汽轮机主汽阀关闭时间超标原因分析及处理措施

Over standard of main steam valve's closing time in a high-pressure steam turbine:reason analysis and countermeasures

亚临界600MW机组在停机时,汽轮机主汽阀应在300ms以内迅速关闭,快速切断高压汽源,使汽轮机转速下降,以防止汽轮机超速事故的发生。台山电厂亚临界600MW机组自投产以来,在机组停机时经常发生主汽阀关闭时间超标,在机组高负荷下关闭时间超标现象更加严重。经分析原因为阀杆弯曲、弹簧力不足、卧式杠杆连接受力复杂。为此,提出了将卧式杠杆式主汽阀改造为油动机直连式主汽阀,同时加大弹簧力的解决方案。方案实施后,主汽阀在所有状态下的关闭时间均合适且稳定性高。

During shutdown of the subcritical 600 MW unit turbines,the main steam valve should be closed tightly and rapidly within 300 ms,thus to quickly cut down the high pressure steam source,slow down the turbine speed,and prevent turbine over speed accidents.However,since the commissioning of subcritical 600MW steam turbine unit in Taishan Power Plant,the closing time of high pressure main steam valve always exceeded 300 ms during the shutdown.Especially,this phenomenon aggravated when the steam turbine ran at high load.Therefore,the reason was analyzed,and the valve stem bending,insufficient spring force and complicate connection force of horizontal lever were considered as the maj or causes.Finally,several countermeasures were put forward,such as transforming the mode that the lever is connected to the main steam valve into the one that the servomotor is directly connected the main steam valve,meanwhile, increasing the spring force.