What is the selection standard for check valves?

1. Check valves should be installed on equipment, devices and pipelines in order to prevent medium countercurrent.

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

3. Horizontal lift check valves should be used in horizontal pipelines with nominal diameter of 50mm.

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

5. For the inlet pipeline of the pump, the bottom valve should be selected. The bottom valve is generally 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 than the swing type, and has larger fluid resistance. Horizontal type should be installed in horizontal pipeline, and vertical type should be installed in vertical pipeline.

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

8. Swing check valves should not be made into small caliber valves, and can be made into high working pressure. The nominal pressure can reach 42 MPa, and the nominal diameter can also be large, up to 2000 mm. It can be applied to any working medium and any working temperature range according to the material of shell and seal. Medium is water, steam, gas, corrosive medium, oil, medicine, etc. The working temperature range of the medium is - 196 - 800 C.

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

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

11. Diaphragm check valves are suitable for pipelines prone to water hammer. Diaphragm can eliminate water hammer when medium countercurrent occurs. They are generally used in low-pressure and normal-temperature pipelines, especially in tap water pipelines. The working temperature of medium is between - 12-120 degrees C and the working pressure is less than 1.6 MPa. However, diaphragm check valves can achieve a larger caliber, and DN can reach a maximum of more than 2000 mm. ;

12. Spherical check valves are suitable for medium and low pressure pipelines and can be made into large caliber.

13. The shell material of the spherical check valve can be made of stainless steel, and the hollow sphere of the seal can be wrapped in PTFE engineering plastics. Therefore, it can also be used in pipelines of general corrosive media. The working temperature is between - 101 - 150 C, the nominal pressure is less than 4.0 MPa, and the nominal pass range is between DN200 - DN1200.

14. When choosing 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 valves that may meet the required closing speed.

15. Check valves for compressible fluids can be selected according to similar methods for incompressible fluids. If the range of medium flow is large, a deceleration device can be used for the check valves for compressible fluids. If the medium flow stops and starts rapidly and continuously, as in the case of the outlet of the compressor, a lifting check valve is used.

16. Check valves should be sized accordingly. Valve suppliers must provide data on selected sizes so as to find the size of valves when they are fully open at a given flow rate.

17. For high and medium pressure check valves below DN50mm, vertical lift check valves and 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 selected.

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 spherical check valves should be selected.

21. For low pressure check valves with DN greater than 50 mm and less than 2000 mm, butterfly check valves and diaphragm check valves should be selected.

22. For pipelines requiring less or no water hammer when closing, slow-closing swing check valve and slow-closing butterfly check valve should be selected.