Mercer Valve Pressure Relief Valve 91-12P11VA7I1

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 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?

Mobile testing units are similar to offsite testing

The valve is removed from the application

This enables a thorough inspection

Mobile testing units can save time because transporting the valve isn’t necessary

Mobile test units are often not set up to test all types and sizes

The testing equipment on a mobile test unit can vary

Some mobile test units have test stands similar to an offsite test stand, allowing for larger valves to be tested accurately

Other mobile test units are set up only for smaller valves

In each case, the limitations of the test stand should be documented and the test stand should only be used for the sizes and pressure that it is designed for;

For dependable performance, PRVs must be maintained regularly.

Mercer Valve Co., Inc. recommends its PRVs are inspected and tested annually.; After the valve has been in installed and a service history has been established, the testing and inspection frequency may be adjusted.

Some guidelines for testing frequencies are found in NB-23, API 576, and API 598.; Additionally, government jurisdiction should be reviewed.; When maintenance is done, qualified repair personnel should perform it.; Qualified repair personnel conducting the annual inspection and testing may alter the maintenance schedule based on the service conditions.

During the inspection, a visual inspection, a set pressure verification, and a leak check should be completed.; These tests can be performed while the PRV is installed on its system or when it’s on a testing bench.; The PRV can only be tested while on its application if there is a method and procedure to apply a controlled pressure to the PRV’s inlet without exceeding any limits of the system.

A visual inspection is used to identify if the PRV is installed properly, is correct for the application, and doesn’t have apparent problems.

Check the nameplate information to verify that the valve is installed on the proper service. A missing nameplate requires immediate addressing.

If the valve is installed on gas/vapor service, the nameplate’s capacity will indicate an air capacity at standard conditions.

If the valve is on liquid service, the nameplate will indicate a water capacity.

Check the seal wire. A broken seal wire indicates that an unqualified person has adjusted the set pressure this also removes any warranty the valve had.

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

Cap and Seal Wire in good condition

Flanged Connections show no signs of wear or improper fastening

Threaded Connections are undamaged

Outlet free of corrosion or debris accumulation

External Surface and attachments are undamaged

Valve Tag information corresponds to the service conditions

If any of the checks fail, the valve should be replaced or repaired immediately

Sign off on the visual inspection