SD66
4
MAINTENANCE
Most problems associated with pneumatic instruments can be prevented by providing clean, dry, oil-free instrument
air (see Instrument Air Requirements). If these requirements are met, routine maintenance should not be necessary.
Cleaning of the plunger and the supply and exhaust ports may be required, on an occasional basis, as outlined in the
Cleaning section.
CAUTION
Before disassembling the instrument, turn off supply air pressure to the instrument.
Troubleshooting
Table 1 provides troubleshooting information in a symptom, cause, and remedy format. Symptoms are listed in the
order they are most likely
to
occur.
Table 1 Troubleshooting
SYMPTOM CAUSE
REMEDY
Plunger is not seating properly in
supply port due to dirt, chips, etc.
Refer to Maintenance, Cleaning and clean
plunger and supply port.
Exhaust port is clogged due to build up
on the plunger and/or exhaust port.
Refer to Maintenance, Cleaning and clean
plunger and exhaust port.
Output pressure will not
decrease or decreases with a
decrease in input pressure.
Exhaust port is obstructed. Clear
obstruction.
Plunger is not seating properly in
exhaust port due to dirt, chips, etc.
Refer to Maintenance, Cleaning and clean
plunger and exhaust port.
Supply port is clogged due to build up
on the plunger and/or supply port.
Refer to Maintenance, Cleaning and clean
plunger and supply port.
Output pressure will not
increase or increases with an
increase in input pressure.
Supply pressure is too low.
Raise supply pressure.
Ruptured input diaphragm or output
diaphragm assembly.
Refer to Maintenance to replace input
diaphragm or output diaphragm assembly.
Excessive exhaust from
exhaust vent.
Plunger is not seating properly in
exhaust port due to dirt, chips, etc.
Refer to Maintenance, Cleaning and clean
plunger and exhaust port.
Cleaning
To clean the plunger and the supply and exhaust ports:
1.
Remove supply and input pressures.
2.
Remove the retaining nut from the bottom forging (see Parts List). The plunger and plunger spring should fall
out.
3.
Clean the plunger with non-abrasive solvent.
4.
Clean the supply and exhaust ports with non-abrasive solvent (see Figure 2). The supply port is readily
accessible; the exhaust port can be reached with a tobacco pipe cleaner.
NOTE
If there is excessive buildup on the supply or exhaust port, the relay must be
disassembled for thorough cleaning. Refer to the Parts List for parts orientation during
disassembly and assembly.
5.
Refer to the Parts List and install the plunger, plunger spring, and retaining nut.
6.
Check the calibration of the Relay per the following Calibration.
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