bp rp4-1.pdf

RP 4-1

DRAINAGE SYSTEMS

November 1994

Copyright © The British Petroleum Company p.l.c.

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Copyright © The British Petroleum Company p.l.c.

All rights reserved. The information contained in this documentis subject to the terms and conditions of the agreement orcontract under which the document was supplied to therecipient's organisation. None of the information contained inthis document shall be disclosed outside the recipient's ownorganisation without the prior written permission of Manager,Standards, BP International Limited, unless the terms of suchagreement or contract expressly allow.

BP GROUP RECOMMENDED PRACTICES AND SPECIFICATIONS FOR ENGINEERING

Issue Date November 1994

Doc. No. RP 4-1 Latest Amendment DateDocument Title

DRAINAGE SYSTEMS

(Replaces BP Engineering CP 5)

APPLICABILITYRegional Applicability: International

SCOPE AND PURPOSE

This document gives guidance on the design, construction, operation and maintenance ofdrainage systems in land-based installations.

AMENDMENTSAmd Date Page(s) Description___________________________________________________________________

CUSTODIAN (See Quarterly Status List for Contact)

Civil Engineering & Geotechnics

Issued by:-Engineering Practices Group, BP International Limited, Research & Engineering CentreChertsey Road, Sunbury-on-Thames, Middlesex, TW16 7LN, UNITED KINGDOMTel: +44 1932 76 4067 Fax: +44 1932 76 4077 Telex: 296041

RP 4-1DRAINAGE SYSTEMS PAGE iv

CONTENTSSection Page

FOREWORD ................................................................................................................. i

1. INTRODUCTION................................................................................................... 11.1 Scope .................................................................................................................. 11.3 Legislation and Standards .................................................................................... 1

2. DESIGN OF DRAINAGE SYSTEMS.................................................................... 22.1 General................................................................................................................ 22.2 Integration with Processes ................................................................................... 22.3 Waste Minimisation ............................................................................................. 22.4 Fugitive Emissions of Hydrocarbon Gases............................................................ 22.5 Future Developments........................................................................................... 32.6 Design Factors..................................................................................................... 32.7 Effluents .............................................................................................................. 32.8 Effluent Types ..................................................................................................... 42.9 Effluent Segregation ............................................................................................ 62.10 Types of System ............................................................................................... 7

3. EFFLUENT VOLUMES......................................................................................... 93.2 Rainfall Intensities.............................................................................................. 103.3 Firewater Volumes ............................................................................................ 103.4 Groundwater Infiltration .................................................................................... 133.5 Bunded Tank Area Flow Capacity ..................................................................... 133.6 Water Discharge ................................................................................................ 13

4. LAYOUT AND CONFIGURATION ................................................................... 134.2 Process Areas .................................................................................................... 134.3 Offsites Areas .................................................................................................... 164.4 Treatment .......................................................................................................... 204.5 Measurement ..................................................................................................... 21

5. HYDRAULIC DESIGN ........................................................................................ 215.1 General.............................................................................................................. 215.2 Gravity-based Drainage Systems........................................................................ 215.3 Closed Drainage Systems................................................................................... 25

6. STRUCTURAL DESIGN OF BURIED PIPEWORK......................................... 306.1 Backfill.............................................................................................................. 306.2 Road and Rail Crossings .................................................................................... 306.3 Loads During Testing ........................................................................................ 316.4 Thermal Expansion ............................................................................................ 316.5 Submerged Pipes ............................................................................................... 316.6 Settlement ......................................................................................................... 31

RP 4-1DRAINAGE SYSTEMS PAGE v

7. SECONDARY CONTAINMENT......................................................................... 317.2 Exfiltration ........................................................................................................ 317.3 Infiltration ......................................................................................................... 32

8. ANCILLARY STRUCTURES.............................................................................. 328.1 Manholes........................................................................................................... 328.2 Gully Traps........................................................................................................ 378.3 Open Ditches and Channels................................................................................ 388.4 Effluent Collection and Treatment (Neutralisation) Pits...................................... 398.5 Pumping Sumps................................................................................................. 398.6 Soakaways and Land Drains .............................................................................. 398.7 Cesspools and Septic Tanks............................................................................... 39

9. CONTROL OF FUGITIVE GAS EMISSIONS AND VENTING OFDRAINAGE SYSTEMS........................................................................................ 409.1 Control of Fugitive Gas Emissions ..................................................................... 409.2 Design of Vents for Open Gravity Drainage Systems ......................................... 419.3 Extraction and Treatment of Vented Gases ........................................................ 42

10. MATERIALS ........................................................................................................ 4310.1 General........................................................................................................... 4310.2 Resistance to Effluents.................................................................................... 4310.3 Strength.......................................................................................................... 4410.4 Joints .............................................................................................................. 4410.5 Other .............................................................................................................. 44

11. CONSTRUCTION AND WORKMANSHIP....................................................... 4411.1 Introduction.................................................................................................... 4411.2 Construction................................................................................................... 4511.3 Connections to Existing Sewers ...................................................................... 4511.4 Testing ........................................................................................................... 4511.5 Back-filling..................................................................................................... 4611.6 Cleaning ......................................................................................................... 46

12. OPERATION AND MAINTENANCE................................................................. 4612.2 Cleaning ......................................................................................................... 4612.3 Inspection....................................................................................................... 4712.4 Rehabilitation.................................................................................................. 4812.5 Operational Procedures (Closed System Only) ................................................ 49

TABLE 1 ..................................................................................................................... 51SUMMARY OF ALTERNATIVE DRAINAGE SYSTEMS................................... 51

TABLE 2A................................................................................................................... 52MATERIAL SELECTION...................................................................................... 52

TABLE 2B................................................................................................................... 53MATERIAL SELECTION...................................................................................... 53

RP 4-1DRAINAGE SYSTEMS PAGE vi

FIGURE 1 ................................................................................................................... 54PRESSURISED DRAINAGE SYSTEM - TYPICAL ARRANGEMENTS ............. 54

FIGURE 2 ................................................................................................................... 55PRESSURISED DRAINAGE SYSTEM -............................................................... 55TYPICAL CONNECTION ARRANGEMENT....................................................... 55

FIGURE 3 ................................................................................................................... 56PRESSURISED DRAINAGE SYSTEM -............................................................... 56TYPICAL LINE DIAGRAM OF COLLECTION SYSTEM ................................... 56

FIGURE 4 ................................................................................................................... 57PUMPED DRAINAGE SYSTEM - TYPICAL ARRANGEMENTS....................... 57

FIGURE 5 ................................................................................................................... 58MANHOLE GULLY DETAIL................................................................................ 58

FIGURE 6 ................................................................................................................... 59TYPICAL SEALED MANHOLE COVERS ........................................................... 59

FIGURE 7 ................................................................................................................... 60TYPICAL STANDARD 150 MM GULLY TRAP .................................................. 60

FIGURE 8 ................................................................................................................... 61TRAPPING OF DRAIN INLETS TO MANHOLES ............................................... 61

FIGURE 9 ................................................................................................................... 62TYPICAL OFFSITES STORAGE TANK OILY AND CLEAN WATERDRAINAGE LAYOUT........................................................................................... 62

APPENDIX A.............................................................................................................. 63DEFINITIONS AND ABBREVIATIONS .............................................................. 63

APPENDIX B.............................................................................................................. 64LIST OF REFERENCED DOCUMENTS............................................................... 64

RP 4-1DRAINAGE SYSTEMS PAGE i

FOREWORD

Introduction to BP Group Recommended Practices and Specifications for Engineering

The Introductory Volume contains a series of documents that provide an introduction to theBP Group Recommended Practices and Specifications for Engineering (RPSEs). In particular,the 'General Foreword' sets out the philosophy of the RPSEs. Other documents in theIntroductory Volume provide general guidance on using the RPSEs and backgroundinformation to Engineering Standards in BP. There are also recommendations for specificdefinitions and requirements.

Value of this Recommended Practice

This document represents the accumulated knowledge of BP in onshore drainage from avariety of operating sites and projects. There are no comprehensive external documentsaddressing this specialised area, other documents being concerned predominantly with urbanwastewater drainage. Provision of adequate drainage systems has wide ranging safety andenvironmental implications which are addressed in this document to allow cost effective designto be achieved.

Application

Text in italics is Commentary. Commentary provides background information which supportsthe requirements of the Recommended Practice, and may discuss alternative options.

This document may refer to local, national or international regulations but the responsibility toensure compliance with legislation and any other statutory requirement lies with the user. Theuser should adapt or supplement this document to ensure compliance for the specificapplication.

Principal Changes from Previous Edition

Alternatives to gravity flow drainage; inspection and rehabilitation; and workmanship andconstruction, are now covered.

Feedback and Further Information

Users are invited to feed back any comments and to detail experiences in the application ofBP RPSE's, to assist in the process of their continuous improvement.

For feedback and further information, please contact Standards Group, BP International or theCustodian. See Quarterly Status List for contacts.

RP 4-1DRAINAGE SYSTEMS PAGE 1

1. INTRODUCTION

1.1 Scope

This Recommended Practice gives guidance on the design,construction, operation and maintenance of drainage systems inrefineries, terminals, pipeline associated installations, chemical plants,drill-sites and jetties.

The design recommendations given are intended to form the basis of adetailed design package to be prepared prior to construction tender.

It does not include requirements for drainage systems on offshoreplatforms, which are covered in BP Group RP 44-11.

Guidelines are provided for the design of open and closed systems. Forclosed systems, reference should be made to BP Group RP 42-1, PipingSystems for detailed specification of material where appropriate

This Recommended Practice does not include a comprehensive listing of alllegislation, regulations, codes of practice and standards applicable to the detaileddesign of drainage systems. It is the responsibility of the designer to ensure that themost recent version of the appropriate codes of practice and standards relevant tothe proposed location are used for the design, construction and testing of thesystems.

1.2 The basic requirement for the drainage system is to provide a safe,reliable and economic system for the collection and transport ofeffluents and surface water to treatment areas and discharge points.Due regard should be given to the effect of effluent beyond the point ofdischarge with respect to quantities and quality of the effluent. Theoverall system should be kept as simple as possible in terms ofconstruction, operation and maintenance; usually this means that open,gravity based drainage systems will be used for wastewater effluentdrainage where legislation permits.

The design of plant drainage and sewer systems shall be subject toOwner's approval.

It is recommended that the conceptual design is agreed with the Owner, prior todetailed design.

1.3 Legislation and Standards

The handling and disposal of effluents and surface water drainage issubject to the approval of the local authorities and the subject oflegislation within that country or state. Standards relating to gaseous


emissions, contaminants, and waste sludges shall be considered togetherwith the quality and quantity of effluent discharged. When constructingor upgrading a drainage system, consideration should be given tomeeting new, and possible future, standards.

When Standards set by the local authority, BP standards and currentlegislation are different, the most onerous standard shall be adopted.

2. DESIGN OF DRAINAGE SYSTEMS

2.1 General

It is essential for the drainage system to be considered in the very earlystages of the design of a plant as part of the initial infrastructuredevelopment layout.

In the UK, the drainage systems shall be designed generally in accordance with BS8005 and BS 6297 where applicable, except as otherwise described below.Elsewhere, equivalent local standards will be subject to review by BP.

2.2 Integration with Processes

Consideration should be given to the integration of drainage into theprocess facilities. If process conditions permit, this may providefinancial savings.

It may be useful to incorporate the drainage system into the P&I diagram.

2.3 Waste Minimisation

The principles of waste minimisation should be followed.

Every effort should be made to reduce unnecessary mixing of water, oils andchemicals before entering the drainage system e.g. oil slops can be collected indrums and not poured into the drains, solid wastes can be screened and localseparators used. Such procedures should be revised and equipment modified so thatwaste is reduced.

2.4 Fugitive Emissions of Hydrocarbon Gases

Fugitive emissions of hydrocarbon gases from conventional gravitydrainage systems can be reduced by changing work practices andmethods of operation (see section 9). New drain systems can beinstalled which can almost eradicate fugitive emissions (see clause2.10.2). These new drains are however expensive to install and morecomplex to operate. The major cost savings are derived by avoidingdischarge of oily materials into the drainage system.


2.5 Future Developments

The future use of technology to automatically monitor flow-rates and effluentcomposition in drainage systems may allow operations to be better regulated.

2.6 Design Factors

There are many factors to be taken into account when considering theselection and planning of a drainage system. The following is a list oftechnical and financial considerations to be assessed by the designer:-

(a) Safety of the system with respect to the site for which it isselected.

(b) The nature and quantity of effluent to be conveyed.

(c) Effluent segregation requirements.

(d) Legislative/environmental/social considerations.

(e) Cost:-

(i) construction(ii) operation and maintenance.

(f) Design life.

(g) Location of existing buildings and services (to be connected ornegotiated).

(h) Topography of the site.

(i) Method of construction and associated disruption of operations.

(j) Material, jointing method, size, length and depth of pipework.

(k) Condition of existing service.

(l) Secondary containment requirements.

(m) Site ground conditions which may affect the method andmaterials of construction and consequently the cost.

(n) Ground contamination


2.7 Effluents

The range of possible effluents can vary significantly. At an early stageof design every source of effluent should be identified.

The characteristics of all materials present in the system should beassessed. These include the estimated maximum and minimum rates offlow, concentration, the maximum temperature (and temperaturefluctuations) of the effluent, possible chemical reactions, effluentpressure upon entry and details of any possible future additionalmaterials in the system. Every effort should be made to segregate cleanand contaminated water.

Where connecting to existing plant or drainage systems, effluent details should beprovided by BP. Otherwise the process design contractor should provide thisinformation.

2.8 Effluent Types

A range of possible effluents is described below; these descriptions area guide, and there are no distinct boundaries between the categories.Exact definitions will depend on legislation and the treatment facilitiesavailable.

2.8.1 Clean Water

Water that is not liable to be contaminated under normal operatingconditions and can normally be discharged from the site without furthertreatment.

This will usually originate as rainwater or in some cases as emergency fire coolingwater.

2.8.2 Contaminated Water

Water from areas liable to be contaminated e.g.:-

(a) Run-off from contaminated paved areas.

(b) The use of hoses for wash-down and fire-fighting incontaminated areas.

(c) Laboratory wastes

Some areas may be contaminated indirectly, e.g. by particle fall-out from stacks -this may even come from outside the site boundary.

2.8.3 Oily-water


Water contaminated by oil to varying degrees may originate at thefollowing sources:-(a) Drainage from pipe trenches.

(b) Spillages and leaks from process equipment.

(c) Cooling-water from water cooled glands and bearings.

(d) Drainage from sample points, level gauges, drain cocks etc.

(e) Water from transformer bays.

(f) Pump stations, meter proving stations, manifolds, roof drainsfrom floating storage tanks.

(g) Drainage from circulating cooling-water systems which may becontaminated with oil.

2.8.4 Acids, Chemicals, Solvents and Other Process Fluids

Discharges of these effluents should generally be regulated as part ofthe production process. Reference should be made to P&I diagrams fordetails.

These effluents should preferably be intercepted and re-processed rather thandischarged after treatment.

2.8.5 Liquefied Gas LPG/LNG

Discharges from spills and routine maintenance.

2.8.6 Lead-alkyl Compounds

Lead-alkyl compounds are found at the following sources:-

(a) Leaded motor spirit tankage(b) TEL/TML blending plants(c) Leaded motor spirit pumps

2.8.7 Detergents

Detergents may be used in washing-down plant or vehicles.

2.8.8 Solids


Solid waste can be either particulate matter such as clay particles, or aproduct of the industrial process such as pellets or granules.

Solid effluents should be avoided wherever possible (with the exceptionof 2.8.9).

2.8.9 Domestic Sewage

This includes waste from toilets, washrooms, kitchens and cleanerssinks, (but not from laboratories)

Domestic sewage systems are also known as "Foul" or "Sanitary" drainage systems.

2.9 Effluent Segregation

2.9.1 The number and types of systems have to be optimised because of limitson cost and the available space taken by the systems.

Ideally each effluent will have its own segregated drainage system with each systemspecified in terms of capacity, ancillary structures, fittings and materials inaccordance with the particular requirements of that effluent. The waste treatmentfacility would also be effluent specific, hence more efficient.

2.9.2 The degree of effluent segregation will depend on various factors thatare covered below:-

2.9.2.1 System Specification

The specification and features of a system containing a mixture ofeffluents shall be those of the effluent that requires the highest level ofintegrity and treatment. All branches and feeders joining the systemshall also meet this specification unless special precautions are taken toisolate them, e.g. suitable water seals.

If the effluent requiring most treatment is of sufficiently low concentration forlegislation not to apply, the requirement for the highest level of integrity may bevaried.

2.9.2.2 Reactions

Physical, chemical or biological reactions between effluents may restrictthe amount of mixing allowed, e.g. detergents in oily wastes harm thetreatment process, and solvent mixing with water (at temperature abovesolvent boiling point) causes boil-outs - a release of vapour.

2.9.2.3 Treatment


The dilution of a concentrated effluent by large volumes of water mayreduce the effectiveness of the treatment process and cause the cost oftreatment to rise as the size of the plant required (perhaps bylegislation) increases.

2.9.2.4 Varying Flow Rates

To prevent siltation and blockages in the pipes, a minimum velocityshall be achieved. This may be compromised if a shared system is sizedto cater for intermittent large flows while the continuous flows aresmaller (see clauses 5.2.3 to 5.2.6).

2.10 Types of System

Vented piped gravity drain systems are cheap and commonly used.Higher integrity drainage systems should be considered if the increase incosts can be justified for reasons such as environmental, safety orlegislative requirements.

The following sections provide guidance on types of drainage systemand their basic features. Table 1 lists the advantages and disadvantagesof the main drainage system types.

Table 1 is intended to provide initial guidance. The final type(s) of system and thefeatures required will depend on the types and quantities of effluent to be drained,and the legislative requirements.

2.10.1 Open Gravity Systems

2.10.1.1 Vented Piped Gravity Drain System.

The effluent flows in pipes laid to suitable falls between manholes. Themanhole inlets shall be trapped and manholes vented. Traps are requiredto prevent the spread of fire when the effluent system containsflammable gases or liquids. Vents are needed to maintain atmosphericpressure in each section of pipe avoiding pressure locks developing inthe system. Gullies are also trapped. Vapours expelled from the systemshould be kept to a minimum.

Traps in manholes are achieved by installing dip pipes as shown inFigure 8.

In the case of third-party or acquired installations, existing traps may consist of atotally submerged system controlled by a weir in the downstream manhole or by useof a system with conventional 'straight-through' manholes but with totallysubmerged pipes laid as inverted siphons.

2.10.1.2 Ditch Gravity Drain System


The effluent flows in open channels or drains normally lined, and laid tofalls or level. The channels/ditches shall be trapped to prevent spread offire.

2.10.2 Closed Systems

There may be legislation or safety reasons to restrict gaseous emissionsto atmosphere from drainage systems. If this is the case, certain oily-water and chemical systems will need to be closed to the atmosphere.Process information should also be used to identify which effluentstreams should also be closed.

There are three types of closed system that can be considered:-

(a) Closed gravity systems(b) Pumped systems(c) Pressurised systems (or vapour recovery/purged systems)

The United States is leading the way with rigorous legislation on air quality andground contamination related to drainage systems on industrial sites. There arerestrictions on the amount of Volatile Organic Compounds (VOCs) that can bereleased to the atmosphere. Several European countries are also developinglegislation that will have an impact on the types of drainage system commonly usedby BP, such as vented systems with traditional un-contained, spigot and socketpipes.

In all cases the maximum process pressure must be established and used to designthe pipework.

2.10.2.1 Closed Gravity Systems

The system is configured as a conventional gravity system with sealedaccess manholes and with a gas vent collecting system. The materialsand construction techniques used are of a higher integrity than withopen systems. Generally joints are welded and tested to higherstandards.

Connections to the drainage system are by air-tight connections attanks, bunds, process units, etc. At changes of gradient and direction,bends are used instead of manholes. Changes of pipe size are madeusing flat backed tapers. Connections from laterals to the main sewerline are by flat tees or branches.

To ease cleaning of the system, rodding points are provided; these takethe form of a 'Y' branch on the sewer pipe with the branch pointingupwards and extended to a suitable access point.

2.10.2.2 Pumped Systems


Pumped systems are closest to normal process lines and may be runbelow or above ground. Two types of pumped system may beconsidered in the drainage design:-

(a) Effluent lift stations to lift flow from one gravity system anddeliver to a second similar system. Such stations contain onlyshort lengths of pressurised pumping main local to the liftstation.

(b) Pumping stations with associated pumping mains to lift anddeliver to a distant treatment facility. Such systems contain longlengths of pressurised pumping main. These are normallylocated above ground but can be buried as necessary.

The main components of pumped systems are:-

(1) Localised gravity systems feeding to the lift/pumping stationsump.

(2) The effluent lift/pumping station

(3) A pressurised pumping main

2.10.2.3 Pressurised Systems

The pressurised drainage system flows under gravity but without theaccess manholes and without conventional venting. The vapour spaceabove the liquid flow is large enough to allow displacement of gasesabove the liquid level. The air space is then filled with an inert gas atlow positive pressure.

The inert gas is injected at discrete points in the system to preventaccumulation of hazardous vapours. Venting of the inert vapour mixedgas is provided at a controlled vent facility where the gases areremoved for treatment.

Connections to the drainage system are by air-tight connections thatwill have a pressure reducing and isolating valve. These connections aregenerally above ground for ease of access.

Bends, pipe size changes, connections to laterals and rodding points areas for closed gravity systems (see clause 2.10.2.1).

This system is difficult to operate and maintain, and is expensive toinstall and operate.


3. EFFLUENT VOLUMES

3.1 Systems draining paved and/or unpaved areas should be designed forthe greater of the following:-

either

(a) Firewater case = Firewater plus effluent, or

(b) Rainwater case = Rainwater plus effluent

'Effluent' includes all dry-weather flow. Usually process and domesticeffluents flow continuously in comparatively limited volumes. Thesevolumes can be obtained from process information or standard tables.Drainage systems carrying these effluents shall not be allowed to flood.

It is more difficult to determine water quantities, whether the source israin or firewater. Guidance is given below on how to estimate likelyvolumes:-

3.2 Rainfall Intensities

3.2.1 A range of storm return periods between 1 and 10 years should be usedfor different areas on a site depending on how acceptable the risk offlooding is in each catchment area and the balance of risk and cost.

For example in tank-farms where risk is low and some flooding could be tolerated areturn period of average once in 1 year would be acceptable. Where designcapacity cannot be exceeded so frequently, e.g. sections of treatment plant, then anacceptable return period would be higher e.g. average once in 10 years.

A storm with an average return period of once in 10 years will be of the order of25% to 50% greater than a one year return period storm, although this will dependon the rainfall history of the area. This will affect the size of the drainage systemrequired.

3.2.2 The contributing area for rainfall drainage to the sewers shall beassumed to be 100% of the paved area.

The contribution of runoff from unpaved areas should be considered ona case by case basis. This may constitute a significant proportion of theflow.

Where the time of concentration is less than 10 minutes, the maximumhourly rate of rainfall may be applied as a 'flat' rate.

Where rainfall rates are not specified, design should be based on formulae derivedfrom local records, or in the UK on Table 3 of BS 8005


3.3 Firewater Volumes

3.3.1 Area - Fire Exposed Envelope

The area in which a fire should be contained shall be determined. Thiscould be a bunded area or a part of a process unit. The area shall bedetermined by considering the consequence of a fire incident spreadingfrom one area to another. (Fire Risk Analysis - see BP Group RP 24-1).

3.3.2 Volumes

The volumes of firewater should be contained or controlled in apredetermined area (fire exposed envelope) such that the firewater doesnot cause spread of the fire by flowing into adjacent areas. Watershould be directed into the drainage system and/or areas where thewater can do no harm.

There are several methods of calculating firewater volumes. The first inclause 3.3.2.1 is recommended for initial sizing of the firewater system.For a more accurate calculation of volumes the methods in clauses3.3.2.2 to 3.3.2.5 should be followed, referring to BP Group RP 24-1.

3.3.2.1 Preliminary Design

As a guide, the total firewater demand for installations having a fire risk/hazard istypically between 800m3/hr and 2000m3/hr. Usually an average rate of 1360m3/hrwill be sufficient unless the plant is particularly congested, when a higher figureshould be used.

For preliminary design purposes it should be assumed that water will be applied asfollows:

(a) 70% evenly distributed over an area of 1000m2 located anywhere withinthe process area.

This is intended to cater for large plant areas where the firewater wouldrealistically be concentrated over a section only (i.e. 1000m2 - and notdispersed over the whole area resulting in an inadequately designed draincapacity.

(b) 100% evenly distributed over the whole of the process area.

For process areas of smaller than 1430m2, the maximum design intensity should notexceed that given by (a), unless BP specify otherwise.

In assessing the total firewater demand for any site, the area of plant with thelargest firewater demand will be used as the governing factor. However, should thisdemand exceed 2000m3/hr, consideration should be given to separation of part ofthe area or plant in question by passive means (e.g. physical separation by firewalls to reduce the demand to a more reasonable level.


3.3.2.2 Minimum Flow

Minimum flow is that required to contain the fire and is not normallyused for design of drainage systems.

Guidance is given in BP Group RP 24-1 on the volume of water that may be appliedin different types of process or tank storage areas and is based on the surface areaof plant and volumes of cooling water applied per unit area.

3.3.2.3. Design Flow

This should ideally be used as the basis of drainage design and is thefigure contained in the pre-fire plans. The design flow is based on theminimum flow and is adjusted in the fire risk analysis and firewaterlosses deducted.

Design Flow = Min. Flow + ∧V1(actual output) - ∧V2(firewater losses)

Typically the increase from minimum flow to design flow is 25% to 30% dependingon the equipment used, as the equipment can exceed its rated output. Mobilemonitors may need to deliver twice the volume of water to achieve the same coveras a fixed system.

3.3.2.4 Firewater Losses

It is recognised that some losses will occur between the firewater beingapplied and the water entering the drainage system; due to over-spray,evaporation, infiltration into surrounding ground etc. These losses willbe influenced by factors including climatic conditions, groundinfiltration (see clause 3.4), duration of water application, type ofapplication and structural types, and should be assessed on a case bycase basis.

3.3.2.5 Maximum Flow

This is the total flow rate from all the fire-fighting equipment (bothfixed and mobile) that could conceivably be directed on to a fire in a fireexposed envelope.

The consequences of over-application of water by flooding the drainage systemshould be evaluated with respect to escalating the fire. Maximum flow rates shouldonly be used if it is likely that design flow rates would be exceeded by the fire-fighters.

3.3.3 Combined Flow Rates

The consequences of applying design flow rates (or parts of these) toadjacent areas must be considered.


If for example a tank on fire threatens 3 adjacent bunded tanks, then the totalamount of water that must be drained is the design flow for each of the tanks, plusany allowance for foam for the tank on fire.

The design of downstream pipework must allow for the combination offlow rates from adjacent areas. Also the design of effluent treatmentand discharge facilities should be checked against combined flow rates.

3.4 Groundwater Infiltration

No allowance for groundwater infiltration should be made in the designof new drainage systems. In the analysis of existing systems, anallowance may be made based on site observations.

3.5 Bunded Tank Area Flow Capacity

The flow capacity of a bunded tank area drainage system shall allow forthe greater of:-

(a) Drainage of all accumulated rainwater within the bund in lessthan 4 hours.

(b) Continuous drainage of firewater used for cooling purposes (seeclause 3.3.1).

In both cases the tank base must not become submerged.

3.6 Water Discharge

Many countries require all drainage, including that used for fire protection to berendered harmless before being discharged into Local Authority drains, rivers, orthe sea. The exception to this is where water is being used for the protection of life.Proposals for new facilities must be referred to BP (Client) for approval (see clause4.4.2).

4. LAYOUT AND CONFIGURATION

4.1 The layout of the drainage systems should be decided at the same timeas the plant layout. The impact on drainage systems of futuredevelopments in plant, waste treatment facilities and improved practicessuch as waste treatment and vent gas extraction should also beconsidered.

Main drain lines should run along the edge of plant areas and roadswhenever possible, to minimise the impact of future drainage work onoperational areas.


4.2 Process Areas

4.2.1 Paved Areas

Process units are paved and divided into catchment areas to containwater using paving gradients and kerbing/bunds. The catchment areasare arranged and drained in such a way as to prevent, in a fire incident,the spread of firewater and/or flammable liquids to unaffected areas(see clause 3.3.1).

4.2.2 Area Layout

The shape and size of the catchment area draining to eachmanhole/gully should be related to the process equipment which itsurrounds so that ideally any leakage of liquids from that equipment willnot be directed under any other item of equipment before reaching adrainage system. This layout should be determined at an early stage ofdesign, in conjunction with the plant layout and using risk assessmenttechniques. The size of each catchment area should be minimised, whiletaking account of the most efficient drainage layout.

Within process areas, paving should be sloped at a gradient no flatterthan 1 in 80 in large open areas or 1 in 60 in restricted areas. Thevertical fall across paving should not exceed 250 mm. The use of 100mm kerbing/bunding around the perimeter of the catchment area andaround sensitive process units will aid containment of firewater and theseparation of effluents.

In determining the shape and features of each catchment area, it isimportant to maintain safe and convenient access routes for people andvehicles. Kerbs in certain areas may create trip hazards and limitvehicle access - ramps may be necessary.

4.2.3 Entry Points for Effluent into the Drain System

There are four main types of collection point for effluent entering thedrain system; manhole gullies, gully-traps, tundishes and channels.

All manhole gullies, gully-traps and tundishes shall be provided withrodding points.

4.2.3.1 Manhole Gullies

Where rain/firewater is to be drained from paved areas a combinedmanhole gully in the centre of each catchment area provides greatercapacity and a simpler system than a number of smaller gullies leadingto a trapped manhole. Figure 5 shows typical details for a manholegully. Details of manhole gullies are given in clause 8.1.3.


4.2.3.2 Gully Trap Connections

Individual trapped gullies are appropriate where lower volumes ofeffluent have to be collected. Figure 7 shows typical details for a 150mm gully trap. Within process plot limits, gullies should generally beconnected by individual lines from each to a manhole, which shall betrapped on entry to the manhole, in accordance with Figure 8.

Where the physical obstruction of foundations makes it difficult for gullies to beconnected to manholes in their section of the process area, connections may bemade to adjacent areas provided that they are suitably trapped.

Each end of the pipe connecting a gully to a manhole is to be trapped using a waterseal. This can lead to the following "double-trapping" effects.

(a) Depression of water seals and escape of vapour through the weakest.

(b) Increase in flow resistance; requiring additional hydraulic head on theupstream side of the gully to maintain hydraulic capacity. This can lead toflooding.

Hydraulic analysis of this situation has shown that the "BP Standard 100 mm gully"fails in case (a) above by allowing vapours to be released back into the processarea. Larger sized gullies (150 mm [see Figure 7] and 200 mm) designed inaccordance with clause 8.2.2 permit sufficient head to prevent escape of vapoursupstream and overcome the flow resistance in (b). However, where possible it isrecommended that combined manhole gullies (see clause 4.3.1) are used toovercome the double trapping effect.

4.2.3.3 Process Drain Connections

Process drain connections should be via tundishes.

Where several process drains connect to the underground drain system at the sameor closely adjacent locations, collector drains and branches may be used. In suchcases the collector drain shall be connected direct to a manhole, and trapped onentry.

4.2.3.4 Drainage Channels

Drainage channels are a suitable way to collect flows (especially largevolumes of water), when the risk of fire spreading due to flammableliquids and vapours is minimal and a combined drainage system isappropriate.

The disadvantage of open channels is that they could contain burning hydrocarbonfor the unrestricted length of the channel.

The use of concrete channels can simplify the drainage layout by reducing thenumber of manholes and associated underground pipework. The grading of thepaving can also be simplified with a single fall to the channel. Several proprietary


drainage channel systems are available. However, some of these contain plasticcomponents or polymer/concrete mixes which may be susceptible to chemical orhydrocarbon damage, and should be checked for suitability before use.


4.2.3.5 Valves

Valves may be incorporated into open and closed systems to isolatesections of pipe. Where located underground these should be mountedin suitable concrete valve pits.

4.2.4 Manhole Location

Manhole location should be determined at an early stage in layoutdesign. This will allow vents to discharge in safe areas with theminimum length of underground vent pipe.

Manholes should generally not be located in access-ways within processunits or where crane outriggers may be placed. When located outsideor on the edge of process units, they should, where possible, be at least5 metres (16 ft) from the edge of any road.

4.2.5 Drains Crossing Foundations

Drains should not be laid below or through structural foundations. Thedrainage system and foundations should be designed so that drains canbe laid above the upper surface of any foundation which they cross.

Precautions should be taken to allow for differential settlement where drains laid inunsupported ground (outside the limits of a piled foundation) join those laid withinor above a foundation.

Drainage positions and foundation types should be examined at an early stage withrespect to groundwater conditions to ensure compatibility.

4.2.6 Other Features

Placing roofs over items of process equipment or tanks will reduce the amount ofrainwater that becomes contaminated. This is especially useful where there is a lowfire-risk or where the firewater drain could be valved.

4.3 Offsites Areas

4.3.1 Oily Water

4.3.1.1 Oily Water From Storage Tanks

Water draw-off from oil storage tanks and roof drains (floating roofsonly) should be drained to the oily-water drainage system (see Figure9).

The most efficient way to carry out draw-off is to use an automatic valve whichshuts when the amount of oil reaches a pre-determined level. If this is not possible,then some form of segregation at source, usually consisting of a sump connected to


the oily water system may be necessary if control of the draw-off cannot beguaranteed. Excess oil released into the sump can be recovered.

The connection to the oily water system should be valved outside thebund. Ideally this valve should remain closed except when draining oilywater, under control, from the area.

If there are areas within the bunded area which are heavilycontaminated with oil (e.g. under valves/manifolds), they should ideallybe paved and connected to the oily water system (instead of the cleanwater system).

The storage areas should be sized to contain any products which arespilled, until they can either be passed into the drainage system orreturned to a tank.

The tops of the walls of any sumps should be sufficiently high to prevent rainwaterfrom within the bund flooding into the sumps during periods of intense andprolonged rain.

4.3.1.2 Oily Water From Storage Tanks With Leaded Product

Effluent from leaded motor spirit tanks shall pass to a combinedseparator within the bunded area. Water shall be drained off to the oilywater drainage system and motor spirit pumped back into the storagetanks. The outlet to the pit shall connect to a valve, outside the bund.This valve will normally be kept closed, so that drainage is only let intothe system when known to be lead free. See Figure 9.

The tops of the walls of any sumps should be at the elevation indicated in clause4.3.1.1.

4.3.1.3 Oily Water From Other Leaded Product Areas

Effluent from leaded motor spirit pumps shall pass to a combinedseparator within the bunded area. Water shall be drained off to the oilywater drainage system and motor spirit recovered.

Drainage from TEL/TML Blending Plants shall be intercepted by aholding pit. The outlet to the pit shall connect to a valve which willnormally be kept closed.

4.3.1.4 Oily Water From Transformer Bays

Generally, drainage will be to the oily water system via a trapped gully.Where transformer bays are remote from an oily water sewer, dischargemay be to a clean sewer although it is recommended that a valvedcollecting sump is used.


The requirement for oily-water drainage can be removed in areas of high rainfall ifa roof is constructed over the transformer bay and a sump is used to collectintermittent spills which can then be pumped out.

4.3.2 Clean Effluent

4.3.2.1 Clean Water From Storage Tank Areas

Rain and firewater from storage tank areas should be drained by theclean water drainage system, (see Figure 9).

Where the surface of the storage area is not naturally impermeable, alining material (rigid or flexible) will be required for both the surfaceand any features such as ditches and sumps. It is important to ensurethat any lining material is integrated properly with any under-tank liningsystem.

The surface of the ground within tank bunds should be graded to ashallow open channel around the inside of the bund. This shoulddischarge into a silt chamber and then via a pipe drain through thebund. The drain should be valved outside the bund in a convenientposition to enable the discharge to be controlled without an operatorhaving to enter the bunded area. Ideally the valve should be normallyclosed .

Where necessary to meet local authority or statutory requirements,interceptor pits should be provided. These would generally be sitedoutside the bund but before final discharge from the site.

4.3.2.2 Clean Water From Storage Tank Areas With Leaded Product

Requirements for clean water drainage are the same as for clause4.3.2.1

4.3.2.3 Clean Water From LPG Storage Areas

The drainage of surface water from the area around and under liquefiedgas storage vessels should be discussed and agreed with BP.

LPG storage areas in the UK are designed in accordance with HSG 34.

Excessive amounts of LPG will depress the water seals in the system and allow LPGto pass through the traps. This negates both the integrity of the trap and thehydraulic performance of the system.

If there is a discharge of LPG, there is a possibility that the gully seal may freeze.This phenomenon has previously been taken advantage of by designing LPG tankbund outlets so that the water seal freezes quickly to prevent loss of containment.Further advice is necessary if this is being considered as a solution.


4.3.2.4 Clean Water From Area Land Drainage

Rainwater falling on unpaved un-contaminated ground within theprocess area should normally be disposed of by natural percolation intothe subsoil and evaporation. Where the land is not sufficientlypermeable for this to be effective without undue ponding, the surfaceshould be graded to suitably located trapped gullies discharging to aburied pipe system. Where this is not practicable, land drains should beprovided.

Where pipe drains are required, they should be arranged to discharge into theclean water drainage system or such other system as may be specified by BP. It maybe necessary to remove additional sludge and grit from this system, and so largersumps should be provided.

4.3.3 Drainage from Buildings

4.3.3.1 Industrial Buildings/Workshops

Floor drains in pump or compressor houses and workshops shall beconnected to fully trapped and vented manholes when they form part ofa system draining oily or chemical contaminants. There shall be nopossibility of hazardous gases entering the building from the drainagesystem.

4.3.3.2 Control Rooms

No drains are permitted within control rooms. In other areas of controlbuildings, electric substations and switchrooms, the appropriate type ofdrainage systems (usually sewage wastewater) are allowed.

4.3.3.3 Laboratory Drainage

To maintain control over waste disposal, laboratory collection pointsshould be used. Uncontaminated waste liquids can be drained to thesewage wastewater system.

It is not good practice to dispose of laboratory waste via the sink system, as this caninvolve the need for costly glass drainage systems within the laboratory.

4.3.4 Other Buildings

Other buildings can generally be connected to the sewage wastewatersystem, when only "domestic type" waste is being drained. Canteensshall be connected via a grease trap.


4.4 Treatment

4.4.1 Effluent Treatment

The treatment of oily and chemical waste and subsequent dischargemust conform to the requirements of the local and national authorities,in addition to meeting BP's own requirements relating to health, safetyand the environment.

It is anticipated that an effluent treatment plant would feature low shear pumps,storage capacity, primary separation, filters and biological treatment.

4.4.2 Holding Basins

The discharge of the system will be specified by BP.

Although some local authorities may permit direct discharge into a river or the sea,it should generally be assumed that future, more onerous requirements may requiresome form of holding basin and/or treatment plant to be installed. Specificprovisions should be made for example to accommodate future requirements onlayout and the direction of flow.

A suitable holding basin would be designed to capture and retain the first 10 mm ofrainfall (or equivalent firewater) from paved areas.

4.4.3 Sewage Treatment

All means of sewage handling and treatment must conform to therequirements of the Local Authority and BP.

Failing any such requirements, the design and construction should be inaccordance with the British Standard Codes of Practice or approved alternatives.

The drainage should preferably be discharged to the nearest Local Authority sewer.Where this is not economical, or practicable, biological treatment may benecessary. In the case of isolated buildings there are three alternatives to the aboveoptions; cesspools, septic tanks and prefabricated sewage treatment plants.Cesspools are the most basic and cheapest, but septic tanks are the preferredchoice where there is no possibility of polluting underground potable watersupplies.

4.4.4 Removal Of Solids

Process solids such as pellets and granules are best removed at source,before entering the drainage system, using screens which can beregularly cleaned. Alternatively, a decanting system further downstreammay be appropriate when the solids are coming from a number ofsources.


4.5 Measurement

4.5.1 Effluent Discharge Rate

A simple weir or monitoring device should be installed at or near thefinal effluent discharge point.

5. HYDRAULIC DESIGN

5.1 General

Most drainage systems will be gravity based open drainage systems. Onoccasion, particularly for process drainage, closed drains may beappropriate because of technical, safety or legislative requirements. Thedesign methods and criteria for both open and closed systems areclosely related.

The following sections describe methods and criteria for gravitysystems (open and closed) and then set out the different methods forthe other two types of closed system: pumped and pressurised.

Gases or vapours which may be carried forward with the effluent orevolved during the course of treatment or due to contact with othereffluent may affect the flow regime of the system.

Hydraulic design involves consideration of the following:-

(a) Maximum and minimum flows.

(b) Sediment transport capacity.

(c) Degree of surcharge, or controlled flooding, that can betolerated.

(d) Hydraulic capacity required which necessitates determination ofpipe size, gradient and condition, nature of the liquid to becarried and vapour pressure likely to arise in the system.

5.2 Gravity-based Drainage Systems

5.2.1 The following guidelines apply to open gravity systems wherecontrolled surcharging is allowed; and closed gravity systems with part-full (0.7d) pipes (i.e. no surcharging), operating at or near toatmospheric pressure. (d = Internal diameter of pipe). For equipmentrequirements of closed gravity systems see section 5.3.1.


5.2.2 Design Methods

It is recommended that the Colebrook-White formula is used for thedesign of gravity drainage systems.

For most drainage designs, hand methods of calculation are adequate for the smallareas involved. Where firewater (including dry-weather effluent flow) is the criticaldesign case, these constant flows shall directly provide the design flows throughoutthe system. Where the rainfall case (including dry-weather effluent flow) is to bechecked, flows should be calculated throughout the system by the Modified RationalMethod, or the procedures of BS 8005 or similar document.

Design may be carried out by computer if appropriate software is available. Steadystate design can be carried out by spreadsheet. Rational Method design can bedone using proprietary software such as Hydraulics Research Ltd's WALLRUS andSPIDA.

Some software allows direct production of sewer long sections for import intopropriety CAD software. More complex computer programs are available for thedesign and analysis of large and complex sewer networks. Examples areWALLRUS-SIM and WALLRUS-HYD in the UK and the US Stormwatermanagement model (SWMM). Such programs should only be used for drainage if:-

(a) Rainwater flows are critical; and(b) The design involves major modifications to an existing drainage system

that may result in under capacity of existing sewers

Calculation of open channel flows should be done using the Manning formula.

5.2.3 Velocities

Velocities shall be kept within a range that prevents damage to thepipes and fittings and allows self-cleansing.

Pipe runs should be designed to accommodate the maximum expectedflow when running just full. For some lengths of drain the flow from theemergency use of fire hoses may greatly exceed the normal process andrainwater flows.

5.2.4 Design Velocity

The design velocity (from combined process and rainwater flows)should be about 1 m/s. Velocities for firewater or emergency flows mayexceed this.

5.2.5 Minimum Velocity

All piped drains shall, if possible, be designed to attain a minimumvelocity of 0.75 m/s either from process flows alone, or from combinedprocess and rainwater flows (return period of 1 in 2 months). This


velocity shall be attained a minimum of 6 times per year to achieveperiodic cleansing of the drains.

5.2.6 Maximum Velocity

High velocities present problems due to the high friction losses andhence head-losses. If design velocities exceed 3 m/s at any point in thesystem, the pipe manufacturer should be consulted to ensure no erosionwill take place.

In oily-water systems velocities should not exceed 1.2 m/s to avoidemulsification.

5.2.7 Open Ditches

All ditches in fine sands or silts should be lined. In unlined open ditches,the velocity should be kept sufficiently low to prevent scouring. Thisvelocity shall be selected according to local soil conditions andconstruction, but may typically be in the range 0.5 to 0.8 m/s.

Where the velocity is likely to be high (e.g. greater than 0.8 m/s), suchthat scouring of the bed or sides would result, ditches in cohesive soilsor coarse sands are to be suitably revetted.

Higher velocities will be necessary where oily-water is being drained.

If considered necessary, ditches may be bottomed in concrete to facilitate cleaning.

5.2.8 Siltation

The introduction of solids into the drainage system should be avoidedwhere possible.

The drainage system should be capable of carrying any solids in thesystem with minimum maintenance effort.

Where minimum velocities for periodic cleansing of the system cannotbe obtained through process or rainwater flows, flushing facilitiesshould be installed to provide a flow of 0.75 m/s in each pipe run of thesystem.

Flushing facilities should be actively considered at arid sites with occasional orunreliable rainfall, or where large quantities of sediment are likely to enter thesystem.

Fine solid particulate matter such as clay particles from stormwater runoff onunpaved areas should wherever possible be excluded from oily-water drains. The


solids adhere to oil droplets forming neutrally buoyant particles which are difficultto separate in a gravity oily-water separator.Where lengths of sewer are designed to be permanently flooded eitherfor hydraulic reasons or for reasons of safety (e.g. ditch firetraps), thedesign flows should be increased by 10% as an allowance for siltation.

In more complex situations, where large quantities of solid material mayenter the system, further analysis is necessary.

5.2.9 Surcharging and Flooding

In open gravity systems only, surcharging of the drains may be takeninto account in emergency conditions (or extreme rainfall) in order toprovide sufficient hydraulic capacity, provided that surface flooding isnot thereby increased. Under these maximum flow conditions, thehydraulic gradient within the drainage system can extend no higher than300 mm below any point of entry into the system.

If there is a risk of flooding, each drainage catchment area should beassessed using a recognised risk assessment technique.

Where some flooding can be accepted, then any sensitive areas should be bunded orkerbed, and the water directed away using the paving falls. Allowing flooding in acontrolled manner in safe areas can provide additional storage for the drainagesystem, until the peak flow conditions have eased.

5.2.10 Pipe Roughness

In assessing the frictional head-loss of the effluents flowing in thedrains, pipe roughness factors (ks) shall be chosen to take account ofthe likely mature condition of the pipe, having due regard to thematerials of construction and the nature of the effluents drained. Theuse of conservative values will increase the hydraulic gradient and depthof the system and consequently the cost of excavation required to meetthe design flow.

Where effluent is likely to produce large quantities of chemical precipitate, theroughness values will be greatly increased. Special consideration of roughnessvalues will be necessary in such conditions. An increase in ks from 0.3 mm to 6.0mm reflecting a 10% loss in cross-section due to precipitate build-up will reducethe design flow by nearly 40%.

5.2.11 Head-losses at Manholes and Fittings

All hydraulic designs of sewers should take due account of the likelyhead-losses at manholes and fittings. These losses will be dependentupon the detailed design and it is not therefore possible to give exactfigures - most design manuals provide approximations.


By choosing certain standard details, head-losses can be reduced. For example, theintroduction of a socket or bell-mouth outlet instead of a plain straight-end pipewill reduce the exit head-losses by between 40% and 80%. Alternative sections willincrease cost though, bell-mouths are approximately 3 times more expensive thanplain ends, although sockets are only 1.1 times more expensive (based on averageUK costs).

5.2.12 Gradients

Trench excavation is usually limited to 6 m depth because ofconstruction difficulties and associated high cost - especially wherewater tables are high. Physical difficulties with the accurate laying ofpipe laying at very flat gradients dictates a minimum gradient.Recommended minimum gradients for pipe size ranges are givenbelow:-

Pipe Internal Diameter GradientLess than 150 mm 1 in 80150 mm to 450 mm 1 in 250Greater than 450 mm 1 in 500

In the UK, reference should be made to BS 8301 for foul drainage, to ensure thatall pipes are self-cleansing.

5.3 Closed Drainage Systems

The following section covers the equipment requirements for closedgravity systems (see section 5.2 for hydraulic design) and the hydraulicdesign of pumped and pressurised systems.

5.3.1 Equipment Requirements for Closed Gravity Systems

5.3.1.1 General

Backflow from high pressure to low pressure systems across commondrain systems in the event of mal-operation should be considered duringdesign.

5.3.1.2 Drainage Lines and Headers

All drainage lines should fall towards a closed drain drum.

5.3.1.3 Closed Drain Drum

Sizing of the closed drain drum should be based on the largest item ofequipment likely to be drained to the closed drain drum and thecontents of inlet drains.


For very large vessels, there should be provision to reduce the inventory to aminimum using normal process outlets. The size of the drain drum can then bebased on the lowest practical inventory of the vessel and piping. Consider supplyoperations and the likely overflow from storage tanks.

The requirement for electric heaters to maintain the temperature of theliquid in the drum should be considered.

An extra-high-liquid-level switch shall be provided in the centre sectionof the drum. Operation of this switch should open an emergency dumpvalve.

Operation of the extra-high-liquid-level switch shall cause an emergency dumpvalve to open, allowing the drum contents to discharge. It should be noted that thehigh-level control should be designed to avoid the risk of liquid carry-over to theflare system.

5.3.2 Pumped Systems

Flows from process units, tanks, drains, etc. are fed by short gravitysections designed by conventional methods to the pumping station wetwell. Figure 4 provides typical details of the arrangement of a pumpeddrainage system.

Pumping station design should be in accordance with BP Group RP 4-3 or othersuitable codes, such as BS 8005 and WAA Sewers for Adoption.

Wet wells and pumping mains shall not be oversized in order to avoidexcessive retention times of the effluent.

Pumps should be located in dry wells or above ground to facilitatemaintenance and removal. Wet wells shall be of air tight constructionwith adequate venting to provide hydraulic stability.

If wet-well pumps are used (with lifting guide rails for maintenance), then the air-tight construction requirement remains and must not be compromised.

Pump heads and capacities should be chosen to accommodate bothnormal process flows and emergency fire water flows or rainwaterflows. Separate pumps may be needed for each of these duties, howeverno less than 33% standby capacity shall be provided at all pumpingstations.

Pump and pumping pipework design should be carried out by normalhand methods of calculation. Pump and pipe capacities shall be definedas peak flows in the system.

Emulsification of oil globules makes treatment and separation difficult.For liquids containing oils, pumping stations shall be designed using


low speed screw impeller pumps to minimise emulsification. Pumpingplant should generally be low speed centrifugal pumps with operatingspeeds below 970 rpm. However, consideration should be given to theuse of Archimedean screw pumps, particular care being taken in thedesign to achieve adequate venting of the screw.

Computer aided analysis should be used to determine transientpressures due to pump operation or failure.

Proprietary programs are available for this analysis.

In order to limit both silting and emulsion, all pumping mains shall bedesigned for a velocity of between 0.8 and 1.2 m/s for maximumprocess flows alone, or from combined process and rainwater flows. Ingeneral, high velocities present more problems due to the high frictionlosses and, hence, head-losses.

In assessing the frictional head-loss of the effluents flowing in thepumping mains, pipe roughness factors should be chosen to takeaccount of the likely mature condition of the pipe, having due regard tothe materials of construction and the nature of the effluents drained.

The Colebrook-White formula should be used for relating friction ofpipe walls, gradient, flow and pipe diameter for aqueous liquids. Thefollowing values shall be used for assessing friction loss in rising mainsfor all pipework:-

Operating velocity < 1.0 m/s k = 6.0 mm

Operating velocity 1.0 - 1.2 m/s k = 3.0 mm

Operating velocity 1.2 - 1.4 m/s k = 1.5 mm

Operating velocity > 1.4 m/s k = 0.6 mm

Where effluent is likely to produce large quantities of chemicalprecipitate the roughness value shown above may be increased and thehydraulic capacity substantially reduced. Individual assessment ofroughness shall be carried out for such systems and may require:-

(a) Research of parameters used in existing drainage designs forsimilar processes, or

(b) Site measurement of friction losses in similar lines.

For pumped systems where hazardous vapours are generated, ventingshould be provided at all entry points to the pumped system and to


pumping station wet wells. All hazardous vapours should be removedand transferred by a closed piping system to a treatment plant.

All mechanical and electrical equipment should be designed for therequired hazardous area classification.

5.3.3 Pressurised Systems

The main design requirement of the pressurised system is that all liquidsand gases entering and/or generated within the system are containedand released from the system through controlled outlets.

The pressurised system is designed in a similar manner to an opengravity drainage system except that the pipes shall always run part fullto maintain the continuous gas phase above the liquid flow. The designof the system cannot therefore permit full pipe flow or surchargeconditions to occur.

Design of pressurised systems normally forms part of the design scope for theprocess design package.

Figures 2, 3 and 4 provide typical details and layout arrangements for apressurised drainage system.

The design criteria to be adopted for a pressurised system are thosedetailed previously for gravity drainage systems with the additionalcriteria described below:-

Since the maintenance of the continuous gas phase is requiredthroughout the system, the design flows into the system require carefulconsideration (clause 12.5.1). The design shall be carried out for thetotal flows from all connections or for a combination of the flows, if itis determined that the flows can be adequately regulated.

To avoid surcharge and hydraulic instability the system is designed for amaximum operating depth of flow in the sewer of 0.7d.

In order to limit siltation within the sewers and maintain self cleansing,minimum flow velocities of 0.5 m/s are required.


Detailed design of the pipe bends and junctions is required to avoidhigh local head-losses and consequent surcharge of the system. Thefollowing measures are recommended to avoid excessive head-losses:-

Change in pipe diameterFlat backed tapers to be used withlevel soffits

BendsLimit velocities to less than 1.2 m/sUse Pipe bends of radius >3d.Limit bends to angles of 45 degrees orless

JunctionsLimit losses to 0.1dBranches to be used with level soffitsUse 45 degree junctions

Detailed design and management of the gas phase is critical to theoperation of the system. The main design features for gas systems aredetailed below:-

All tapers for changes of pipe size and tees of branches are designedwith level soffits so that the continuous gas phase is maintained abovethe liquid surface.

Connections to the drainage system are valved in order to givecontrolled discharge into the system. Pressure reducing arrangements(valves or liquid seals) are required at each connection point to preventover-pressurising the drainage system.

Inert gas injection points are required at the connection points tomaintain the inert gas levels.

Inert gas/liquid vapour removal is required at the pumpingstation/treatment works located at the downstream end of the system.

Rodding/cleaning points require an isolating valve and an inert gaspurging system to prevent release of vapours during use. The roddingpoints are located upstream of all connections to the system, at majorchanges in direction of the main sewers (greater than 45 degrees) and atappropriate points along the straight length of the sewers (adjacent tobranches and at a maximum spacing of 50 m).

The gas pressure system is designed to operate at low pressures,between 1 and 5 psi.

Effluent sampling points can be provided at each connection point.


6. STRUCTURAL DESIGN OF BURIED PIPEWORK

6.1 Backfill

6.1.1 Examples of suitable backfill configurations for rigid and flexible pipesare given in national standards and pipe manufacturers information.

The installation of pipes in the ground should result in the constructionof a composite soil/pipe structure. It is essential for the integrity of thepipe system that the pipe material, its strength class or wall thickness,and the bedding should be designed having due regard for the surfaceloads which may be applied, the type and quality of soil and backfill,and the quality of workmanship which may reasonably be expected atthat particular site.

Where drains are in short runs of small diameter (e.g. within processareas), the bedding and backfill may be of nominal design with respectto pipe strength, except where vehicular or other exceptional top loadsmay be applied. For these exceptions and for long runs of largediameter pipework (e.g. in tankage and other extensive areas) thepipe/soil structure should be designed to make maximum use of thesoils' properties.

In all cases where backfill is required to provide support to surfaceconstruction, e.g. paving or pipe supports, the backfill should be ofsimilar material and compaction to the surrounding soil.

6.1.2 Additional Requirements for Flexible Pipes

The maximum deflection should be limited to 50% of the maximumvalue stated by the manufacturer.

Where flexible pipes are laid underground in poor soil conditions, itmay be necessary to use imported bedding and backfill in order toachieve the desired soil strength for the type and thickness of pipe beingused. In such cases the ability of the natural soil of the trench sides tosupport the compacted embedment should be checked and the trenchand/or backfill and/or pipe designs modified as necessary.

6.2 Road and Rail Crossings

Where pipe runs laid in open cut trenches cross under roads andrailways, pipes and their bedding should be designed to support themaximum expected applied load with an adequate factor of safety e.g.>1.5. Where it is not possible to provide pipe and/or backfill ofsufficient strength, the whole pipe should be installed in an adequateload bearing sleeve, or protected by a reinforced concrete slab.


For rigid pipes of 300 mm diameter or less, structural concretehaunching, surround or arched capping is an acceptable alternative tosleeving. Where such concrete protection is used movement jointsconsisting of a minimum of 25 mm of compressible packing should beprovided in the concrete at each flexible joint of the pipe.

6.3 Loads During Testing

Pressure pipelines such as pumped effluent lines and deep invertedsiphons will be tested to a pressure equal to either 1.5 times theworking pressure or the sum of the working pressure and the surgepressure, whichever is the greater (in accordance with BS 8010). Thepipe structural design should therefore allow for hydrostatic pressure incombination with the various possible external loads.

6.4 Thermal Expansion

Sufficient movement joints should be provided in the pipe so that thepipe may freely expand and contract. Where this is not possible,manholes shall be designed to resist thrusts applied to the walls by suchthermal expansion or contraction (see clause 8.1.8).

6.5 Submerged Pipes

If it is intended that sections of pipes remain full to act as traps, then themethod of jointing should be examined to ensure integrity. Otherwisepipes should be at such levels and gradients that liquids are not retainedin any part of the system, except manholes.

6.6 Settlement

Due account should be taken of likely future ground settlementsparticularly where constructing on reclaimed or filled land.

7. SECONDARY CONTAINMENT

7.1 Secondary containment of the drainage system may be necessary toprevent leakage and/or damage to the piping materials and to meetlegislative requirements.

All components of the system shall be contained to the same standard.

7.2 Exfiltration

The effect on the surrounding ground of leakage of effluents (bothaggressive and non-aggressive) from the drain should be assessed and


include chemical reactions, dissolution, or flocculation. Contaminationof groundwater and/or soil, and damage to foundations must beavoided.

Secondary containment may take several forms:-

(a) Advanced: e.g., double pipes and concrete trenches. With thesesystems, provision can be made for leak detection. Thecontainment system can drain to a collection sump(s) and can bevented to prevent accumulation of hazardous vapours.

(b) Basic: e.g., membrane pipe 'jackets' and membrane trench lining.Leak detection is more difficult, but effluents will be contained.

7.3 Infiltration

Installing drainage systems in contaminated ground may adverselyaffect the pipe materials and lead to accelerated corrosion and loss ofintegrity.

Composite pipe materials can be used to protect the outside of the pipe,e.g. plastic coated ductile-iron pipe. The material chosen will depend onthe compatibility with the aggressive chemical in the ground and theeffluent being carried.

8. ANCILLARY STRUCTURES

8.1 Manholes

8.1.1 General

Manholes in open drainage systems shall be located where pipediameter, gradient or direction change and at all major junctions. Forsewers of less than 0.9 m diameter manholes should not be more than100 m apart. For larger sewers the spacing may be up to 100 times thepipe diameter, up to a maximum of 200 metres.

8.1.2 Trapping

The influent drains in all manholes, other than manholes on sanitarydrains and certain chemical drains (see exceptions below), shall beeffectively trapped in the manner shown on Figure 8.

If due to unavoidable circumstances it is necessary to depart from this drawing thealternative proposals should provide for adequate seal of 230 mm, and facilitiesabove the water level in the manhole for rodding, whilst at the same time permittingany separated oil to travel in the normal direction of flow, and not to be held up inthe system.


There are two exceptions to the above where trapping can be omitted:-

(1) Where the manhole is in a safe area and is only necessary for achange in pipe direction or gradient. No additional influent pipesare connected. If any are added at a future date, then themanhole must be modified to include a trap and a vent. Thismodification may alter the hydraulic flow and so should beconsidered at the initial design stage.

(2) For certain chemical effluents carrying solids in suspension itmay not be desirable to trap drain lines at manholes. Suchdrains, should be identified in the particular Plant Specification,and should preferably have manholes of the catchpit type.

8.1.3 Combined Manhole-Gully

Specific guidelines for combined manhole gullies are given below:-

The sealed area of the gully shall be not less than the open grated areaof the gully. This reduces the seal depth required to prevent vapourescape and the effects of evaporation in hot climates.

The grate over the open areas of the gully shall be arranged for easyremoval. The cover over the sealed part of the gully shall be secured toprevent removal during normal operations.

It is important to ensure that the size and design of the gully grating will not restrictthe maximum capacity of the outlet pipe.

Details of a typical combined manhole gully are given in Figure 5

8.1.4 Design to Control Leakage

For oily water and chemical sewer systems all manholes should bedesigned as water retaining structures. This will take into account bothexternal water pressure from ground water and internal water pressurefrom the effluents in the manhole. Walls should be not less than 225mm thick and all pipes through the walls shall be sealed. Puddle flangesshould be used for sealing, where possible.

As an alternative to puddle flanges, the use of self-sealing sodium bentonite sealsaround the pipe can be considered. These expand upon contact with water.

Construction joints should also be sealed at the kickers and vertical joints withEDPM nitrile chemical resistant water bars or sodium bentonite seals.

Guidelines for the design of water retaining structures are provided in BS 8007.


8.1.5 Internal Protection

Chemical manholes should generally be protected internally asdescribed below, either:-

(a) A suitable continuous chemical resistant membrane should beapplied to the walls and base slab. The walls and base slabshould then be lined with 105 mm thick chemical resistantbricks, bedded and jointed in a suitable chemical resistantmortar. The joints should not exceed 3 mm thick, or

(b) Sheet plastic linings to manholes, pits, etc. should be adequatelyanchored to base, walls and roof of structure. Such anchoringshould take account of possible unbalanced hydrostatic pressurebetween the lining and the structure. Joints to such liningsshould be tested by high voltage spark testing. Where this is notpossible, joints should be of a multi-pass welded type, or

(c) Suitable protective tanking for the effluents being drainedshould be applied to the internal surfaces of the manhole inaccordance with the manufacturers instructions, and

(d) The under-side of the roof slab should be protected with asuitable chemical resistant membrane.

Good surface preparation for all linings is essential. For resins this shouldcomprise mechanical abrasion (or as a minimum nail or chemical etching),particularly in the splash zone.

8.1.6 External Protection

Where the soil or ground water contains chemicals which may have adeleterious effect on concrete this shall be allowed for in the detailingand mix design for concrete structures. In severe conditions thestructures should be tanked externally.

External tanking can comprise sheet liners, resins or proprietary sodium bentonitesheets in geotextile/board form (except in saline conditions where the expansionproperties of the clay are reduced).

8.1.7 Other Types of Manhole

For clean water and sanitary sewer systems, manholes may be of pre-cast concrete construction (or if shallow, of brickwork) provided thatlong-term settlement or other movement of the surrounding ground isnot expected.


Catchpit Manholes

Catchpits should have a flat base slab, the finished level of the base slabbeing at least 150 mm below the invert level of the outgoing drainpipe.The retention time in the manhole should be at least 1 minute.

Where there is a particular problem with solids, then it may be better to provide aspecific chamber for removal of the material rather than relying on maintenanceprocedures.

8.1.8 Design for Movement

Flexible joints shall be provided at connections to all structuresincluding thrust blocks, valve chambers, manholes, rodding eyes etc.The joints shall be as follows:-

(a) first joint less than or equal to one pipe diameter or 550 mmfrom the structure whichever is greater.

(b) second joint not less than two pipe diameters or 450 mm fromthe first joint whichever is greater for pipe diameters up to 750mm or from 450 mm to 750 mm for pipe diameters up to 1000mm (see clause 6.4).

8.1.9 Manhole Roof Slabs

Consideration should be given to constructing the roof of the manhole as a slab,with cast-in lifting lugs. It can be removed for construction and major repairs,enabling work to be carried out more safely and efficiently.

8.1.10 Manhole Covers

Sealed manhole covers shall be used within or adjacent to process arealimits and other hazardous areas, and in offsite areas on manholes whichare trapped or located near roadways.

The cover seal referred to above shall be of the type shown in Figure 6.The sealant shall be selected with due regard to any solvents with whichit may come into contact.

Where subject to high vehicular traffic flows or heavy mobile equipment, gas-sealedmanhole covers can be rebated into the manhole and covered by a normal heavyduty or structural cover. This reduces the risk of sealant being squeezed out andthe consequent loss in integrity.

For clean water drains, or land drains, minimum sizes should provide aclear opening of 550 mm diameter or 600 mm x 450 mm.


Manhole covers should be located over the outlet side of the manhole, to allow theinsertion of jetting equipment, CCTV survey equipment and flow monitors. This willaid maintenance procedures.

For oily water, chemical or acid drains, manhole covers should providea minimum clear opening of 750 mm x 600 mm as it may be expectedthat access will be required for personnel wearing breathing apparatus.

Chemical Manhole Covers

Chemical manhole covers should be of the double seal type where theeffluent is liable to give off poisonous or flammable vapours, and shouldbe protected with a suitable chemical resistant paint on the under-side.Covers should also bear a clear warning of the hazardous nature of themanhole contents.

Colour Coded Covers

Consideration can be given to colour coding manhole covers (by painting) toindicate the type of effluent being drained. This aids identification of the correctsystem in the event of having to pump effluent directly into a manhole in anemergency or during inspections and repair.

8.1.11 Rodding Points

Rodding points should preferably be provided which do not requireaccess to the manholes.

8.1.12 Sumps

Where volumes of sludge and grit are large enough to necessitateregular cleaning of the manholes, a sump incorporated into the base canimprove collection.

8.1.13 Access

Access to manholes should be by portable wooden ladders. However,step irons should also be provided in all manholes (except chemicalmanholes), to allow escape in emergencies.

Step irons should be of galvanised steel and set into the wall of themanhole at 300 mm centres, vertically and staggered.

The use of step irons for regular access should be discouraged as the integrity ofthe steps cannot be guaranteed, especially where contaminated effluents are beingdrained.


8.1.14 Design for Maintenance

At the design stage, it may advantageous to make allowance withinmanholes for additional connections to be made in the future.

Access space in the manhole for suction cleaning should be consideredat the design stage. There should be no corner within a manhole lessthan 300 mm square.

8.1.15 Manhole Identification System

For all new drainage systems a manhole identification system isrecommended.

All manholes should have cast on to them a code which identifies the type ofeffluent, a reference to the area it services and an identification number. Thisshould be cast into the top of the manhole lid, or be a corrosion proof plate. Afurther refinement of this which could save much investigation work at a later dateis the simple addition of arrows showing connections, flow direction and diameters.

Identification can also be applied retrospectively and may be used in conjunctionwith colour coded covers (see clause 8.1.10).

8.2 Gully Traps

8.2.1 Gullies shall be capable of draining the maximum water volume withoutextensive flooding of paved areas occurring.

Within hazardous process area limits, other hazardous areas, and suchnon-hazardous areas as may be connected into an oily water drainagesystem, drainage gullies shall be trapped with a depth of seal not lessthan 150 mm and should have adequate provision for rodding.

In other, non-hazardous areas, such as administration areas, gullies maybe of concrete or stoneware, which should be concrete encased.

The use of plastic gullies is not recommended unless it can be shown that theground does not (or will not) contain deleterious contaminants such ashydrocarbons, which would damage the gully. Plastic gullies should not be used inany process area or areas where oily or chemical effluents are drained.

8.2.2 Gully Design

Gullies should be designed to meet the following requirements:-

The depth from the top of the gully grating to the top of the gully outletpipe shall be greater than 230 mm. This will allow full flow to passthrough the outlet pipe and prevent escape of vapours.


The hydraulic capacity of each gully shall be defined as that flow whichpasses through the gully grating without surcharge.

The pipe downstream of the gully shall act as the major hydrauliccontrol of the flow.

Where appropriate the standard 150 mm gully trap shown on Figure 7should be used.

Use of the BP 'Standard 100 mm gully' should be discontinued (see clause 4.2.3.2)

8.3 Open Ditches and Channels

8.3.1 Where the velocity is likely to be high (e.g. greater than 0.8 m/s), (seeclause 5.2.7), such that scouring of the bed or sides would result,ditches in cohesive soils or coarse sands are to be suitably revetted. Allditches in fine sands or silts should be lined.

If considered necessary, ditches may be bottomed in concrete tofacilitate cleaning.

8.3.2 Firetraps

Trapping facilities should be provided to prevent fire spreading fromone area to another via ditches. Such fire traps should consist of aminimum 9 m length of permanently flooded pipe with access sumps ateach end.

Access to the sumps should be provided for tanker suction hoses.

The location and spacing of firetraps should reflect the different usageof the areas through which the drain runs e.g. process areas, black oilstankage, white oils tankage, LPG storage areas etc. In no event shouldthe spacing of firetraps be greater than 200 m.

8.3.3 Open Drainage Channels in Process Areas

Open drainage channels in process areas should be of reinforcedconcrete construction and the base slab should be laid to falls of not lessthan 1 in 60 and wherever possible, of 1 in 40.

Recessed channel grating covers should be provided to suit theconditions specified, in the particular plant specification. Themechanical strength of these gratings shall be as described in clause8.3.5.

8.3.4 Open Drainage Channels for Chemical Effluents


Open drainage channels for carrying corrosive effluent should beconstructed as for clause 8.3.3, and should be lined throughoutinternally as for chemical manholes (see clause 8.1.5).

8.3.5 Channel Grating Covers

Channel grating covers shall be of sufficient mechanical strength tosupport the loads as defined in BP Group RP 4-3.

8.4 Effluent Collection and Treatment (Neutralisation) Pits

Similar comments apply as for manholes. It is desirable that acidiceffluent should be neutralised at or near source. Retained batchoperation is preferred for neutralisation systems. Neutralised effluentshould be discharged to the appropriate drainage system as specified byBP.

Effluent collection and treatment pits shall be designed and constructedto the same criteria as for chemical manholes (see clause 8.1.5).

Special consideration shall be given to thermal movement and the general stabilityof linings.

Provision should be made to allow removal of precipitates left by theneutralisation process.

8.5 Pumping Sumps

Any pumping sumps required in oily water drainage systems, should beso designed that separated oil can be readily collected and pumpedaway to the recovered oil system or other suitable place of disposal.

8.6 Soakaways and Land Drains

Soakaways and Land Drains are to be provided for clean water useonly.

8.7 Cesspools and Septic Tanks

Cesspools, and septic tanks should, unless agreed otherwise with thedesigner, be of prefabricated, glass-reinforced plastic constructioninstalled strictly in accordance with the manufacturer's instructions.


9. CONTROL OF FUGITIVE GAS EMISSIONS AND VENTING OFDRAINAGE SYSTEMS

9.1 Control of Fugitive Gas Emissions

9.1.1 General

Fugitive emissions of hydrocarbon gases from conventional gravitydrainage systems can be reduced by changing work practices andmethods of operation. New drain systems can be installed which canalmost eradicate fugitive emissions. These new drains are howeverexpensive to install and more complex to operate. Major cost savingscan be derived by avoiding discharge of oily materials into the drainagesystem.

9.1.2 Location of gaseous emissions from drains

There are three main sources of fugitive gas emissions from refinery oil,water/gravity drain systems:

(a) at the point of entry to the drainage system(b) at vents and manholes along the drainage system, and(c) at the point of exit which could be a treatment plant, a pond, or

final discharge during maintenance

9.1.2.1 Emission at point of entry

It is normal for entry points to be open to the atmosphere as aretundishes and catch basins. It is also common for entry points to betrapped. This is a safety feature in reducing risk of spread offire/explosion, it also minimises gas escape from the piped system.

Emission at points of entry can be avoided by providing a continuousconnection into the drainage system. This however is inappropriate inmany cases due to the need for pressure interface control between anyplant and drainage systems.

The surface area of hydrocarbon exposed to the atmosphere at the entrypoint should be kept to a minimum. Freefall of effluent and oversizetundishes and catch basins should be avoided.

9.1.2.2 Emission at Vents

The majority of emissions from vents in gravity drainage systems arecaused by changes in the volume of liquid in the piped system. In asteady state flow condition very little gas leaves the system through thevents. Large increases in volumes of effluent contained in the piped


drainage system will cause corresponding large volumes of gas to beemitted.

To minimise emissions from the vents the flow conditions should bekept as steady as possible. It is desirable to avoid sudden largedischarges of process water or ballast water. Rainstorm and emergencyfire water are the single biggest contributions to large changes ineffluent volumes. If rain and fire water can be diverted to a segregated'clean-water system', this would significantly reduce gaseous emissionfrom the source.

9.1.2.3 Emission at point of exit

The effluent will discharge into some form of pond, chamber, sump ortank with an increased surface area. Ideally open ponds or chambersshould have a floating cover (zero air space).

Floating covers are restrictive if any form of mechanical treatment is required; thecontainer then is covered forming void spaces beneath the cover. The void is likelyto contain high percentages of hydrocarbon gas which should be contained and/ortreated.

9.1.2.4 Emission during Inspection and Maintenance

Access to the drainage system is affected by lifting the manhole coversand exposing the gaseous void inside the manhole. It is no longernecessary to purge the air spaces in the drainage system beforeinspection. Explosion proof cameras and light systems are nowavailable for remote inspection of the drains (see clause 12.3).

All cleaning work, when materials such as sludges have to be removedand disposed of (see clause 12.2), should be conducted in such a way asto minimise emissions to air.

9.2 Design of Vents for Open Gravity Drainage Systems

9.2.1 General (Open Gravity Systems)

Where necessary, manholes (and treatment pits) shall be fitted with 100mm minimum diameter vent pipes. These will be required both forhydraulic reasons and where gaseous effluents (especially toxic orexplosive) may be discharged into the system or where gas mayotherwise be released from the effluent (for example by contact with ahotter effluent stream).

Vent pipes shall be arranged with a fall, to drain condensation back tothe manhole. Any materials susceptible to corrosion shall be suitablyprotected.


9.2.2 Vent pipes Discharging to Atmosphere (Open Gravity Systems)

Where it is permissible to discharge to atmosphere, vent pipes shalldischarge in open air, clear of areas accessible to personnel and at least15 m away from any permanent source of ignition. Particular attentionshall be given to ensure that vapours cannot be admitted to a buildingvia air intakes or windows and vents shall be a minimum of 5 m fromsuch openings.

Where venting gases may be ignited by an intermittent ignition source(for example a lightning strike in an exposed location) a flameprotection device shall be fitted. The device should be of a typerequiring the minimum of maintenance consistent with being suitable forthe gases present in the sewer. It shall be mounted so that it does nottrap condensation and it should be readily accessible for maintenance.

Vent pipes should be distinctively marked to warn personnel of thehazardous nature of the vapours which may be emitted.

9.3 Extraction and Treatment of Vented Gases

Where it is not permissible to discharge directly to atmosphere,drainage systems will incorporate extraction of gases. Treatment ofthese vented gases should be carried out by proprietary treatmentmethods and will require detailed treatability and design studies for thetypes of gases extracted. Methods which are commonly used fortreatment are:-

Hydrocarbon vapours:-

(a) capture and direct to flare stack(b) capture and direct to activated carbon plant

Water miscible vapours:-

(a) capture and direct to water scrubbers(b) capture and return to effluent flow

Due to increasing legislation, flaring off hydrocarbon vapour may not beacceptable.

In assessing the feasibility of activated carbon plant, account should be taken ofdisposal/replacement costs of spent carbon and use of carbon regenerationequipment.


10. MATERIALS

10.1 General

The choice of material will depend on the type of effluents beingdrained. Particular attention shall be paid to the effects on the materialsof all possible changes in physical, chemical and biological properties.Aggressive conditions in the soil and possible movements of the soil orof drainage structures shall also be taken into account. The degree ofintegrity of the drainage system should be established, and the methodof proving continuing integrity should be identified.

Pressure testing of pipework is the most direct method of establishing integrity, butthis has cost implications with regards to material choice.

It is essential that any pipe material to be used under process areasshould be chosen so that the possibility of damage is minimised.

Where future access to pipes will not be possible, the use of higher specificationmaterials should be investigated (this is to include the types of joint system for eachmaterial).

A pre-installation survey is recommended so that methods of corrosion protection,the suitability of the natural soils for embedment, and design of structures,including anchorages, are all given full consideration.

Materials for drainage pipework should be chosen from those shown inTables 2A and 2B. Other materials may be used only with the priorapproval of BP. However, for chemical effluents, the suitability of eachmaterial proposed should be confirmed in writing with themanufacturer, and shall be subject to BP approval.

The specifications given in the material tables are predominantly UK based. Whenworking elsewhere, the local standards should be used providing they specifyacceptable performance.

The installation of chemical resistant materials should be carried out byspecialists having experience of the materials specified.

The main features to be assessed when considering the suitability ofmaterials are:-

10.2 Resistance to Effluents

The material and its jointing should be completely impervious andresistant to degradation by the effluents being carried, and anycontamination present in the ground.


10.3 Strength

The material should have sufficient mechanical strength to support theloads it will be required to carry in conjunction with a designed backfill(see clause 6.1).

Where the material is subject to long-term loading, such as buriedpipework, it should not be subject to creep.

The material should, wherever possible, possess some flexibleproperties, either inherently or by virtue of its jointing system.

10.4 Joints

Joint integrity should be maintained for the design life of the drainagesystem or for as long as directed by BP.

Flexibly-jointed pipework shall be provided for all undergroundapplications unless otherwise agreed by BP.

Joint rings for such pipework should conform to BS 2494 or equivalent.

Jointing materials should have resistance to the specified chemical andphysical conditions at least equal to that of the materials being joined.

For oily water sewers, oil drains and for any other drain system to beburied in potentially hydrocarbon contaminated ground, joint rings andgaskets shall be of Acrylonitrile Butadiene Rubber (NBR), and anyexternal corrosion protection coatings to the pipes and fittings shall behydrocarbon resistant.

10.5 Other

Membranes for secondary linings to manholes, effluent collection andtreatment pits and open drainage channels should be resistant to thechemical conditions prevailing in the drain system and the ground inwhich the system is being laid (see clauses 8.1.5 and 8.1.6).

11. CONSTRUCTION AND WORKMANSHIP

11.1 Introduction

This chapter specifies general requirements for the construction andworkmanship of drainage systems in refineries, terminals, storage andpipeline associated installations, and chemical plants.


Specifications for closed drainage systems which are regarded asprocess plant pipework should be in accordance with BP Group RP 42-1, Piping Systems.

Where reference is made to spigot and socket pipes, the same guidelines generallyapply to other types of pipes.

11.2 Construction

Unless agreed otherwise by the designer, drainage works should becarried out in accordance with a specification based on BP Group RP4-1 Drainage Systems and the requirements of local standards.

11.3 Connections to Existing Sewers

Connections to existing sewers should be made either by way of a pipesaddle, a new manhole or a new branch into an existing manhole.Before entering, breaking into, or connecting to an existing sewer, drainor manhole, the contractor should give notice of his intention to do soto the authority responsible for the pipe to which the connection is tobe made.

The proposed method of connection is to be agreed by BP beforecommencing any work. Construction is to be carried out under thesupervision of BP.

Connections using vitrified clay or concrete pipe on clean surface watersewers may use a pipe saddle connection where the incoming sewerinvert is equal to or higher than the soffit level of the existing sewer,and the incoming sewer pipe is of a smaller diameter than the existing.

A new manhole connection should be made where the existing sewerpipe has been bedded in concrete or where the sewer flow cannot bestopped off during connection. This connection may be used for anytype of pipe. Sanitary effluent sewers should be connected only by thismethod.

A new branch connection into an existing manhole should be used forall sewer conditions other than those referred to above.

11.4 Testing

All sewers and drains with water-tight joints, regardless of pipe size,and all manholes should be tested. The test pressure should beappropriate to the class of pipe, the material used, the workingpressure, and in accordance with national standards.


In the UK BS 8005 is the standard for testing and should be used for all testing,except oily and contaminated drainage systems.

Oily and contaminated drainage systems should show no detectable losswhen tested.

BS 8005 is too lax for testing oily and contaminated drainage systems, in that it isallows a certain amount of leakage to take place (1 litre/hr/m [dia]/m[length])

11.5 Back-filling

Back-filling should be carried out as soon as possible after the drain runhas been satisfactorily tested.

11.6 Cleaning

The interiors of pipes, manholes, gullies and pits should be left cleanand free from all rubbish and surplus material.

On completion, all manholes, drains and sewers, other than Frenchdrains, should be flushed from end to end with water and left clean andfree from all obstructions.

Consideration should be given to camera inspection prior to acceptance of thedrainage system.

12. OPERATION AND MAINTENANCE

12.1 Regular inspection, and maintenance, is essential to the operation of alldrainage systems. To preserve or improve the hydraulic performance, itis necessary to remove debris, prevent leakage and repair damage.

Each section of the drainage system should be categorised according toit's importance in the system; this will be reflected in the time betweeninspections. Importance will depend on the nature of the plant or areabeing drained and where in the system the pipe is located.

To facilitate the inspection and maintenance of the drainage system, asystem maintenance layout should be produced, either as one of thedesign contractor's deliverables or as part of an overall site drainagemaintenance plan.

The plan would show main drain lines and manholes, with identification numbers(see clause 8.1.15). Also see clause 8.1.10 - coloured covers.


12.2 Cleaning

Drains require periodic cleaning to remove silts, sludges andprecipitates which impair the performance of the system. The mostcommon method uses pressurised water jets. When this action is carriedout, the seals on the system will be temporarily broken. This increasesthe risk of any vapours spreading through the system and ignitionoccurring at a remote location.

When cleaning closed systems, that are not permitted by legislation torelease gas to the atmosphere, the system will have to be purged priorto opening any jetting points.

Sludge that collects in the drainage system and waste treatment plant is acontaminated material, impairs the hydraulic flow and can be expensive to disposeof.

12.3 Inspection

The following section generally covers Open Systems with conventionalconstruction, additional specific guidelines for alternative closedsystems are provided in clauses 12.5.1 and 12.5.2.

Inspection will be manual or remote, depending on three main factors -size of pipes, type of effluent carried and whether the system is open orclosed. The principles of the inspection are the same whichever methodis used.

In the UK, the WAA Manual of Sewer Condition Classification and Model Contractdocuments for manhole location surveys and non man-entry sewer inspection,provide guidance on the procedures involved in an inspection.

In addition to periodic surveys of the drainage system, routineinspections should be made of the following features; manhole coverseals and sealant (especially after covers have been moved), vent pipes(for blockages or flame-protection device damage) and water-trap seals(in manholes, tundishes and gullies). This is essential to continual safeoperation of the system.

12.3.1 Pressure Testing

This can prove the integrity of a system, but not the condition. Pressure testing ofconcrete and clay pipes is not normally possible because of natural leakage.

12.3.2 Remote Imaging Systems

All other systems will require some form of remote inspection.


Generally closed circuit television cameras (CCTV) or SONAR are mostappropriate for most drainage systems. The use of computer recognition systemsenables the analysis of video tape records for pipe defects to be made moreefficiently. The equipment used shall meet safety regulations for hazardous areas. Itmay need to be explosion proof, otherwise over-pumping and purging may benecessary. This will remove one advantage of remote inspection where access canbe made without interrupting the flow. All components of an explosion proof CCTVsystem would require BASEEFA or similar approval.

12.3.3 Man Access

Man access can be achieved in open systems where pipes are greaterthan 600 mm in diameter, but working is difficult in sizes below 900mm. Safety rules will determine whether entry can be permitted withoutdraining or over-pumping the system. All work will meet safetyregulations for working in confined spaces.

Because of the hazardous nature of the drainage systems, man access into thedrainage system should only be carried out when no other method is available.

12.4 Rehabilitation

12.4.1 There are three options for rehabilitation; replacement, renewal andrenovation.

The choice of technique will depend on the individual conditions of the site, the costand nuisance involved with disruption and the delay compared to the costs of eachmethod.

12.4.2 Replacement

The complete reconstruction of a system to take account of new flowsand future development in addition to the existing flow.

12.4.3 Renewal

Reconstruction to a design that caters only for original design flows.The route of the new system can be different to the existing, and analternative construction method can be used.

12.4.4 Renovation

This option is used to extend the design life of a drainage system, withthe same design flows continuing.

In operational plants it is advantageous if repairs can be done from within the pipe,without the disruption of excavation. Such trenchless technology is becomingincreasingly available. Repairs can be either structural or non-structural. Thereare a variety of methods which can be used.


Structural repairs include inserting rigid pipe sections inside the existing pipeand/or grouting around the pipe perimeter with cementitious or resin based grouts.

Non-structural repairs include patching with composite resin based materials ormortars, relining with flexible membranes cast in-situ, and injecting resins intocracks. Robotic methods have been developed which can carry out a range ofpatching and injection repairs without disrupting flows. Care needs to be taken withthe joint between repair materials and the existing pipe section. This has been thelocation for failure in the past. Manufacturers should be consulted to ensure thatrepair materials and techniques are compatible with the effluents being carried.

12.5 Operational Procedures (Closed System Only)

The following section describes the additional operation andmaintenance procedures for alternative closed drainage systems:-

12.5.1 Pressurised Systems

Operation of the System

Operation of the system requires maintenance of the invert/vapour gas phase abovethe liquid flow throughout the system.

Prior to releasing effluent into the system, the system is purged with the inert gas.Following completion of this operation, the system is filled with inert gas to thesystem pressure.

Effluent can then be drained into the system at the controlled rates determined bythe design, thus maintaining the continuous gas phase above the liquid level.

During operation, the gas pressure will gradually increase as volatile gases aregenerated from the effluent flow. The design will allow the gas pressure to increaseuntil the upper system pressure is reached, at this point a gas relief mechanismlocated at the downstream end of the system will open and the mix of inert gas andvapour will be extracted. The extracted gas is removed by a closed piping system toa treatment plant (see clause 9.3).

Extraction of gases continues until a low set pressure is reached, at which pointfurther inert gas is injected into the system to return the pressure and to maintainthe purging effect within the system.

Operation of the system is more difficult than a normal gravity system, since flowsinto the pressurised system have to be carefully monitored to maintain the gasphase above the liquid level.

Maintenance of the System

Maintenance of a pressurised system is more complex than an open gravity systemas access to the system is restricted. Ensuring correct operation of the effluent flowsinto the system and thus retaining the gas phase will reduce the maintenancerequirements.

Regular maintenance of the mechanical and electrical equipment associated withthe gas injection and removal system is required for satisfactory operation.


Repair or removal of pipework within the system will be more difficult than aconventional open gravity system since the pipelines require isolation and purgingto remove any hazardous gases.When installed below ground, secondary containment will make maintenance easierto carry out, particularly with respect to location and isolation of leaks to thesystem.

12.5.2 Pumped Systems

Operation and Maintenance of the System

Operation of the system is controlled by the liquid levels in the pumping station wetwell.

Effluent is pumped, either to a high level gravity pipeline, an underground pipelineor direct to a remote treatment facility.

Repair or removal of pipework within an aboveground pumped system will be easierthan a gravity system since the pipes are laid above ground level and will generallybe of flanged joints.

Where hazardous liquids or gases exist, maintenance within the wet wells will bedifficult, since the sumps are not free draining, a separate drain down facility needsto be provided with a system of purging the air space.


DrainageSystem

Advantages Disadvantages

Open Gravity

Open system -Most basic form ofdrainage.No environmentalconstraints onvapour discharge.

Design, construction, materials andoperation/maintenance are conventionaland well known/provenGenerally fail-safeDesign caters for variable flowsCan operate under surchargeVapours easily ventedRelatively low operation and maintenancecostFire hazard can be controlled

Extensive systems expensive toconstruct due to depthMay require containmentRequires oil interceptors and fire trapsRequires regular venting (open) or gasremoval (at collection drum/pit for closed)If laid in ground, possible exfiltration

ClosedGravity

Closed system -No emissionsallowed toatmosphere.

Design, construction, materials andoperation/maintenance are conventionaland well known/provenGenerally fail-safeDesign caters for variable flowsRelatively low operation costFire hazard can be controlled

Extensive systems expensive toconstruct due to depthMay require containmentRequires regular gas removal (at collectiondrum/pit for closed)If laid in ground, possible exfiltrationHigher maintenance cost than open gravityDifficult to inspect

Pumped

Closed system - Noemissions allowed toatmosphere

Design, construction, materialsand operation/maintenance areconventional and well known/proven.Design caters for variable flows.Pipework can be laid above ground or inshallow excavation.Design caters for segregation of effluents.Fire hazard can be controlled.Gaseous emissions to atmosphere areminimal.Higher integrity pipework.Easily pressure tested to prove integrity.

Dependent upon m/e plant,Requires standby system for confidence ofoperation.Requires dedicated reception point.Expensive to cater for large variable flows.High operation and maintenance costs.Possible septicity/chemical attack inpumping mains.Materials of construction for plant may beexpensive.

Pressurised

Closed system - Noemissions allowed toatmosphere

Design, construction and materials forpiping system well known/proven.Generally fail-safe for effluent flow.Fire hazard can be controlled.Possible to convert from existing gravitysystem.Pipework can be laid above groundGaseous emissions to atmosphere areminimal.Higher integrity pipework.Easily pressure tested to prove integrity.

Overall design, construction andoperation/maintenance not wellknown/proven.Air-tight system required.Design caters for fixed flows.Design of gas system expensive andspecialist.Extensive systems very expensive toconstruct (if below ground).If laid in ground, possible exfiltration.High operation and maintenance cost.Not suited to surface water run-off orfirewater.

TABLE 1

SUMMARY OF ALTERNATIVE DRAINAGE SYSTEMS

RP

4-1D

RA

INA

GE

SYST

EM

SPA

GE

53

Material SpecificationService for which material is

suitable/unsuitableSystem

TypeJointing Type Size Range Comments

Wat

er

Oily

Wat

er

Oil

Sol

vent

Cau

stic

Aci

d

Che

mic

al

Fou

l Sew

age

Gra

vity

Pre

ssur

e*

Fla

nged

Wel

ded

Spi

got/S

ocke

t

(mm)

Carbon steel API 5L Y1 Y Y Y Y3 Y1 Y1 Y Y Y Y2 Y2 Y 60-220 1 Special precaution to be taken in use e.g. internal linings

and Cement lined BS 534 (BS 2633) BS 534 2 Good for above ground and pressure mains

carbon steel BS 1600 (butt weld) 3 Stainless steel should be used at high temperatures

API 5L BS 2971 Materials for jointing need to be checked in relation to the service

BS 3602 Provision for thermal expansion and differential movement required

BS 3604 Screwed and coupled joints also available

BS 3605 Cathodic protection may be necessary below ground

BS 4515 Special protection required externally if laid in ground

Ductile Iron BS 4772 Y Y Y N N N N Y Y Y Y N Y 80-1600 Normally used below ground

ISO 2531 (BS 4772) External protection should be provided in aggressive soil conditions

(Table 45) Max pressure rating 40 bar

Provision for flexibility should be made

Vitrified Clay BS 65 Y N N Y Y Y Y Y Y N N N Y 100-1000 Care should be excercised during laying of pipes and the provision of bedding

(BS 65) Problem with in-line valves if required

Sleeved joints are also available

Jointing material can also be made from various materials - consult manufacturer

Specially suitable at normal temperatures and normally suitable at high temperatures

Not suited to cyclic variations in temperaure

Chemical resistant pipes available

Reinforced BS 5911 Y Y N N N N N Y Y N N N Y1 150-2400 1 Flexible joints incorporating an "O" ring gasket of a high quality rubber material

and (reinforced) Not recommended for effluent containing sulphide

Prestressed BS 5178 Special precautions should be taken in aggressive ground conditions

Concrete (prestressed)

Reference should be made to corrosion resistance charts for specific chemicals and effluents Y Suitable/applicable

Refer to pipe manufacturer prior to specifying any pipe application N Unsuitable/not applicable

* Pressure refers to both pumped and pressurised systems

TA

BL

E 2A

MA

TE

RIA

L SE

LE

CT

ION

RP

4-1D

RA

INA

GE

SYST

EM

SPA

GE

54

Material SpecificationService for which material is

suitable/unsuitableSystem

TypeJointing Type Size Range Comments

Wat

er

Oily

Wat

er

Oil

Sol

vent

Cau

stic

Aci

d

Che

mic

al

Fou

l Sew

age

Gra

vity

Pre

ssur

e*

Fla

nged

Wel

ded

Spi

got/S

ocke

t

(mm)

UPVC BS 3505 Y Y N N N N Y1 Y Y Y N Y2 Y 160-400 1 Inorganic chemical wastes (not nitric acid)

BS 3506 (BS 6464) (BS 5481) 2 Chemicals can affect solvent welded joints

BS 5481 Flexible pipeline design more complex than rigid pipe design

BS 4660 Good supervision required during installation

Choice of plastic material determined by effluent constituents

ABS BS 5391 Y Y N N N N Y Y Y Y N Y Y 12-225

BS 5392

Polyethylene BS 5556 Y Y N N Y Y Y Y Y Y N Y Y

BS 6437 (BS 6464)

BS 6572

BS 6730

BS 7336

Polypropylene BS 4991 Y Y N N Y Y Y Y Y Y N Y Y Polypropylene can be fusion welded

GRE and GRP BS 5480 Y Y Y2 Y2 Y Y Y Y Y1 N Y N Y 50-2500 1 Low Pressure applications only

(Glass BS 6464 (BS 6464) 2 Check long-term stability of material and consider likelihood of fire damage in pipe

reinforced API 5LR Choice of resin/epoxy and pipe details determined by effluent constituents

plastic/epoxy) Good supervision required during installation

Expensive if special resins required

Stainless steel BS 3605 Y Y Y Y Y Y Y Y Y N Y Y Y 60-1000 Very expensive

austenite (BS 4870) Good for drainage effluent containing hydrocarbons, nitric acid and caustic effluents

type 304 (BS 4871)

Glass N N N Y Y Y N Y n/a n/a n/a n/a n/a Laboratory drains only

Very Expensive

Reference should be made to corrosion resistance charts for specific chemicals and effluents Y Suitable/applicable

Refer to pipe manufacturer prior to specifying any pipe application N Unsuitable/not applicable

* Pressure refers to both pumped and pressurised systems

TA

BL

E 2B

MA

TE

RIA

L SE

LE

CT

ION


Clean Water 2.8.1.

OpenNo vents/traps (2.10.1)

Contaminated Water 2.8.2

Holding BasinEffluent TreatmentUnit (ETU)Vents/Traps? (2.10.1)

Detergent 2.8.7

Oily Water(Low VOC) 2.8.3

Open

Vents & TrapsSealed manholeETU (2.10.1)

Sewage 2.8.9

No vents/trapsSewage - treatment

Solids 2.8.8

No traps

Chemicals 2.8.4

Non-aggressive

Sealed Manhole?Vents/Traps?Neutralisation Pit?MaterialsHolding Basin (2.10.1)

Chemicals 2.10.2

Aggressive

ClosedMaterialsNeutralisation Pit?

High Volatile Organic Compounds (VOC) Oily Water

All Closed Systems (2.10.2)

Gravity (2.10.2.1) Pumped (2.10.2.2) Pressurised (2.10.2.3)

No ManholeSealed Joints

Non-emulsifying pumpsHigher spec’n materialsSealed tundishes

Vapour ExtractionSuction pumpsScrubberSealed tundishes

Clause numbers refer to text? indicates options to be considered

Basic treatment& drainagerequirements

Complexdrainage& expensivetreatment

FIGURE 1

PRESSURISED DRAINAGE SYSTEM- TYPICAL ARRANGEMENTS

RP

4-1D

RA

INA

GE

SYST

EM

SPA

GE

56

FIG

UR

E 2

PR

ESSU

RISE

D D

RA

INA

GE

SYST

EM

-T

YP

ICA

L C

ON

NE

CT

ION

AR

RA

NG

EM

EN

T

RP

4-1D

RA

INA

GE

SYST

EM

SPA

GE

57

FIG

UR

E 3

PR

ESSU

RISE

D D

RA

INA

GE

SYST

EM

-T

YP

ICA

L L

INE

DIA

GR

AM

OF

CO

LL

EC

TIO

N SY

STE

M

RP

4-1D

RA

INA

GE

SYST

EM

SPA

GE

58

FIG

UR

E 4

PU

MP

ED

DR

AIN

AG

E SY

STE

M - T

YP

ICA

L A

RR

AN

GE

ME

NT

S


FIGURE 5MANHOLE GULLY DETAIL


10mm min.

Sealing Material

Section of frame

Section of cover

SINGLE SEAL DOUBLE SEAL

FIGURE 6

TYPICAL SEALED MANHOLE COVERS


Notes:1. Actual method of hingeing airtight lid to be decided by the manufacturer. Hinge pin to be

of mild steel galvanised.2. Material cast iron to be BS 1452.3. The trap is shown to a manufacturers' design for a UK project.4. Flanged sockets equal to BS 4622 to be used in conjunction with trap where connection to

flanged pipes is required.

FIGURE 7

TYPICAL STANDARD 150 MM GULLY TRAP

RP

4-1D

RA

INA

GE

SYST

EM

SPA

GE

62

FIG

UR

E 8

TR

AP

PIN

G O

F D

RA

IN IN

LE

TS T

O M

AN

HO

LE

S


Notes:

* If a product spillage occurs, and clean water could become contaminated, close valve andthen recover locally or allow to pass to final separator.

** Leaded or special products not suitable for mixing in the oily water system, must beretained in a local separator, until the product can be recovered. The water remaining canthen be allowed to drain to the oily water system.

FIGURE 9

TYPICAL OFFSITES STORAGE TANK OILY AND CLEAN WATER DRAINAGELAYOUT


APPENDIX A

DEFINITIONS AND ABBREVIATIONS

Definitions

Standardised definitions may be found in the BP Group RPSEs Introductory Volume.

Abbreviations

ABS Acrylonitrile Butadiene StyreneBASEEFA British Approvals Service for Equipment in Flammable Atmospheresd Internal Pipe DiameterGRE Glass Reinforced EpoxyGRP Glass Reinforced Plasticsks Surface Roughness (m or mm)EDPM Ethylene - propylene terpolymerTEL Tetraethyl LeadTML Tetramethyl LeadUPVC Unplasticized Polyvinyl ChlorideVOC Volatile Organic CompoundWAA Water Authorities Association


APPENDIX B

LIST OF REFERENCED DOCUMENTS

A reference invokes the latest published issue or amendment unless stated otherwise.

Referenced standards may be replaced by equivalent standards that are internationally orotherwise recognised provided that it can be shown to the satisfaction of the purchaser'sprofessional engineer that they meet or exceed the requirements of the referenced standards.

British Standards

BS 2494 Elastomeric Seals for Joints in Pipework and Pipelines

BS 6297 Design and Installation of Small Sewage Treatment Works and Cesspools

BS 8005 Sewerage: Parts 0 to 5

BS 8007 Design of Concrete Structures for Retaining Aqueous Liquids

BS 8010 Code of Practice for Pipelines

BS 8301 Building Drainage

BP Group Documents

BP Group RP 4-3 Civil Engineering(replaces BP CP 4)

BP Group RP 24-1 Fire Protection - Onshore(replaces BP CP 15)

BP Group RP 42-1 Piping Systems(replaces BP CP 12)

BP Group RP 44-11 Drainage - Offshore(replaces BP CP 47)

Other Documents

HSG 34 Health & Safety Guideline

WAA (Water Authorities Association) Sewers For Adoption


Documents Referenced from Table 2A and 2B

API 5L Specification for Line Pipe

API 5L RSpecification for Line Pipe

BS 65 Vitrified Clay Pipes, Fittings and Ducts, also FlexibleMechanical Joints for Use Solely with Surface Water Pipes andFittings

BS 534 Steel Pipes, Joints & Specials for Water and Sewage

BS 1600 Dimensions of Steel Pipe for the Petroleum Industry

BS 3505 Unplasticized Polyvinyl Chloride Pressure Pipes for ColdPotable Water

BS 3506 Unplasticized PVC Pipes for Industrial Purposes

BS 3602 Steel Pipes and Tubes for Pressure Purposes: Carbon andCarbon Steel with Specified Elevated Temperature Properties

BS 3604 Steel Pipes and Tubes for Pressure Purposes: Ferritic AlloySteel with Elevated Temperature Properties

BS 3605 Austenitic Stainless Steel Pipes and Tubes for PressurePurposes

BS 4515 Process of Welding of Steel Pipelines

BS 4660 Unplasticized PVC Pipe & Plastics Fittings Nominal Sizes 110and 160 for below Ground Gravity Drainage and Sewerage

BS 4772 Ductile Iron Pipes and Fittings

BS 4991 Propylene Copolymer Pressure Pipe

BS 5178 Prestressed Concrete Pipes and Fittings for Drainage andSewerage

BS 5336 Polyethylene Fusion Fittings with Integral Heating Elements forUse with Polyethylene Pipes for the Conveyance of GaseousFuels

BS 5391 Acrylonitrile Butadiene Styrene Pressure Pipe: Pipe forIndustrial Uses


BS 5392 ABS - Fittings for Use with ABS Pressure Pipe Part 1

BS 5480 Glass Reinforced Plastics, Joints and Fittings for Use for WaterSupply or Sewerage

BS 5481 Unplasticized PVC Pipe & Fittings for Gravity Sewers

BS 5556 General Requirements for Dimensions and Pressure Rating ofPipe of Thermoplastics Materials

BS 5911 Precast Concrete Pipes and Fittings for Drainage and Sewerage

BS 6437 Polyethylene Pipes (Type 50) in Metric Diameters for GeneralPurposes

BS 6464 Reinforced Plastics Pipes, Fittings and Joints for Process Plant

BS 6572 Blue Polyethylene Pipes up to Nominal Size 63 for BelowGround Use for Potable Water

BS 6730 Black Polyethylene Pipes up to Nominal Size 63 for AboveGround Use for Potable Water

ISO 2531 Ductile Iron Pipes, Fittings and Accessories for Pressure

bp rp4-1.pdf

Documents

engineering practices

bp international limited

design of drainage systems

bp group recommended

british petroleum company

drainage systemsnovember

purposethis document

maintenance ofdrainage