Reliability evaluation of a Gas Turbine Water Wash System – A case study

• The availability of this system is crucial to recovering compressor efficiency.
• The Gas Turbine Water Wash System is crucial for to keep turbines in good conditions.
• The reliability analysis will allow to schedule a frequency preventative maintenance.
• The article allows a better understanding of the causes of major failure events.
• The water wash system can be taken as 76% reliable based on a 300 h running time.

In this article, a reliability analysis was carried out on a Gas Turbine Water Wash System used for washing the compressors of three (3) GE Frame 7 EA Gas Turbines using Weibull Distribution. Note that availability of this system is crucial to recovering compressor efficiency and by extension generation capability that has been lost due to contaminants on the compressor blades. This system therefore, helps maintain and improve the reliability of the turbine and of plant-wide generation. The reliability analysis covered two failure modes for each piece of equipment and took into account the reliability of the system in two operational modes, off-line washing cycle and online washing cycle for a 300 h operational time. Based on the results obtained it can be concluded that the entire water wash system can be taken as 76% reliable based on a 300 h running time. It is more reliable to perform an online water wash than an off-line water wash by at least 4% based on a 300 h operating time. This increased reliability of the water wash system to perform an online water wash is due to an off-line water wash requiring additional equipment which must be run in series.In addition to the aforementioned analysis fault trees were created to model two scenarios which relate directly to the efficiency of the gas turbine compressors and the generation capability of the turbine: (1) the likelihood of no water being present when conducting a water wash; and (2) the likelihood of cold water being sent to the water wash manifold. Based on the estimated reliabilities, the likelihood of no water being present when conducting a water wash was found to be 3.7% and the likelihood of cold water being sent to the water wash manifold is 1.6%.