Mercer Valve Pressure Relief Valve 95-65B12001

During the set pressure inspection, the set pressure is verified in accordance with the ASME Boiler and Pressure Vessel Code.

For all valves set 70 psi (500 kPa) and above, the set pressure has a tolerance of ±3% of the nameplate set pressure.

For all set pressure below 70 psi (500 kPa), the tolerance is ±2 psi (±15 kPa) of the nameplate set pressure.

If the valve has a CDTP associated with it due to temperature and/ or backpressure, the test pressure is checked to the CDTP.

Even with a CDTP, the set pressure tolerance is calculated based on the actual nameplate set pressure.

The set pressure test should be performed before (if it passes the visual inspection) and after any repairs.

The set pressure is inspected to the definition listed in NB-18, a publication by the National Board of Pressure Vessel Inspectors, which is found at http://www.nationalboard.org/.

This publication lists all ASME Boiler and Pressure Vessel Code certified pressure relief valves.

It indicates the correct set pressure definition and other characteristics of a valve.

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.

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

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

For analog gauges, is only the middle 1/3 or less of the gauge used?

Is each 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

Note any issues found during the visual inspection

If the valve fails the visual inspection, do not proceed with set pressure inspection and leak inspection

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

Enter the lift measurement (difference between initial and final position)

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

Does the lift meet the minimum requirement?

Sign off on the valve lift check

Warning: This inspection requires trained personnel with PPE!

Set pressure of the valve verified?

Note: Leak tests are always performed below the set pressure of the valve, usually at a certain percentage of the set pressure.

The leak check is usually performed at 90% of the set pressure or 5 psi (34.5 kPa) below the set pressure, whichever is greater.

If the valve has a CDTP, the leak test pressure will be below the CDTP in lieu of the set pressure.

Mercer Valve should be contacted for proper leak pressure and specification for the valve.

In the tests, the pressure is held steady for a length of time and the valve is observed for any leakage.

Did the valve pass the leak inspection?