Instruction Manual
D104197X012
NPS 8 CHP Valve
September 2016
10
For the spring‐loaded PTFE V‐ring packing shown in figure 2,
tighten the packing flange nuts until the shoulder on the
packing follower contacts the bonnet.
For graphite packing,
tighten the packing flange nuts to the maximum recommended torque shown in table 2. Then,
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 2. Then, tighten the remaining flange nuts until the
packing flange is level and at a 90‐degree angle to the valve stem.
17. Mount the actuator on the valve body assembly, and reconnect the actuator and valve plug stems according to the
procedures in the appropriate actuator instruction manual.
Trim Removal
Note
Avoid personal injury by supporting the valve properly while removing the trim or while servicing the trim or internal body.
Key numbers referenced in this procedure are shown in figure 4, except where indicated.
1. Remove the actuator and bonnet by following steps 1 through 6 of the replacing packing procedure. Observe all
warnings and cautions in that procedure.
2. Lift the valve stem and attached valve plug out of the valve body. If the valve plug is to be reused, tape or otherwise
protect the valve plug stem and the valve plug seating surface to prevent scratches.
3. Lift out the cage (key 2) and the bonnet gasket (key 15) and three cage gaskets (key 16).
4. Remove the seat ring (key 6) and the seat ring gasket (key 17).
5. Inspect the parts for wear or damage and replace if needed.
6. Refer to the Valve Plug Maintenance procedure or to the Lapping Seats procedure.
Valve Plug Maintenance
Key numbers used in this procedure are shown in figure 4, except where indicated.
1. With the valve plug (key 3) removed according to the trim removal procedure, proceed as appropriate:
For the CHPT valve,
work the retaining ring (key 9) off the valve plug with a screwdriver. Carefully slide the backup ring,
anti‐extrusion rings (keys 8 and 10), and seal ring (key 7) off the valve plug.
2. To replace the valve plug stem (key 4), drive out the pin (key 5), and unscrew the stem from the valve plug.
CAUTION
Never reuse an old stem with a new valve plug. Using an old stem with a new plug requires drilling a new pin hole in the
stem. This weakens the stem and may cause the stem to fail in service. If a new valve plug is required, always order a valve
plug, stem, and pin as an assembly. Specify the correct part number of each of the three parts, but state that the parts are
being ordered as an assembly. A used valve plug may be reused with a new stem.
