Lapping Metal Seats (Bore Seal Constructions); Remachining Metal Seats (Bore Seal Constructions); Trim Replacement (Bore Seal Constructions) - Fisher EHD series Instruction Manual

EH Valves NPS 8 through 14
June 2017
Figure 7. Stake the Threads of the Bore Seal Retainer
DEFORM THREAD TO
STAKE Bore Seal RETAINER
PISTON
RING
RETAINER
Bore Seal
METAL
PLUG
SEAL
FLOW DOWN
A6779
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 9).
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 9).
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.

Lapping Metal Seats (Bore Seal Constructions)

Before installing a new Bore Seal plug seal, lap the lower seating surface (valve plug to seat ring, figure 9) following
appropriate procedures in the Lapping Seats section of this manual.

Remachining Metal Seats (Bore Seal Constructions)

A valve plug with a Bore Seal metal plug seal features two seating surfaces. One seating surface is found where the
valve plug contacts the seat ring. The second seating surface is found where the Bore Seal plug seal contacts the upper
seating surface in the cage. The cage does not require any machining, even when the plug and / or seat ring have been
machined.

Trim Replacement (Bore Seal Constructions)

1. Apply a suitable high‐temperature lubricant to the inside diameter of the Bore Seal plug seal. Also, lubricate the
outside diameter of the valve plug where the Bore Seal plug seal must be pressed into the proper sealing position
(figure 5).
2. Orient the Bore Seal plug seal for correct sealing action based on the process fluid flow direction through the valve.
20
Figure 8. Installing the Bore Seal Plug Seal
Using the Installation Tool
INSTALLATION
TOOL
Bore Seal
METAL
PLUG
VALVE
SEAL
PLUG
A6778
NOTE: PRESS THE INSTALLATION TOOL OVER THE VALVE PLUG UNTIL THE TOOL
CONTACTS THE HORIZONTAL REFERENCE SURFACE OF THE VALVE PLUG.
Instruction Manual
D100392X012
HORIZONTAL
REFERENCE
SURFACE
FLOW DOWN
VALVE
PLUG