A valve which automatically discharges fluid to prevent a pre-determined safe pressure being exceeded. It is generally used for compressible fluids such as steam and other gases which demand quick over-pressure relief.
TYPES OF SAFETY VALVE
Ordinary safety valve
A valve in which the disk lifts automatically at least D/24, where 24 = bore of valve seat.
The valves may be:
a. Direct spring loaded
In which the load is applied directly to the disk by a spring.
b. Lever and weight loaded
In which the load is applied to the disk by a weight acting through a lever and fulcrum.
High lift safety valve
A safety valve in which the disk lifts automatically at least D/12,
(where D = bore of valve seat.)
Full lift safety valve
A safety valve in which the disk lifts automatically a distance giving, when the disk is fully lifted, a discharge area round the edge of the valve seat equal to the area through the seat orifice after deducting the area of guides or other obstructions.