Fisher D4 Instruction Manual page 12

D4 Valve
July 2015
is against the O‐ring (key 25). Also, make sure that it is assembled for installation with the diaphragm on the loading
pressure side and the lockwasher (key 43) and lower spring seat (key 28) are on the spring side.
4. Fasten the diaphragm and diaphragm plate assembly on the stem with hex nuts (key 42). Place the diaphragm and
diaphragm plate, and stem assembly into the lower casing and bonnet. Install the travel indicator (key 32) on the
stem as the bottom of the stem enters the yoke window.
CAUTION
Over‐tightening the diaphragm casing cap screws and nuts (keys 45 and 46) can damage the diaphragm. Do not exceed 27
NSm (20 lbfSft) torque.
5. Replace the spring (key 30) on the diaphragm plate (key 40). Replace the upper spring seat (key 29). Position the
upper casing (key 23) on the lower casing (key 39). Insert the cap screws (key 45) and tighten the hex nuts (key 46).
Torque the casing cap screws evenly to 27 NSm (20 lbfSft) using a crisscross pattern.
6. Adjust the initial spring set per the Spring Adjustment section in this manual.
Actuator (Spring‐to‐Open)
WARNING
Observe the warning at the start of the Maintenance section.
Refer to figure 5.
Before disassembling the actuator, disassemble the valve plug, seat ring, and packing according to instructions in this
manual.
Disassembly
1. Unscrew the spring case assembly (key 27). Turn the adjusting screw nut (key 44) counterclockwise to remove all
spring compression. Remove the adjusting screw nut, upper spring seat, and spring (keys 44, 29, and 30)
2. Unscrew the casing cap screws and hex nuts (keys 45 and 46), and remove the upper casing assembly (key 23) from
the lower casing (key 39). Remove the cotter pin (key 36) and unscrew the adjusting stem (key 31).
3. Lift out the diaphragm (key 15), diaphragm plate (key 40), and stem assembly. Remove the travel indicator (key 32)
when the bottom of the stem enters the yoke window.
4. To replace the diaphragm (key 15), separate the diaphragm assembly by using a wrench on the hex nuts (key 42) to
unscrew the assembly.
5. Separate the parts‐‐diaphragm washer, actuator O‐ring (keys 41 and 25), diaphragm, and diaphragm plate, (keys 15
and 40).
6. Inspect the diaphragm and the actuator O‐ring for damage or deterioration, and replace if necessary. If the
diaphragm is replaced, a new O‐ring should also be installed.
7. Inspect the stem O‐ring (key 19) and bonnet bushing (key 20); replace if necessary. To inspect the casing O‐ring
(key 18), remove the cap screws (key 38) and lift off the lower casing (key 39). Replace the O‐ring if necessary.
Inspect the adjusting stem bushing (key 26) and actuator stem O‐ring (key 53). Replace if necessary.
8. If the hammer nut needs to be removed from the bonnet, the spring pins (key 7) can be removed with locking
pliers.
Assembly
1. Before starting assembly, make sure all parts are clean and in good condition. There should be no burrs or sharp
edges on any threads or surfaces that might cut or damage an O‐ring, bushing, the packing, or the diaphragm.
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Instruction Manual
D103042X012