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Spring check valves are designed to allow fluid to flow in one direction while preventing backflow. They consist of a valve body with an inlet and outlet port, a spring-loaded disc or ball that sits on the seat of the valve body, and a spring that keeps the disc or ball in place. The operation of spring check valves is simple yet effective. When fluid flows through the valve in the correct direction, it pushes the disc or ball away from the seat, allowing it to pass through. However, when there is a reversal of flow or pressure drop on the downstream side of the valve, the spring forces the disc or ball back onto its seat, preventing backflow. Spring check valves come in various sizes and materials to suit different applications. They are reliable and require minimal maintenance, making them popular choices for many industries.

The requirements for selecting a spring check valve are as follows:

1. To prevent the reverse flow of the medium, check valves should be installed on the equipment, devices and pipelines.

2. Check valves are generally suitable for clean media, and should not be used for media 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 valves can only be installed in horizontal pipelines.

5. 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 to the top.

6. Compared with the swing type, the lifting type has better sealing and greater fluid resistance. The horizontal type should be installed on horizontal pipes, and the vertical type should be installed on vertical pipes.

7. The installation position of the swing check valve is not limited. It can be installed on a horizontal, vertical or inclined pipeline. 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 with a small diameter should not be manufactured, but the swing check valve with high pressure can be made. The nominal pressure can reach 42MPa, and the nominal diameter can also be very large, the maximum can reach more than 2000mm. Depending on the material of the shell and the seal, a swing check valve can be applied to any working medium and working temperature. The medium can be water, steam, gas, corrosive medium, oil and medicine. The working temperature range of the medium is between -196 to 800°C.

9. The swing check valve is suitable for 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 the vertical or inclined pipeline.

11. Diaphragm check valves are 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 on low-pressure and normal-temperature pipelines, especially for tap water pipelines. The temperature is between -12°C to 120°C, and the working pressure is less than 1.6MPa. The diaphragm check valve can be made with a larger diameter, and the maximum size can reach more than 2000mm.

12. Ball check valves are suitable for medium and low-pressure pipelines and can be made with large diameters.

13. The shell 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 the pipeline transporting general corrosive media. The working temperature is -101℃ to 150℃; the nominal pressure is less than and equal to 4.0MPa, and the nominal diameter is between DN200 and DN1200.

14. When selecting a check valve for incompressible fluids, the required closing speed must first be evaluated, and then select the type of check valve that may meet the closing speed.

15. When selecting a check valve for compressible fluid, it can be selected according to a similar method for a check valve for an incompressible fluid. If the medium flow is stopped and started rapidly in succession, as in the outlet of a compressor, a lift check valve can be used.

16. The corresponding size of the check valve should be determined. The valve supplier must provide the data for the selected size, so that the valve size can be determined when the valve is fully open at a given flow rate.

17. For high and medium-pressure check valves below DN50mm, vertical lifting check valves and straight-through lifting check valves should be selected.

18. For low-pressure check valves below DN50mm, butterfly check valves, vertical lifting check valves and diaphragm check valves should be chosen.

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

20. For medium and low-pressure check valves with DN greater than 200mm and less than 1200mm, it is advisable to choose a non-wearing spherical check valve.

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 that require relatively little water hammer or no water hammer when closing, slow-closing swing check valves and slow-closing butterfly check valves should be selected.