RECENT ADVANCES IN ACHIEVING AND MAINTAINING HIGH TURBINE BLADE AVAILABILITY

This paper presents a summary of recent advances in performance, reliability, availability, and maintainability of steam and gas turbine blades as related to the electric power plant industry. Improved turbine inlet temperature, resistance against creep/fatigue crack growth, and service life of today's blades are a direct result of advan ced design, materials, fabrication processes, and inspection methods. In addition, advanced methods of heat transfer enhancement such as the use of turbulators in the cooling passages of combustion turbine blades as well as protective coating of the blade surface have increased resistance to thermal shock and oxidation/corrosion at higher temperatures. Due to the cyclic 'nature of current load generation (peak demand versus base load), it is imperative for utilities to closely monitor (on-line, off-line) and periodically inspect the condition of turbine blades in a reliable manner. The present level of sensor technology does not allow for direct on-line monitoring of combustion turbine blades. However, monitoring of steam turbine blades can be performed by special sensors mounted on the blade or turbine casing and transmitting data for processing and evaluation by an operator or to an expert system software. Inspection and fault diagnostics are accomplished by using advanced NDE methods and analysis software for both steam and gas turbine described in this paper.