Selection standard of check valve?

1. In order to prevent reverse flow of medium, check valve should be installed on equipment, device and pipeline;

2. Check valve is generally suitable for clean medium, not suitable for medium containing solid particles and viscosity;

3. Generally, the horizontal lifting check valve should be selected on the horizontal pipeline with nominal diameter of 50 mm;

4. Straight through lifting check valve can only be installed in horizontal pipeline;

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

6. The lift type has better sealing performance than the swing type, and the fluid resistance is larger. The horizontal type should be installed on the horizontal pipe, and the vertical type should be installed on the vertical pipe;

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

8. Swing check valve should not be made into a small diameter valve, but can be made into a very high working pressure. The nominal pressure can reach 42MPa, and the nominal diameter can also be large, and the maximum can be more than 2000mm. According to the different materials of shell and seal, it can be applied to any working medium and any working temperature range. The medium is water, steam, gas, corrosive medium, oil, medicine, etc. The working temperature of the medium ranges from - 196 ℃ to 800 ℃;

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

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

11. The diaphragm check valve is suitable for the pipeline which is easy to produce water hammer. The diaphragm can eliminate the water hammer produced by the reverse flow of medium. It is generally used in the low pressure and normal temperature pipeline, especially for the water pipeline. The working temperature of the medium is between - 12 ℃ and 120 ℃ and the working pressure is less than 1.6Mpa. However, the diaphragm check valve can be larger in diameter, and the maximum DN can be more than 2000mm ;

12. The ball check valve is suitable for medium and low pressure pipeline 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 sealing element can be wrapped with polytetrafluoroethylene engineering plastics, so it can also be used in the pipeline of general corrosive medium. The working temperature is between - 101 ℃ and 150 ℃, the nominal pressure is less than 4.0Mpa, and the nominal diameter range is between DN200 and DN 1200;

14. For the selection of check valve for incompressible fluid, the first step is to 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. For compressible fluid, the check valve can be selected according to the similar method of the check valve for incompressible fluid. If the range of medium flow is large, a deceleration device can be used for the check valve used for compressible fluid. If the medium flow continuously stops and starts quickly, such as at the outlet of the compressor, the lifting check valve is used;

16. The 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 can be found when the valve is fully open at a given flow rate;

17. For high and medium pressure check valves below DN50 mm, vertical lifting check valves and straight through lifting check valves should be selected;

18. Butterfly check valve, vertical lifting check valve and diaphragm check valve should be selected for low pressure check valve with diameter less than 50 mm;

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

20. For medium and low pressure check valves with DN greater than 200 mm and less than 1200 mm, wear-free ball check valves should be selected;

21. Butterfly check valve and diaphragm check valve should be selected for low pressure check valve with DN greater than 50mm and less than 2000mm;

22. For pipelines with small water hammer impact or no water hammer when closing, slow closing swing check valve and slow closing butterfly check valve should be selected.