Page 367 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Be st Practice 6 .6
Be st Practice 6 .7 Gas Turbine Best Practices

Best
Best Practice 6.6Practice 6.6
Set up a modular change out agreement for both industrial Industrial change-outs can also be accomplished in much less time
and aero-derivative gas turbines to minimize downtime than in the past, and most vendors offer a ‘modular’ approach to gas
and optimize MTTR. generator and power turbine change outs.
Currently (2010), most gas turbine models have an available mod-
ular change-out agreement that will greatly minimize downtime for Lessons Learned
repair. Failure to justify and execute modular change-out agree-
Perform a life cycle analysis to compare the cost of the offered ments have cost end users significant downtime for repair,
agreement to the savings in downtime and corresponding revenue with corresponding revenue losses during the extended
gains from increased operation time. maintenance periods.
Aero-derivative complete change outs (gas generator and power
turbine) can be accomplished in as little as 36 hours, depending on the Benchmarks
location and facilities available. This best practice has been used since 1988, when a modular change-
Hybrid change outs (aero-derivative gas generator and industrial out agreement for an aero-derivative generator set was purchased,
power turbine) can also be accomplished in 36 hours or less, and do which guaranteed a 36 hour complete turbine change-out. The
not require alignment, since the power turbine rarely requires mainte- agreement paid off in 1989 when the turbine suffered a complete failure
nance, and the gas generator is aero-dynamically coupled (connection resulting from lack of anti-freeze being added to the water wash
duct between gas generator outlet and power turbine inlet). system during the winter months.

B.P. 6.6. Supporting Material

See B.P. 6.1 for supporting material.

Best
Best Practice 6.7Practice 6.7
Utilize a self-cleaning turbine inlet air filter (pulse type) the turbine to frequent clean or wash cycles, which will
sized for 1" H 2 O clean pressure drop to minimize the effect eventually require an additional shutdown for
of fouling on turbine power output. maintenance.
Review proposed vendor experience and design during the bidding
stage of the project to ensure proper filter size and clean filter differ- Benchmarks
ential pressure.
This best practice has been used since 1987, when project re-
quirements for a turbine generator set were defined and included
Lessons Learned
a pulse type inlet air filter sized for 1" clean pressure drop. Since that
Failure to select a pulse type inlet air filter of adequate size time, this practice has been followed on all gas turbine projects and
has resulted in reduced turbine power output, and corre- has resulted in maximum reliability and has minimized the necessity to
sponding loss of production revenue. It has also exposed clean the turbines.

B.P. 6.7. Supporting Material

Inlet and exhaust system Figure 6.7.2 presents the function definition of gas turbine
inlet filters and a picture of each type.
Pulse type air filters have gained wide acceptance in regions
The inlet and exhaust systems provide the engine with an ac-
ceptable level of inlet air filtration, moisture removal and noise of excessive dust (desert regions) and in regions of very low
temperature conditions. They are highly efficient and can be
reduction. Figure 6.7.1 shows a typical arrangement for a simple
cycle installation. changed on-line. Figure 6.7.3 presents facts concerning this type
There are two basic types of gas turbine air filters in use today: of filter.
Regardless of the type of air filter (pulse or conventional),
- Pulse air type filters are often ‘staged’ to meet local conditions. Figure 6.7.4
- Conventional staged type contains details concerning this application.

338