GE Power Systems
COMPRESSOR WATER WASH SYSTEM General
Functional Description During the washing operation, water or wash solution is delivered to the gas turbine in the proper mix ratio and the proper pressure, temperature and flow rate to wash the gas turbine compressor. Refer to Gas Turbine Compressor Cleaning GEI–41042M, Table 3 for proper pressures, temperatures, and flow rates for this gas turbine.
Gas turbines can experience a loss of performance during operation as result of deposits of contaminants on internal components. The deposits of atmospheric contaminants on compressor parts occurs with the ingestion of air. The ingested air may contain dirt, dust, insects and hydrocarbon fumes. A large portion of these can be removed before they get to the compressor by inlet air filtration. The dry contaminants that pass through the filters as well as wet contaminants, such as hydrocarbon fumes, have to be removed from the compressor by washing with hot water or a water–detergent water–detergent solution followed by a water rinse.
System Requirements Water used for washing turbine parts should be reasonably clean so that it does not cause fouling or corrosion in itself. Distilled or deionized water is recommended. Water Water quality requirements are listed in Table 1 of GEI–41042M. Oily or varnished oil deposits on internal gas turbine parts require that a detergent solution be used during the washing operation. The detergent shall meet the requirements in Table A1 of GEI–41042M.
On–base Supplied Equipment The on–base equipment supplied with this compressor wash system consists of piping from the package connection on the base, motor operated water injection valves, and the appropriate spray manifolds. In addition, there are package connections in the drain lines from the inlet plenum, combustion area, exhaust frame and the exhaust plenum.
Compressor Washing Frequency The frequency of compressor washing depends upon the severity and type of atmospheric contamination which fouls the compressor and reduces performance. The recommended method for establishing the frequency is to monitor gas turbine performance, comparing the routine performance with the baseline performance to observe the trends.
Off–base Equipment The off–base equipment supplied is an enclosed water wash skid containing a wash water tank, a detergent tank and a centrifugal water pump and motor (88TW–1) with a venturi eductor used to mix the detergent with the wash water. A needle valve used i n conjunction with a flowmeter is used to set the detergent flow to the level recommended by the detergent manufacturer. manufacturer. The water tank is equipped with heaters to bring the wash water to the proper temperature and the skid itself is equipped with a heater, blower and vent fan to maintain the skid in the proper temperature range. A00215
The comparison will show performance trends. If the performance has fallen significantly, and compressor fouling is suspected, it should be verified by visual inspection. This visual inspection should include inspection of the compressor inlet bellmouth, inlet guide vanes and the first and possibly the second stage of the compressor blades. If the performance loss is due to compressor fouling, compressor cleaning should be initiated. For oily deposits, a water–detergent wash followed by a water rinse is required. If only dry deposits are found, water alone may be sufficient. 1
COMPRESSOR WATER WASH SYSTEM
GE Power Systems NOTE
Mandatory Precautions
Inspection should be made for the source of the oily deposits. If possible, corrective action should be taken.
When doing an off–line wash it is extremely important that all water be drain from all piping and that all valving be returned to its normal running position. Failure to do so may result in damage to the gas turbine and/or its components. Refer to TIL 1179–2 for further information.
CAUTION The differential temperature between the wash water and the interstage wheelspace temperature must not be greater than 67 °C (120°F) to prevent thermal shock to the hot gas parts. For wash water of 82 °C (180°F), the maximum wheelspace temperature must be no greater than 149 °C (300°F) as measured by the wheelspace thermocouple readings on the turbine control panel.
Before water washing of the compressor begins, the turbine blading temperature must be low enough so that the wash water does not cause thermal shock. To reduce this difference, the wash water may be heated and the turbine kept on crank until the wheelspace temperatures drop to an acceptable level. The wheelspace temperatures are read at the control panel.
WARNING The water wash operation involves water under high pressure. Caution must be exercised to ensure the proper positioning of all valves during this operation. Since the water may also be hot, necessary precautions should be taken in handling valves, pipes, and potentially hot surfaces.
Washing System Operation
On–line Washing
NOTE Before water washing the compressor, inspect the inlet plenum and gas turbine bellmouth for large accumulations of atmospheric contaminants which could be washed into the compressor. The deposits can be removed by washing with a garden hose.
On–line washing is done with the unit at full speed and the load at or less than 95% rated load. Certain precautions must be taken when performing an on– line wash during low ambient temperature conditions; see Gas Turbine Compressor Cleaning GEI–41042M and TIL 1153–3 for further information.
Water Wash Procedures
Off–line Washing
To perform cleaning designed for this particular unit, refer to the system schematic and the device summary to verify the wash system equipment furnished. Follow the steps outlined in the appropriate section(s) below.
Off–line water washing should be scheduled during a normal shutdown, if possible. This will allow enough time for the internal machine temperatures to drop to the required levels for the washing. The time required to cool the machine can be shortened by maintaining the unit at crank speed. During this cooling of the turbine, the wash water is to be heated to the proper level. COMPRESSOR WATER WASH SYSTEM
Off–line Compressor Wash Procedure On the water wash skid, in the Annunciator/Control Panel, the following settings must be initiated: 2
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GE Power Systems 1. Water Temperature Setpoint switch to HOT.
2. Close the hand valves on the flame detectors.
2. Operation Selector switch to MANUAL.
3. Arrange any valves in the exhaust plenum drain piping to divert effluent from the sludge tank to the waste water tank. Open the main wash water drain valve at the bottom of the exhaust plenum.
NOTE It will take approximately 9–15 hours for the water to heat up to the proper washing temperature.
4. Open the inlet plenum drain valve. 5. If a valve is installed in the line supplying compressor discharge air to the false start drain valve, close it.
Make certain the turbine is shut down. Select the “Water Wash On/Off Line” control display on the turbine control primary operator interface and click on the OFF–LINE WW ON target. At this time, the turbine is prohibited from firing.
6. Switch the motor controller for the turbine exhaust frame cooling fan motors, 88TK–1 and 88TK–2 in the manual “ON” position (if provided).
Select CRANK at the Master Select of the Main Display at the operator interface for the SPEEDTRONIC™ Mark V control.
NOTE This step is necessary to prevent water wash from entering the exhaust frame cooling system during the wash cycle.
Initiate a turbine START signal. The turbine will accelerate to full continuous crank speed. The cranking motor will maintain the unit on crank until the stop signal is given.
The atomizing air system (if provided) is isolated in the following manner: 1. Close butterfly valve on inlet side of atomizing air system from AD–8 line.
The cooldown procedure must be continued until the wheelspace temperatures are within 67 °C (120°F) of the wash water temperature.
2. Open all low point drains in the atomizing air lines.
NOTE
3. Open the atomizing air separator drain valve (if provided).
The turbine may be allowed to cool down on slow roll if time permits.
4. Open vent valve on suction side of CA2, booster atomizing air compressor.
During the crank cycle, manually place the following in the positions indicated and in the order listed:
5. Open vent valve on pressure side of CA1, main atomizing air compressor.
1. The flow through false start drain valves must be diverted from the sludge tank to a wash water effluent tank.
6. Open the breaker at the motor control center for 88AB, the drive motor for the booster atomizing air compressor, CA2.
NOTE The false start drain flow or any flow that goes normally to the sludge tank must be diverted from its “normal” path into the sludge tank, to a wash water effluent drain to prevent an overflow of the sludge tank. Additionally, the false start drain effluent should be visible to evaluate the effectiveness of the wash cycle. A00215
Using the schematic for the cooling and sealing air system, the cooling and sealing air circuitry should be isolated in the following manner: 1. Close the valves in the fifth–stage compressor extraction air lines. 1. Close the valves in the eleventh–stage compressor extraction air lines. 3
COMPRESSOR WATER WASH SYSTEM
GE Power Systems 2. Close any and all compressor discharge extraction valving (AD–n).
by using the respective pushbuttons in the motor control panel:
3. Open the drain valve on the bearing sealing air separator.
1. Start the main wash pump 2. Open detergent isolation valve on line between the venturi and detergent tank.
4. Open needle valve (low point drain on AD–3) upstream of WW9 connection for drainage during the wash cycle, (if provided).
3. While monitoring the flow meter, adjust the flow metering valve as necessary until the proper detergent/water mix ratio is obtained. Refer to detergent manufacturer’s recommendations.
5. Open low point drain on bearing sealing air line, (if provided).
4. Wash/detergent solution should run into the compressor for approximately 3–5 minutes . Allow enough flow time to displace water in the lines between the wash skid and the compressor wash manifold nozzles.
6. If the turbine has a self–cleaning inlet filter, close the block valve and open the drain valve on the supply line to the self–cleaning filters. The water wash skid should now be checked for operational readiness. Determine if the following conditions exist:
5. Initiate the turbine STOP signal and close 20TW–1 using the pushbutton station.
1. The water tank is full.
6. Close detergent isolation valve. (This valve should be closed at all times, except when being used to add detergent.)
2. The detergent tank is full. 3. The water temperature is at the required level.
7. Shut off the main wash pump.
4. The valve on the main wash pump suction side is open.
During the coastdown and immediately afterward, allow the turbine to soak for approximately 20 minutes. After the soak time is complete initiate a turbine START signal.
5. The shutoff isolation valve in the water supply line to the skid is closed. This is done to prevent unheated water from entering the water tank once a wash is initiated.
Open the water wash shutoff valve, 20TW–1, using the pushbutton station 20TW–1/PB at the turbine. Allow the turbine to reach full continuous crank speed.
To minimize thermal shock to the hot gas path parts the operator must verify that all turbine wheelspace temperatures have cooled to within 67 °C (120°F) [149°C (300°F) maximum] of the wash water temperature.
Start the water pump on the skid. Rinse the compressor by pumping clear water from the skid with the main wash pump. Rinse the compressor for 15–20 minutes or until the rinse water runs clear.
When doing a water/detergent wash, refer to the detergent manufacturer’s instructions for the proper detergent/wash ratio.
After washing is complete, initiate a turbine STOP signal and shut off the water pump. Allow the turbine to dry while coasting down.
Open the water wash valve at the compressor using the pushbutton 20TW–1/PB. This pushbutton is located near the 20TW–1 valve near the inlet plenum.
NOTE Experience will determine the proper time intervals for the various wash operations or whether repetition of the above procedure is necessary to restore lost performance.
Allow the turbine to reach crank speed. Initiate the appropriate devices on the water wash skid. The following devices can be manually started COMPRESSOR WATER WASH SYSTEM
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GE Power Systems Return all valves on the skid to their normal position.
CAUTION It is important that the line that allows waste fuel to drain to the sludge tank be kept open after water washing and during normal turbine startup and operation, so that fuel or water which may accumulate in the exhaust plenum can continuously drain out of the plenum. Accumulation of waste fuel in the exhaust plenum is potentially hazardous.
Close wash water injection solenoid valve, 20TW–1, using the pushbutton station. After the turbine has stopped, initiate a turbine START signal with the master operation selector switch in the CRANK position. Allow the turbine to accelerate to crank speed. Allow the turbine to dry for 20 minutes at crank speed.
Switch the motor controller for the turbine exhaust frame cooling fan motors 88TK–1 and 88TK–2, into the “AUTO” mode (if provided).
Initiate a turbine STOP signal. Click on the OFF–LINE WW OFF target on the “Water Wash On/Off Line” control display.
Select OFF at the Master Select of the Main Display at the operator interface for the SPEEDTRONIC ™ Mark V control.
NOTE When OFF–LINE WW OFF is selected, the permissive is in place to allow the turbine to fire and the permissive is removed to allow the 20TW–1 valve to be opened.
In the annunciator/control panel on the skid, set water temperature setpoint to “COLD” and the Operation Selector switch to “AUTO”. Initiate a turbine START signal within 24 hours after completion of the DRY cycle and allow it to accelerate to, and remain at, full speed for a minimum of five minutes.
Return all valving to their previous full–speed operation positions.
The gas turbine is now available for commercial service and may be loaded.
NOTE
NOTE
Allow the water to drain from the lines while the above restorations are being performed.
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Check for air leakage from all drains.
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COMPRESSOR WATER WASH SYSTEM
GE Power Systems
GE Power Systems Training General Electric Company One River Road Schenectady, NY 12345
COMPRESSOR WATER WASH SYSTEM
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