Replacing Packing And Trim - Fisher 128-PQC Instruction Manual

Use lock-out procedures to be sure
that the above measures stay in effect
while you work on the equipment.
Valve parts are subject to normal wear and must be
inspected and replaced as necessary. Inspection and
maintenance frequency depends on the severity of
service conditions. This section includes instructions
for packing and trim maintenance, changing the main
spring range, reversing the action, and replacing ac-
tuator parts.
Because of the care Fisher Controls takes in meeting
all manufacturing requirements (heat treating, dimen-
sional tolerances, etc.), use only replacement parts
manufactured or furnished by Fisher Controls.
All maintenance operations can be performed with the
valve in the line.

Replacing Packing and Trim

Perform these procedures either when using a com-
plete replacement packing and trim assembly or when
replacing individual packing and trim parts. Replace-
ment packing and trim assembly part numbers are
listed in the Parts List . Packing and trim assembly key
numbers are referenced in figure 5. Control valve as-
sembly key numbers are shown in figure 7 for the
valve body and in figure 8 for the actuator except
where indicated. Most packing and trim assembly key
numbers are duplicated in both figure 5 and figure 7.
1. Isolate the control valve from the line pressure, re-
lease pressure from both sides of the valve body, and
drain the process media from both sides of the valve.
Also shut-off all pressure lines to the actuator and re-
lease all pressure from the actuator. Use lock-out pro-
cedures to be sure that the above measures stay in
effect while you work on the equipment.
If the valve is equipped with an optional handjack, be
sure the handjack assembly is not restricting the valve
from closing. Rotate the handles or handjack body
(key 48 or 47 in figure 9), if necessary, to allow the
main springs (key 19) to close the valve.
2. Remove the four nuts (key 14) from the integral
screws of the lower diaphragm casing. Disconnect the
input signal line, and lift the actuator and attached trim
parts out of the valve body. Cleaning or other neces-
sary maintenance may be performed on any accessi-
ble areas. The actuator and attached trim parts may
be turned over and the valve body used to hold them
as an aid in further maintenance.
3. To disassemble trim and gain access to packing
parts or seal O-rings, unscrew the valve plug (key 3A)
and remove the packing box washer (key 4).
15A5781-C/DOC
Figure 4. Installing Replacement Packing
and Trim Assembly on Valve Stem
4. Pull the packing box (key 9), O-ring retainer (key
39), O-ring (key 11), and diaphragm casing O-ring
(key 35) off the stem.
5. Install the packing and trim assembly or individual
parts over the stem as shown in figure 4. With a pack-
ing and trim assembly, remove the assembly from the
tube (key 42), but do not remove the web sleeve (key
43) from the assembly. The sleeve helps to keep the
assembly parts in place during installation; roll back
the sleeve as necessary during installation of the as-
sembly.
If installing nitrile/cotton packing, lubricate the packing
rings (key 8) with Dow-Corning No. 3 silicon-base lu-
bricant or equivalent.
6. If installing a packing and trim assembly, continue
pushing the assembly onto the stem until the stem
pushes the valve plug and cage (key 2) away from the
packing box washer (key 4). Roll the sleeve back just
past the packing box (key 9).
7. Push the packing box all the way onto the stem
until the packing box, the O-ring (key 11), the O-ring
retainer (key 39), and the diaphragm casing O-ring
(key 35) are sealed against the diaphragm casing.
Make sure the O-rings are positioned properly so that
they will not be cut when the other parts are com-
128-PQC
5