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SECTION 3 – MAINTENANCE
3-2
4. Replace the diaphragm (07-0038 or 07-1006) when the diaphragm is no longer flexible.
Note that these diaphragms are consumable items, use at temperatures above 300°F
reduces the useful life.
Thermocouple (Slurry Cup)
Inspect the thermocouple to ensure that it is straight, and the threaded collar is positioned
with two threads showing on the lower side. Inspect the threaded collar and gland nut for
clean and well-formed threading. Worn threading on either part presents a safety hazard to
the operator. If the threads are damaged, the thermocouple may blow out under pressure.
Inspect the exterior of the probe for thinning or nicking. Replace any or all components as
required.
Thermocouple (Oil)
Inspect the thermocouple to ensure that the threaded collar is positioned with two threads
showing on the lower side. Inspect the threaded collar and gland nut for clean and well-
formed threading. Worn threading on either part presents a safety hazard to the operator. If
the threads are damaged, the thermocouple may blow out under pressure. Inspect the exterior
of the probe for thinning or nicking. Replace any or all components as required.
Monthly
Potentiometer Mechanism
The potentiometer mechanism must be completely disassembled and cleaned. If any of the
following components exhibit signs of wear, they must be replaced as follows.
Resistor Replacement
1. Remove the shaft bearing retainer and contact arm.
2. Remove the oil resistor, using care not to damage the slot.
3. Position the new resistor, straight side down, with equal overlap from the contact strips to
the end of the winding.
4. Seat the resistor firmly in the slot (use a block of wood to press into position). The
top surface of the resistor must be level.
5. Lightly burnish the resistance wire by rubbing the top surface with a hardened drill rod
shank. This will ensure that the contact arm slides smoothly.
6. Rotate the contact arm by hand. Affirm that the arm rotates smoothly and maintains
contact with the resistor from contact strip to contact strip with no dragging. If necessary,
adjust the arm by bending it up or down.
7. Adjust the position of the stop arm on the center shaft in order to obtain strip-to-strip
travel of the contact arm. All set screws must be tight.
8. Replace the shaft bearing retainer.
9. Calibrate the potentiometer.
Calibration Spring Replacement
1. Remove the shaft bearing retainer and contact arm.
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