Check valve selection criteria are as follows:

For medium reverse flow, check valves shall be installed on equipment, devices and pipelines;

Check valve is generally suitable for clean medium, should not be used for containing solid particles and viscosity of the larger medium;

Generally, vertical lifting check valve shall be selected on the horizontal pipeline with a nominal pass of 50mm;

Straight-through lifting check valve can be installed in both horizontal and vertical pipelines;

For the inlet pipeline of the pump, the bottom valve should be selected. The bottom valve is generally only installed on the vertical pipeline of the pump inlet, and the medium flows from the bottom up;

The lifting type swing type has good sealing performance and large fluid resistance. The horizontal type should be installed on the horizontal pipe and the vertical type should be installed on the vertical pipe;

The installation position of the swing check valve is not limited, it can be installed in the horizontal, vertical or inclined pipeline, such as installed in the vertical pipe, the medium flow from the bottom to the top;

Swing check valve should not be made into small diameter valves, can be made into a very high working pressure, PN can reach 42MPa, and DN can also be very large, can reach more than 2000mm. According to the shell and seals of different materials can be applied to any working medium and any working temperature range. The medium is water, steam, gas, corrosive medium, oil, medicine, etc. Medium working temperature range between -196-800 ℃;

Applicable occasions are low-pressure large-diameter, and installation occasions are limited;

The installation position of the butterfly check valve is not limited. It can be installed on the horizontal pipeline or on the vertical or inclined pipeline;

Diaphragm check valve is suitable for pipelines prone to water hammer. Diaphragm can well eliminate water hammer generated when medium flows back. It is generally used on low pressure and normal temperature pipelines, especially on tap water pipelines. Generally, the working temperature of medium is between -12-120 ℃ and the working pressure is <1.6MPa. However, diaphragm check valve can achieve larger diameter and DN can reach more than 2000mm;

Ball check valve is suitable for medium and low pressure pipelines and can be made into large diameter;

The shell material of the ball check valve can be made of stainless steel, and the hollow sphere of the seal can be wrapped with polytetrafluoroethylene engineering plastics, so it can also be applied to pipelines of general corrosive media. The working temperature is between -101-150 ℃, the nominal pressure is ≤ 4.0MPa, and the nominal passage range is between 200-1200;

When selecting check valves for incompressible fluids, the first step is to evaluate the required closing speed. The second step is to select the type of check valve that may meet the required closing speed;

The choice of check valve for compressible fluid can be made according to the similar method of check valve for incompressible fluid. If the medium flow range is large, the check valve for compressible fluid can use a deceleration device. If the medium flow is continuously and rapidly stopped and started, such as the outlet of compressor, lift check valve is used;

The size of the response of the check valve shall be determined, and the valve supplier must provide the data of the selected size, so that the valve size when the valve is fully open at a given flow rate can be found;

For the high and medium pressure check valve below DN50mm, vertical lifting check valve and straight-through lifting check valve should be selected;

For low-pressure check valves below DN50mm, butterfly check valves, vertical lift check valves and diaphragm check valves should be selected;

For high and medium pressure check valves with DN greater than 50mm and less than 600mm, swing check valves should be selected;

For DN greater than 200mm, less than 1200mm of the low pressure check valve, it is appropriate to use wear-free ball check valve;

For low pressure check valves with DN greater than 50mm and less than 2000mm, butterfly check valves and diaphragm check valves are selected;

For pipelines with relatively small water hammer impact or no water hammer when required to be closed, slow-closing swing check valve and slow-closing butterfly check valve should be selected.