Maintenance; Actuator; Size 80 Disassembly - Fisher 657 Sizes 80 Instruction Manual

2. Measure dimension B as shown in figure 4. Cut
length of spacers as follows:
a. If it is desired to decrease spring compression,
make the spacers approximately 3/16-inch (4.8
mm) longer than dimension B.
b. If it is desired to increase spring compression,
make the spacers approximately 3/16-inch (4.8
mm) shorter than either dimension B plus the
amount of adjustment required or dimension B plus
valve travel, whichever is less.
3. Whenever the total amount of adjustment required
is greater than valve travel, the adjustment must be
made in two or more steps, and the amount of adjust-
ment taken in each step must be less than valve trav-
el.
4. Pressure the actuator to attain full travel. Cautious-
ly insert the spacers at equal intervals around the
spring seat (key 11, figure 6). The spacers must be
seated squarely when in use or they may slip out of
position. Keeping hands and tools away from the
spring and spring seat, slowly decrease loading pres-
sure until the spring force holds the spacers firmly be-
tween the spring seat and lower diaphragm casing
(key 5, figure 6).
5. Loosen the jam nut. The adjusting nut can now be
rotated clockwise (when viewed from the diaphragm
casings) to increase the loading pressure required to
start actuator stem travel or counterclockwise to de-
crease the pressure required to start travel.
6. Pressure the actuator to move the spring seat
away from the spacers, and carefully remove the
spacers.
7. If the total adjustment required was greater than
valve travel, repeat the procedure. It will be necessary
to make new spacers using the new dimension B and
the remaining adjustment required or valve travel,
whichever is less. Tighten the jam nut when adjust-
ment is complete.

Maintenance

Actuator parts are subject to normal wear and must be
inspected and replaced when necessary. The frequen-
cy of inspection and replacement depends on the se-
verity of service conditions. Because of the care
Fisher Controls takes in meeting all manufacturing re-
quirements (such as heat treating and dimensional
tolerances), use only replacement parts manufactured
or furnished by Fisher Controls.
Type 657 Sizes 80 & 100
WARNING
Avoid personal injury or property dam-
age from sudden release of process
pressure or bursting of parts. Before
performing any maintenance opera-
tions:
D Disconnect any operating lines pro-
viding air pressure, electric power, or a
control signal to the actuator. Be sure
the actuator cannot suddenly open or
close the valve.
D Use bypass valves or completely
shut off the process to isolate the valve
from process pressure. Relieve process
pressure from both sides of the valve.
Drain the process media from both
sides of the valve.
D Vent the power actuator loading
pressure and relieve any actuator spring
precompression.
D Use lock-out procedures to be sure
that the above measures stay in effect
while you work on the equipment.
The maintenance instructions are divided into four
sections: actuator (sizes 80 and 100); side-mounted
handwheel assembly (manual operator); hydraulic
snubber; and top-mounted handwheel assembly (ad-
justable-up travel stop).

Actuator

This procedure describes how the actuator can be
completely disassembled and assembled. When in-
spection or repairs are required, disassemble only
those parts necessary to accomplish the job; then,
start the assembly at the appropriate step.
Key numbers refer to figure 5 for size 80 actuators and
figure 6 for size 100 actuators.

Size 80 Disassembly

1. Bypass the control valve. Reduce the loading pres-
sure to atmospheric, and remove the tubing or piping
from the top of the diaphragm casing (key 1).
WARNING
To avoid personal injury from the pre-
compressed spring force thrusting the
upper diaphragm casing (key 1) away
from the actuator, relieve spring com-
pression (step 2, below), and carefully
remove casing cap screws (key 22) (step
4, below).
5