Mercer Valve Pressure Relief Valve 95-85S16021

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: This inspection requires trained personnel with PPE!

Set pressure of the valve verified?

Note: Leak test pressure should be 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.

Contact Mercer Valve 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

Warning: Only qualified repair personnel should perform this maintenance.

Is there pressure within the main valve or pilot valve?

If there is pressure, remove it before servicing.

Visual inspection: Is the PRV installed properly and correct for the application?

Visual inspection: Any apparent problems with the PRV?

Nameplate check: Is the valve installed on the proper service?

Seal wire check: Is the seal wire broken?

Damage inspection: Any damage to the valve?

Flow inspection: Any issues that would keep the valve from opening or inhibit flow?

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.

9500 Series valves tags inspection

Issues found during the inspection

Sign off on the visual inspection