Gas Turbine Blade Failures - Causes, Avoidance, And Troubleshooting.

Tutorialpg. 129-180With blading problems accounting for as many as 42 percent of the failures in gas turbines (Allianz, 1 978) and with its severe effect on plant availability, there is a pressing need for a unified treatment of the causes, failure modes, and troubleshooting to assist plant engineers in tackling blade failure problems. This paper provides a comprehensive practical treatment of the subject, taking into account the complex nature of blading problems, influence of the operating environment, design factors, and maintenance practices. Blade failure modes such as fatigue, environmental attack, creep, erosion, and embrittlement are addressed along with a synopsis of design tools to review blade reliability. Peripheral issues affecting blade integrity such as fuel and blade quality control are addressed. A blade failure troubleshooting chart is furnished to assist users in diagnosing common failure modes. The object of this paper is to show, in the context of blading problems, the interrelationship between design, operation, maintenance, and the operational envelope. Several case studies are presented dealing with a variety of failure modes. The treatment focuses on practical troubleshooting of blading problems augmented, in some cases, by the use of analytical tools. APPENDIX A provides applicable tools, rules of thumb, and formulae that can be used by gas turbine users for design review and troubleshooting