debswana spec 462001

DS SPEC 462001

Document status Approved Copyright

ISSUE 0 1 November 2004 of 14

Debswana Specification Boilers: Electrode Boilers Operating Below 200°C

DS SPEC 462001



1 SCOPE 3

2 TECHNICAL REQUIREMENTS TO BE SPECIFIED BY THE ENGINEER 3

3 DEFINITIONS 3

4 REQUIREMENTS 3 4.1 RATING AND DUTY DESCRIPTION 3 4.2 GUARANTEE 4 4.3 INFORMATION TO BE PROVIDED BY THE CONTRACTOR WITH THE TENDER 4 4.4 MATERIALS OF CONSTRUCTION 5 4.5 MECHANICAL EQUIPMENT 5 4.6 ELECTRICAL EQUIPMENT 6 4.7 INSTRUMENTATION 9 4.8 CORROSION PROTECTION 9 4.9 NOISE LEVELS 9 5 QUALITY ASSURANCE REQUIREMENTS 10

6 TEST AND INSPECTION METHODS 10 6.1 PERFORMANCE TEST AT SITE 10 6.2 WORKS TEST AND INSPECTION 11 APPENDIX A: RELATED DOCUMENTS 12

APPENDIX B: RECORD OF AMENDMENTS 12

APPENDIX C: TECHNICAL AND OPERATING DATA 13

APPENDIX D: EQUIPMENT DETAILS 14

DS SPEC 462001



1 SCOPE

This specification details the requirements for electrode boilers operating below 200°C.

2 TECHNICAL REQUIREMENTS TO BE SPECIFIED BY THE ENGINEER • Title, issue, reference number and date of the specification

• The completed Data Sheet.

3 DEFINITIONS

For the purpose of this specification the following definitions shall apply:

APPROVED/ ACCEPTABLE

: Approved by and acceptable to the Engineer in writing

BS : British Standard

QAR : Quality Assurance Representative; A quality surveillance agency appointed by the Engineer

SANS : South African National Standards

DS : Debswana

ENGINEER : The Consulting Mechanical and Electrical or his technical representative appointed in writing

The following terms are specified in the General Conditions of Contract:

• Debswana, Company, Contractor, Engineer

4 REQUIREMENTS

4.1 RATING AND DUTY DESCRIPTION

4.1.1 The electrode boiler: shall produce dry saturated steam.

4.1.2 The boiler shall operate indoors: 24 hours per day, 365 days per year and shall be designed to facilitate inspection, cleaning, maintenance and repairs to ensure satisfactory operation under the atmospheric, seismic and corrosive conditions prevailing at the site.

4.1.3 The capacity and operating parameters: of the boiler shall be as specified in the Data Sheet. The boiler shall meet the capacity specified continuously under the most adverse conditions specified.

4.1.4 The boiler and all its associated equipment: shall be the manufacturers normal design for the service specified and spares shall be readily available in South Africa.

DS SPEC 462001



4.2 GUARANTEE

4.2.1 Performance guarantee

4.2.1.1 The performance of the boiler: shall be in accordance with the requirements of this specification and the information in the Data Sheets shall be guaranteed by the Contractor.

4.2.1.2 The performance parameters: to be verified and guaranteed shall be:

Boiler maximum capacity; Boiler continuous capacity, pressure, temperature; Power input; Thermal efficiency; Feed water temperature; Ability of boiler to operate continuously on feed water specified; Blow down water used and control of conductivity of water; Automatic load control; Boiler minimum turn down; Function of all safety devices.

4.2.1.3 The Contractor shall guarantee: the operation of the equipment supplied for one year under the design conditions and shall undertake to rectify at his cost any defects caused by faulty design, materials or workmanship.

4.2.2 Compliance with specification

4.2.2.1 The Contractor shall: at his own expense, remedy any defects or failure in performance within one month on the receipt of notification in writing from the Company advising of non-compliance with the Contract.

4.2.2.2 After the faults have been corrected: the plant shall be retested at the Contractor's expense.

4.2.2.3 If after the one month notification period: the Contractor has not rectified the plant, the Company shall have the right to reject the plant or take such steps which are necessary to complete all outstanding work at the Contractor's expense.

4.2.2.4 No penalty payment: shall be accepted by the Company as compensation for non-compliance with the Contract or failure to meet any guarantee.

4.3 INFORMATION TO BE PROVIDED BY THE CONTRACTOR WITH THE TENDER • Description of the equipment offered

• General arrangement and sectional drawings showing concepts and details of major items

• Reference lists of similar installations

DS SPEC 462001



• The drawings and data listed in the following schedules:

DESCRIPTION WITH TENDER AFTER CONTRACT AWARD

FOR APPROVAL DUE DATE CERT. PRINTS DUE DATE

Dimensioned outline drawings 1 3P 1 wk 4P+1R 2 wks Sectional drawings 1 3P 1 wk 4P+1R 2 wks Foundation drawings outline only 1 3P 1 wk 4P+1R 2 wks Installation drawings with connection details

1 4P+1R 2 wks

Diagrammatic piping drawings 1 4P+1R 2 wks Wiring schematic 1 3P 1 wk 4P+1R 4 wks Commissioning, initial and recommended maintenance spares list

5P 4 wks

Erection, operation, maintenance instructions fault finding and special tools

5P 4 wks

Equipment data sheet 1 Performance curves 1 5P 4 wks Manufacturing fabrication/construction programme

1 5P 2 wks

Manufacturing inspection and test reports for equipment

2 Monthly

Packing lists with shipping weights and dimensions

Names of suppliers of proprietary items

1

Utility requirements e.g. water, air and fuel

1 2P 4 wks

Control schematic diagram 1 3P 1wk 4P + 1R 4 wks Comprehensive parts register 5P 4 wks Full mechanical and electrical specifications

1 3P 1 wk 5P 4 wks

Cable schedule 3P 1 wk 4P + 1R 6 wks Copies of final tender 3

P = Print

R = Reproducible

4.4 MATERIALS OF CONSTRUCTION

4.4.1 Materials: shall be the Contractor's normal supply for the duty specified, and shall be in accordance with the requirements of BS 1894.

4.4.2 All steam and condensate piping: shall be lagged.

4.5 MECHANICAL EQUIPMENT

4.5.1 The electrode boiler and associated equipment: shall be supplied and manufactured in accordance with the requirements of:

4.5.1.1 BS 1894: the design and manufacture of electric boilers of welded construction.

4.5.1.2 The Minerals Act (Act 50, 1991).

DS SPEC 462001



4.5.1.3 The Occupational Health and Safety Act (Act 85, 1993).

4.5.1.3.1 A skid mounted packaged electrode boiler unit: shall be supplied in which steam is generated by resistance to the passage of alternating electric current in water.

4.5.1.3.2 One lockable safety valve: shall be supplied with each boiler and shall have on orifice area sufficient to prevent the steam pressure rising 10% above the authorised working gauge pressure.

4.5.1.3.3 An exhaust vent line: shall be supplied to vent steam from each safety valve to a safe point not more than 10 metres away. In the design of these vent lines adequate allowance shall be made for capacity and expansion and the safety valves shall not be subjected to stress.

4.5.1.3.4 Each boiler: shall be supplied with a feed/hotwell tank, which shall have a minimum live feed water storage for half an hour when the boiler is steaming at continuous maximum rate. The tank shall have provision made for the following: level control valve for feed inlet, feed outlet, condensate return and feed recirculating.

4.5.1.3.5 The feed pump: shall be capable of delivering water to meet the requirements of boiler operating at maximum output.

4.5.1.3.6 The by-pass on the boiler level control valve: shall be arranged so that there is always a positive flow through the feed pump under all operating conditions.

4.5.1.3.7 A non-return valve: shall be placed on the feed discharge to ensure that it is not possible to drain the boiler back through the feed pump when it is not operating.

4.5.1.3.8 The boiler shall be fitted: with an automatic blow down valve (with automatic opening in the event of a power failure) to prevent excessive dissolved solids build up.

4.5.1.3.9 The boiler shall be designed: to operate continuously on the feed water specified. Any limitation on the period of uninterrupted operation with regard to feed water or electrode life shall, be specified by the Tenderer.

4.5.1.3.10 The boiler and integral pipework: shall be lagged to give an economical heat insulation system.

4.5.1.3.11 Adequate allowance: for maintenance, access and inspection shall be made on the package units.

4.5.1.3.12 All flanges: shall be in accordance with the requirements of SANS 1123.

4.5.1.3.13 Companion flanges: shall be supplied where the Contractor is unable to supply equipment with flanges in accordance with the requirements of SANS 1123.

4.5.1.3.14 All moving parts: shall be protected by guards which shall be approved.

4.6 ELECTRICAL EQUIPMENT

4.6.1 All electrical equipment: shall be approved.

DS SPEC 462001



4.6.2 The cast iron electrode assembly: shall be supported from and be removable with the top cover of the pressure vessel. The electrical connections to the electrodes shall pass through the top cover via porcelain insulators, designed to avoid lateral strain. A neutral shield, insulated from the pressure vessel shall be provided and this shall be supported from the top cover with porcelain insulators.

The neutral shield shall be designed to be sacrificial.

4.6.3 A totally enclosed sheet steel panel: with front lockable door shall be manufactured to house all the electrical components and control wiring. The panel shall be designed with a separate compartment for the main supply busbars and connections.

The following equipment shall be mounted on the panel door:

4.6.3.1 Ammeter: electrode amperage. The maximum amperage shall be marked on the face.

4.6.3.2 Feed water pump: off/on switch.

4.6.3.3 Load setting switch: percentage maximum load required from boiler.

4.6.3.4 Hand/auto/off blow down selector switch.

4.6.3.5 Lamp indication red: H T Breaker "closed".

Lamp indication green: H T Breaker "tripped".

4.6.3.6 Push button for H T Breaker "on".

Push button for H T Breaker "off".

4.6.3.7 Lamp indication red: Auxiliary power "on".

Lamp indication green: Auxiliary power "off".

All other electrical control equipment i.e. timers and contactors etc. shall be mounted in the panel and be wired in accordance with the requirements of Debswana 544002 for low voltage switchgear.

A main electrode supply circuit breaker shall not be provided.

4.6.4 Provision shall be made: to accept a separate auxiliary power supply from an alternative supply source for the feed pump motor.

4.6.5 Power supply:

4.6.5.1 Main power supply: shall be either top or bottom entry.

Top entry shall be either for cables or encapsulated busbars.

Provision shall be made for landing of cables etc.

Irrespective of whether the panel is top or bottom entry, it shall be vermin proof.

DS SPEC 462001



4.6.5.2 Main circuit breaker: The incoming power shall be fed via a suitable rated incoming circuit breaker capable of interrupting a short circuit current stated in the data sheet under system fault level.

4.6.5.3 A separate 0.5kVA, 110V or 220V control transformer: shall be provided. It shall be supplied from the main electrode busbars.

4.6.6 Earth protection

4.6.6.1 Stray currents: (between electrodes/neutral screen and boiler).

The boiler shall be fed directly from its own dedicated transformer and no other supply shall be taken from it. The neutral point of the transformer shall be earthed through a 27ohm 10amp continuously rated resistance. A 100 : 1 CT (ring type) shall be fitted between the neutral point and resistance. This C T shall be connected to a 1amp Adit relay on the transformer primary supply H T panel.

The Adit relay shall be connected into the H T tripping circuit to trip the H T Breaker if stray currents flow between the neutral screen/electrodes and the shell. An indicator shall be required to be installed on the boiler control panel to indicate the reason for the boiler trip.

4.6.6.2 Earth monitoring protection: (touch potential) a 100ohm 1amp continuously rated resistance shall be installed between the tank and earth through a 5amp Adit relay mounted on the H T panel. The Adit relay shall be connected into the tripping circuit to trip the H T Breaker if there is current flow in the resistance.

(Note: This shall indicate that there is a large resistance in the earth bonding of the boiler tank i.e. poor earth bond). An indicator shall be required to be installed in the boiler control panel to indicate the reason for the boiler trip.

4.6.6.3 All metallic parts: other than the insulated electrodes shall be solidly banded together.

4.6.7 The following controls: shall be incorporated in the overall operational system of boiler.

4.6.7.1 Modulating pressure control: the automatic current control according to the fluctuation in the steam pressure.

4.6.7.2 Conductivity valve: a solenoid valve actuated by a timer for a set time to bleed water from the boiler inside the area of neutral screen to keep the conductivity of the water at an acceptable level.

4.6.7.3 High limit pressure control: shall be designed to operate above the working pressure of the boiler and, when activated, open the load control valve to drain water from the boiler, thus reducing the load or eventually stopping the generation of steam.

4.6.7.4 Load control valve: similar to the conductivity valve but operated from the control relay by the steam pressure above the operating pressure or the hand control being turned to a lower setting. This allows water to escape from the boiler into the feed tank to reduce the steam production. If the hand control is set at zero to shut down the boiler, it shall lower the level to just below the bottom of the electrodes so that no current can pass.

DS SPEC 462001



4.6.7.5 Automatic blowdown valve: system shall be installed consisting of a motorised valve, a timer for measuring the intervals in hours between blowing down and a timer for measuring the length of operation in seconds.

4.6.7.6 No volt solenoid valve: shall be fitted to open if control power is lost, i.e. the boiler vessel shall drain empty.

4.6.7.7 Over-current control: shall be fitted to control the current if a large overload is called for, i.e. if the boiler is started with a high water level or water with a low/cold conductivity level. A solenoid valve shall discharge the excess water to bring the load back to the normal setting.

4.6.7.8 Feed water and blow down tank: with an inlet supply water level control valve shall be supplied. The tank shall be mounted so that:

4.6.7.8.1 Feed water pump shall be fitted between tank and boiler vessel. Hand valve and check valves shall be installed between the pump and the tank.

4.6.7.8.2 All dumped or water returned from the circuit shall be drained into feed the water tank. Blow down and bleed water shall be dumped into the drain.

4.6.7.9 Master pressure switch control: where two or more electrode boilers are to be used on a common circuit, it could be required that a master pressure switch control be fitted to control all the boilers.

4.6.7.10 Load reduction (MD control): provision shall be made in the control circuit that loads can be reduced immediately to 30% of full load current and be held there until unlatched. (Required for maximum demand control).

4.7 INSTRUMENTATION

4.7.1 All instrumentation equipment: shall be approved.

4.7.2 The boiler supplying steam on demand: shall have its load controlled by the steam pressure in the steam discharge manifold.

4.7.3 The boiler instrumentation such as pressure gauge and sight glass: shall be supplied in accordance with the requirements of the Minerals Act (Act 50, 1991).

4.8 CORROSION PROTECTION

4.8.1 The corrosion protection system used: shall be approved.

4.8.2 Equipment, which is lagged: shall be given a primary coat only.

4.8.3 Shell insulation: shall be approved and used with a non-rust metallic protection cover, eg. baked enamel or stainless steel.

4.9 NOISE LEVELS

The noise levels of all equipment shall not exceed 85dBA measured at a distance of 1 metre from the equipment.

DS SPEC 462001



5 QUALITY ASSURANCE REQUIREMENTS

Debswana QAP 100 shall apply.

6 TEST AND INSPECTION METHODS

6.1 PERFORMANCE TEST AT SITE

6.1.1 The Contractor: shall witness the statutory boiler hydraulic test with the Company personnel.

6.1.2 The site performance test: shall be conducted by the Contractor within 3 months of commissioning. The Contractor shall advise the Engineer of the date he proposes to perform the site test and shall give the Engineer one-week notice to make arrangements to witness the tests.

6.1.3 Once stable conditions have been reached: the performance test shall be conducted on a continuous basis for a maximum period of 3 hours during which time measurements and samples shall be taken at two-minute intervals.

6.1.4 Three site performance tests: shall be conducted and shall be as follows:

6.1.4.1 Capacity test at maximum continuous rating.

6.1.4.2 Capacity test at normal continuous rating.

6.1.4.3 Test on the performance of the boiler controls.

To verify compliance with the guarantee, the following parameters shall be measured during the site capacity tests:

6.1.4.3.1 Steam flow.

6.1.4.3.2 Steam temperature, pressure and dryness.

6.1.4.3.3 Feed water temperature, flow and analysis.

6.1.4.3.4 Power input.

6.1.4.3.5 Thermal efficiency.

6.1.5 A site performance test: shall be performed to verify the performance and the ability of the instrumentation to control the following parameters:

6.1.5.1 Boiler load.

6.1.5.2 Conductivity of feed water.

6.1.5.3 Boiler level control.

6.1.6 The method of test, sampling and interpretation of results: shall be mutually agreed upon between the Engineer and the Contractor. It is the Contractor's responsibility to prove to the satisfaction of the Engineer that the equipment supplied operates in accordance with the most adverse process requirements specified in the Data Sheet.

DS SPEC 462001



6.2 WORKS TEST AND INSPECTION

6.2.1 All equipment: shall be inspected at the Contractor's premises prior to delivery to ensure compliance with the requirements of this specification, the Minerals Act (Act 50, 1991) and BS1894.

6.2.2 The Contractor: shall appoint an approved inspection authority at his own cost to approve and certify that the boiler has been manufactured in accordance with the requirements of BS 1894.

6.2.3 Before delivery to site and where practical: equipment shall be trial-assembled and the leading dimensions checked.

6.2.4 All the statutory inspection documentation: shall be supplied.

DS SPEC 462001



APPENDIX A: RELATED DOCUMENTS

Debswana 538/13 : Low voltage (525V) squirrel cage induction motors up to 150kW

Debswana 544/2 : Low voltage switchgear

Debswana QAP 100 : Quality management systems for critical and major products

BS 759 : Valves, gauges and other safety fittings for application to boilers and to piping installations for and in connection with boilers

BS 1894 : Specification for the design and manufacture of electrode boilers of welded construction

BS 5970 : Code of practice for thermal insulation of pipework and equipment (in the temperature range -100°C to +870°C)

SANS 1123 : Steel pipe flanges

The Minerals Act (Act 50, 1991)

The Occupational Health and Safety Act (Act 85, 1993)

APPENDIX B: RECORD OF AMENDMENTS

Nil

DS SPEC 462001



APPENDIX C: TECHNICAL AND OPERATING DATA

TO BE COMPLETED BY THE COMPANY

Operating conditions 1. Operating environment

• Location • Ambient temperature max min • Environment conditions • Operating schedule hrs/day min days/year

2. Service details 2.1 Steam output requirements for boiler at steam discharge manifold:

• Pressure kPa • Temperature °C • Normal continuous steam flow kg/h • Peak continuous steam flow kg/h

• Max percentage moisture in steam

%

2.2 Power supply available:

System fault level KA Electrode voltage 525V - 380V 3 phase and neutral Auxiliary voltage 525V - 380V 3 phase Control voltage 220V - 110V single phase

2.3 Master pressure switch control Required Not required

2.4 Electrode power supply entry Top entry cable

Top entry busbars

Bottom entry cable

Bottom entry 2.5 Feed water detail

Total dissolved solid (max) Conductivity Total hardness Ph

2.6 Condensate return water is required to be fed into feed water tank Yes No

DS SPEC 462001



APPENDIX D: EQUIPMENT DETAILS

TO BE COMPLETED BY THE CONTRACTOR 1. OPERATING PARAMETERS

Steam output for one boiler at steam discharge manifold • Pressure kPa absolute • Temperature °C • Maximum continuous

rating

Steam flow kg/hr Percentage moisture in steam % Power consumption kW Thermal efficiency % Feed water temperature °C Electrode voltage V Electrode current Amps Total dissolved solids mg/litre

2. COMPONENT DETAILS 2.1 Boiler

• Height mm • Diameter mm • Plate thickness mm • Plate material • Type of thermal insulation • Thickness of thermal insulation mm

2.2 Electrode • ....................................................…………. • ..............…..................................…………. • Current density amps/mm2 • Distance to boiler shell mm • Method of power control ............................ • Life of electrodes Years

2.3 Insulators 2.4 Feed pump

• Type of pump • Max flow kg/hr • Discharge pressure m • Speed rpm • Motor power kW • Motor voltage V

2.5 Instrumentation • Method of load control...........……………………………… • Method of level control .........……………………………… • Method of T.D.S. control .…………………………….........

debswana spec 462001

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