Mercer Valve Pressure Relief Valve 91-12K22VA7U6

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!

Internal parts visual inspection

Warning: Only trained personnel should perform this procedure

Valve removed from the application

Thorough inspection of the valve performed

Is transporting the valve necessary?

Select the type of mobile test unit used

Document the limitations of the test stand

Test stand used only for the sizes and pressure it is designed for

Warning: This inspection requires trained personnel with PPE!

Seat inspected for cuts and abrasions?

Seat polished and restored if minor scratches or abrasions found?

Seat replaced if deep abrasions and cuts found?

Enter the diameter, Ds, of the nozzle

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

Spherical surface polished if minor imperfections exist?

Warning: This inspection requires trained personnel with PPE!

Refer to NB-18 for set pressure definition and other valve characteristics

Use correct fluid for testing: nitrogen or compressed air for gas/vapor service, water for liquid service

Set pressure discrepancy can vary outside of ASME tolerances if incorrect fluid is used

Rate of system pressure increase should be slow when pressure is within 15% of the set pressure

Set pressure testing procedures are as follows:

Check the set pressure definition from NB-18

For Mercer 9100 Series valves, a crisp “pop” is the definition of set pressure for both gas/vapor and liquid valves

Rigidly connect the valve to a test fixture