Enviro-Seal Bellows Seal Bonnet; Trim Replacement (C-Seal Constructions); Replacing A Plain Or Extension Bonnet With An Enviro-Seal Bellows Seal Bonnet (Stem/Bellows Assembly) - Fisher Design ED series Instruction Manual

Design ED & EAD Class 125-600
the valve closes and the C-seal retainer
will strike the seating area of the cage,
preventing the valve from closing.

Trim Replacement (C-seal Constructions)

1. Apply a suitable high-temperature lubricant to the
inside diameter of the C-seal plug seal. Also, lubricate
the outside diameter of the valve plug where the
C-seal plug seal must be pressed into the proper
sealing position (figure 6).
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 6).
D The open interior of the C-seal plug seal must
face down in a valve with flow-down construction
(figure 6).
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 Fisher or a tool could be
manufactured following the dimensions
given in Figure 7.
3. Place the C-seal plug seal over the top of the valve
plug and press it onto the plug using the 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 8).
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 9) to secure the C-seal retainer.
6. Replace the piston ring(s) following instructions in
the Trim Replacement section of this manual.
7. Return the seat ring, cage, plug/retainer assembly,
and stem to the valve body and completely
reassemble the valve package following the
appropriate instructions in the Trim Replacement
section of this manual.
16
Note
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.

ENVIRO-SEAL Bellows Seal Bonnet

Replacing a Plain or Extension Bonnet
with an ENVIRO-SEAL Bellows Seal
Bonnet (Stem/Bellows Assembly)
1. Remove the actuator and bonnet according to
steps 1 through 5 of the Replacing Packing procedure
in the Maintenance section.
2. Lift out the cage.
3. Remove and discard the existing bonnet gasket.
Cover the valve body opening to protect sealing
surfaces and to prevent foreign material from entering
the valve body cavity.
The ENVIRO-SEAL stem/bellows
assembly for Design E valves is
available only with a threaded and drilled
plug/adaptor/stem connection. The
existing valve plug can be reused with
the new stem/bellows assembly or a new
plug can be installed.
4. Inspect the existing valve plug. If the plug is in good
condition, it can be reused with the new
ENVIRO-SEAL stem/bellows assembly. To remove the
existing valve plug from the stem, first, place the
existing plug stem assembly 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 or
drill out the pin (key 8).
Note