Valve Plug Maintenance; Assembly - Fisher Design ED series Instruction Manual

Design ED & EAD Class 125-600
Assemble the valve to the extent that the cage and the
cage retainer and bonnet spacer (if used) are in place
and the bonnet is bolted to the valve. A simple handle
can be made from a piece of strap iron locked to the
valve plug stem with nuts. Rotate the handle
alternately in each direction to lap the seats. After
lapping, remove the bonnet and clean the seat
surfaces. Completely assemble as described in the
Assembly portion of the Trim Maintenance procedure
and test the valve for shutoff. Repeat the lapping
procedure if leakage is still excessive.

Valve Plug Maintenance

Except where indicated, key numbers in this section
are referenced in figure 19 for standard 1- through
6-inch constructions, figure 20 for Whisper Trim III
detail, figure 21 for the 8-inch Design ED valve, and
figures 22 and 23 for WhisperFlo trim. Some valve
plug constructions require three piston rings (key 6).
CAUTION
To avoid the piston ring (key 6) not
sealing properly, be careful not to
scratch the surfaces of the ring groove
in the valve plug or any of the surfaces
of the replacement ring.
1. With the valve plug (key 2) removed according to
the Disassembly portion of the Trim Maintenance
procedure, proceed as appropriate:
For the carbon-filled PTFE piston ring, The ring is
split in one place. If there is visible damage, spread
the ring slightly and remove it from the groove in the
valve plug.
To install a carbon-filled PTFE piston ring, Spread
the ring apart slightly at the split and install it over the
stem and into the groove in the valve plug. The open
side must face along the stem, depending on flow
directions, as shown in view A of figure 19.
For the graphite piston ring, The ring can be easily
removed since it is in two pieces. A new graphite
piston ring is furnished as a complete ring. Use a vise
with smooth or taped jaws to break this replacement
ring into halves. Place the new ring in the vise so that
the jaws will compress the ring into an oval. Slowly
compress the ring until it snaps on both sides. If one
side snaps first, do not try to tear or cut the other side.
Instead, keep compressing the ring until the other side
snaps. Be sure to match the broken ends when
installing the ring in the valve plug groove.
10
CAUTION
Never reuse an old stem or adaptor with
a new valve plug. Using an old stem or
adaptor with a new plug requires drilling
a new pin hole in the stem (or adaptor in
case an ENVIRO-SEAL bellows seal
bonnet is being used). This drilling
weakens the stem or adaptor and may
cause failure in service. However, a used
valve plug may be reused with a new
stem or adaptor.
For plain bonnets and style 1 extension
bonnets, the valve plug (key 2), valve
stem (key 7), and pin (key 8) are
available completely assembled. Refer to
the Key 2, 7, and 8 Valve Plug and Stem
Assembly tables in the Parts List.
2. To replace the valve stem (key 7), drive out the pin
(key 8). Unscrew the valve plug from the stem or
adaptor.
3. To replace the adaptor (key 24, figure 18) on
ENVIRO-SEAL bellows seal bonnets, place the plug
stem assembly and valve plug in a soft-jaw chuck or
other type of vise so that the jaws grip a portion of the
valve plug that is not a seating surface. Drive out the
pin (key 36, figure 18). Reverse the plug stem
assembly and valve plug in the soft-jaw chuck or vise.
Grip the flat areas on the valve stem just below the
threads for the actuator/stem connection. Unscrew the
valve plug/adaptor assembly (key 24, figure 18) from
the valve stem assembly (key 20, figure 18).
4. Screw the new stem or adaptor into the valve plug.
Tighten to the torque value given in table 5. Refer to
table 5 to select the proper drill size. Drill through the
stem or adaptor, using the hole in the valve plug as a
guide. Remove any chips or burrs and drive in a new
pin to lock the assembly.
5. For ENVIRO-SEAL bellows seal bonnets, grip the
flats of the stem extending out of the top of the bellows
shroud with a soft-jaw chuck or other type of vise.
Screw the valve plug/adaptor assembly onto the valve
stem. Tighten as necessary to align the pin hole in the
stem with one of the holes in the adaptor. Secure the
adaptor to the stem with a new pin.

Assembly

Except where indicated, key numbers are referenced
in figure 19 for standard 1-through 6-inch
constructions, figure 20 for Whisper Trim III detail,
figure 21 for the 8-inch Design ED valve, and figures
22 and 23 for WhisperFlo trim.
Note