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Inspection and Maintenance
Major Inspection
The Major Inspection involves inspection of all of the major "flange-to-flange" components of the
gas turbine which are subject to wear during normal turbine operation. This inspection includes ele-
ments of the Combustion and Hot Gas Path inspections. In addition, casings are inspected for cracks
and erosion, rotor and stator blades are to be checked for tip clearance, rubs, bowing, cracking, and
warpages. Shrouds are checked for clearance, erosion, rubbing and build-up. Seals and hook fits of
nozzles and diaphragms are inspected for rubs, erosion, fretting or thermal deterioration. The com-
pressor and inlet are inspected for fouling, erosion, corrosion, and leakage. Bearings and seals are
inspected for clearance and wear. All clearances are checked against their original values.
Inspection Intervals
It is important to develop a schedule of inspection intervals and maintenance procedures based on the
utilization of the equipment and the experience accumulated during its operation. A schedule developed
in this manner wi ll result in minimum downtime and lowest overall maintenance costs.
Contact your GE Company representative for these intervals.
Special Inspections
Variable Inlet Guide Vanes Bushing Inspection
GE recommends the following procedure for inspection of inlet guide vanes for bushing wear:
Caution should be exercised to ensure that the inlet guide vane controls have been rendered inoper-
able during measurement and inspection. Failure to do so could result in injury to personnel.
With the gas turbine shut-down and the inlet guide vanes secured in the normally open position for
loaded operation (84 degrees in most instances), use a dial indicator to measure motion normal to
the vane chord. Position the indicator to read as close to the vane inner button as possible, then de-
flect the vane to both sides of the bushing clearance and record the full dial indicator reading. It is
important to note that any residue in the clearance area be removed prior to measuring bushing clear-
ances with the dial indicator.
Variable inlet guide vanes should be inspected for bushing wear according to a schedule as listed
in Table 1-1. Special attention should be paid to the clearance limits as defined in the table. If any
clearance measured is equal to or greater than that in the table, immediate action should be taken
to replace the bushing(s).
On units fitted with chemloy bushings (GE drawing numbers 315A9681 and 339A9913) that do not
exceed the wear limits specified, verify that the bushings are not loose in the inner segment holes.
If bushings are loose or free to turn, restake the segments to tighten the bushing fit. Do not overstake,
the inlet guide vanes should be free to actuate.
Customers should contact their local GE Power Generation Field Office for assistance in imple-
menting these new inspection procedures and ordering the new design bushings as necessary.
Introduction
I–5
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