Steam Turbine Blades:Considerations in Design and a Survey of Blade Failures

摘要

Thermo-mechanical considerations and material selection criteria for the design of steam turbine blades are discussed from the mechanical engineers point of view in the first two sections of this report. Sources of vibratory excitation, the response of blades to these excitations, the stress levels and load histories that result from this response, and various design features incorporated into steam turbine LP blading to minimize or resist these stresses are covered. Blading alloy properties of concern to the blade designer are discussed and compared, and parameters to be used in fatigue testing recommended. The third section of the report describes several blade failure surveys. In addition to a literature survey, results of a questionnaire on LP blade failures to American utilities and a review of recent Westinghouse experience are presented. Correlations between the number of failures and parameters such as blade life, failure location in the turbine and on the blades, alloy, deposit chemistry, steam source, feedwater treatment, cooling water source, balance of plant problems, and temperature and pressure at the failed row are attempted.