Analysis of Cause of Low Pressure Rotor Fracture in Supercritical Unit
Author of the article:HUANG Qiaosheng;ZHANG Yalin;MOU Shenzhou;LI Qiubai;LIU Yuhai
Author's Workplace：Guodian Science and Technology Research Institute Co.,Ltd.,Wuhan 430066,China;Guodian Henan Electric Power Co.,Ltd.,Wuhan 450000,China
Key Words：pill test magnetic memory corrosion medium salt accumulation analysis
Abstract：
A blade fracture accident occurred in a supercritical 600 MW unit.Optical microscopy,scanning electron microscopy and magnetic memory detector were used to analyze the metallographic structure of the blade,the composition of the scale layer(corrosion product)on the blade surface and the stress distribution of the blade.The results show that the quality of blade shot peening is poor,pitting corrosion pits are generated in the corrosive environment,and micro-cracks are formed in the pitting corrosion pits on the edge of steam inlet side.Under the action of centrifugal force and alternating steam flow force in operation,stress concentration is generated,and crack propagation occurs until fatigue fracture occurs.In order to ensure the safe operation of the steam turbine,it is proposed to strengthen the quality supervision of aerated water,inspect the micro-defects such as pitting corrosion during the inspection of the cylinder in overhaul,and adopt spraying technology to protect the blade surface.
