1、 Working principle of check valve

Check valve refers to a valve that automatically opens and closes the valve disc by relying on the flow of the medium itself to prevent medium backflow. It is also known as a check valve, one-way valve, backflow valve, and backpressure valve. Check valve is an automatic valve that mainly functions to prevent medium backflow, prevent pump and drive motor reversal, and prevent the discharge of container medium. Check valves can also be used on pipelines that provide supply to auxiliary systems whose pressure may rise above the system pressure. Check valves can be mainly divided into swing check valves (rotating according to the center of gravity) and lift check valves (moving along the axis).

The function of a check valve of this type is to only allow the medium to flow in one direction and prevent flow in the opposite direction. Usually, this type of valve operates automatically, and under the pressure of fluid flowing in one direction, the valve disc opens; When the fluid flows in the opposite direction, the valve seat is cut off by the fluid pressure and the self weight of the valve disc, which acts on the valve seat.


2、 Selection of check valve:

1. To prevent media backflow, check valves should be installed on equipment, devices, and pipelines;

2. Check valves are generally suitable for clean media and are not suitable for media containing solid particles and high viscosity;

3. Horizontal lift check valves should generally be used on horizontal pipelines with a nominal diameter of 50mm;

4. Direct lift check valves can only be installed in horizontal pipelines;

5. For the inlet pipeline of the water pump, it is advisable to use a bottom valve. The bottom valve is generally only installed on the vertical pipeline of the pump inlet, and the medium flows from bottom to top;

6. The lifting type has better sealing performance and greater fluid resistance compared to the rotary type. It is recommended to install it on a horizontal pipeline for horizontal installation and on a vertical pipeline for vertical installation;

7. The installation position of the swing check valve is not limited. It can be installed on horizontal, vertical, or inclined pipelines. If installed on vertical pipelines, the medium flow direction should be from bottom to top;

8. The swing check valve can be suitable for any working medium and any working temperature range depending on the material of the housing and sealing components. The media include water, steam, gas, corrosive media, oil products, drugs, etc. The working temperature range of the medium is between -196-800 ℃;

9. The rotary check valve is suitable for low pressure and large diameter applications, and its installation is limited;

10. The installation position of butterfly check valves is not limited and can be installed on horizontal pipelines, as well as vertical or inclined pipelines;


3、 Check valve structure

Check valves can be divided into three types based on their structure: lift check valves, swing check valves, and butterfly check valves. Lift check valves can be divided into two types: vertical and straight through. Swing check valves are divided into three types: single disc, double disc, and multi disc. Butterfly check valves are divided into butterfly double disc, butterfly single disc, and the above types of check valves can be connected in four forms: threaded connection, flange connection, welding, and clamp connection.