Mercer Valve Pressure Relief Valve 91-12O33BA7CG

Warning: This procedure requires trained personnel!

Are two pressure gauges used for testing?

Are the gauges reading identical values within their respective tolerances?

Select the type of the first gauge

Select the type of the second gauge

Does the analog (dial) gauge respond to pressure quickly and give accurate readings?

Are quick pressure increases seen on the digital gauge readings?

Do the test gauges have at least 0.25% accuracy over their full scale?

Is the portion of the gauge used selected so that the tolerance of it is more stringent than the set pressure’s tolerance?

Seat inspected for cuts and abrasions

Seat polished and restored if minor scratches or abrasions are present

Seat replaced if damaged with deep abrasions and cuts

Diameter, Ds, of the nozzle measured

Spherical surface portion that engages the seat examined

Spherical surface polished if minor imperfections exist

Disk replaced if spherical surface is damaged or scratched

The following general procedure is recommended for the disassembling of a 9100 Series PRV

Non-standard or “special” configurations are possible and these instructions may not be reflective of them

A special configuration is indicated by a special code at the end of the PRV’s part number

Always make sure there is no pressure in the system prior to removing a PRV

The 9100 Series contains several different orifice sizes

For most C to G orifices, the valves are bottom entry type with the bonnet integral to the body cavity

These valves have a removable inlet base

Larger orifice sized valves are top entry types and have removable bonnets

Warning: This procedure requires trained personnel with PPE!

Is the valve accessible for inspection?

If the valve is not accessible, report the issue to the maintenance team and stop the procedure

Are the internal parts observable for visual inspection?

Are block valves present for set pressure testing?

Is the volume under the valve sufficient for accurate set pressure testing?

Is the gauge placement correct for accurate pressure reading?

Warning: This inspection requires trained personnel with PPE!

The set pressure inspection is performed in accordance with the ASME BPVC.

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 correct fluid for testing has to be used to achieve accurate results.

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.

The procedures for testing set pressure are as follows.

Check the set pressure definition from NB-18.