Mercer Valve Pressure Relief Valve 91-17D61T14I1

Warning: This inspection requires trained personnel with PPE!

Set pressure of the valve verified?

Enter the set pressure of the valve

Enter the leak test pressure (90% of the set pressure or 5 psi below the set pressure, whichever is greater)

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

Pressure held steady during the test?

Any leakage observed during the test?

Select the method used for testing leakage

If the valve has a CDTP, the leak test pressure will be below the CDTP in lieu of the set pressure

During the visual inspection, the pressure relief valve is checked for any potential issues that may restrict the operation of the valve

This inspection will be performed with the valve still assembled but the valve should not be pressurized for the safety of the person performing the inspection

Corrosion and damage to the valve are some of the common problems found in the visual inspection

Some of the items that should be checked in the visual inspection are as follows

Cap and Seal Wire - The valve cap and seal wire should be checked first on all inspections

These parts prevent adjustment tampering

On the seal wire, there is a pressed security seal that has an impression on it to indicate the certified company that last adjusted the set point the valve

When this seal wire is cut or removed, it indicates that someone may have adjusted the set point or altered the valve

This voids any warranty the valve had

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

Seat inspected for cuts and abrasions

Seat polished and restored if minor scratches or abrasions are present

Seat replaced if deep abrasions and cuts are present

Diameter, Ds, of the nozzle measured

Spherical surface portion that engages the seat is clean and smooth

Spherical surface polished if minor imperfections exist

Disk replaced if spherical surface is damaged or scratched

Warning: This procedure requires trained personnel with PPE!

Place the PRV in an arbor press upside down

Does the PRV's set spring have initial tension?

Place a rod through the inlet that touches the disk. The rod should fit in the inlet base without damaging the seat or touching the side walls of the nozzle insert.

The lift is the measurement of the displacement of the disk from the closed position to the mechanical stops at the fully open position.

The shaft of the arbor press will press against the rod sticking out of the valve inlet base.

Apply a slight force using the arbor press to find the lift.

Enter the displacement of the arbor press shaft as measured by the dial indicator. This is the PRV's lift.

The minimum lift for certified PRVs can be found in NB-18 publication, which is located on the National Board website www.nationalboard.org.