Assembly - Fisher 655 Instruction Manual

Type 655 and 655R
e. Rotate the entire actuator until the actuator
stem disengages from the valve plug stem.
3. Turn the adjusting screw (key 10) counterclockwise
out of the yoke (key 7) to relieve all spring compres-
sion.
4. To remove the upper diaphragm casing (key 1),
unscrew the cap screws (key 19) for size 3A and 4A
actuators or the cap screws and hex nuts (keys 19
and 20) for all other sizes.
5. Remove the diaphragm (key 2); then, lift the dia-
phragm plate (key 4) and actuator stem assembly out
of the actuator body. Also, remove the spring and the
lower spring seat (key 9).
6. For size 3A and 4A actuators, remove the lower
diaphragm casing (key 5).
7. Remove the cap screw (key 3), and separate the
diaphragm plate from the actuator stem.
8. For size 3B through 46 actuators, unscrew the cap
screws (key 21), and remove the lower diaphragm
casing (key 5). Some Type 655R actuators will have
travel stops (key 13, not shown) in place of three of
these six cap screws.
9. If a top-mounted handwheel assembly is used, re-
fer to steps 4 through 8 of the Disassembly portion of
the Top-Mounted Handwheel section.

Assembly

This procedure assumes that the actuator is complete-
ly disassembled. If it is not, start the instructions at the
appropriate step.
1. Before starting assembly, apply Molykote No. 77 or
equivalent lubricant to the threads and the bearing end
of the adjusting screw (key 10) as indicated in figure 5
by the letter A.
2. For size 3A and 4A actuators, set the lower dia-
phragm casing (key 5) onto the yoke (key 7).
3. For size 3B through 46 actuators, install the lower
diaphragm casing (key 5), and secure it with the cap
screws (key 21). Some Type 655R actuators will have
travel stops (key 13, not shown) in place of three of
these six cap screws.
4. Install the lower spring seat (key 9) and the actua-
tor spring (key 6).
To take some of the slack out of the dia-
phragm (key 2) at the bolt circle, turn the
adjusting screw into the yoke (key 7) to
raise the diaphragm plate (key 4). This
will also ensure that the diaphragm will
8
Note
have enough slack inside the casings for
efficient travel.
5. Secure the diaphragm plate (key 4) to the actuator
stem (key 8) with the cap screw (key 3), and install
this assembly into the actuator. Install the diaphragm,
making sure that the patterned side of the diaphragm
is next to the diaphragm plate.
When replacing the upper diaphragm
casing (key 1), be sure there are no
wrinkles in the diaphragm that might
cause the diaphragm to tear or allow
leakage.
6. Place the upper diaphragm casing onto the lower
diaphragm casing. For size 3A and 4A actuators, se-
cure the casings with the cap screws (key 19). For all
other actuator sizes, secure the casing with the cap
screws and hex nuts (keys 19 and 20). Tighten the
cap screws to no more than 20 foot-pounds (27 new-
ton-meters) of torque using an even, crisscross pat-
tern.
7. Mount the actuator onto the valve by following the
procedures outlined in the Actuator Mounting portion
of the installation section.
8. Connect the pressure control line by following the
procedures outlined in the Loading Connections por-
tion of the Installation section.
9. To start up and adjust the actuator, follow the pro-
cedures outlined in the Startup section of this instruc-
tion manual.
Top-Mounted Handwheel
Top-mounted handwheel assemblies (figures 6, 7 and
8) are usually used as adjustable travel stops to limit
full upward travel of the actuator stem. Turning the
handwheel clockwise forces the actuator stem down-
ward, while turning the handwheel counterclockwise
allows the spring to force the actuator stem upward. If
the actuator is used with a push-down-to-close valve,
full opening of the valve plug can be restricted through
the appropriate positioning of the top-mounted hand-
wheel. If the actuator is used with a push-down-to-
open valve, closing of the valve plug can be restricted
by using the handwheel. A locknut (key 27, figures 6
and 7; key 137, figure 8) is used to hold the hand-
wheel in position.
Instructions are given below for complete disassembly
and assembly. Perform the disassembly only as nec-
essary to accomplish the required maintenance; then,
begin the assembly at the appropriate step.
Key numbers refer to figure 6 for size 3A and 4A, fig-
ure 7 for size 3B and 4B, and figure 8 for size 32
through 46 top-mounted handwheel assemblies.
Note