Gas Turbine Handbook : Principles and Practices

Hardware 41
land based aero-derivative version is normally provided with a 120-
gallon synthetic oil reservoir. An aero-derivative gas turbine package
requires 400 gallons of turbine light oil for the power turbine and
the driven equipment (pump, compressor, or generator). Even though
synthetic oils have better heat transfer capabilities and are fire resistant,
they are more expensive. Lubrication systems are addressed in
detail in Chapter 6.
INSPECTION AND REPLACEMENT
One major asset of the aero-derivative industrial engine is the
boroscope capability built into the design. Boroscoping facilitates inspection
of critical internal parts without disassembling the engine.
Complete boroscoping of the aero-derivative engine can be accomplished
in an hour. There are no provisions for boroscoping the heavy
industrial gas turbine. The heavy-industrial units must be disassembled
for all inspections. The inspection and replacement of the
fuel nozzles, combustor, and transition duct of a heavy industrial gas
turbine with 10 to 12 can-annular combustors takes about 24 hours
(96 man-hours not including cool-down time). Some very resourceful
field technicians have developed techniques to boroscope the combustor,
first stage turbine nozzles, and last stage compressor stators of
the heavy industrial gas turbine. However, their efforts have not been
embraced by the equipment manufacturers. Boroscoping techniques
are discussed in greater detail in Chapter 13.
In contrast, inspection of the aero-derivative combustors and
nozzles can be accomplished in 4 1/2 hours (9 man-hours). Removal
and replacement of the combustors on the aero-derivative gas turbine
can take 4 to 30 hours (8 to 75 man-hours) depending on the combustor
configuration. Also, removal and replacement of the turbine
section can be accomplished in 18 to 30 hours (up to 75 man-hours).
On a heavy industrial, a turbine inspection alone takes 80 hours
(480 man-hours). If blades are removed and replaced, an additional 8
hours is required. If more than several new or replacement blades are
installed, the unit must be field balanced, which is time consuming.
If field balancing can not be satisfactorily completed, the rotor must
be removed, transported to a repair facility, balanced, and returned to
the site.