Safety valve or pressure relief valve has a vital role in a factory/industry, safety valves release automatically the excess pressure if it has reached its setting value so as not to endanger the equipment, workers and the surrounding environment.
In order for the safety valve to function according to its specifications, it is necessary to conduct testing both when the equipment is operating and in conditions not operating by using a unit of testing equipment.
There are several techniques that make it possible to do safety valve testing, among others:
Tests on actual operations: This technique has the advantage of guaranteeing that all operating characters from the valve, set pressure, lift and bow down are acceptable. But this method of testing is often impractical and sometimes even impossible to do.
Test on non-operation: The test is in a non-operating condition where the valve is removed and tested using a test bench in the shop.
Cold Differential Pressure Test:
The test is done by giving static pressure from inside, where the safety valve is set to start popping on a test bench. This test condition is not exactly the same as the operating conditions so that the amount of pressure is determined by including corrections for operating conditions such as back pressure or temperature correction. Thus, it is expected that the same pressure value will be obtained if the safety valve is tested under actual operating conditions.
Tightness test aims to test leaks in the safety valve and is done after completion/success in test popping and setting the pressure according to specifications.
Tightness test according to API 527 standard is done by closing the outlet channel with a cover plate equipped with tubing which is inserted into a water container to observe the leakage level as in the following figure:
In the case of pressure the test is 90% of the pressure setting, or 0.0350 bar under set pressure if the pressure is set below 3.5 bar.
Testing can be done by referring to a technical standard (eg API) or standard from manufacturer valve. Before testing the safety valve must be inspected first.
The test fluid used depends on the type of safety valve and service:
a. Gas testing:
The safety valve is set and set in dry conditions with pressurized air or nitrogen from the bottle.
b. Liquid testing:
Valves are regulated and set using pressurized oil or clean water.