Pressure Safety Valves (PSV) or Pressure Relief Valves are important instruments in the process / manufacturing industry to protect enclosed equipment or vessels from over-pressure scenarios.
A pressure safety valve (PSV) protects the concerned equipment or vessel in case of pressure build up, by opening up and releasing the fluid service to lower the internal pressure.
PSV design, procurement & installation
Safety valves are designed by analyzing the concerned equipment, related fluid service, then simulating the overpressure scenario to finally perform pressure safety valve sizing calculations.
Based on the sizing calculations, PSV datasheet is prepared and a safety valve is procured and then installed on the equipment to be protected.
But, before the plant is operational and one can rely on the PSV to protect the equipment from overpressure, it is important that the PSV has been tested.
There are two ways for testing a PSV.
In site or online PSV testing
If the valve is already operational, in situ psv testing would prove more cost effective as it can allow the plant operations to go on while testing is being done.
But on the other hand, per valve PSV testing costs are much higher.
Bench testing for PSVs
Bench testing for PSVs requires removing the relieving devices from their installation and then carrying out a full functional test to check how the valve behaves in case of over pressure scenario.
Correspondingly, PSV testing cost on per valve basis turns out to be quite low in the bench testing case. But it can result in loss of production involving equipment shutdown and removal of valve for testing purpose.
Following factors are closely examined during a PSV test -
- The valve should open up at set pressure of the PSV.
- The discharge fluid rate should be achieved corresponding to PSV datasheet for overpressure scenario.
- When the pressure is lowered, the valve seat should come down and close tightly.