Instruction Manual
D101634X012
HP and HPA Valves
October 2014
26
CAUTION
To avoid excessive leakage and seat erosion, the valve plug must be initially seated with sufficient force to overcome the
resistance of the C-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 through the valve, this force will adequately drive
the valve plug to the seat ring, thus giving the C-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 C-seal Trim
Trim Removal (C-seal Constructions)
1. Remove the valve actuator and bonnet following the appropriate instructions in the Replacing Packing section in
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 c aution when removing piston ring(s) and C-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 C-seal plug seal), cage, and seat ring from the valve body following the
appropriate instructions in the Trim Removal section in this manual.
3. Locate the staked thread on top of the valve plug (figure 13). 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) fromthegroove(s)intheC-sealretainer.
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,theholewillbefoundintheuppergroove.
6. Selectanappropriatetoolsuchasapunchandplacethetipofthetoolintotheholewiththebodyofthetoolheld
tangent to the outside diameter of the retainer. Strike the tool with a hammer to rotate the retainer and free it from
thevalveplug.Removetheretainerfromtheplug.
7. Use an appropriate tool such as a flat-blade screwdriver to pry the C-seal plug seal off the plug. Use caution to avoid
scratches or other damage to the sealing surfaces where the C-seal plug seal makes contact with the valve plug
(figure 14).
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