How does a check valve achieve the opening and closing of the valve? Opening and closing of check valve: The opening and closing parts are circular discs and act on their own weight and medium pressure to block medium backflow. The medium flows in from the inlet end (lower side) and out from the outlet end (upper side). How does the inlet pressure check valve achieve the opening and closing of the valve?

止回阀阀门的打开和关闭：启闭件为圆形阀瓣并靠自身重量及介质压力产生动作来阻断介质倒流。

Opening and closing of check valve: The opening and closing parts are circular discs and act on their own weight and medium pressure to block medium backflow.

介质从进口端(下侧)流入，从出口端(上侧)流出。当进口压力大于阀瓣重量及其流动阻力之和时，阀门被开启。反之，介质倒流时阀门则关闭。旋启式止回阀有一个斜置并能绕轴旋转的阀瓣，工作原理与升降式止回阀相似。

The medium flows in from the inlet end (lower side) and out from the outlet end (upper side). When the inlet pressure is greater than the sum of the weight of the valve disc and its flow resistance, the valve is opened. On the contrary, when the medium flows back, the valve closes. The swing check valve has a valve disc that is tilted and can rotate around the axis, and its working principle is similar to that of a lift check valve.

止回阀常用作抽水装置的底阀，可以阻止水的回流。止固阀与截止阀组合使用，可起到隔离的作用。缺点是阻力大，关闭时密封性差。

A check valve is commonly used as the bottom valve of a pumping device to prevent water from flowing back. The combination of a check valve and a shut-off valve can provide safe isolation. The disadvantage is high resistance and poor sealing when closing.

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止回阀按结构划分，可分为升降式止回阀、旋启式止回阀和蝶式止回阀三种：

Check valves can be divided into three types according to their structure: lift check valves, swing check valves, and butterfly check valves:

1、升降式止回阀分为立式和卧式两种。

1. Lift check valves are divided into two types: vertical and horizontal.

2、旋启式止回阀分为单瓣式、双瓣式和多瓣式三种。

2. Swing check valves are divided into three types: single disc, double disc, and multi disc.

3、蝶式止回阀为直通式。

3. The butterfly check valve is a straight through type.