In 1994, the Dutch utilities started a five-year program aimed at 1) reduction of the forced unavailability of their gas turbine fleet and 2) keeping the operational and maintenance cost down. The project approaches its completion so now is the time to evaluate what it has delivered. Subjects of the project were the development of on-line and off-line diagnostic techniques, blade life management systems, optimization strategies for maintenance, air filtration and compressor washing, evaluation of NOx control techniques and evaluation and development of test methods for repair and reconditioning techniques. This paper gives an overview of the project achievements and a look at the evolution of the unavailability in the course of the years until 1995.

New (on-line) techniques developed are e.g. a flame stability monitoring system, correlating operational parameters to burner characteristics, a pyrometer with high spatial resolution and a tip shroud deflection monitor. Off-line inspection techniques include the development of a combined in-situ crack detection and sizing instrument as well as a method for measuring alumina depletion from coatings. REMLIF6, a life estimating algorithm for GE Frame 6 turbine blade and nozzles has been completed. Recommendations for optimized filter exchange and compressor washing schedules have been formulated. Development of the forced unavailability shows less problems related to turbine blading, possibly related to better knowledge on blade temperatures, and liners. An increase in burner related problems is noticeable, associated with the introduction of Low-NOx combustion. Overall the forced unavailability figures are going down and a number of problems in recent years has been solved quicker because of tools and knowledge developed in the project. The evolution of maintenance cost is under study.

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