compressor maintenance water washing

1 /GE Title or job number /

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Maintenance Considerations


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Effects of Air Quality

• Air quality affects maintenance and operating costs.

• Dirt, Dust, salt, and oil cause compressor blade erosion, corrosion, and fouling.

• Ingestion of oil vapor, smoke, sea salt, and industrial vapors can cause fouling.

• Corrosion causes pitting in compressor blades leading to cracking.

• Surface roughness and blade contour changes reduce output and thermal efficiency.


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Effects of Air Quality (continued)

Deterioration of Gas Turbine Performance due to Compressor Blade Fouling


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• Preventing recoverable losses– Recoverable losses account for 70% to 85% of the performance losses.– On-line compressor washing can maintain compressor efficiency. – Off-line systems can clean heavily fouled compressors.– Fouling can be minimized by maintaining inlet filtration system and inlet

evaporative coolers. – Periodic inspection and prompt repair of compressor blades help control fouling.


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• Preventing non-recoverable losses– Non-recoverable losses are not caused by deposits.– Non-recoverable losses occur due to:

– Blade surface roughness– Erosion– Blade tip rubs– Changes in nozzle throat area– Increase in bucket tip clearance– Leakages

– Regular monitoring of performance parameters can help prevent compressor deterioration.


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Maintenance Recommendations

• Quality of intake air affects the performance of a gas turbine. Airborne contaminants in a compressor can cause:

– Erosion– Corrosion – Fouling

• The operating environment and filtration level of a compressor determine the type and rate of fouling. To minimize fouling:

– Reduce oil leaks and ingestion of oily constituents– Filter the incoming air


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Maintenance Recommendations (continued)

• Use compressor washing to:– Slow down corrosion– Reduce the formation of fouling deposits– Maintain compressor performance


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Methods for detecting a fouled compressor:

• Visual inspection: Involves inspecting the compressor inlet, bellmouth, IGVs, and early stage blades

• Performance monitoring: Involves comparing the gas turbine data with the base-line data for monitoring trends


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Turbine Maintenance


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Turbine Maintenance



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Performance Degradation

Compressor Erosion

• It is caused by the presence of excessive quantities of particulates such as sand or fly ash.

• Significant blade erosion can occur if 20 micron particles enter a compressor.

• Orifices and valve seats are more susceptible to compressor erosion.


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Performance Degradation (continued)

Compressor Corrosion

• Is caused by noxious fumes or ash-forming substances present in the fuel:– aluminum– calcium– iron– nickel– potassium– sodium– silicon– magnesium


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• Increases surface roughness and causes pitting that lead to:– decreased compressor airflow and efficiency– reduced gas turbine output and overall thermal efficiency


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Compressor Fouling

• Is caused by liquid or solid particles accumulated on compressor blades

• Leads to reduced air flow

• Leads to lower compressor efficiency

• Leads to lower compressor pressure ratio


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Fouling Deposits

• Consist of varying amounts of:– moisture– oil– soot– water-soluble constituents– insoluble dirt– corrosion products of the compressor blading material

• Are held together by moisture and oil


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Compressor Maintenance


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Compressor Washing

• Is an effective method for preventing fouling in the compressor of a gas turbine

• Slows down the progress of corrosion and increases blade life

• Reduces the formation of fouling deposits by corrosion products

• Ensures maximum available power output, improved fuel efficiency, and reduced wear and tear on machine components

• Is done by injecting a solution of water and detergent into the bellmouth and then rinsing the compressor with water and/or water and detergent solution

• Can be performed while the turbine is operating or after it is shut down


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Compressor Washing (continued)

• Methods of compressor washing:– On-line compressor washing– Off-line compressor washing

• On-line compressor washing aims at extending the period between off-line washes through frequent washings of short duration.

• Off-line compressor washing is performed if a compressor is heavily fouled.


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Compressor Washing (continued)

The washing solution used for off-line and on-line compressor washing must meet the quality specifications listed in the following table:

6.5 to 7.5pH (determined by glass electrode)

0.5 ppmTotal alkali metal and other metals

5 ppmTotal solids (dissolved and undissolved)

On-line washing

6.5 to 7.5pH (determined by glass electrode)

1.0 ppmOther metals

25 ppmTotal alkali metal

100 ppmTotal solids (dissolved and undissolved)

Off-line washing

Quality Specification


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Compressor Washing (continued)Turbine Performance Degradation Curves


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On-Line Compressor Washing

• Is performed to maintain compressor efficiency and is performed before significant fouling has occurred in the compressor

• Involves injecting water into the compressor while the turbine is operating at full speed

• Can be performed without shutting down the gas turbine, and therefore, is used to supplement off-line washing


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On-Line Compressor Washing (continued)

• In an on-line compressor washing, the addition of water increases the compressor pressure ratio and reduces the surge margin.

• Recommendations before performing on-line washing:– The washing solution must meet the quality specification prescribed by

GE.– The turbine must be operating at full speed and must not be in process

of shutting down.– The compressor inlet temperature must be greater than 50° F.


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On-Line Compressor Washing (continued)

Procedure for on-line compressor washing:

1. Select ON-LINE WATER WASH ON from the water wash control display on the turbine control panel.

2. On-line wash water injection valve opens and water flows through the on-line wash water spray manifolds into the compressor.

3. On-line wash cycle begins and continues approximately for 30 minutes.

4. On-line wash water pump automatically shuts down at the end of the on-line wash cycle. On-line wash can be stopped at any time by selecting ON-LINE WATER WASH OFF.

5. Select BASE LOAD or any other desired load target to return the gas turbine unit to normal service.


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Off-Line Compressor Washing

• Includes injecting water into the compressor when the turbine is turned at cranking speed and requires the turbine to be shut down

• Isolates all air extraction points and drains all low points to prevent effluents from entering the piping systems

• Is performed when the compressor performance degrades by 10% due to fouling or the compressor is heavily fouled


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Off-Line Compressor Washing (continued)

Preparation for off-line compressor washing:

• Washing solution and the detergent concentrate must meet the prescribed quality specifications.

• The gas turbine must be shut down and allowed to cool.

• The differential temperature between the wash water and the interstage wheelspace temperatures must not be greater than 120° F (67° C).

• The operating compressor should be de-energized during the pulse mode water wash cycle.

• The inlet plenum and the bellmouth should be cleaned.


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Procedure for off-line compressor washing

1. On the Turbine Main control display screen, place the Master Select switch in the CRANK position.

2. Select OFF-LINE WATER WASH ON from the Water Wash control display.

3. From the Main Control display, initiate a turbine START signal.

4. Select CONTINUE WASH to inject the detergent/water solution into the unit.

5. Select RINSE to begin the rinse cycle.

6. Select END RINSE CYCLE to terminate the rinse mode.

7. Select STOP from the Turbine Control Panel interface display.

8. Select WATER WASH OFF from the Turbine Control Panel interface display.

9. Open the Gas Fuel manifold low point drains.


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Drying process: After washing, the compressor is drained and the remaining water or the cleaning solution is dried. It involves the following steps:

• Start the unit backup for the drying cycle.

• Select Master Reset, and then select START. The gas turbine is allowed to drain and dry for 20 minutes.

• Check the drain ports visually to ensure that all effluent has drained out of the unit.

• Initialize the turbine STOP signal and close the drying cycle .

• Select OFF from the turbine control panel interface to end the drying cycle.


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Considerations after washing:

• Return the drain valves on the gas turbine to their normal positions

• Shut down the exhaust frame blowers at the motor control center

• Return the operator selector switch to AUTO and the water temperature setpoint switch to COLD

• Start the gas turbine within 24 hours after completion of the drying cycle

• Operate the turbine at full speed for a minimum of five minutes


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Performance Restoration after Washing

After washing:

• Performance of the compressor increases. An increase of 10% in the BASE load power is quite common.

• Use the procedure in GEK 28166 for generator drive machines to asses the machine performance and compare the performance data.

• Implement the concept of regular compressor washing to maintain performance of the turbine.


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Performance Restoration after Washing (continued)

compressor maintenance water washing

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