Critical Components Life Update for Gas Turbine Engines: Case Study of an International Collaboration

Abstract

The paper describes results of the international collaboration that led to revision of the declared lives for critical components of a turbo-prop gas turbine engine. Four nations contributed to the program—Australia, Canada, USA and South Africa under the auspices of a Component Improvement Program led by the Original Equipment Manufacturer (OEM). This international collaboration was initiated as a result of the decrease in the declared life for some critical components of this engine by the OEM. The core of the program consisted of a detailed stress analysis performed in South Africa, and spin rig testing of selected life-limited, rotating turbine components—two stages of discs and two stages of spacers—performed in Australia and Canada. The general objectives of the program were to provide more accurate low cycle fatigue crack initiation data and to verify crack growth life analysis techniques using advanced 2D and 3D finite element analyses and spin rig testing for selected components. The crack initiation results are used to improve the life management procedures. Since the OEM does not recommend using life limits that exceed the safe crack initiation life of the rotating turbine components, the crack growth analysis results are used only for risk assessment and risk management by the engine operators. The basis of analytical techniques used for preparing the tests as well as the testing procedures are described. In addition, the development of NDE (Non Destructive Evaluation) methods and the inspections of these components during and after the tests are discussed. The economical benefits of such an international collaboration are demonstrated. The uniqueness of this approach to life revision of critical components of gas turbine engines, particularly for engines that have been in operation for many years, includes close cooperation of an international team of the engine manufacturer, the major engine users and their respective scientific organizations. In addition, a significant amount of operational experience that has been accumulated by the OEM, has allowed for verification of the spin rig test results.