Analysis and proper selection of valves is one of the key requirements for reliable operation of a water or wastewater system . Selection criteria of valves includes capacity, pressure loss, controllability, torque, cavitation and transients. Properly selected and designed valves for water supply systems must have good hydraulic performance, reliable operation, reasonable initial cost and low maintenance cost. The key to achieving such a system is a thorough initial design. Valves serve a variety of functions as mentioned :
- Isolation / Shut-off of pipe sections
- Prevent reverse flow to protect pumps from reverse rotation and prevent pipe from draining
- Provide safe filling of pipeline
- Release air during filling and operation
- Vacuum relief during draining or pipe rupture
- Control flow
- Control pressure or water level
- Cause or control cavitation
Each of these applications requires different considerations. Broadly, the valves are segregated in two sections :
- Conventional valves
- Control valves
Under the conventional category, the most used valves are :
- Gate valve
- Butterfly valve
- Non-return valve
- Air valve
