Mercer Valve Pressure Relief Valve 91-28E51T11I1

Warning: This procedure requires trained personnel!

Are two pressure gauges used for testing?

Are the gauges reading identical values within their respective tolerances?

Select the type of the first gauge

Select the type of the second gauge

Does the analog gauge respond to pressure quickly and give accurate readings?

Are quick pressure increases seen on the digital gauge readings?

Does the test gauge have at least 0.25% accuracy over their full scale?

Is the portion of the gauge used selected so that the tolerance of it is more stringent than the set pressure’s tolerance?

Warning: This inspection requires trained personnel with PPE!

Set pressure of the valve verified?

Enter the set pressure of the valve

Contact Mercer Valve Co., Inc. for proper leak pressure and specification for the valve

Pressure held steady during the test?

Any leakage observed during the test?

Before this test is performed, the valve must have had its set pressure examined

There are several methods used in testing for leakage

For dependable performance, PRVs must be maintained regularly.

Mercer Valve Co., Inc. recommends its PRVs are inspected and tested annually.; After the valve has been in installed and a service history has been established, the testing and inspection frequency may be adjusted.

Some guidelines for testing frequencies are found in NB-23, API 576, and API 598.; Additionally, government jurisdiction should be reviewed.; When maintenance is done, qualified repair personnel should perform it.; Qualified repair personnel conducting the annual inspection and testing may alter the maintenance schedule based on the service conditions.

During the inspection, a visual inspection, a set pressure verification, and a leak check should be completed.; These tests can be performed while the PRV is installed on its system or when it’s on a testing bench.; The PRV can only be tested while on its application if there is a method and procedure to apply a controlled pressure to the PRV’s inlet without exceeding any limits of the system.

A visual inspection is used to identify if the PRV is installed properly, is correct for the application, and doesn’t have apparent problems.

Check the nameplate information to verify that the valve is installed on the proper service. A missing nameplate requires immediate addressing.

If the valve is installed on gas/vapor service, the nameplate’s capacity will indicate an air capacity at standard conditions.

If the valve is on liquid service, the nameplate will indicate a water capacity.

Check the seal wire. A broken seal wire indicates that an unqualified person has adjusted the set pressure this also removes any warranty the valve had.

Warning: This inspection requires trained personnel with PPE!

Refer to NB-18 for ASME BPVC certified pressure relief valves and correct set pressure definition

Use nitrogen or compressed air for gas/vapor service and water for liquid service

Set pressure discrepancy can vary outside of ASME tolerances if incorrect fluid is used

Rate of system pressure increase should be slow when within 15% of the set pressure

Pressure increase rate should not exceed 2 psi/sec (15 kPa/sec) within this range

Slow pressure increase helps to accurately read the pressure gauge

Common set pressure definitions: 'Pop' - a crisp pop sound from the valve; 'First Audible Sound' - the first sound heard from the outlet of the valve; 'First Steady Stream' - a continuous stream from the outlet of the valve

Check the set pressure definition from NB-18

Warning: Ensure the valve is not pressurized before starting the inspection

Cap and Seal Wire in good condition

Flanged Connections in good condition

Threaded Connections in good condition

Outlet free of corrosion or debris

External Surface free of damage

Valve Tag information corresponds to service conditions

If any of the above checks fail, the valve should be replaced or repaired immediately

Sign off on the visual inspection