As stated above, the bypass valve is open and atomizing air is recalculating. After a short time delay, to allow the pressure ratio (regulated by valve YPR54) of the atomizing air system to reach a lower level, solenoid valve 20PL-l is energized. The system then starts operating to purge the oil passages in the oil fuel nozzles during gas fuel operation. The purge air system is necessary to prevent of oil fuel in the nozzle oil passages, during gas fuel operation, and in of the nozzles as a result of oil fuel cooking. The purge system minimizes such fouling, and keeps the oil fuel nozzle clean and ready for operation when oil fuel operation is resumed.
The small flow of air through the atomizing air passages of the oil fuel nozzle also prevents entry of any combustion products that could foul this section of the oil fuel nozzle. When solenoid valve 20PL-1 is energized, operating air (from the turbine compressor discharge) is admitted to the diaphragm of purge air valve VA19 which opens, allowing purge air (atomized) to flow into the purge air manifold on the turbine. A porous filter (FA3) is installed in the purge air check valves, one for each nozzle, are connected into the oil feed lines to the nozzles.
These purge air check valves prevent oil fuel from entering the purge air system when the machine is operating on oil fuel. Similarly, the oil fuel check valves installed in the oil piping to the oil fuel, it will drain out of the purge air manifold through the normally open port of the three-way purge air valve. “Tell-Tale” leak-off piping connected to the purge valve vent port provides a visual means for determining the general condition of the check valves. There should not be any leakage.
6.1.4 Water Wash Provisions
When water washing the gas turbine’s compressor section and turbine sections it is important to keep water out of the atomizing air system. To keep water out of the atomizing air system, the system inlet and discharge are equipped with vent valves and an isolation valve or full area spacers. The vent valves are used to avoid completely throttling or deadening the compressors, and the drain valves to remove any leakage past the isolation valves.
During normal operation of the gas turbine, the vent and drain valves must be closed and the isolation valves or spacers must be opened. Before initiating water wash, the isolation valve must be closed or blank area spacers installed to keep water out of the atomizing air system. The vent valves must be opened to allow air to pass through the atomizing air compressors.
The small flow of air through the atomizing air passages of the oil fuel nozzle also prevents entry of any combustion products that could foul this section of the oil fuel nozzle. When solenoid valve 20PL-1 is energized, operating air (from the turbine compressor discharge) is admitted to the diaphragm of purge air valve VA19 which opens, allowing purge air (atomized) to flow into the purge air manifold on the turbine. A porous filter (FA3) is installed in the purge air check valves, one for each nozzle, are connected into the oil feed lines to the nozzles.
These purge air check valves prevent oil fuel from entering the purge air system when the machine is operating on oil fuel. Similarly, the oil fuel check valves installed in the oil piping to the oil fuel, it will drain out of the purge air manifold through the normally open port of the three-way purge air valve. “Tell-Tale” leak-off piping connected to the purge valve vent port provides a visual means for determining the general condition of the check valves. There should not be any leakage.
6.1.4 Water Wash Provisions
When water washing the gas turbine’s compressor section and turbine sections it is important to keep water out of the atomizing air system. To keep water out of the atomizing air system, the system inlet and discharge are equipped with vent valves and an isolation valve or full area spacers. The vent valves are used to avoid completely throttling or deadening the compressors, and the drain valves to remove any leakage past the isolation valves.
During normal operation of the gas turbine, the vent and drain valves must be closed and the isolation valves or spacers must be opened. Before initiating water wash, the isolation valve must be closed or blank area spacers installed to keep water out of the atomizing air system. The vent valves must be opened to allow air to pass through the atomizing air compressors.
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