Introduction
For proper working of control valves there are some tests .they are commonly called as control valve pressure test.There are 3 types of Control valve pressure tests
Body test
- For body test blind the output of control valve using blind flange
- Valve should be fully opened position either control valve is NO or NC. It should be open at the time of test.
- The other important parameter to check is body rating of control valve.
Body rating is the amount of total pressure which the body and stem seal can withstand without leaking.
- If the body rating is 300 psi
- The pressure of water that should give through inlet of control valve is 300 * 1.5 = 450 psi
- With the help of pump produce 450 psi in the control valve and with the help of master gauge we can make sure that pressure is 450 psi
- Then close the mechanical valve.
- Check whether any leakage of water through outlet of control valve.
- If there is no leakage the body test is passed.
Seat leakage test(flow test)
- For flow test outlet of the control valve should be open
- The valve should be fully closed
- The procedure is same as body test
- Apply 450 psi to the valve and check for any leakage.
- If there is leakage i.e. due to trim damage, seat ring damage, actuator and valve stem are not properly connected and aligned.
Function test
- Check whether the valve is properly assembled.
- The valve, i/p converter, current generator, and instrument air supply are set up.
- Instrument air supply Is checked. It is set according to the i/p converter requirements
- 4 ma current signal is applied to the i/p converter the valve stem shall be in 0% travel
- When 20 ma is applied 100% travel should be done
- If the valve stem travel indication didn’t show correctly then calibration is to done.
