Gas Turbine Off-Line Compressor Washing Operation

Functional description
The wash water solution in the proper mix is delivered to the turbine unit at the proper pressure, temperature and flow rate to wash the gas turbine.

Wash solution from the skid flows from the customer's connection through the motorized valve 20 TW-1 to the compressor spray manifold. The valve is motor-driven and is manually opened by a push-button 43 TW-1/PB. It is closed automatically when the wash selector switch is in the OFF position.

During compressor washing, valve 20 TW-1 is opened allowing the wash solution from the skid to flow into the compressor spray manifold and through the spray nozzles into the compressor bell-mouth to accomplish the washing.

False start drain valves (VA17) shown on the washing diagram are opened for washing purpose. Air pressure from the discharge of the unit’s axial-flow compressor is used to actuate these valves. Valves VA 17 drain excessive water from the combustion chambers.

Off-line washing procedure
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. The differential temperature between the wash water and the interstage wheelspace temperature must not be greater than 120°F (67°C). For wash water of 180°F (82, 3°C), the maximum wheelspace temperature must be no greater than 300°F (149°C) as measured by the digital thermocouple readout system on the turbine control panel.

Scheduling of the water wash should occur during the normal machine shut down. This would allow sufficient time for the internal machine temperature to drop to acceptable levels for the washing.

During the cooling of the turbine, the wash water is to be heated to the proper level.

WARNING: The water wash operation involves water under high pressure. Caution must be exercised to insure the proper valve is either in a fixed open or a fixed closed position at any time during system operation

NOTE: Before water washing the compressor, inspect the inlet plenum and gas turbine bell-mouth for large accumulations of atmospheric contaminants which could be washed into the compressor. These deposits can be removed by washing with a garden hose.

Prepare the atomizing air circuit, the cooling and sealing air circuit and the skid. The compressor OFF-LINE washing is done with the machine cold, at crank speed so to have a good cleaning of the rotor. The washing compressor selection will led to the opening of the IGV.

The valves that have been operated before the compressor washing operation must be returned to their previous positions to allow the turbine to fire.


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