During the debugging and operation of relay hydraulic hoist in Shuikou hydropower station, the automatic opening and closing action broke down. The reason may be that the unexpected opening of hydraulic single- direction valve with pressure pre- release function causes the pressure unloading of rodless cavity of no-load cylinder. The pressure drop at electro- hydraulic directional control valve port and oil return filter is calculated to obtain the pressure value at the control port of hydraulic single-direction valve. Base on analysis of the force on the hydraulic single-direction valve core, it is confirmed that the hydraulic single-direction valve would open in reverse direction. The solution is to reinstall the hydraulic single-direction valve without pressure pre- release under low pressure working condition.

水口水电站接力式液压启闭机在调试及运行过程中出现自动启闭动作中止故障，分析原因可能是带预释 压液控单向阀的意外开启造成了空载缸无杆腔压力卸荷。对电液换向阀阀口及回油过滤器压降进行计算，得到 液控单向阀控制口压力值，根据液控单向阀阀芯受力平衡公式，确认液控单向阀会反向开启。对此提出了解决方 案：在低压工作条件下，换用不带预释压功能的液控单向阀。