Mercer Valve Pressure Relief Valve 81-11151T18G21

During the set pressure inspection, the set pressure is verified in accordance with the ASME BPVC.

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

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

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 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 BPVC certified pressure relief valves.

It indicates the correct set pressure definition and other characteristics of a valve.; The set pressure has been defined to achieve a particular operational characteristics.; If the wrong set pressure definition is used in the inspection test, the valve's set pressure will not be accurate and it may not operate appropriately.

The correct fluid for testing has to be used to achieve accurate results.; For gas/vapor service, nitrogen or compressed air is used as the test fluid, while for liquid service, water is used.; If the incorrect fluid is used during the testing, the test's results will be inaccurate.; Depending on the size of the valve and its set pressure, the set pressure discrepancy can vary outside of ASME tolerances.

Setting procedures should be in accordance with ASME PTC 25.; The rate of the system pressure increase should be slow when the pressure is within 15% of the set pressure. Within this range, the rate should never be more than 2psi/sec (15kPa/sec).; Ideally each pressure increment on the pressure gauge should be clearly read as the pressure is increased. Slow pressure increase helps to accurately read the pressure gauge.

Warning: This procedure requires trained personnel with PPE!

If system is not operational, report the issues to the maintenance team and stop the procedure

Is the outlet pipe still attached?

Are the internal parts observable for visual inspection?

Are block valves present for set pressure testing?

Enter the volume under the valve

The following general procedure is recommended for the inspection of an 8100 Series PRV.

New parts should be inspected.

1. Inspect the seat for cuts and abrasions. The seat is the non-metallic element in the nozzle subassembly.

a) If there are only minor scratches or abrasions, the seat may be polished and restored.

b) Polish the seat area lightly with a fine grade abrasive pad. Be careful not to damage the soft seat.

c) If the seat is damaged with deep abrasions and cuts, it should be replaced.

2. Referring to Figure 29, measure the diameter Ds of the nozzle. This diameter must be in the range of values listed in Table

ORIFICE SIZE - ½", NOZZLE DIAMETER Ds, in (mm), 0.620 (15.75) - MINIMUM, 0.622 (15.80) - MAXIMUM

ORIFICE SIZE -¾", NOZZLE DIAMETER Ds, in (mm) 0.914 (23.22) - MINIMUM, 0.916 (23.27) - MAXIMUM

Warning: This maintenance check requires qualified repair personnel!

Is the PRV correct for the application?

Are there any apparent problems with the PRV?

Is the nameplate information correct?

Is there any damage to the valve?

Are there any issues that would keep the valve from opening or inhibit flow?

Are there any problems found during the visual inspection?

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

Details of the security seal on the seal wire

Flanges Connections in good condition

Threaded Connection in good condition

Outlet free from corrosion or debris

External Surface free from damage

Details of any external attachments damage