A circulating water plant or circulating water system is an arrangement of flow of water in fossil-fuel power station, chemical plants and in oil refineries. The system is required because various industrial process plants uses heat exchanger, and also for active fire protection measures. In chemical plants, for example in caustic soda production, water is needed in bulk quantity for preparation of brine. The circulating water system in any plant consists of a circulator pump, which develops an appropriate hydraulic head, and pipelines to circulate the water in the entire plant.
See also: Circulator pump. Circulating water systems are normally of the wet pit type, but for sea water circulation, both the wet pit type and the concrete volute type are employed.[1] In some industries, one or two stand-by pumps are also connected parallel to CW pumps. It is recommended that these pumps must be constantly driven by constant speed squirrel cage induction motors. CW pumps are designed as per IS:9137,[2] [3] standards of the Hydraulic Institute, USA or equivalent.
See also: Cooling tower. In the present era, mechanical induced draft–type cooling towers are employed in cooling of water. Performance testing of cooling towers (both IDCT and NDCT) shall be carriedout as per ATC-105[4] at a time when the atmospheric conditions are within the permissible limits of deviation from the design conditions. As guidelines of Central Electricity Authority, two mechanical draft cooling towers Or one natural draft cooling tower must be established for each 500 MW unit in power plants. The cooling towers are designed as per Cooling Tower Institute codes.
Some coastal power stations or chemical plants intake water from sea for condenser cooling. They either use closed cycle cooling by using cooling towers or once through cooling. Selection of type of system is based on the thermal pollution effect on sea water and techno-economics based on the distance of power station from the coast and cost of pumping sea water. Due to high salt concentration, it is necessary for circulating water make up.
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| Sr No. | IS CODE | Specification |
|---|---|---|
| 1 | IS: 804 | Rectangular pressed steel tanks |
| 2 | IS: 1239 | Mild steel tubes, tubular & other wrought steel fittings |
| 3 | IS: 1520 | Horizontal, centrifugal pumps for clear, cold fresh water |
| 4 | IS: 1536 | Centrifugally cast (spun) iron pressure pipes for water, gas andsewage |
| 5 | IS: 1537 | Vertically cast iron pressure pipes for water, gas and sewage |
| 6 | IS: 1710 | Vertical turbine pumps for clear, cold fresh water |
| 7 | IS: 2002 | Steel plates for boilers |
| 8 | IS: 2062 | structural steel (Fusion welding quality) |
| 9 | IS: 2594 | Horizontal mild steel welded storage tanks |
| 10 | IS: 2825 | Code for unfired pressure vessels |
| 11 | IS: 3589 | Electrical welded pipes for water, gas & sewage (200 to2000mm) |
| 12 | IS: 3832 | Hand-operated chain pulley block |
| 13 | IS: 4682 | Code of practice for lining of vessels and equipment forchemical processes-rubber lining |
| 14 | IS: 5120 | Technical requirements for rotodynamic special purposepumps |
| 15 | IS: 5639 | Pumps handling chemicals and corrosive liquids |
| 16 | IS: 5659 | Pumps for process water |
| 17 | IS: 6393 | Steel pipe flanges |
| 18 | IS: 6547 | Electric chain hoist |
| 19 | BS: 5155 | Cast iron & carbon steel butterfly valves for general purpose |
| 20 | AWWA-C-504 | Rubber seated butterfly valves |