Fisher D4 Instruction Manual page 11

Instruction Manual
D103042X012
Before disassembling the actuator, disassemble the valve plug, seat ring, and packing according to instructions in this
manual.
Disassembly
1. Loosen the adjusting screw nut (key 44) and turn the adjusting screw (key 31) counterclockwise to remove all
spring compression.
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).
3. Remove the spring seat (key 29) and actuator spring (key 30).
4. Lift out the diaphragm, diaphragm plate, and stem assembly. Remove the travel indicator (key 32) when the
bottom of the stem enters the yoke window.
5. To replace the diaphragm (key 15), separate the diaphragm assembly by using a wrench on the hex nuts (key 42) to
unscrew the assembly.
6. Separate the parts‐‐diaphragm washer, actuator O‐ring (keys 41 and 25), diaphragm, and diaphragm plate, (keys 15
and 40).
7. 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.
8. 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.
9. 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.
When replacing O‐rings and bushings, be sure the O‐ring or bushing groove is clean and undamaged. Using a
general purpose lubricant (key 49), lubricate all bushings and O‐rings and the threads of parts that have to pass
through the bushings and O‐rings.
CAUTION
The threads on factory‐produced valve stems have been specially machined to avoid O‐ring, bushing, or packing damage
during trim maintenance. Use of other than a factory‐produced valve stem may result in early stem O‐ring, bushing, and
packing failure.
Note
Do not lubricate cap screws (key 38) before inserting them in the following procedure.
2. Place the hammer nut and spring pins on the bonnet, if removed. Install the casing O‐ring (key 18), the stem O‐ring
(key 19), and the bonnet bushing (key 20). Position the lower casing (key 39) on the bonnet. Insert the
nonlubricated cap screws (key 38), and torque to 49 NSm (36 lbfSft).
WARNING
The spring pins must always be in place during valve operation. They provide a safeguard against injury when the unit is
being disassembled.
3. Assemble the diaphragm plate assembly. Place the patterned side of the diaphragm (key 15) against the diaphragm
plate (key 40). Be sure to turn the diaphragm washer (key 41) so that the side that is beveled on the inside diameter
D4 Valve
July 2015
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