Optimisation of gas turbine performance is a key consideration for power and industrial plant operators. Such activity returns dividends in the form of improved output and heat rate recovery, but also has a beneficial impact on equipment lifecycle and maintenance costs. Gas turbines compress very large quantities of air through the compressor stage. This stage of the power cycle consumes up to 60% of the energy involved in operating the engine. Consequently, any efficiency degradation of the compressor will significantly impact the overall machine efficiency. Due to large amounts of air passing through the compressor, other contaminants, even in small concentration, have the ability to travel into the compressor and coat or foul the working surfaces. Over time, this results in lower efficiency and output. Since fouling of turbine compressors is almost unavoidable, even with modern air filter treatment, compressor cleaning is required to maintain overall gas turbine efficiency. The use of an offline and/or online water wash system, to periodically clean blade surfaces, is a typical method used to minimise compressor fouling. An offline wash applies water and a wetting agent when the machine is unfired, at ambient temperature, and operated at a lower speed. An online wash only applies water when the machine is fired at full operating speed. Use of a well designed water wash system can maintain higher turbine efficiencies, significantly improving profitability, without impacting the durability of compressor components. This paper will review lessons learned from the application of over 1000 run hours, the methods to optimise a compressor utilising a water wash program and data that demonstrates an improvement of output and heat rate recovery.
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