Gas Turbine Handbook : Principles and Practices

Boroscope Inspection 209
the gas turbine would help identify the problem area.
Compressor vibration could be indicative of a failed compressor
blade or imbalance created by contaminant flaking off an airfoil. The
failed blade, blade portion, or loose contaminant could be so small
that it has an insignificant influence on compressor efficiency. A boroscope
inspection will provide the direction to either increase water
washing efforts, overhaul the unit, or continue running the unit.
ASSESSING DAMAGE TO
INTERNAL ENGINE COMPONENTS
For convenience in assessing engine health, some manufacturers
have installed boroscope ports in strategic locations throughout their
engines. Figure 13-3 is a schematic representation of a gas turbine
with the typical location of boroscope ports indicated. However, manufacturers
are not consistent as to the location of boroscope ports on
different engine types and models. Therefore, an inspector must use
every opening available or, as in some cases, openings that are easily
created by removing an engine component (such as fuel nozzles,
pressure or temperature probes, etc.). In general, boroscope ports are
located in the combustor and in the turbine. The combustor boroscope
port can be used to view the condition of the fuel nozzles, the combustion
liner, the first stage turbine nozzles, and the first stage turbine
Figure 13-3. Courtesy of United Technologies Corporation, Pratt &
Whitney Canada. Schematic cross-section of the FT8 aero-derivative
gas turbine with the location of boroscope ports indicated.