Mercer Valve Pressure Relief Valve 91-12HQ3NA7XC

Warning: This procedure requires trained personnel!

Are two pressure gauges available for testing?

Are the gauges reading identical values within their respective tolerances?

If the gauges are not reading identical values, both should be checked for calibration.

Is at least one of the gauges an analog (dial) gauge that is not liquid filled?

Is the second gauge a digital gauge?

Digital gauges have to be used carefully because quick pressure increases are not always seen on the gauge readings.

Enter the accuracy of the test gauges over their full scale.

The portion of the gauge used should be 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

Enter the leak test pressure (90% of the set pressure or 5 psi below the set pressure, whichever is greater)

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?

Select the method used for testing leakage

For API STD 527, zero bubbles must be observed for one minute to pass leak inspection

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 set pressure definition and other valve characteristics

Use correct fluid for testing: nitrogen or compressed air for gas/vapor service, water for liquid service

Setting procedures should be in accordance with ASME PTC 25

Slowly increase the pressure when within 15% of the set pressure, not more than 2 psi/sec

Common set pressure definitions: 'Pop', 'First Audible Sound', 'First Steady Stream'

Valve connected to a test fixture?

Enter the pressure at which the valve opens

Did the valve open at less than 1.5 times the expected set pressure?

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

Flanged Connections in good condition

Outlet free from corrosion or debris

Valve Tag information verified and 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