Replacement Of Installed Bore Seal Trim; Trim Removal (Bore Seal Constructions) - Fisher EHD series Instruction Manual

Instruction Manual
D100392X012
CAUTION
To avoid excessive leakage and seat erosion, the valve plug must be initially seated with sufficient force to overcome the
resistance of the Bore Seal plug seal and contact the seat ring. You can correctly seat the valve plug by using the same force
calculated for full load when sizing your actuator. With no pressure drop across the valve, this force will adequately drive
the valve plug to the seat ring, thus giving the Bore Seal plug seal a predetermined permanent set. Once this is done, the
plug/retainer assembly, the cage, and the seat ring become a matched set.
With full actuator force applied and the valve plug fully seated, align the actuator travel indicator scale with the lower end
of valve travel. Refer to the appropriate actuator instruction manual for information on this procedure.

Replacement of Installed Bore Seal Trim

Trim Removal (Bore Seal Constructions)

1. Remove the valve actuator and bonnet following the appropriate instructions in the Replacing Packing section of
this manual.
CAUTION
To avoid leakage when the valve is returned to service, use appropriate methods and materials to protect all sealing
surfaces of the trim parts during maintenance.
Use caution when removing piston ring(s) and the Bore Seal plug seal to avoid scratching any sealing surface.
CAUTION
Do not remove the valve stem from the plug/retainer assembly unless you are planning to replace the valve stem.
Never reuse an old valve stem with a new plug or reinstall a valve stem after it has been removed. Replacing a valve stem
requires drilling a new pin hole in the stem. This drilling weakens the stem and may cause failure in service. However, a
used valve plug may be reused with a new valve stem.
2. Remove the plug/retainer assembly (with Bore Seal plug seal), cage, and seat ring from the valve body following the
appropriate instructions in the Trim Removal section of this manual.
3. Locate the staked thread on top of the valve plug (figure 7). The staked thread secures the retainer. Use a drill with a
1/8 inch bit to drill out the staked area of the thread. Drill approximately 1/8 inch into the metal to remove the
staking.
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(s) from the groove(s) in the Bore Seal retainer.
5. After removing the piston ring(s), locate the 1/4‐inch diameter hole in the groove. In a retainer with two piston ring
grooves, the hole will be found in the upper 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.
EH Valves NPS 8 through 14
June 2017
19