Circulating water plant

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.
System description.
Circulating water pumps.
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. 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, standards of the Hydraulic Institute, USA or equivalent.
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 carried
out as per ATC-105 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.
CW treatment system.
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.
Mechanical description of CW plants.
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Codes and standards.
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