一、前言我国东方汽轮机制造厂生产的N75—90—1型汽轮机第20级叶根为外包双T型。曾因该级叶根发生断裂而造成严重事故。例如广东韶关电厂的6号机在投运的两年内,就在叶根、叶片处发生三次断裂事故,仅74年8月一次事故就损坏了该级叶片55片,严重地威胁机组的安全运行。由于该级叶根探测面较小,目前国内生产的超声波探头均大于可以放置探头的探测 First, the foreword China’s Dongfang Turbine Manufacturing N75-90-1 steam turbine production level 20 root outsourcing double T-type. Have caused a serious accident because of the level of root rupture. For example, Shaoguan Power Plant’s No. 6 machine in operation within three years, in the root, the blade occurred three rupture of the accident, only 74 years in August an accident that damaged the level of 55 blades, a serious threat to the safe operation of the unit . Because this level of root detection surface is small, the current domestic production of ultrasonic probes are larger than the probes can be placed probe