660MW超临界机组轴向位移异常事故分析及防范

汽轮机转子由推力轴承轴向定位,轴向位移反映其轴向推力的变化情况,是汽轮机通流部分动静间隙安全可靠的保障。某660 MW超临界机组在运行过程中多次出现轴向位移突然闪跳甚至导致机组跳闸的现象。通过对机组轴向位移历史数据的分析,对现场高压调门与喷嘴室间导汽管上的疏水管阀布置进行检查,找出事故由高压调节阀CV1开出后导汽管冷水汽进入汽机高压缸通流部分造成轴向推力突然增大引起。针对此影响机组运行的重大安全隐患,提出了防范措施,为类似机组安全运行和维护提供警示和参考。

Analysis and Prevention of Abnormal Axial Displacement Accident of 660 MW Supercritical Unit

The steam turbine rotor is axially positioned by the thrust bearing, and the axial displacement reflects the change of its axial thrust, which is a safe and reliable guarantee for the dynamic and static clearance of the flow passage part of steam turbine. During the operation of a 660 MW supercritical unit, the axial displacement suddenly flashes and even causes the unit trip. Based on the analysis of the historical data of the axial displacement of the unit, the arrangement of the drain pipe valve on the steam guide pipe between the site high-pressure regulating valve and the nozzle chamber is checked, and it is found that the accident is caused by the sudden increase of the axial thrust caused by the cold water steam in the steam guide pipe entering the flow part of the high-pressure cylinder of the turbine after the high-pressure regulating valve CV1 is opened. In view of the major potential safety hazards affecting the operation of the unit, preventive measures are proposed to provide warnings and references for the safe operation and maintenance of similar units.