Emerson Process Management FISHER 657 - Manual (Page 11)

Instruction Manual
D100306X012
657 Actuator (30-70 and 87)
December 2010
11
Actuator Maintenance
This procedure describes how the actuator can be completely disassembled and assembled. When inspection 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 figures 6, 7, or 8 unless otherwise indicated. Figure 6 shows the sizes 30 through 60 actuators,
figure 7 illustrates the sizes 70 actuator, and figure 8 shows the size 87 actuator.
Actuator Disassembly
1. Bypass the control valve. Reduce the loading pressure to atmospheric, and remove the tubing or piping from the
upper diaphragm casing (key 1).
WARNING
To avoid personal injury from the precompressed spring force thrusting the upper diaphragm casing (key 1) away from the
actuator, relieve spring compression (step 2, below), and carefully remove casing cap screws (key 22) (step 4, below).
2. Thread the spring adjuster (key 12) out of the yoke (key 9) until all spring compression is relieved.
3. If required, remove the actuator from the valve body by separating the stem connector (key 26) and removing the
yoke locknut or, for the size 87 actuator, the stud bolt nuts. Separate the stem connector by loosening the stem
nuts (keys 15 and 16) and unscrewing the two cap screws.
4. Remove the diaphragm casing cap screws and nuts (keys 22 and 23), then lift off the upper diaphragm casing (key
1).
5. Remove the actuator diaphragm (key 2).
6. Remove the diaphragm plate, actuator stem, and cap screw (keys 4, 10 and 3) as an assembly. This assembly can be
broken down further, if required, by removing the cap screw (key 3).
7. Remove the actuator spring (key 6) and the spring seat (key 11).
8. If required, remove the lower diaphragm casing (key 5) from the yoke (key 9) by loosening the cap screws (key 8)
that hold it in place.
9. If required, remove the spring adjuster (key 12) by unscrewing it from the yoke (key 9).
Actuator Assembly
1. Coat the threads and the spring seat bearing surface of the spring adjuster (key 12) with lithium grease (key 241),
and thread the spring adjuster into the yoke (key 9). Place the spring seat (key 11) in the yoke on the spring adjuster
and turn the spring adjuster to ensure that threads are properly engaged.
2. Position the lower diaphragm casing (key 5) on the yoke (key 9), and fasten the parts together by installing and
evenly tightening the cap screws (key 8).
3. Set the actuator spring (key 6) squarely onto the spring seat (key 11).
4. If the diaphragm plate and actuator stem (keys 4 and 10) are separate, fasten them together using the cap screw
and washer (keys 3 and 25). Coat the cap screw threads with lithium grease (key 241). Tighten the cap screw (key 3)
to 41 N
Sm (30 lbfSft) torque for size 30 actuators, 54 NSm (40 lbfSft) torque for size 34 and 40 actuators, or 149
N Sm (110 lbfSft) torque for size 45 to 87 actuators. Slide the actuator stem and diaphragm plate (keys 10 and 4)
into the yoke (key 9) so that the actuator spring (key 6) fits squarely between the diaphragm plate and the spring
seat (key 11). Then slide the diaphragm rod through the spring adjuster (key 12).
5. Place the diaphragm (key 2) pattern‐side up on the diaphragm plate (key 4). Align the holes in the diaphragm and
the lower diaphragm casing (key 5).