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Acirculating water plant orcirculating water system is an arrangement of flow of water infossil-fuel power stations,chemical plants, andoil refineries. Such a system is required because variousindustrial process plants usesheat exchangers, and also foractive fire protection measures. In chemical plants, for example incaustic soda production, water is needed in bulk for the preparation ofbrine. The circulating water system in any plant consists of acirculator pump, which develops an appropriatehydraulic head, andpipelines to circulate the water in the entire plant.
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 standby pumps are also connected parallel to CW pumps. It is recommended that these pumps must be constantly driven by constant-speedsquirrel-cageinduction motors. CW pumps are designed as per IS:9137,[2][3] standards of the Hydraulic Institute, USA, or equivalent.
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 carried out 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 ofCentral Electricity Authority, two mechanical-draftcooling 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 forcondenser cooling. They use either closed-cycle cooling by using cooling towers or once-through cooling. The selection of the type of system is based on the thermal pollution effect on seawater and techno-economics based on the distance of the power station from the coast and the cost of pumping seawater.
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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, and sewage |
| 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 to 2000mm) |
| 12 | IS: 3832 | Hand-operated chain pulley block |
| 13 | IS: 4682 | Code of practice for lining of vessels and equipment for chemical processes-rubber lining |
| 14 | IS: 5120 | Technical requirements for rotodynamic special-purpose pumps |
| 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 |
