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the air supply or disconnect the instrument signal.
By observing the indicator plate, the disc should
either fail open or closed. If incorrect, refer to the
Reversing the Actuator section in the appropriate
Actuator Maintenance Instructions.
PREVENTIVE MAINTENANCE
At least once every six months, check for proper opera-
tion by following the preventive maintenance steps
outlined below. These steps can be performed while
the valve is in line and, in some cases, without interrupt-
ing service. If an internal problem is suspected, refer to
the Disassembly and Reassembly section.
1. Look for signs of gasket leakage through body and
line flanges. Tighten flange bolting if necessary.
2. Note if any corrosive fumes or process drippings
are damaging the valve.
3. Clean valve and paint any areas of severe oxidation.
4. Check packing box bolting for proper tightness.
Packing nuts should be slightly over finger-tight;
however, tighten as necessary to prevent stem
leakage.
CAUTION: Do not overtighten packing.
5. If valve is supplied with a lubricator, check lubricant
supply and add lubricant if necessary.
6. If possible, stroke valve and check for smooth, full-
stroke operation by observing the disc position
indicator plate mounted on the transfer case. Un-
steady movement of the disc could indicate an
internal valve problem (jerky motion is normal when-
ever Grafoil packing is used).
7. Check positioner calibration by observing the
gauges and the disc position indicator plate. Make
sure the positioner is calibrated to the correct
range. Push the positioner cleanout plunger (Model
80R positioner only) several times to clear any
possible restrictions.
A – Dual Seat
NOTE: Item numbers correspond directly to the bill of material. Refer to the bill of material for specific part numbers.
B – Metal Seat
Figure 1: Seat Retainer Configurations
8. Remove transfer case cover plate and make sure
the positioner linkage and internal actuator parts
are securely fastened. Also, check for air leaks
through actuator stem seal, using a soap solution.
CAUTION: Never apply air to the actuator with-
out the cover plate installed; otherwise, the
unsupported shaft may sustain damage.
9. Be sure that all accessories, brackets and bolting
are securely fastened.
10. If possible, remove air supply and observe stroke
plate for correct fail-safe action.
11. Spray soap solution around the cylinder retaining
ring and the adjusting screw to check for air leaks
through the O-rings.
12. Clean any dirt or other foreign material from the
exposed portion of the shaft.
13. If an air filter is supplied, check and replace car-
tridge if necessary.
DISASSEMBLY AND REASSEMBLY
Removing Valve From Line
If an internal problem is suspected with the valve and
disassembly is required, remove the valve from the line
by proceeding as follows:
WARNING: Depressurize line to atmospheric
pressure, drain all process fluids and decon-
taminate the valve (if caustic or hazardous materials
are present). Failure to do so can cause serious
injury.
1. Make sure valve is fully closed.
NOTE: On valves with fail-open action, air pres-
sure must be supplied under the actuator piston to
close the valve. If the valve is supplied with a
handwheel, it can be used to close the valve.
C – Soft Seat
D – Seat Insert /
Snap-ring
10-3
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