4
SPECIFICATION DWS 1940
DESIGN, MANUFACTURE, SUPPLY, DELIVERY,
INSTALLATION AND COMMISSIONING OF
PACKAGE WATER TREATMENT PLAN
July 1994
RMH/(CD)10008318.TS/p1s1
DWS 1940
PACKAGE PLANT
RMH/(CD)10008318.TS/p3s1
DWS 1940
PACKAGE PLANT
CONTENTS
CLAUSE PAGE NUMBER
1. SCOPE ......
2. INTERPRETATIONS ......
2.1 Supporting specifications ......
3. MATERIALS AND EQUIPMENT ......
3.1 Selection against corrosion ......
3.2 Guarantee ......
3.3 Information and technical data at tendering ......
4. PLANT REQUIRED AND DELIVERIES ......
5. FILTER ......
5.1 Filter media ......
5.2 Pipework ......
5.3 Flow meters ......
5.4 Valves ......
6. LINE DOSING EQUIPMENT ......
6.1 Lime slurry suspension tank ......
6.2 Lime slurry pump ......
7. COAGULANT DOSING EQUIPMENT ......
7.1 Make-up tanks ......
7.2 Transfer pumps ......
8. PIPING FOR CHEMICALS ......
9. ELECTRICAL INSTALLATION ......
10. TOLERANCES ......
11. FINAL COMPLETION ......
12. MAINTENANCE OBLIGATION ......
13. OPERATING AND MAINTENANCE MANUAL ......
14. OPERATING INSTRUCTION BOARD ......
15. TESTING ......
16. MEASUREMENT AND PAYMENT ......
THE TOTAL NUMBER OF PAGES IN THIS SPECIFICATION IS 8
RMH/(CD)10008318.TS/p3s1
DWS 1940
PACKAGE PLANT
1. SCOPE
This specification covers the design, manufacture, supply, delivery, installation, commissioning and maintenance for a 12 months and 24 months guarantee period of the package water treatment plant consisting of filter units, chemical dosing equipment, associated pumps, pipeworks, valves and other ancillary equipment for the treatment of potable water.
2. INTERPRETATIONS
2.1 Supporting specifications
Where this specification is required in a project, project drawings and the project specification shall form part of the contract document.
Reference is made to the latest issues of the following standards:
DWS 1130 Design, manufacture and supply of steel pipes, specials and fittings for duties up to 4.6 Mpa design pressure.
DWS 1131 Lining and coating of steel pipes and specials.
DWS 2510 Valves.
DWS 1930 Supply, installation and commissioning of water treatment plant equipment.
Section 3 Specifications for electrical equipment.
SABS 1200 As applicable.
SABS 241 Water for domestic supplies.
SABS 533 Black polyethylene pipes for the conveyance of liquids.
SABS 558 Cast iron surface boxes, manhole and inspection covers and frames.
SABS 664 Cast iron gate valves for waterworks.
SABS 746 Cast iron pipes and pipe fittings for use above ground in drainage installations.
SABS 763 Hot-dip (galvanised) zinc coating.
SABS 1024 Welded steel fabric for concrete reinforcement.
SABS 044 Welding.
SABS 0142 Wiring of premises.
BS 1247 Manhole step irons.
BS 4504 Circular flanges of pipes, valves and fittings (PN designated).
BS 4994 Design and construction of vessels and tanks in reinforced plastics.
DWS 1940
PACKAGE PLANT
BS 4999 General requirements for rotating electrical machines.
IEC 144 Degrees of protection of enclosures for low-voltage switchgear and control gear.
Act 6/1983 Machinery and occupational safety act.
3. MATERIALS AND EQUIPMENT
3.1 Selection against corrosion
In a water treatment plant the very corrosive nature of the environment and the substances in contact with the materials and equipment requires that special attention shall be given to the selection of materials and equipment capable of withstanding corrosion due to these circumstances.
Any material or equipment showing signs of corrosion during the Maintenance Period shall be rejected and replaced by the Contractor at his own expense with material or equipment resistant to corrosion as shown by a re-test.
3.2 Guarantee
All equipment shall be guaranteed against faulty design, materials and workmanship for a period of two (2) years from the date of final completion. During this period the contractor shall attend to and rectify, at his own cost, any defects which can be attributed to faulty design, materials and workmanship. Normal wear and tear shall be excluded.
3.3 Information and technical data at tendering
Full information and technical data on all materials and equipment offered, shall be supplied at the tendering stage. Manufacturer’s pamphlets and catalogues shall be edited and clearly marked so as to describe the particular equipment offered.
4. PLANT REQUIRED AND DELIVERIES
The Contractor shall be responsible for off-loading all the material and equipment at the site as well as the storing of such material in a depot indicated by the Engineer.
No delivery shall take place on Saturdays, Sundays or statutory non-working days unless special arrangements have been made with and agreed to by the Engineer. The Contractor shall be solely responsible for obtaining transport permits and clearance from road or rail authorities for the transporting and delivery of materials and equipment as well as the compliance with the requirements of such bodies.
The Contractor shall be responsible for the supply, delivery, installation and commissioning of the following:
(a) The treatment unit together with all the mechanical equipment, valves, pumps, interconnecting pipework and electrical work necessary for the correct functioning of the whole.
(b) Chemical dosing apparatus, including a chlorinator and/or all the other treatment equipment required to ensure that the treated water is potable in conformity with SABS 241.
(c) All electrical equipment on the distribution side of a power supply point.
(d) Any other equipment included in the quotation by the Contractor.
DWS 1940
PACKAGE PLANT
5. FILTER
The multimedia sand filter can be manual or automatic in operation.
5.1 Filter media
The grading and the depth of the filter bed shall be such, that the turbidity of the filtered water shall be less than 1 NTU and the turbidity of the settled water being up to 7.5 NTU.
Backwashing of the filter should take place not more than once daily.
5.2 Pipework
The requirements for the pipework are as follows:
(a) Pipework shall be steel or uPVC.
The steel pipes, specials and fittings shall be manufactured in accordance with Specification DWS1130.
Steel pipework shall be epoxy lined and coated in accordance with Specification DWS 1131.
The uPVC pipes, specials and fittings shall comply with SABS 533 Part 2 (latest issue).
(b) Pipe diameters not specified shall be determined by the Contractor to suit equipment offered and shall conform to the required flow rates.
(c) Pipework shall be adequately supported by brackets or other suitable methods. Additional support shall be provided if required by the Engineer.
5.3 Flow meters
Flow meters shall be supplied and installed in the filtered water stream as well as the backwash water pipeline to indicate the filtered and backwash water flow rate.
An integrator is required for each flow meter.
5.4 Valves
Valves supplied shall be suitable for class NP 16 uPVC piping.
All power operated valves shall be provided with a handwheel or other acceptable control for manual operation.
All metallic valves supplied shall be in accordance with the Standard Specification for the Supply of Valves, DWS 2510.
The Technical Schedules included in this document shall be completed at the time of tendering.
6. LIME DOSING EQUIPMENT
If dosing is required and it is not possible to dose Na2CO3 (Sodium carbonate) in soluble form with an ordinary dosing pump, then the following equipment will be required.
DWS 1940
PACKAGE PLANT
6.1 Lime slurry suspension tank
The circular slurry suspension tank shall be manufactured from type 304 L stainless steel or fibre glass that shall comply with BS 4994 (Specification for Design and Construction of Vessels and Tanks in Reinforced Plastics).
The make-up water introduced shall be maintained at a constant level by means of a ball float valve.
All lime slurry suspension piping shall be minimum 50 mm NB uPVC (Class PN 16).
To keep the lime in suspension, an electrically driven stirrer unit shall be fitted to the suspension tank.
The impeller shall be at the centre of the tank and not more than 100 mm from the tank bottom.
To prevent lumps of dry lime from leaving the tank, the outlets shall be protected by metal mesh of suitable corrosion resistance, appropriately sized.
The shaft and propeller of the stirrer shall be stainless steel type 304 L.
6.2 Lime slurry pump
All parts of the pump that come in contact with the lime slurry shall be fabricated of stainless steel.
Clean water injector for flushing the pump shall be installed between the tank and the pump.
The timer must so control the solenoid valve that every injection of clean water shall last 10 seconds at 1 - 2 hours intervals.
6.3 Lime slurry suspension tank needs an adequately sized drainage valve.
7. COAGULANT DOSING EQUIPMENT
7.1 Make-up tanks
(a) Each make-up tank shall be equipped with an electrically driven stirrer unit. The shaft and propeller of the stirrer shall be stainless steel.
(b) The suitable sized motor of the stirrer shall be 220V 50Hz, dust and waterproof unit. All cabling between the stirrer and wallsocket shall be in plastic conduits.
(c) The stirrer shall be fixed to a stainless steel or better support straddling the make-up tank and properly anchored to the floor.
(d) A minimum of two make-up tanks are required.
7.2 Transfer pumps
If it is not possible to dose out of one mixing tank then the requirements regarding the supply of coagulant transfer pumps are as follows:
(a) The pumps shall be plastic pumps capable of handling highly corrosive solution/suspension, e.g. ferric chloride.
(b) The pumping head shall be determined by the Contractor.
DWS 1940
PACKAGE PLANT
(c) A pump shall be capable of transferring the full volume of make-up tank within one (1) hour.
8. PIPING FOR CHEMICALS
All piping to be used for the transfer of diluted chemicals shall be either class NP 16 uPVC or rubber suitable for handling highly corrosive solution/suspensive, e.g. ferric chloride. Diameters of piping shall be sized by the Contractor to suit the required flow rates. The minimum pipe diameter shall be 25 mm.
All piping shall be properly supported/fixed. For piping along walls, ceilings, floors, etc. AVS-PE pipe clamps or equal approved shall be used.
All components of valves shall be from suitable plastic materials.
Installation of these valves into pipelines shall be by means of unions facilitating easy removal.
Handles of valves shall be so positioned that the handle is in line with piping when open and at right angle to the line of piping when closed.
Galvanised mild steel piping may be used for the supply of service water if approved by the Engineer.
9. ELECTRICAL INSTALLATION
All electrical installation shall conform the SABS 0142.
10. TOLERANCES
Tolerances are to be such that the equipment performs within the requirements of this specification.
11. FINAL COMPLETION
On final completion all work in terms of the contract shall be completed. A certificate of completion will then be issued.
12. MAINTENANCE OBLIGATION
The Contractor shall maintain all equipment provided in a good working order during the maintenance period, and shall specify in his tender the number of routine maintenance visits to be undertaken.
The maintenance period shall commence on the day following the final completion, as agreed to by the Engineer.
The Employer reserves the right to undertake any emergency repair work during the maintenance period without the prior consent of the Contractor. The Engineer has the right to decide whether the emergency exists and shall notify the Contractor accordingly. Should this emergency repair work be caused by poor material, faulty workmanship or neglect on the part of the Contractor, the Employer may deduct the cost of the repair work from the outstanding retention money owing to the Contractor.
DWS 1940
PACKAGE PLANT
13. OPERATION AND MAINTENANCE MANUAL
Five comprehensive copies of operation and maintenance instructions in the form of hard covered manuals with a rear pocket enclosing prints of relevant as-built drawings shall be supplied.
All manuals shall be supplied prior to handover/acceptance of equipment. The Completion Certificate will neither be issued nor will the corresponding payment be made until the above manuals and drawings have been supplied.
Operating instruction shall include -
- index;
- pre-start check list;
- step by step description of the approved procedures for all modes of operation of equipment; and
- description of required safety checks.
Maintenance manual shall include -
- index;
- details of routine and regular maintenance work which the manufacturer considers necessary to maintain equipment in satisfactory running order;
- instruction for the repair or replacement of warn or damaged parts;
- schedules of routine testing of electrical equipment (as recommended by specific suppliers);
- spare parts list;
- particular technical data of equipment;
- preference list, including local agents for supply and repairs of specific equipment; and
- all schematic wiring diagrams pertaining to technical equipment.
The Contractor shall, in addition to supplying the above information, undertake to instruct departmental staff and satisfy himself that they are capable of operating all equipment when it has been commissioned.
14. OPERATING INSTRUCTION BOARD
An approved concise operating instruction notice board in "engraved aluminium" shall be supplied and erected at the most appropriate place by the Contractor. Letters shall not be smaller than 8 mm.
15. TESTING
On completion of the installation and as soon as convenient for the client, but not later than five weeks after completion, the complete works shall be started up, tested, and commissioned to the satisfaction of the Engineer.
16. MEASUREMENT AND PAYMENT
The progress payments shall be made during the course of the contract as follows:
- On successful design, manufacture and delivery of the equipment, a lump sum payment of 60% of the contract value shall be made.
- After successful erection another payment of 20% of the contract value shall be made.
- On successful commissioning, testing and training of the works supervisor, a payment of 15% of the contract value shall be made.
- The remaining 5% of the contract value shall be paid after the 12 month maintenance period.