It is two critical time in the operation of a pipeline.
During filling, air that occupies the empty pipe must be evacuated ahead of the incoming liquid in a controlled and efficient manner so that surge and water hammer are minimized and liquid completely fills the pipe. During draining, whether planne dor unexpected, air must be admitted into the system to replacethe out flowing liquid to avoid excessive vacuum and possible pipeline damage.
Air release valve are designed to release accumulated air pockets from the system, while pressured pipelines. Air pocket sincrease energy consumption because pumping operation willbe at higher water heads to overcome pressured air.
Air release valves are have function to protect high shockand surge pressure, water hammer and liquid overflow fromfresh or sea water pipelines.