The purpose of using a check valve is to prevent the backflow of the medium. Generally, a check valve should be installed at the outlet of the pump. In addition, a check valve should also be installed at the outlet of the compressor. In short, in order to prevent the backflow of the medium, a check valve should be installed on the equipment, device or pipeline.Generally, a vertical lift check valve is used on a horizontal pipeline with a nominal diameter of 50mm. Straight-through lift check valves can be installed on both horizontal and vertical pipelines. The bottom valve is generally only installed on the vertical pipeline at the inlet of the pump, and the medium flows from bottom to top.            The swing check valve can be made into a very high working pressure, PN can reach 42MPa, and the DN can also be very large, up to 2000mm or more. Depending on the material of the shell and the seal, it can be used for any working medium and any working temperature range. The medium is water, steam, gas, corrosive medium, oil, food, medicine, etc. The medium working temperature range is between -196~800℃. The installation position of the swing check valve is not restricted. It is usually installed on the horizontal pipeline, but it can also be installed on the vertical pipeline or the inclined pipeline.

The applicable occasions of the butterfly check valve are low-pressure and large-diameter, and the installation occasions are limited. Because the working pressure of the butterfly check valve cannot 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 check valve can be made into a clamp type, which is generally installed between the two flanges of the pipeline, using the clamp connection form.The installation position of the butterfly check valve is not restricted. It can be installed on the horizontal pipeline, or on the vertical pipeline or the inclined pipeline.
The diaphragm check valve is suitable for pipelines that are prone to water hammer. The diaphragm can well eliminate the water hammer caused by the backflow of the medium. Because the working temperature and use pressure of the diaphragm check valve are limited by the diaphragm material, it is generally used in low-pressure and normal temperature pipelines, especially suitable for tap water pipelines. The general medium working temperature is between -20~120℃, and the working pressure is <1.6MPa, but the diaphragm check valve can be made of larger diameter, and the maximum DN can reach more than 2000mm.Diaphragm check valves have excellent water hammer resistance, simple structure and low manufacturing cost, so they have been widely used in recent years.
Since the seal of the ball check valve is a sphere coated with rubber, it has good sealing performance, reliable operation and good water hammer resistance; and since the seal can be a single ball or multiple balls, it can be made into a large diameter. However, its seal is a hollow sphere coated with rubber, which is not suitable for high-pressure pipelines, but only for medium and low-pressure pipelines.Since the shell material of the ball check valve can be made of stainless steel, and the hollow sphere of the seal can be coated with polytetrafluoroethylene engineering plastics, it can also be used in pipelines with general corrosive media. The operating temperature of this type of check valve is between -101~150℃, the nominal pressure is ≤4.0MPa, and the nominal diameter range is between 200~1200mm.