进口止回阀按止回功能分类以及如何选型
进口止回阀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。
止回阀包括旋启式止回阀和升降式止回阀。
进口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*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。
进口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 to prevent the backflow valve media This type of valve is the role of the media to only allow flow in one direction, but also to prevent the direction of flow. Normally this valve works automatically, in a direction of fluid flow under pressure, the valve opens; the opposite direction of fluid flow, fluid pressure and valve from the self-overlap effect on the valve seat, thereby cutting off flow. Which belongs to this type of check valve valve, which includes the swing check valve and lift check valves. Swing check valve with ordinary hinge, there is a door the same as freedom against the valve seat surface tilt. To ensure that every time the valve seat surface to reach the appropriate position, the valve flap hinge design, the valve has to have enough swing space, and a real disc, full with the valve seat. Valve can all be made ??of metal, can also be embedded in the metal on leather, rubber, or synthetic cover, depending on performance requirements. Swing check valve in the fully open position, the fluid pressure is almost free of obstruction, so the pressure drop through the valve is relatively small. Valve lift check valve located in the valve body seat sealing surface. In addition to this valve is free to lift the valve, the valve the same as the rest, the fluid pressure to the valve lift from the valve seat sealing surface, return media led down to the valve seat, and cut off the flow. Depending on conditions, the valve can be all metal construction, it can be rack mounted in the valve rubber or rubber ring form. The same as the cut-off valve, lift check valve fluid through the channel is narrow, so by the lift check valve pressure drop than the swing check valve bigger, and swing check valve flow restrictions very little.
