Flowserve Valtek Beta Positioners for Control Valves - Manual (Page 9)

24-9 Flowserve Corporation, Valtek Control Products, Tel. USA 801 489 8611
4. Reattach the feedback screw to the new instrument
diaphragm assembly (49) by applying a small
amount of threadlocking compound (Loctite #222 or
equivalent) to the threads. Twist the feedback screw
into the instrument diaphragm assembly (49) until it
is approximately flush with the bottom of the dia-
phragm assembly (49). However, make sure it
doesn’t protrude through.
5. Carefully fold up the corners of the smaller dia-
phragm on the diaphragm assembly (49) and care-
fully work it through the hole in the instrument
capsule base (43). Rotate the diaphragm assembly
so the small tapped hole in the diaphragm assembly
(49) hub is oriented downward closest to the mount-
ing base. Install the lower diaphragm retaining plate
(50) and the upper diaphragm retaining plate (42)
over the diaphragm assembly (49) making sure that
all the diaphragm corners are lying flat. Install and
securely tighten the four screws (39). Apply a small
amount of Loctite #222 to the shorter threaded
portion of the spring and stud assembly (45, 46, 47)
and screw it into the diaphragm center hub until the
spring coil (46) bottoms out against the center hub.
Thread nut (38) onto the longer portion of the stud
assembly until it bottoms out against the top of the
coil spring (46).
6. Reinstall the summing beam assembly (41) with
four screws (36) with a small amount of Loctite #222
or equivalent applied to each screw. Be careful not
to bend the thin flexures on the summing beam.
With the bottom nut (38) threaded down against the
top of the spring coil (46), install the top nut (38) and
tighten it firmly, attaching the summing beam as-
sembly (41) to the diaphragm assembly. Install a
new O-ring (48) in the instrument capsule base.
Install the two mounting screws (35) and fasten the
assembly securely to positioner base (7).
7. To reinstall the pilot valve assembly (40, 52), re-
place the three pilot valve O-rings (54). Compress
the leaf spring on the end of the summing beam
assembly (41) and carefully engage the notched
end of pilot valve assembly (40, 52) with the beam
spring. Slide the pilot valve assembly (40, 52) care-
fully until it is aligned with its mounting holes and
fasten securely with two screws (53).
8. Return range arm (13) to the base (7) and secure
with snap ring (8). Reinstall the feedback spring (34)
with one end engaging the feedback screw on the
instrument diaphragm assembly (49) and the other
end engaging the zero screw (24). Then calibrate
positioner according to “Calibration” section of this
document.
or sticking. To operate properly, the spool (40)
should slide freely and fall through the spool valve
body (52) by its own weight when held vertically.
Clean both the pilot valve spool (40) and body (52)
with a degreasing solvent. When clean, insert the
spool (40) back into the body (52) and move it back
and forth to ensure that it slides freely for proper
operation. If the spool (40) doesn’t slide freely,
reclean or replace it.
CAUTION: Do not apply oil or grease to the
spool. It will adversely affect the performance of
the positioner.
Removal and Repair of Instrument
Capsule Assembly
To remove and repair the instrument capsule assembly,
refer to Figure 4 or 17, and proceed as follows.
NOTE: If the instrument capsule assembly is damaged,
the entire instrument capsule assembly with the sum-
ming beam is available as a spare part and can be
replaced as a unit. It can also be disassembled and only
the soft goods replaced.
1. To replace the entire instrument capsule assembly,
first remove the pilot valve assembly (40, 52) as
described in steps 1 and 2 in the preceding section.
Then remove the two screws (35) fastening it to the
base. Make sure the new instrument capsule O-ring
(48) is installed in the base of the instrument capsule
assembly. Install the two mounting screws (35) and
tighten. Reinstall the pilot valve assembly (40, 52)
as described in step 7.
2. If you wish to disassemble the instrument capsule
and replace diaphragms, then proceed as follows:
Remove the pilot valve assembly (40, 52) as
described in steps 1 and 2 of the preceding section.
Remove the instrument capsule assembly from the
positioner base by removing two screws (35).
Remove the nut (38) from the top of the summing
beam assembly (41). Remove the four screws (36)
that attach the summing beam assembly (41) to the
assembly of the instrument capsule body (43), then
remove the summing beam assembly (41).
3. Remove the four screws (39) holding the upper
diaphragm retaining plate (42) to the instrument
capsule assembly. Remove the upper diaphragm
retaining plate (42) and the lower diaphragm retain-
ing plate (50) from the assembly. Carefully push the
diaphragm assembly (49) through the hole and out
the bottom of the instrument capsule base. Examine
the instrument diaphragm assembly (49) for wear or
failure and replace if necessary. When replacing the
diaphragm assembly (49), remove and save the
feedback screw from this assembly.