210 MW汽轮机大轴弯曲原因分析及直轴方法

某厂一台210MW汽轮机在机组冷态起动过程中出现了大轴弯曲的事故，详细描述了事故发生的经过。通过分析运行参数的变化和汽缸的结构,得出汽轮机振动异常的原因：汽缸夹层加热蒸汽带水和疏水门未打开，造成了叶轮动、静磨擦；轴封蒸汽过热度太低和失压过长，造成了轴封局部变形。根据运行规程分析了事故发生时运行人员处理不当之处：没有及时发现汽缸温度变化；机组振动异常时没有及时打闸停机；打闸停机后没有及时破坏真空；开机过程中没有投入振动保护。在分析了各种直轴方法的基础上，确定采用应力松弛法进行直轴，并介绍了这种方法的工艺。直轴后大轴在高压转子联轴器处的挠度为0．06mm,基本达到原状态水平。

Analysis of Main Shaft Bending of a 210 MW Steam Turbine and Shaft Straightening Method

This paper detailedly describes the main shaft bending accident of a 210 MW steam turbine in some power plant during cold startup of the unit.Upon analysis of the change in operation parameters and the structure of the cylinder,the reasons for the abnormal vibration of the turbine are found,which include blade wheel friction caused by the water in the heating steam at the cylinder interlayer besides the unopened drainage valve,and the local deformation of the gland seal resulting from excessively low superheat degree of steam and prolonged loss of pressure at the gland seal.According to relevant operational codes,the misoperation of the operators during the accident is analyzed,who failed to timely discover the temperature change of the cylinder,to timely trip the unit upon its abnormal vibration,to timely disrupt the vacuum after tripping the unit,and to actuate the vibration protection during startup of the unit.The paper also describes the procedure of the stress relaxation method that was decided to be used after analyzing various shaft straightening means.After the straightening of the shaft,the deflection at the HP rotor coupling was 0.06 mm,basically reaching the original level.