Fisher EWS Series Instruction Manual page 17

Instruction Manual
Form 2376
March 2007
where the C-seal plug seal must be pressed into the
proper sealing position (figure 9).
2. Orient the C-seal plug seal for correct sealing
action based on the process fluid flow direction
through the valve.
D The open interior of the C-seal plug seal must
face up in a valve with flow-up construction
(figure 9).
D The open interior of the C-seal plug seal must
face down in a valve with flow-down construction
(figure 9).
An installation tool must be used to
properly position the C-seal plug seal
on the valve plug. A tool is available as
a spare part from Emerson Process
Management or a tool could be
manufactured following the
dimensions given in figure 10.
3. Place the C-seal plug seal over the top of the
valve plug and press the C-seal plug seal onto the
plug using the C-seal installation tool. Carefully
press the C-seal plug seal onto the plug until the
installation tool contacts the horizontal reference
surface of the valve plug (figure 11).
4. Apply a suitable high-temperature lubricant to the
threads on the plug. Then, place the C-seal retainer
onto the plug and tighten the retainer using an
appropriate tool such as a strap wrench.
5. Using an appropriate tool such as a center
punch, stake the threads on top of the plug in one
place (figure 12) to secure the C-seal retainer.
6. Install the new plug/retainer assembly with C-seal
plug seal on the new stem following the appropriate
instructions in the Trim Replacement section of this
manual.
7. Install piston rings by following instructions in the
Trim Replacement section of this manual.
8. Remove the existing valve actuator and bonnet
following the appropriate instructions in the
Replacing Packing section in this manual.
Note
CAUTION
Do not remove the existing valve stem
from the valve plug 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.
9. Remove the existing valve stem and plug, cage,
and seat ring from the valve body following the
appropriate instructions in the Trim Removal section
in this manual.
10. Replace all gaskets according to appropriate
instructions in the Trim Replacement section in this
manual.
11. Install the new seat ring, cage, valve
plug/retainer assembly, and stem into the valve body
and completely reassemble the valve package
following the appropriate instructions in the Trim
Replacement section in this manual.
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 applying the full actuator load. 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.
EW Valve
17