Trim Maintenance; Trim Removal - Fisher NPS 12 Instruction Manual

Large ET and ED Valves
July 2014
16. Install new packing and the metal packing box parts according to the appropriate arrangement in figure 3. Place a
smooth-edged pipe over the valve stem, and gently tap each soft packing part into the packing box one piece at a
time, being sure that air is not trapped between adjacent soft parts.
17. Slide the packing follower, upper wiper, and packing flange (keys 13, 12, and 3, figure 4) into position. Lubricate
the packing flange studs (key 4, figure 4) and the faces of the packing flange nuts (key 5, figure 4). Replace the
packing flange nuts.
18. For spring-loaded PTFE V-ring packing, tighten the packing flange nuts until the shoulder on the packing follower
(key 13, figure 4) contacts the bonnet.
For graphite packing, tighten the packing flange nuts to the maximum recommended torque shown in table 3. Then,
loosen the packing flange nuts and retighten them to the recommended minimum torque shown in table 3.
For other packing types, tighten the packing flange nuts alternately in small, equal increments until one of the nuts
reaches the minimum recommended torque shown in table 3. Then, tighten the remaining flange nut until the
packing flange (key 3, figure 4) is at a 90-degree angle to the valve stem.
19. Mount the actuator on the valve assembly, and reconnect the actuator and valve stem according to the procedure
in the appropriate actuator instruction manual. Check for leakage around the packing follower when the valve is
being put into service. Retighten the packing flange nuts as required.

Trim Maintenance

Trim Removal

Except where indicated, key numbers in this section are shown in figure 6 for ET valves and in figure 5 for ED valves.
1. Isolate the control valve from the line pressure, release pressure from both sides of the valve body, and drain the
process media from both sides of the valve. If using a power actuator, also shut off all pressure lines to the power
actuator, release all pressure from the actuator, and use lock-out procedures to prevent injury while you work on
the equipment.
2. Remove the actuator and the bonnet according to steps 2 through 5 of the Replacing Packing Section.
CAUTION
Use care to avoid damaging gasket surfaces.
The surface finish of the valve stem (key 7) is critical for making a good packing seal. The inside surface of the cage or cage
assembly (key 3) is critical for smooth operation of the valve plug and for making a seal with the seal ring (key 28). The
seating surfaces of the valve plug (key 2) and seat ring (key 9) are critical for proper shutoff. Assume all these parts are in
good condition, and protect them accordingly unless inspection reveals otherwise.
3. Packing parts can be removed if desired. Replace these parts as described in the Packing Replacement section.
4. Lift the valve plug and stem assembly out of the valve body and set it on a protective surface. If the valve plug is to
be reused, protect the valve plug seating surface to prevent scratches.
5. Install screws or bolts into the tapped holes in the top of the cage assembly (key 3), and carefully lift it out of the
valve body. Remove the gaskets (keys 10 and 11).
6. Proceed as appropriate:
For ET valves (figure 5), the valve has a seat ring seal ring (key 6). Inspect this seal ring, and remove it if replacement is
necessary. The seat ring is screwed into the cage and secured with two tack welds, one on each side of the cage.
Remove the tack welds by grinding or filing them off.
12
Instruction Manual
D103553X012