How to Choose Different Types of Check Valves

A check valve is a valve whose opening and closing parts are circular discs and which rely on their own weight and medium pressure to produce movement to block the backflow of the medium. It belongs to the category of automatic valves, also known as non-return valves, one-way valves , return valves or isolation valves. The disc movement modes are divided into lift type and swing type. The lift check valve is similar to the stop valve in structure, only lacking the valve stem that drives the disc. The medium flows in from the inlet end (lower side) and flows out from the outlet end (upper side). When the inlet pressure is greater than the sum of the weight of the disc and its flow resistance, the valve is opened. On the contrary, when the medium flows back, the valve is closed. The swing check valve has a disc that is tilted and can rotate around the axis, and its working principle is similar to that of the lift check valve. Check valves are often used as bottom valves of pumping devices to prevent water from flowing back.

How to choose check valve type:

1. In order to prevent the medium from flowing back, check valves should be installed on equipment, devices and pipelines;

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

3. For the water pump inlet pipeline, it is advisable to use a foot valve. The foot valve is generally only installed on the vertical pipeline at the pump inlet, and the medium flows from bottom to top;

4. The installation position of the swing check valve is not restricted. It can be installed on horizontal, vertical or inclined pipelines. If installed on a vertical pipeline, the medium should flow from bottom to top;

5. Swing check valves are not suitable for small-caliber valves. They can be made into very high working pressures, with a nominal pressure of up to 42MPa, and a large nominal diameter, up to 2000mm or more. Depending on the material of the shell and seal, it can be used for any working medium and any working temperature range. The medium is water, steam, gas, corrosive medium, oil, medicine, etc. The working temperature range of the medium is between -196--800℃;

6. The swing check valve is suitable for low pressure and large diameter occasions, and the installation occasions are limited;

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

8. Ball check valves are suitable for medium and low pressure pipelines and can be made into large diameters;

9. 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 used in pipelines with general corrosive media. The working temperature is between -101--150℃, the nominal pressure is ≤4.0MPa, and the nominal diameter range is between DN200-DN1200;

10. When selecting a check valve for an incompressible fluid, 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.

11. The check valve should be sized accordingly. The valve supplier must provide data on the selected size so that the valve size can be found when the valve is fully open at a given flow rate.

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

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

14. For low-pressure check valves with DN greater than 50mm and less than 2000mm, butterfly check valves should be used.

15. For pipelines that require relatively small or no water hammer when closing, slow-closing swing check valves and slow-closing butterfly check valves should be used.