​How to select a check valve?

Check valves are both closed-circuit valves and functional valves. Wherever there is a need to prevent the backflow of the medium, check valves should be installed. Therefore, a check valve is generally installed at the outlet of the pump. When selecting check valves, the following requirements should be met

The installation position of the check valve

For instance, gravity lift check valves can only be installed on horizontal pipelines. The bottom valve can only be installed on the vertical pipeline of the suction pipe of the water pump. The installation position of swing check valves is not restricted. They can be installed on horizontal pipelines or vertical pipelines.

(2) The medium conveyed through the pipeline

The type of check valve should be determined based on the medium conveyed in the pipeline.

(3) The backflow velocity of the medium is relatively large

If the backflow velocity of the medium in the pipeline is relatively high, a check valve with a slow-closing device should be selected.

(4) Limitation of the check valve

The application scope of check valves is limited by their structural form and manufacturing materials.

1) Butterfly check valves are suitable for low-pressure large-diameter pipelines, and their installation sites are restricted because the nominal pressure of butterfly check valves cannot be made too high. The installation position of butterfly check valves is not restricted. They are usually installed on horizontal pipelines, but can also be installed on vertical or inclined pipelines.

2) Diaphragm check valves are suitable for pipelines prone to water hammer, and the diaphragm can effectively eliminate water hammer. However, due to the limitations of the diaphragm material on the working temperature and operating pressure of diaphragm check valves, they are generally used in low-pressure, normal-temperature pipelines with working temperatures ranging from -20 to 120℃ and working pressures p≤1.6MPa, and are particularly suitable for water supply pipelines.

3) Spherical check valves have excellent sealing performance and reliable operation due to the fact that the sealing parts are rubber-coated spheres. Moreover, as the sealing parts can be single balls or multiple balls, they can be made in large diameters. However, its seal is a hollow sphere covered with rubber, which is not suitable for high-pressure pipelines and is only applicable to medium and low-pressure pipelines.