The hot section of the gas turbine can get damaged by the presence of hydrocarbon liquid in the fuel gas. It will plug nozzles due to explosion and fire during the combustion cycles.
The hydrocarbon liquid can get into the turbine supply line from the gas scrubber through the sources:
- Pressure and gas flowrate exceed the scrubber capacity
- Surge in hydrocarbon due to fluctuation in gas pressure
- Wrong operation of the centrifugal separator
- Foaming in the pipeline leading to the scrubber
Some examples of the deterioration to the turbine caused by fuel gas:
- High temperature in the compression chamber can cause distress to the blades
- Hydrocarbon liquid in the fuel gas that is not burned can ignite and create failure for the transition piece
- Back pressure built up can also cause compressor surge
In order to prevent the hydrocarbon liquid in fuel gas, it needs to be treated and have a superheat temperature of at least 500F above the hydrocarbon dew point.
The below also are probable causes of turbine deterioration:
- Improper alignment can cause higher bearing loads
- Rotor needs balancing
- Loss in the compressor or generator
- Problems in gearbox and coupling
- Damaged combustion nozzle
- Bearing wear
- Component creeping
Note: Turbine Blade Tip clearance increases will cause a drop in compressor efficiency. A good rule of thumb is a 1% increase in Blade Tip clearance will cause about a 1% drop in compressor efficiency and decrease the engine efficiency about 1% and a loss of power more than 1%.