non return valve

例句：

1. 1. The valve is designed to prevent fluid from flowing backwards when the pressure drops.
   这个阀门设计成在压力下降时防止流体反向流动。
2. 2. The engineer used a non-return valve to control the flow of oil during maintenance.
   工程师使用了一个无回阀来控制维护期间的油流。
3. 3. The pilot valve is essential for maintaining proper pressure in the system.
   主蒸汽阀对于保持系统内适当的压力至关重要。