Lapping Metal Seats (Bore Seal Constructions); Remachining Metal Seats (Bore Seal Constructions) - Fisher NPS 12 Instruction Manual

Large et and ed valves

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Large ET and ED Valves

July 2014

Figure 10. Stake the Threads of the Bore Seal Retainer

DEFORM THREAD TO

STAKE Bore Seal RETAINER

PISTON

RING

RETAINER

Bore Seal

METAL

PLUG

SEAL

A6779

4. Locate the break between sections of the piston ring(s). Using an appropriate tool such as a flat-blade screwdriver,

carefully pry out the piston ring from the groove in the Bore Seal retainer.

5. After removing the piston ring, locate the 1/4-inch diameter hole in the groove.

6. Select an appropriate tool such as a punch and place the tip of the tool into the hole with the body of the tool held

tangent to the outside diameter of the retainer. Strike the tool with a hammer to rotate the retainer and free it from

the valve plug. Remove the retainer from the plug.

7. Use an appropriate tool such as a flat-blade screwdriver to pry the Bore Seal plug seal off the plug. Use caution to

avoid scratches or other damage to the sealing surfaces where the Bore Seal plug seal makes contact with the valve

plug (figure 11).

8. Inspect the lower seating surface where the valve plug contacts the seat ring for wear or damage which would

prevent proper operation of the valve. Also, inspect the upper seating surface inside the cage where the Bore Seal

plug seal contacts the cage, and inspect the sealing surface where the Bore Seal plug seal makes contact with the

plug (figure 11).

9. Replace or repair trim parts according to the following procedure for lapping metal seats, remachining metal seats,

or other valve plug maintenance procedures as appropriate.