Valve Plug Maintenance; Trim Replacement - Fisher EUT-2 Instruction Manual

EU and EW Series Valves
ring can be improved by lapping. (Deep nicks should
be machined out rather than ground out.) Use a
good quality lapping compound of a mixture of 280
to 600-grit. Apply the compound to the bottom of the
valve plug.
Assemble the valve to the extent that the cage or
cage assembly is in place and the bonnet is bolted
to the valve body. 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 the valve as described in the Trim
Replacement section, 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 shown in figure 8 for EUT-2 and EWT-2 valves
and in figure 7 for EUD and EWD valves.
CAUTION
For valves with a PTFE seal ring
(figure 6), if replacing the valve plug
seal ring (key 28), be careful not to
scratch the surfaces of the ring groove
in the valve plug or any of the surfaces
of the replacement ring, or the
replacement ring may not seal
properly.
1. Remove the valve plug (key 2) according to the
Disassembly section.
2. For seal-ring constructions, carefully pry or cut
the seal ring (key 28, figure 6) from its groove in the
plug.
Install the replacement spring-loaded seal ring with
the open side facing the top or bottom of the valve
plug, depending on flow direction. The open side of
the seal ring should face up (toward the actuator) in
flow-up installations and down in flow-down
installations.
To install the seal ring, first lubricate it with
general-purpose, lithium-base lubricant. Then gently
stretch the seal ring and work it over the top edge of
the valve plug. Give the PTFE material in the seal
ring time to cold flow during the stretching
12
procedure. Avoid jerking sharply on the ring.
Stretching the seal ring over the valve plug might
make it seem loose when it is in the groove, but it
will shrink to its original size after you have installed
the plug into the cage.
3. For piston-ring constructions, each of the
piston rings (key 28, figure 6) is in two pieces;
remove the pieces.
Each new graphite piston ring is furnished as a
complete ring, and each must be broken into two
approximately equal portions. Do this by placing the
ring on edge on a smooth, hard surface and striking
the ring squarely with a hammer. Be sure to match
the broken ends when installing the ring sections in
the valve plug grooves.
CAUTION
Never reuse an old stem (key 7) 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 it to fail in
service. However, a used valve plug
may be reused with a new stem.
4. To replace the valve stem (key 7), drill out the pin
(key 8) and unscrew the stem from the valve plug.
5. Screw the new stem tightly into the valve plug.
Drill through the stem, using a 1/4-inch diameter drill
for the 31.8 mm (1-1/4 inch) stem diameter used in
this valve. Use the hole in the valve plug as a guide.
Remove any chips or burrs, and drive in a new pin to
lock the assembly.

Trim Replacement

Except where indicated, key numbers are shown in
figure 7 and 8.
1. Proceed as appropriate:
For EUT-2 or EWT-2 valves:
For all sizes except NPS 12 and 16 x 12, turn the
seat ring (key 9) into the cage (key 3) with a bar
inserted through the seat ring slots.
For NPS 12 and 16 x 12, insert cap screws in the
two 3/8-inch tapped holes in the bottom of the seat
ring (key 9). Use a bar to pry against the cap screws
and turn the seat ring (key 9) into the cage (key 3).
Instruction Manual
August 2010