Mercer Valve Pressure Relief Valve 95-70P13075

Warning: This procedure requires trained personnel with PPE!

Upload a photo of the valve in closed position

Enter the initial position of the disk

Upload a photo of the valve in fully open position

Enter the final position of the disk

Refer to NB-18 publication for minimum lift for certified PRVs

Sign off on the valve lift check

Warning: This procedure requires trained personnel!

Are two pressure gauges used 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.

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

Is the selected portion of the gauge more stringent than the set pressure’s tolerance?

For analog gauges, only the middle 1/3 or less of the gauge should be used.

Is the gauge calibrated using a dead weight tester?

Sign off on the monthly gauge calibration

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

Cap and Seal Wire in good condition

Flanged Connections in good condition

Outlet free of corrosion or debris

External Surface free of damage

Valve Tag information corresponds to service conditions

Two tags present on 9500 Series valves

If the valve fails any of the above checks, do not proceed with set pressure inspection and leak inspection

Sign off on the visual inspection

- Pressure Relief Valve In Situ Testing

Testing and inspecting in place eliminates the laborious task of removing and handling the valve.

This is especially desirable with large PRVs.

Additionally, not disturbing the existing connections reduces the chance of compromising the existing seals.

This type of testing is very useful when a system cannot be shut down for long lengths of time.

There are disadvantages to this type of testing.

The inspection process is more difficult because the accessibility of the valve is reduced.

The outlet pipe is often still attached and the internal parts are not observable for the visual inspection.

This can also make it difficult to leak check.

For dependable performance, PRVs must be maintained regularly.

Mercer Valve recommends its PRVs are inspected and tested annually.

After the valve has been installed and a service history has been established, the testing and inspection frequency may be adjusted.

Some guidelines for testing frequencies can be found in NB-23, API 576, and API 598.

Additionally, government jurisdiction should be reviewed.

When maintenance is performed, only qualified repair personnel should complete it.

Qualified repair personnel conducting the annual inspection and testing may alter the maintenance schedule based on the service conditions.

Before performing maintenance, it should be ensured there is no pressure within the main valve or pilot valve.

All 6x8 and larger gas modulating pilots will have a check valve on the pilot inlet line to help with dome loading.