引进型600MW汽轮机低压次末级叶片(474mm)事故分析

Failure Analysis on 474 mm Last-stage Blade in 600 MW Westinghouse Turbin

对平圩发电有限公司两台引进型 60 0 MW汽轮机“4 74”叶片、叶根、轮缘事故原因作了分析 ,认为叶片断落的原因主要由于单节线扭振共振、加之某些缺陷引起的应力集中所致 ;叶根、轮缘裂纹的原因 ,主要由于该级叶根设计单薄、强度裕量小 ,诸多因素造成叶根齿受力状况的变化 ,使叶根齿局部应力过大、二阶频率下降落入共振的边缘 ,加之应力集中、过渡区腐蚀环境的影响等 ,使叶根安全裕度下降、累积疲劳所致。

An analysis on cracks on PPGC's two 600 MW Westinghouse designed turbine's last stage 474 mm blade,root and disc edge has been carried out and concluded that the main course of blade cracks is blade resonance,stress concentration in defects and that of the root and disc cracks is root structure design is too weak.With too little strength safety factor,which cause an excessive local stress in blade root,the secondary frenquency decreases and falls into resonance area,and the corrosion enviroment of transition area also accelerates the crack forming.