1. In order to prevent the backflow of the medium, check valves should be installed on the equipment, devices and pipelines;
2. The check valve is generally suitable for clean medium, not suitable for medium containing solid particles and high viscosity;
3. Generally, horizontal lift check valves should be used on horizontal pipes with a nominal diameter of 50mm;
4. Straight-through lift check valve can only be installed in horizontal pipelines;
5. For the pump inlet pipeline, 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 bottom to top;
6. The lifting type has better sealing performance and larger fluid resistance than the swing type. The horizontal type should be installed on the horizontal pipeline, and the vertical type should be installed on the vertical pipeline;
7. The installation position of the swing check valve is not limited. It can be installed on horizontal, vertical or inclined pipelines. If it is installed on a vertical pipeline, the flow direction of the medium should be from bottom to top;
8. The swing check valve should not be made into a small-diameter valve. It can be made into a high working pressure. The nominal pressure can reach 42MPa, and the nominal diameter can also be large, and the maximum can reach more than 2000mm. It can be applied to any working medium and any working temperature range according to the different materials of the shell and seal. The medium is water, steam, gas, corrosive medium, oil, medicine, etc. The working temperature of the medium is between -196--800℃;
9. The applicable occasion of swing check valve is low pressure and large diameter, and the installation occasion is limited;
10. 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;
11. Diaphragm check valve is suitable for pipelines that are prone to water hammer. The diaphragm can well eliminate the water hammer caused by the reverse flow of the medium. It is generally used in low-pressure and normal-temperature pipelines, especially for tap water pipelines. Generally, the medium works. The temperature is between -12--120℃, and the working pressure is less than 1.6MPa, but the diaphragm check valve can achieve a larger diameter, and the maximum DN can reach more than 2000mm;
12. The ball check valve is suitable for medium and low pressure pipelines and can be made into large diameter;
13. 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 plastic, so it can also be used in the pipeline of general corrosive medium, and the working temperature is -101--150 ℃, the nominal pressure is ≤4.0MPa, and the nominal pass range is between DN200-DN1200;
14. When selecting a check valve for incompressible fluids, first evaluate the required closing speed, and the second step is to select the type of check valve that may meet the required closing speed;
15. The selection of check valves for compressible fluids can be selected according to the similar method of check valves for incompressible fluids. If the flow range of the medium is large, the check valves for compressible fluids can be used. A reduction gear, if the medium flow is stopped and started quickly without a break, as at the outlet of a compressor, a lift check valve is used;
16. The corresponding size of the check valve should be determined, and the valve supplier must provide the data of the selected size, so that the valve size when the valve is fully opened at a given flow rate can be found;
17. For high and medium pressure check valves below DN50mm, vertical lift check valves and straight-through lift check valves should be selected;
18. For low pressure check valves below DN50mm, butterfly check valves, vertical lift check valves and diaphragm check valves should be used;
19. For high and medium pressure check valves with DN greater than 50mm and less than 600mm, swing check valves should be used;
20. For medium and low pressure check valves with DN greater than 200mm and less than 1200mm, non-wear spherical check valves should be selected;
21. For low-pressure check valves with DN greater than 50mm and less than 2000mm, butterfly check valves and diaphragm check valves should be selected;
22. For pipelines requiring less water hammer or no water hammer when closed, slow-closing swing check valves and slow-closing butterfly check valves should be used.