change-over valve是什么意思

用法例句

The water injection and gas discharge device is added,the flexible pressure testing sub is used and the high and low pressure water conversion valve body is improved.

通过增加管体注水排气装置、采用柔性试压接头、改进注水端高低压水转换阀体等措施,解决了油管试压机存在的损伤油管螺纹、试压接头消耗快、试压过程密封性能差、生产效率低、安全性差等问题。