## What is a Pressure Reducing Valve?

Many accessories are required in water supply systems to permit its appropriate operation. Like to isolate, regulate and drain pipe sections for test, installation, cleaning and repairs, a number of appurtenances or auxiliaries are generally installed in the pipe line. The appurtenances provided on the pipe line can be broadly classified on following categories.

• Controlling appurtenances
• Protective appurtenances
• Data collecting appurtenances
• Miscellaneous appurtenances

For Controlling and regulating the flow of pipe, different types of valves are used. The selection of valves are depends on duty of valves.

These are used to automatically maintain a reduced pressure within reasonable limits on the downstream side of pipeline. These are mostly used in domestic water supply systems as the fluids flowing at high pressure may damage other domestic water supply systems and other fixtures equipment connected on the line.

Courtesy - CTG India

Such valves are installed in high rise buildings with more than 8 storeys. In a 14 storey building, when the water is allowed to flow downstream for water supply, the pressure at lower storey i,e. On ground floor shall accede 1 kg/cm2 or 1.5 kg/cm2 at outlet, which may harm the fixture and may cause leakages from pipeline too. In such circumstances such PRV are installed on intermediate floor so that pressure in lower storey reduces to within the pressure limits.

When water flows through a pressure reducing valve at the rate given below, with the inlet pressure is being maintained at 1.7225 MPa (17.225 kg/cm2)

The nominal diameters of pressure reducing valves and flow capacities are tabulated as given below:

 Nominal Size (mm) 15 20 25 32 40 50 Flow (Litres/s) 0.63 1.05 1.58 2.56 3.46 4.89

The Various parts of these valves are made of cast iron, steel and other alloys and the design of the valve is made such that in case of failure of any part of the valve, It is capable of maintaining a continuous flow of water to the system.

Pressure reducing Valve (PRV) requires regular maintenance. For this regular maintenance a bypass arrangement with isolating valves provided.  And it allows the maintenance work without taking the main pipeline out of service.

Needle type valves which can be hydraulically controlled or motor operated with a pressure regulator are used for large aqueduct mains.