Mercer Valve Pressure Relief Valve 81-12151T18G21

Warning: This inspection requires trained personnel with PPE!

Enter the set pressure of the valve

Enter the CDTP of the valve if applicable

Contact Mercer Valve Co. Inc. for proper leak pressure and specification for the valve.

Did the pressure hold steady during the test?

Observations during the leak test

Select the method used for testing leakage

Did the valve pass the leak inspection?

Offsite testing allows for the most thorough and accurate testing and inspection. The valves are removed from the units and brought to a shop.

In the shop a valve can be completely tested and inspected.; The shop environment gives the technician the most advantages because more tools are available, there is adequate space to work, and test benches enable accurate results.

All of the same concerns in testing are still present in offsite testing as in situ testing.

The volume of pressure, valve simmer, pressure losses to the gauges, and supply line pressure are all factors in getting an accurate result.

Proper assembly of a test bench is crucial in limiting these effects. The main disadvantage in offsite testing is time.

A valve must be removed from the unit and then transported to the shop. After testing, it is transported back to the field to be installed.

This time frame can be long and cause delays

For gas/vapor valves, there should be approximately 1/4 ft^3 (7 liters) or more capacity below the valve when setting.

This volume is sufficient to test the set pressure for most 4 x 6 M orifices and smaller valves accurately.

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

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: Ensure the valve is not pressurized before starting the inspection

Cap and Seal Wire in good condition

Seal wire has the impression of the certified company

Flanges Connections in good condition

Threaded Connection in good condition

Outlet free from corrosion or debris

External Surface free from damage

Valve Tag information corresponds to the service conditions

If any of the checks fail, do not proceed with set pressure inspection and leak inspection