and construction records package

5.1.12.4 Mechanical Pipe and Fittings

• Pipe steel, PE material certification and data sheets

• Pipe material certification

• Fitting material certification and data sheets – bends, tees, valves, flanges, reducers, “O”Lets, gaskets, bolts

• Fabrication certification and data sheets

5.1.12.5 Corrosion Protection

• Cathodic protection specifications and data sheets

• External / Internal protection (coating) specifications, data sheets

• Joint coating specification and data sheets

• Soil resistivity report

• Cathodic Protection testing report

• Electrical earth testing report

• Cathodic Protection test post locations

• Insulation joint specification and data sheets

• Field testing (CIPPS, current drain tests etc) specification and requirements

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5.1.12.6 Electrical, Instrumentation And Telemetry

• Electrical equipment specifications and data sheets

• Instrumentation equipment specifications and data sheets

• Telemetry equipment specifications and data sheets

• Metering equipment specifications and data sheets

• Gas chromatography equipment specifications and data sheets

• Hazardous area design

• Cable layout proposals

• Fire and gas detection equipment specifications and data sheets

• Power supply equipment specifications and data sheets

5.1.12.7 Welding and Mechanical Testing

• Welding specification

• Welding procedures

• Welder qualification, register and approvals

• Mechanical destructive test data sheets

• NDT - Radiography inspection reports

• NDT - Ultrasonic inspection and MPI inspection reports

5.1.12.8 Swabbing, Gauging and Testing

• Pre test audit report

• Swabbing pig run proposals, report and certification

• Magnetic pig run proposals, report and certification

• Brush pig run proposals, report and certification

• Gauge pig run proposals, report – gauge plate thickness and diameter and certification

• Test limits drawing

• Testing procedure

• Testing equipment calibration certification including pumps, gauges, hoses, test ends etc.

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• Test pressure reports

• Pressure volume plot including hold points and entrained air by volume calculation

• Test pass / fail criteria and certification

• Test pressure and temperature recorder charts / data logger printout

• Test pack to match each test section

5.1.12.9 Drying

• Hydrocarbon and water dew-point report

• Drying procedure

• Instrument and equipment calibration certification

• Soak test report, (Vacuum test only)

• Dryness report

5.1.12.10 Testing, Purging and Commissioning

• Pre test audit report

• Testing procedure and method statements

• Test reports

• Pre-commissioning audit reports

• Purging and Commissioning procedure and method statements

• Commissioning reports

• Post commissioning audit report

5.1.13 Collation Of Handover Documentation

The Project Manager shall manage the collation of documentation including information, forms and certificates for handover documentation.

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SECTION 6 APPENDICES

SECTION 6

APPENDICES

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6 APPENDICES

6.1 References

6.1.1 Igem Standards

IGE/TD/4 Edition 3 Gas Services

IGE/TD/3 Distribution mains

IGE/TD/5 Transport, handling and storage of polyethylene pipes and fittings

IGE/SR/22 Purging of fuel gases

IGE/SR/25 Hazardous area classification of natural gas installations

IGE/SR/26 Horizontal Directional Drilling and Impact Moling

IGE/SR/26a Horizontal Directional Drilling and Impact Moling, Site Operator’s Safety Guide

IGE/SR/9 Edition 2 Safe Working Practice for Pressure Regulating Installations

IGE/TD/1 Edition 4

Supplement 1 Handling, transport and storage of steel pipe, bends and fittings

IGE/TD/3 Edition 4 Steel and PE pipelines for gas distribution

IGE/TD/3 Edition 4

Supplement 1 Handling, transport and storage of PE pipe and fittings

IGE/TD/13 Pressure regulating installations for transmission and distribution systems

IGE/TD/15 Services and metering installations for a gas flow not exceeding 6m3h -1 at supply MOP exceeding 75mbar but not exceeding 2 bar

IGE/TD/101 Adoption of pipe system by a GT – management of UIP activities

IGE/UP/7 Gas installations in timber frame buildings

IGE/UP/8 Gas installations for caravan holiday homes, residential park homes and permanently moored boats

IGE/GL/5 Plant Modification Procedures (with amendments, January 1999)

IGE/GM/6 Specification for low pressure diaphragm and rotary displacement meter installations with badged meter capacities exceeding 6 m3/h (212 ft3/h) but not exceeding 1076 m3/h (38000 ft3/h)

IGE/G/1 Definitions for the End of a Network

IGE/UP/7 Gas Installations in Timber Frame Buildings

IGE/UP/8 Gas Installations for caravans holiday homes, residential park homes and permanently moored boats

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6.1.2 Uk Gas Industry Standards

GIS/E17 Part 2 Technical specification for insulation joints Part 2 - Joints operating at

pressures not greater than 7 bar GIS/E13 pt 1 Technical specification for gas filters (80mm nominal size and above) suitable

for use in the pressure range above 75 mbar and not exceeding 7 bar GIS/E34 Specification For The Procurement Of Pressure Regulating Modules With

Inlet Pressures Above 75 Mbar But Not Exceeding 7 Bar For Regulators With Design Flow Rates Greater Than 6 m3/hr

GIS/F7 Technical specification for steel welding pipe fittings 15mm to 450mm

inclusive nominal size for operating pressures not greater than 7 bar GIS/F9: Part 1 Specification for Metric and Imperial Carbon and Stainless Steel Single

Ferrule Compression Fittings for Tubes. Part 1 - General Requirements GIS/F9: Part 2 Specification for Metric and Imperial Carbon and Stainless Steel

Compression Fittings for Tubes. Part 2 - Evaluation Procedure GIS/L2 Technical specification for steel pipe 15mm to 450mm inclusive nominal size

for service at pressures up to 7 bar (Supplementary and amending specification to BS 3601) + Amendment no.1 (September 1994)

GIS/PL 2-1 Technical specification for polyethylene pipes and fittings for natural gas and

suitable manufactured gas Part 1 - General & PE compounds for use in PE pipes and fittings.

GIS/PL2 Part 2 Technical specification for polyethylene pipes and fittings for natural gas and

suitable manufactured gas Part 2 - Pipes for use at pressures up to 5.5 bar GIS/PL2 Part 4 Technical specification for polyethylene pipes and fittings for natural gas and

suitable manufactured gas. Part 4 - Fusion fittings with integral heating element(s)

GIS/PL2 Part 8 Technical specification for polyethylene pipes and fittings for natural gas and

suitable manufactured gas Part 8 - Pipes for use at pressures up to 7 bar GIS/PL3 Technical specification for Self Anchoring Mechanical Fittings for

Polyethylene Pipe for Natural Gas and Suitable Manufactured Gas GIS/V7 Part 2 Specification for Distribution Valves - Part 2 plastic bodied valves of sizes up

to 180mm suitable for operation at pressures not exceeding 5.5 Bar GIS/V7 Part 1 Technical specification for distribution valves Part 1 - Metal-bodied line valves

for use at pressures up to 16 bar and construction valves for use at pressures up to 7 bar

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6.1.3 European & International Standards

API 5L Specification for line pipe BS 21 Specification for pipe threads for tubes and fittings where pressure-tight joints are made on the threads (metric dimensions)

BS 746

Specification for gas meter unions and adaptors BS 951 Electrical earthing. Clamps for earthing and bonding. Specification BS 1387:1985 Specification for screwed and socketed steel tubes and tubulars and for plain end steel tubes suitable for welding or for screwing to BS 21 pipe threads

BS 1965 Specification for butt-welding pipe fittings for pressure purposes. Carbon steel

BS 3601 Specification for carbon steel pipes and tubes with specified room temperature properties for pressure purposes.

BS 3799 Class 3000 Specification for steel pipe fittings, screwed and socket-welding for the petroleum industry

BS 4504:PN 16 Circular flanges for pipes, valves and fittings (PN designated). Specification for copper alloy and composite flanges

BS 6400-1:2002 Specification for installation of domestic-sized gas meters maximum rated capacity not exceeding 6 m3/h (2nd and 3rd family gases). Low pressure (2nd family gases)

BS 6629

Specification for optical performance of high-visibility garments and accessories for use on the highway

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6.2 Appendix 2 – Gas Industry Terms & Abbreviations

Term Definition

abandonment A section of main whose use has been discontinued.

additional emergency control valve (AECV)

An AECV is a valve, not being the ECV, for shutting off the supply of gas in an emergency, intended for use by a consumer of gas. An AECV may be located within either the meter installation or installation pipework and, as such, may not isolate all of the consumer’s pipework or meter installation.

Note: An AECV performs the same function as the ECV with respect to emergency isolation, usually of an individual premises or dwelling and is required by GS(I&U)R in many situations. It does not, however, denote the end of a network and is always fitted downstream of the ECV. The existence of an AECV does not affect the required existence of an ECV (which is always fitted).

air knife Tool that uses a blast of high pressure air to break up the ground when excavating

alignment clamps Clamps used to hold pipes in the correct position prior to welding or heat fusion.

ambient temperature The environmental temperature.

anchorage Fixing of pipe ends, bends, valves and tees in order to prevent movement.

anchor block A concrete block (with or without reinforcement), used for anchorage.

annulus The space between a carrier pipe and sleeve

anti-shear sleeve A sleeve used to minimise local stresses in rigid PE joints

atmospheric pressure See barometric pressure

back rail Small diameter main at back of properties

bagging off The technique of stopping off the flow through a main, by inserting and inflating bags in the main.

barometric pressure The downward pressure, at any given point in the atmosphere, of the gases directly above that point.

branch A connection usually at right angles, often to a larger main.

butt fusion A method of jointing PE pipes and fittings, where the two pipe ends are heated and brought together to be fused without the use of a separate fitting.

butt welding A method of jointing metallic pipes and fittings where pipes and fittings of the same diameter are welded, by bridging the gap between them with successive deposits of weld metal.

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by-pass A pipe valve and gauge system, used to provide and control the continuity of gas supplies, normally used when alterations to pipelines are carried out.

carrier pipe The existing pipe into which another pipe is inserted.

cathodic protection A method of inhibiting corrosion of buried metallic pipe, fittings etc., by ensuring that they are permanently cathodic, i.e. electrically negative, to the electrolyte in the soil surrounding them.

close circuit television Method used to internally survey pipes

close-fit insertion An insertion technique where the new pipe is in close contact with carrier pipe. See folded pipe, swagelining, rolldown etc.

collar A fitting used to join together the plain ends of two pipes

continuity bond An electrical connection made between two sections of a metallic pipe prior to and during their temporary severance, to prevent sparking from stray currents or static electricity.

controlled gas operation Work undertaken on gas mains where the release of gas is controlled and minimised.

creep Deformation of material over time, under constant stress.

cross bonding Means of ensuring electrical continuity between gas pipe-work and the customer’s electricity supply earth terminal

cut-out A section of pipeline to be isolated for replacement, repair or the installation of an in-line tee to extend supplies.

decay test Test applied before a main is to be decommissioned to establish that there are no services still attached to the main or there are no unknown backfeeds that will prevent the decommissioning

design pressure (dp) The pressure on which design calculations are based

dip pipe A pipe inserted in a pipeline for removal of condensate and other liquids

directional drilling Pipe moling technique

double block and bleed Two flow stopping devices (both of which may be incorporated in an individual block valve of appropriate design) with a vent between them. Also known as a block and bleed.

double block and bleed valve

A valve with two seats and a space between to which is connected a bleed point

duct (also see “sleeve”) An encasement installed to protect a pipe or to facilitate its passage through or under a structure

easement (Property Law) is the right enjoyed by a landowner of making limited use of his/her neighbour’s land as by crossing it to reach his own property

elastomeric electrofusion

A generic term for materials, such as synthetic or natural rubber. Method of jointing PE pipe, using fittings having integral heating coils.

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emergency control valve (ecv)

An Emergency Control (Valve) means a valve for shutting off the supply of gas in an emergency, being a valve intended for use by a consumer of gas

encirclement fitting Two part fittings installed around a pipe jointed together longitudinally and jointed to the pipe circumferentially at each end.

flanged adaptor A fitting with a flange on one side and a suitable fixing for the appropriate pipe on the other.

flexible joint A joint usually incorporating elastomeric seals, designed to accommodate movement of pipes.

foaming off The use of expanding foam injected into the main, which sets to stop the flow of gas

folded pipe Technique where the pipe is folded to reduce its size prior to insertion and is reverted to its original shape by pressure

fusion gauge pressure Pressure shown on a gauge, with no allowance for barometric pressure.

gauging Method of checking for size and suitability of the pipe into which insertion is to take place

Horizontal directional drilling

See Directional Drilling

high density polyethylene (PE100)

PE pipe of higher density and laid to either higher pressure than medium density polyethylene or a thinner wall thickness.

high pressure Operating pressures greater than 7 bar

impact moling A technique utilising a tool (mole) comprising of a percussive hammer

imported backfill Backfill brought from off-site

impressed current A system of cathodic protection, using an external electrical source

insulation joint A fitting having a high electrical resistance

intermediate pressure Operating pressures greater than 2bar but not exceeding 7bar

internal inspection A means of ascertaining the internal condition of a pipe

iris stop Technique for stopping off the flow through a main, by inserting and inflating bags in the main that are supported by a metallic plate

landfill gas The mixture of gas produced as a result of microbial activity, when biodegradable material is deposited in landfill sites.

lateral A pipe forming part of a service, extending from a riser up to and including a primary emergency control valve.

leakage survey A systematic search for escapes of gas.

live insertion Installation of a replacement pipe into an existing pipe, whilst the host pipe remains live and in use.

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low pressure Operating pressures not exceeding 75 mbar.

lower explosive limit (LEL)

The concentration of flammable gas in air, above which ignition can occur.

lower flammable limit (lfl)

The concentration of flammable gas, vapour or mist in air, above which combustion can be sustained.

mains bursting See Pipe Bursting

maintenance The combination of all technical and associated administrative actions intended to retain an item in, or restore it to, a state in which it can perform its required function.

marker plate Plate giving details of buried gas plant.

marker post Post installed close to buried gas plant, to which a marker plate is affixed.

maximum incidental pressure (mip)

The maximum pressure to which the system may be subjected under abnormal conditions.

maximum operating pressure (mop)

The maximum pressure at which a system can be operated continuously under normal conditions.

maximum working pressure

The maximum pressure to which a main will be normally subjected whilst in operation.

medium pressure Operating pressures greater than 75 mbar but not exceeding 2 bar.

melt bead A lip of PE displaced during butt fusion of a pipe.

meter inlet valve (miv) A valve fitted upstream of, and adjacent to, a gas meter to shut off the supply of gas.

mismatch Dimensional irregularity of two pipes to be jointed.

mole See Impact Moling

mole ploughing Technique for installing a continuous length of pipe by pulling a pipe through the ground and feeding the pipe into the trench via the top of the plough

multi layer pipe SDR 21 HDPE

white pipe encased in a protective yellow sleeve with brown longitudinal stripes.

National Geospatial System (NGS)

A computerised map based records system for distribution and transmission mains operating pressure (op) The pressure which occurs within a system under normal conditions.

peak instant demand The highest instantaneous gas demand, normally measured at a rate per hour, which occurs over a 60 second period.

pig A cylindrical device that is inserted into a main to clean/dry the pipeline, gauge its diameter.

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pipe bursting A technique in which the existing pipe is fractured using an internal mechanical force (burster), that forces the fracture pieces into the surrounding ground whilst a new pipe of a similar or larger diameter is drawn in behind the bursting tool. Usually used on cast or spun iron.

pipeline A system of pipework with all associated equipment and stations up to the point of delivery. This pipework is mainly below ground (buried) but includes above ground pipework.

pipe splitting A similar technique to pipe bursting, but the internal mechanical force splits the main with a cutting tool. A new pipe of similar or larger diameter is drawn in behind the splitter tool. Used on ductile iron and steel.

Polyethylene Plastic pipe used in main laying activities.

polyethylene sleeving Polyethylene sheet, which was snugly wrapped around the outside of ductile iron pipes, to provide corrosion protection.

pressure Bar or mbar above atmospheric pressure, i.e. gauge pressure (1 bar = 100,000 Nm m-2)

primary meter A meter connected to a main or service, the index reading of which constitutes the basis of charge for all gas supplied through that main or service.

pup A short make-up piece of pipe.

purge Displacement of one type of gas with another.

purge gas The gas that is used for displacement when purging.

reinstatement The backfilling, compaction and resurfacing of any excavation, in order to restore the surface and its underlying structure to enable it to match its previous performance.

rider A series of pipes constructed to allow the purge of a system to gas.

riser The vertical part of a service leading to one or more primary meter control valves or ECV.

rolldown A Close-fit Insertion technique, where the diameter of the new pipe is reduced by pulling it through concentric rollers. The pipe can be inserted by Slip Lining techniques and is reverted to its original diameter by pressurizing with warm water.

route maps Maps to a scale suitable for showing general details, for example agricultural land, built-up areas, contours and all special crossings.

sacrificial anodes A means of corrosion protection for buried equipment. A mass of relatively electro-positive metal, such as magnesium or zinc, electrically connected to a pipeline, to ensure that the pipe is maintained as the cathode in a galvanic cell.

saddle A fitting that conforms to the shape of a main and is used for making a connection to a main.

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saddle fusion Jointing of a shaped fitting onto the outside wall of a PE pipe.

service A pipe for supplying gas to premises from a distribution main, being any pipe between a distribution main and the outlet of an ECV.

service excess flow valve

A device, installed in an M.P. service, designed to reduce the flow of gas released from a damaged pipe

service head adaptor A fitting used to provide a gas-tight seal between a PE service, its steel

service isolation valve A valve inserted in a service, outside a building, for shutting off the supply of gas

service regulator service tee

Apparatus for automatic regulator of pressure or of volume flow at a selected point within a service

sliplining Insertion of a new pipe by pulling or pushing it into the existing decommissioned pipe

single stage regulator A regulator which breaks down inlet pressure to outlet pressure in a single stage

sleeve (also see “duct”) An encasement inserted into a prepared hole in a structure for the reception of a service

split collar A fitting in two halves, installed around a live main, for making connections or repairing a broken or leaking main

squeeze off Squeezing a pipe to close the bore and stop the flow of gas.

standard dimension ratio (sdr)

The ratio of the outside diameter of a PE pipe to the minimum specified wall thickness

standpipe A small diameter pipe, connected vertically to a pipeline

strength test A specific procedure to verify that pipework meets requirements for mechanical strength

strip maps Maps, to a large scale, showing the route of the pipeline and which may contain marginal notes etc., giving information on land usage, ownership etc. and profiles

syphon A vessel installed at a low point in the pipeline network, to collect condensate and other liquids

swagelining A Close-fit Insertion technique, where the diameter of the new pipe is reduced by pulling it through a circular die. The pipe can then be inserted by slip lining techniques, and subsequently reverts to its original diameter when pressurized.

tightness test A specific procedure to verify that pipework meets requirements for gas tightness

trenchless technology Techniques for installing pipe with minimal excavation

two-stage regulator A regulator which breaks down inlet pressure to outlet pressure in two stages in order to give a compact design with good control of outlet pressure

underpressure tee Split fitting used to take a branch connection from a pressurised pipe

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vent pipe (main) Small diameter pipe, utilised for ventilating gases from a main that is connected vertically the a main and terminated 2.5m above ground level and constructed from steel

vent pipe (service) Small diameter pipe connected vertically to a pipeline and terminated with a flame trap 2.5m above the ground level.

voltstick This is a device for detecting the presence of an AC voltage on exposed metalwork.

wayleave Access to property granted by a landowner for payment, for example to allow NGT access to its towers.

weldolet A forged fitting, of the saddle type, enabling the fabrication of a fully welded branch connection.

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Abbreviations

AE Authorising Engineer

AECV Additional emergency control valve

AGI Above Ground Installation

BS British Standard

CCTV Closed circuit television.

CP Competent Person or Cathodic Protection

CTA Certified Training Achievement

CV Calorific value.

DP Design pressure.

DPC Damp proof course

ECV Emergency control valve.

EIA Environmental Impact Assessment.

HDPE High Density Polyethylene

HP High Pressure

HSE Health and Safety Executive

HS&E Health Safety and Environment

IGEM Institution of Gas Engineers and Managers

IP Intermediate Pressure

LEL Lower Explosive Limit

LFL Lower flammable limit

LOP Lowest operating pressure

LP Low Pressure

LPG Liquefied petroleum gas (commercial butane, C4H10 and commercial propane, C3H8 or mixtures or combinations thereof).

MDPE Medium Density Polyethylene

MIP Maximum incidental pressure.

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MIV Meter inlet valve.

MOP Maximum operating pressure.

MP Medium Pressure

MRS Minimum required strength.

NA Network Analysis

NDT Non-destructive testing.

NRO Non Routine Operation

OP Operating pressure.

PE Polyethylene

PRE Public Reported Escape

PRI Pressure regulating installation.

PSR Pressure System Regulations

PSSR Pressure System Safety Regulations

PTW Permit to Work

PVC Polyvinyl chloride.

QC Quality control.

RO Routine Operation

SDR Standard dimension ratio.

SEFV Service excess flow valve.

SROH Specification for the Reinstatement of Openings in Highways

SCO Safe Control of Operation

SIV Service isolation valve.

STC Safety and Technical Competency Framework

STP Strength test pressure.

SWL Safe Working Load

procedure for the design construction of distribution syste

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