Pressure Relief Valves operate by process pressure. The seat to seal interface is a highly polished disc forced onto a seat by a spring with a known tension. Adjustment of the spring tension dictates the pressure at which the valve will relieve the line pressure i.e. the higher the spring tension, the higher the pressure required to lift the disc off the seat. Some pressure relief valves have a manual over-ride hand lever which can be utilised when the user requires to relieve / dump excess pressure, but where the maximum allowable process pressure has not yet been reached or exceeded.
The primary function of a safety valve is to protect against over-pressurisation of the process piping system. This device ensures that the maximum allowable line pressure can never be exceeded. The secondary function, as described above is for dumping pressure within the system. This can be for operational, or for safety reasons.
|Common Materials of Construction||Material Specifications|
|Standard Carbon Steel||ASTM A105|
|Low temperature Carbon Steel||ASTM LF2|
|Stainless Steel||ASTM A182 F316|
ASTM A182 F316L
ASTM A182 F304
ASTM A182 F304L
ASTM A182 F321
ASTM A182 F347
ASTM A351 CF8M
ASTM A351 CF3M