The purpose of the
check valve is to prevent the reverse flow of the medium. Generally, the
check valve should be installed at the outlet of the pump. In addition, a check valve should be installed at the outlet of the compressor. In short, in order to prevent reverse flow of medium, the
check valve should be installed on equipment, device or pipeline.
Generally, the vertical lifting check valve is selected on the horizontal pipeline with nominal diameter of 50mm. Straight through lifting check valve can be installed in both horizontal and vertical pipelines. The bottom valve is generally only installed in the vertical pipeline of the pump inlet, and the medium flows from bottom to top.
Swing check valves can be made into a very high working pressure. The PN can reach 42MPa, and the DN can also be large. The maximum of the DN 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, food, medicine, etc. The working temperature range of the medium is - 196 ~ 800 ℃.
The installation position of
swing check valves is unlimited. It is usually installed in horizontal pipeline, but it can also be installed in vertical pipeline or inclined pipeline.
The
butterfly check valve is suitable for low pressure and large diameter, and its installation is limited. Because the working pressure of the butterfly check valve can not be very high, but the nominal diameter can be very large, which can reach more than 2000mm. But the nominal pressure is below 6.4Mpa. The butterfly clamp type can be used to connect the two pipes. The installation position of butterfly check valves is not limited. It can be installed in horizontal pipeline, vertical pipeline or inclined pipeline.
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. Because the working temperature and pressure of the diaphragm check valve are limited by diaphragm material, they are usually used in low pressure and normal temperature pipeline, especially in water pipeline. Generally, the working temperature of medium is between - 20 ℃ and 120 ℃, and the working pressure is less than 1.6Mpa. However, the diaphragm check valve can achieve a larger diameter, and the maximum DN can be more than 2000mm. Diaphragm check valves are widely used in recent years because of its excellent water-proof performance, simple structure and low manufacturing cost.
The
ball check valve has good sealing performance, reliable operation and good water hammer resistance because the seal is a ball covered with rubber. Because the seal can be single ball or multi ball, it can be made into large diameter. However, its seal is a hollow ball covered with rubber, which is not suitable for high-pressure pipelines, but only for medium and low-pressure pipelines. Because the shell material of the ball check valve can be made of stainless steel, and the hollow sphere of the sealing element can be coated with polytetrafluoroethylene engineering plastics, it can also be used in the pipeline with general corrosive medium. The working temperature of this kind of check valve is - 101 ~ 150 ℃. Its nominal pressure is ≤ 4.0Mpa, and the nominal diameter range is 200 ~ 1200mm.
