Introduction
Optimal turbine performance is achieved by periodically cleaning compressor stages of the gas turbine. The water wash system provides for washing the turbine when the turbine has been shut down for maintenance (off-line water washing). Off-line water washing may not be initiated until engine surface temperature is < 200 °F (93 ºC).
Refer to F&ID 020020-01-683262, Water Wash System, provided in Chapter 7. Additional details on the turbine water wash system can be found in vendor documentation provided in Chapter 5 of the O&M manual. This section provides an overview of a typical turbine water wash system.
Specifications governing water wash quality, approved cleaning agents, and antifreeze solutions have been included in Appendix A of GE publication GEK-97310 located in Chapter 5 of the O&M manual.
Turbine Water Wash Operation
The customer supplies the recommended amount of chemical concentrate (solvent) through the soap and water fill funnel and the recommended amount of water through water inlet. If necessary, the customer can add antifreeze for engine protection during cold-weather washing.
The normal recommended chemical to water mixture is 1:4 (1 part chemical and 4 parts water).
After permissives have been met, valves open to allow the wash solution to enter the manifold and spray nozzles using customer connection [72] for an on-line water wash and customer connection [72B] for an off-line water wash. The wash solution is pumped and filtered before entering the main skid.
For the wash cycle to begin, SOV-5034 admits the compressed air, filtered to 5 µ, absolute. The air is then regulated by PCV-5028 before entering the diaphragm pump/pneumatic master assembly. Wash cycles last 10 minutes, after which, a purge cycle occurs automatically. The purge cycle uses instrument or compressed air, filtered to 5 µ, absolute, for 1 minute at a pressure of 100–120 psig (689-827 kPag). If a rinse cycle is used, rinse water temperature should range between 150 °F (66 ºC) and 180 °F (82 ºC). After rinsing, drain and clear the tank prior to the next water washing.
Off-Line Water Wash System
The off-line water wash (referred to as a crank-soak wash) consists of the following cycles:
• wash
Initiate an off-line water wash only after the engine surface temperature is < 200 ºF (93 ºC).
Turbine Water Wash Features
Water wash equipment located on the main skid consists of a manifold and spray nozzles and solenoid operated valves.
Water Wash Tank
The water wash tank, located on the water wash cart, has a 45-gal (170L) capacity and receives water and chemical concentrate through customer inlet. The tank is designed to withstand temperatures of 180 ºF (82 ºC).
Water Wash Cart Water Wash Manifold and Spray Nozzles
One manifold services the turbine engine during an off-line water wash and one manifold services the turbine engine during an on-line water wash. Typically, the off-line manifold has nozzles that produce micron droplets at a flow rate of 15 gpm (57 lpm).
Water Wash Gauges and Valves
The ball valve on the tank drain line is normally closed during non-wash cycles. During off-line water wash, wash solution is applied to the atomizing nozzles at 15 gpm (57 lpm) through a 50-µ filter. Solenoid-activated valve SOV-5032 admits off-line wash solution to turbine inlet port S1.
Off-line water wash may not be initiated until gas turbine surface temperatures are less than 200
°F (93 ºC).
Turbine Compressor Cleaning
The water wash provisions are designed to meet the minimum water wash requirements given in the GE manual, GEK-97310, and to minimize exposure of service personnel to concentrated cleaning solvents.
For specific guidelines on cleaning scheduling and recommended solvents, see GE manual, GEK-97310, in Chapter 5 of the O&M manual.
Permissives For Start Of Offline Water Wash
• Turbine Crank Permissive, ref section.
• T48 < 93°C
• T3 < 93°C
• Ambient temperature (TE 4082) > 10°C
If ambient temperature < 10°C the operator must confirm that anti-freeze has been added to water wash fluid by selecting a Antifreeze button on the HMI.
Operator will initiate start of water wash sequencing from HMI, and the logic will perform the following:
1) The hydraulic starter system is started in a Manual Crank mode.
2) The control signal to the hydraulic starter is set to accelerate the GG shaft to 1200 rpm.
3) Open VSV.
4) While accelerating, initiate flow of wash solution to the water wash manifold by opening the water wash supply valve (SOV 5010).
5) At 1200 rpm, de-energize the starter, close the water supply valve, and let engine speed decrease to 100 rpm.
6) At 100 rpm, energize the starter, open the water supply valve, and repeat the cycle until the solution is used up.
7) Upon completion of the injection of the total amount of wash solution, the operator shall give a stop water wash command from the HMI.
8) Deactivate the hydraulic starter.
9) Close VSV.
10) A Normal stop is performed.
11) Begin 10 minute soak timer – displayed on HMI.
Once the soak time is finished, the operator is to rinse the engine by repeating the above procedure.
The turbine should now be started and run at Core Idle speed for 5 minutes to dry. If this operation has not started after 10 minutes an alarm shall be announced to warn the operator.
OPERATOR SCREENS
The GTG Overview screen allows basic monitoring and control of the overall system. Control functions are accessed by faceplate pop-ups. Each control faceplate allows operator interaction and gives associated feedback. The screens displayed by the system software show critical-operating parameters and system set points. Each screen and the information that it contains may be accessed by pressing its corresponding function. Refer to the Water Wash System Operator Screens.
Water Wash Screen
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