Mercer Valve Pressure Relief Valve 91-34F51T14U1

Warning: This procedure requires trained personnel with PPE!

PRV placed in arbor press upside down

PRV's set spring has initial tension

Rod placed through the inlet and touches the disk

Rod sized to fit in the inlet base without damaging the seat or touching the side walls of the nozzle insert

Measurement of the displacement of the disk from the closed position to the mechanical stops at the fully open position

Shaft of the arbor press pressing against the rod sticking out of the valve inlet base

Measurement of the displacement of the arbor press shaft

This measurement will be the PRV's lift

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

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

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

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

Warning: This procedure requires trained personnel with PPE!

Valves transported to the shop?

Warning: This inspection requires trained personnel with PPE!

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?

Enter the diameter, Ds, of the nozzle

Spherical surface portion that engages the seat is clean and smooth?

Spherical surface polished with a fine grade abrasive if minor imperfections exist?

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

Cap and Seal Wire in good condition

Flanged Connections in good condition

Threaded Connections in good condition

Outlet free from corrosion or debris

External Surface free from damage

Valve Tag information corresponds to service conditions

If any of the above checks fail, the valve is deemed dangerous to test and should be replaced or repaired immediately

Sign off on the visual inspection