GE Power Systems
Gas Turbine
Inspection & Maintenance Procedures
Rev. 0 (11/98) IMP–1
Inspection and Maintenance Procedures
Reformated, September 1991
STANDARD MAINTENANCE ITEMS
Pressure Switches and Gauges
The setting of pressure switches and calibration of the gauges can be checked with a dead weight tester,
a regulated source of clean, dry, compressed air or a nitrogen cylinder and a calibrated pressure gauge.
The use of air pressure is generally more convenient and is recommended whenever the air pressure is
sufficient to check the specified switch setting and gauge calibration. To avoid the possibility of oil con-
tamination, it is preferable that air actuated switches and gauges not be tested with the dead weight tester.
CAUTION
Pressure gauges on heavy fuel lines have a medium-
separation diaphragm to keep heavy fuel from solidifying
in the sensing line. Removal of the pressure switch and
loss of the fluid will damage the diaphragm or allow air
into the system. Both events will cause the gauge or switch
to read incorrectly.
Thermometers (Dial Type)
To calibrate a dial-type stem thermometer, immerse the sensor a minimum of two inches (5 cm) in an
agitated bath maintained at a temperature between
1
/
2
and
3
/
4
of its full-scale reading or near the maxi-
mum temperature normally registered by that particular thermometer, if known. By means of an external
adjusting screw, rotate the thermometer dial face until the pointer registers the correct temperature. The
bath temperature must be monitored by a thermal sensing device known to be accurate.
Flowmeter
The ± 1.5% accuracy of the flowmeter should be checked and calibrated by the manufacturer or a quali-
fied facility.
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