GE Frame 5 Service Manual

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during gas path borescope inspections. All interior case surfaces 
should be visually inspected during a major outage.
Key inspection areas for casings are listed below.
•	Bolt holes
•	 Shroud pin and borescope holes in the turbine shell (case)
•	 Compressor stator hooks
•	 Turbine shell shroud hooks
•	 Compressor discharge case struts
•	 Inner barrel and inner barrel bolts
•	 Inlet case bearing surfaces and hooks
•	 Inlet case and exhaust frame gibs and trunions
•	 Extraction manifolds (for foreign...

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Some turbines are required to meet operational requirements 
that are aimed at maintaining grid stability under sudden load 
or capacity changes. Most codes require turbines to remain on 
line in the event of a frequency disturbance. For under-frequency 
operation, the turbine output may decrease with a speed decrease, 
and the net effect on the turbine is minimal. 
In some cases of under-frequency operation, turbine output must 
be increased in order to meet the specification-defined output...

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evaporative coolers, and other inlet systems as well as periodic 
inspection and prompt repair of compressor blading. Refer to 
system-specific maintenance manuals.
There are also non-recoverable losses. In the compressor, these are 
typically caused by nondeposit-related blade surface roughness, 
erosion, and blade tip rubs. In the turbine, nozzle throat area 
changes, bucket tip clearance increases and leakages are potential 
causes. Some degree of unrecoverable performance degradation 
should be...

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Uncoated GTD-450™ material is relatively resistant to corrosion 
while uncoated AISI 403 is more susceptible. Relative susceptibility 
of various compressor blade materials and coatings is shown in 
Figure 31. As noted in GER-3569, aluminum-based (Al) coatings are 
susceptible to erosion damage leading to unprotected sections 
of the blade. Because of this, the GECC-1™ coating was created 
to combine the effects of an Al coating to prevent corrosion and 
a ceramic topcoat to prevent erosion. Water...

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15-minute time period. Data must be taken at regular intervals 
and should be recorded to permit an evaluation of the turbine 
performance and maintenance requirements as a function of 
operating time. This operating inspection data, summarized in 
Figure 33, includes: load versus exhaust temperature, vibration 
level, fuel flow and pressure, bearing metal temperature, lube   
oil pressure, exhaust gas temperatures, exhaust temperature 
spread variation, startup time, and coast-down time. This list...

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Load vs. Exhaust Temperature
The general relationship between load and exhaust temperature 
should be observed and compared to previous data. Ambient 
temperature and barometric pressure will have some effect  
upon the exhaust temperature. High exhaust temperature can   
be an indicator of deterioration of internal parts, excessive leaks   
or a fouled air compressor. For mechanical drive applications,   
it may also be an indication of increased power required by   
the driven equipment.
Vibration...

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•	Inspect combustion chamber components.
•	 Inspect each crossfire tube, retainer and combustion liner.
•	 Inspect combustion liner for TBC spalling, wear, and cracks.
•	 Inspect combustion system and discharge casing for debris and
foreign objects.
•	 Inspect flow sleeve welds for cracking.
•	 Inspect transition piece for wear and cracks.
•	 Inspect fuel nozzles for plugging at tips, erosion of tip holes, and
safety lock of tips.
•	 Inspect impingement sleeves for cracks (where applicable). •...

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•	Visually inspect the compressor inlet, checking the condition
of the inlet guide vanes (IGVs), IGV bushings, and first stage
rotating blades.
•	 Check the condition of IGV actuators and rack-and-pinion gearing.
•	 Verify the calibration of the IGVs.
•	 Visually inspect compressor discharge case struts for signs
of cracking.
•	 Visually inspect compressor discharge case inner barrel
if accessible.
•	 Visually inspect the last-stage buckets and shrouds.
•	 Visually inspect the exhaust diffuser for any...

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stator shrouds, and turbine buckets. To perform this inspection, 
the top half of the turbine shell must be removed. Prior to shell 
removal, proper machine centerline support using mechanical 
jacks is necessary to assure proper alignment of rotor to stator, 
obtain accurate half-shell clearances, and prevent twisting of  
the stator casings. Reference the O&M Manual for unit-specific 
jacking procedures.
Special inspection procedures apply to specific components 
in order to ensure that parts meet...

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repair at the hot gas path inspection. The second- and third-stage 
nozzles may require refurbishment to re-establish the proper axial 
clearances. Normally, turbine nozzles can be repaired several 
times, and it is generally repair cost versus replacement cost that 
dictates the replacement decision.
Coatings play a critical role in protecting the buckets operating 
at high metal temperatures. They ensure that the full capability 
of the high strength superalloy is maintained and that the bucket...