译文：
这种类型的阀门的作用是只允许介质向一个方向流动，而且阻止方向流动。通常这种阀门是自动工作的，在一个方向流动的流体压力作用下，阀瓣打开；流体反方向流动时，由流体压力和阀瓣的自重合阀瓣作用于阀座，从而切断流动。其中止回阀就属于这种类型的阀门，它包括旋启式止回阀和升降式止回阀。旋启式止回阀有一介铰链机构，还有一个像门一样的阀瓣自由地靠在倾斜的阀座表面上。 为了确保阀瓣每次都能到达阀座面的合适位置，阀瓣设计在铰链机构，以便阀瓣具有足够有旋启空间，并使阀瓣真正的、全面的与阀座接触。阀瓣可以全部用金属制成，也可以在金属上镶嵌皮革、橡胶、或者采用合成覆盖面，这取决于使用性能的要求。旋启式止回阀在xx打开的状况下，流体压力几乎不受阻碍，因此通过阀门的压力降相对较小。升降式止回阀的阀瓣座落位于阀体上阀座密封面上。 此阀门除了阀瓣可以自由地升降之外，其余部分如同截止阀一样，流体压力使阀瓣从阀座密封面上抬起，介质回流导致阀瓣回落到阀座上，并切断流动。根据使用条件，阀瓣可以是全金属结构，也可以是在阀瓣架上镶嵌橡胶垫或橡胶环的形式。像截止阀一样，流体通过升降式止回阀的通道也是狭窄的，因此通过升降式止回阀的压力降比旋启式止回阀大些，而且旋启式止回阀的流量受到的限制很少。

“ How to choose the valve to prevent the media back”是由提供的国际阀门新闻，译文仅供参考。另外，中国安全阀网还提供相关产品搜索：、、、、等。

原文：
This type of valve is the role of media in one direction only allows movement, but also to prevent the direction of flow. Usually the valve is automatically work, the fluid flow in one direction under pressure, valve flap open; fluid flow in the opposite direction from the fluid pressure and valve flap valve flap from the coincidence of acting on the valve seat and thus cut off the flow. Check them belonging to this type of valve, which includes Swing check valve and lift check valve. Swing Check Valve with ordinary hinge, there is a door the same as the free flap valve leaning tilt seat surface. In order to ensure that the flap valve seat face every time to reach a suitable position, the valve flap design in the hinge body to valve flap has enough to swing space, and make a real flap valve, comprehensive engagement with the valve seat. Valve flap can all be made of metal can also be embedded in the metal on leather, rubber, or synthetic coverage, depending on the use of performance requirements. Swing check valve in the fully open position, the fluid pressure virtually unimpeded, so the pressure drop through the valve is relatively small. Check the valve lift valve is located in the valve body on the valve seat sealing surface. In addition to this valve flap valve is free to lift, the other part of the same as the cut-off valve, the fluid pressure valve from the valve seat sealing surface of valve lift, medium return valve flap led to a seat on the back, and cut off the flow of. According to conditions of use, the valve flap can be all-metal structure can also be rack mounted in the valve flap rubber mat or rubber ring form. The same as the cut-off valves, fluid channels through the lift valve is narrow, so that by elevating the pressure drop valve Swing check valve than the bigger, and the flow of Swing Check Valve restrictions on rarely.