Flowserve Tandem Rotary Actuators - Manual (Page 4)

4
7. Position the lever arm on the shaft (as shown in
Figure 1) and tighten the linkage bolt securely.
8. Reinstall the positioner, making sure the positioner
follower arm rides underneath the follower pin pressed
into the lever arm.
9. If the yoke plates have been removed, reinstall them
with both sets of yoke plate bolts. If necessary, install
a new piston stem O-ring, piston and spring guide
onto each actuator stem and secure each with the
actuator stem locknut.
10. Being careful not to damage the sliding seal assem-
blies; reinstall both actuator stems through the trans-
fer case until they engage the threaded rod ends.
Turn the piston until the actuator stem and rod end
threads are firmly engaged.
11. Bolt the transfer case cover plate to transfer case.
12. Install both springs and spring buttons.
13. Replace the piston and cylinder O-rings.
14. Slide cylinder down over piston and transfer case.
CAUTION: The cylinder must be perpendicular
with the piston when sliding it over the piston
O-ring. If this is not done, the O-ring could be
damaged.
15. Reinsert both cylinder retaining rings by feeding
each (a little at a time) into the groove in the cylinder.
16. Center the hole in both spring buttons directly under
the adjusting screw hole in the cylinders. Install both
adjusting screws and tighten only enough to provide
an air seal with the gaskets. Do not overtighten.
17. Reconnect the tubing.
Adjusting the External Stroke Stops
After disassembly and reassembly, it may be necessary to
readjust the external stroke stops to avoid unnecessary
overstressing of the shaft on the body disc stop (disc stop
is a safety device designed to protect the seat). The
external stroke stops can be adjusted while the valve is in
line; however, there must be no line pressure on the disc.
To adjust the external stroke stops, proceed as follows:
1. If the valve is out of the line, screw the stroke stop bolts
out far enough to allow the disc to touch the disc stop
in the closed position. If the valve is installed in the line,
cycle the valve to the closed position with very low air
pressure (10 - 15 psi). At this point, the disc should be
resting on the disc stop.
CAUTION: Overstressing the shaft can occur if
full operating torque is applied to the disc stop.
2. Screw the stroke stop in clockwise (as viewed from the
end) until resistance is felt. By turning stroke stop an
additional
1 /
8
- turn, disc should be just off disc stop.
3. Cycle valve open. Adjust the other stroke stop until
disc is 90 degrees from the closed position.
4. Cycle the valve several times to make sure position
indicator returns to the same position with each cycle.
5. Tighten the stroke stop jam nuts.
REVERSING THE ACTUATOR ACTION
The Valdisk transfer case for the tandem actuator is
designed for one failure mode only. Should a different
failure mode be required, contact factory for a different
transfer case.
Troubleshooting Tandem Rotary Actuators
Failure Probable Cause Corrective Action
Actuator moves to failure 1. Failure of an actuator stem O-ring 1. Replace actuator stem O-ring
position, bleeding from 2. Failure of a sliding seal assembly 2. Replace sliding seal assembly
transfer case
Jerky shaft rotation 1. Improper adjustment of lever on shaft causing 1. Readjust lever arm
arm to contact transfer case
2. Worn piston O-ring allowing piston to gall on 2. Replace O-ring; if galling has occurred, replace all
cylinder wall damaged parts
3. Cylinder wall not lubricated 3. Lubricate cylinder wall with silicone lubricant
4. Worn actuator stem O-ring causing actuator 4. Replace O-ring; if actuator stem is galled, replace it
stem to gall on stem collar
5. Valve bearings may have been damaged 5. Replace bearings according to Maintenance Bulletin 10
Excessive leakage 1. Improper adjustment of external stroke stops 1. See “Adjusting the External Stroke Stops” section
through seat 2. Seat damage 2. See Maintenance Bulletin 10 to replace seat ring
Actuator operates, 1. Broken rod end or pivot pin 1. Replace rod end
shaft does not rotate 2. Broken rod end bearing 2. Replace rod end bearing
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