Pressure relief valves are used on liquid storage
tanks and other process vessels or systems to
prevent structural damage due to excess
internal pressure.
Storage tanks are pressurized when liquid is
pumped in, compressing the existing vapor or
when rising temperatures cause increased
evaporation or expansion of existing vapor.
To prevent tank damage, vapor must be allowed
into or out of the tank at specified pressure condition. The volume rate of venting
depends upon the tank size, volatility of the tank contents, the pumping rates and the
temperature.