Circulating water plant

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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.

Chemical plant industrial process plant that manufactures chemicals

A chemical plant is an industrial process plant that manufactures chemicals, usually on a large scale. The general objective of a chemical plant is to create new material wealth via the chemical or biological transformation and or separation of materials. Chemical plants use specialized equipment, units, and technology in the manufacturing process. Other kinds of plants, such as polymer, pharmaceutical, food, and some beverage production facilities, power plants, oil refineries or other refineries, natural gas processing and biochemical plants, water and wastewater treatment, and pollution control equipment use many technologies that have similarities to chemical plant technology such as fluid systems and chemical reactor systems. Some would consider an oil refinery or a pharmaceutical or polymer manufacturer to be effectively a chemical plant.

Oil refinery industrial process plant where crude oil is processed and refined into more useful products

Oil refinery or petroleum refinery is an industrial process plant where crude oil is transformed and refined into more useful products such as petroleum naphtha, gasoline, diesel fuel, asphalt base, heating oil, kerosene, liquefied petroleum gas, jet fuel and fuel oils. Petrochemicals feed stock like ethylene and propylene can also be produced directly by cracking crude oil without the need of using refined products of crude oil such as naphtha.

Heat exchanger piece of equipment built for efficient heat transfer from one medium to another

A heat exchanger is a device used to transfer heat between two or more fluids. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact. They are widely used in space heating, refrigeration, air conditioning, power stations, chemical plants, petrochemical plants, petroleum refineries, natural-gas processing, and sewage treatment. The classic example of a heat exchanger is found in an internal combustion engine in which a circulating fluid known as engine coolant flows through radiator coils and air flows past the coils, which cools the coolant and heats the incoming air. Another example is the heat sink, which is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or a liquid coolant.

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. [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.

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 [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.

The Central Electricity Authority (CEA) was a body that ran the electricity supply industry in England and Wales between 1954 and 1957. The CEA replaced the earlier British Electricity Authority (BEA) as a result of the Electricity Reorganisation (Scotland) Act 1954, which moved responsibility for Scottish electricity supply to the Scottish Office.

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

Source: [5]

Codes and standards

Source: [6]

Sr No. IS CODE Specification
1IS: 804 Rectangular pressed steel tanks
2IS: 1239 Mild steel tubes, tubular & other wrought steel fittings
3IS: 1520 Horizontal, centrifugal pumps for clear, cold fresh water
4IS: 1536Centrifugally cast (spun) iron pressure pipes for water, gas and

sewage

5IS: 1537 Vertically cast iron pressure pipes for water, gas and sewage
6IS: 1710 Vertical turbine pumps for clear, cold fresh water
7IS: 2002 Steel plates for boilers
8IS: 2062 structural steel (Fusion welding quality)
9IS: 2594 Horizontal mild steel welded storage tanks
10IS: 2825 Code for unfired pressure vessels
11IS: 3589 Electrical welded pipes for water, gas & sewage (200 to

2000mm)

12IS: 3832 Hand-operated chain pulley block
13IS: 4682 Code of practice for lining of vessels and equipment for

chemical processes-rubber lining

14IS: 5120 Technical requirements for rotodynamic special purpose

pumps

15IS: 5639 Pumps handling chemicals and corrosive liquids
16IS: 5659 Pumps for process water
17IS: 6393 Steel pipe flanges
18IS: 6547 Electric chain hoist
19BS: 5155 Cast iron & carbon steel butterfly valves for general purpose
20AWWA-C-504 Rubber seated butterfly valves

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References

  1. Standard Design Criteria/Guidelines for Balance of Plant for Thermal Power Project 2 X (500MW or above) Section- 6 (Circulating Water System)
  2. IS 9137 (1978): Code for acceptance test for centrifugal,mixed flow and axial pumps - Class C [MED 20: Mechanical Engineering]
  3. https://law.resource.org/pub/in/bis/S08/is.9137.1978.pdf
  4. Standard Design Criteria/Guidelines for Balance of Plant for Thermal Power Project 2 X (500MW or above) Section- 6 (Circulating Water System) Pg 6-6 Section 6.4.3
  5. Standard Design Criteria/Guidelines for Balance of Plant for Thermal Power Project 2 X (500MW or above) Section- 6 (Circulating Water System) ANNEXURE 6A pG 6-17
  6. Standard Design Criteria/Guidelines for Balance of Plant for Thermal Power Project 2 X (500MW or above) Section- 6 (Circulating Water System) Pg6-15 Section ^.7