核电厂安全壳喷淋系统阀门远传机构电动头失效分析及改进

Failure analysis and improvement for containment spray system valve's remote actuating mechanism in a nuclear power station

某核电厂安全壳喷淋系统阀门远传机构在定期检查中发现电动头的手动和电动操作均失效,且内部行星架存在7处断裂损坏,断口表面粗糙,可见轻度宏观塑性变形。理化检验结果表明,断口上存在大量的缩松类铸造缺陷,断口边缘局部存在碰磨痕迹。分析其原因为电动机启动扭矩大于电动头扭矩保护限值,造成电动头反复启、停,对减速机构行星架施加多次冲击载荷,造成行星架断裂失效。对此,提出了在传动机构出口串接摩擦离合器,增加变频器来控制电动机启动扭矩,提高电动头扭矩保护上限值等措施,实施后该安全壳喷淋系统阀门远传机构电动头运转正常。

Manual and electric operation failure of electric actuator for containment spray system valve＇s remote actuating mechanism was found in regular check of a nuclear power station,seven fractures were found in inner planet carrier with rough surface and mild macroscopic plastic deformation.The physical and chemical inspection results show that large amounts of shrinkage casting defects exist on the fracture area,wear trace exist on the edge of fracture.Analysis shows the failure cause is that motor starting torque is greater than protection level torque of the electric actuator,making the electric actuator stop again and again,applying repeated impact load on the planet carrier of deceleration mechanism,resulting in the failure of the plant carrier.Therefore,many improvement measures were proposed,such as cascading a concatenated friction clutch in the transmission mechanism outlet,increasing starting torque of inverter control motor and protection level torque of the electric actuator.After these measurements were carried out,the containment spray system has been functioning continuously.