Common knowledge on selecting stainless steel check valves

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　　Based on their structure, check valves can be divided into lift-type check valves, swing-type check valves, and butterfly check valves. Lifting check valves can be divided into vertical and horizontal types. Swing check valves are divided into three types: single-disc, double-disc, and multi-disc. The butterfly check valve is of the straight-through type. So what should we keep in mind when choosing them in everyday use? Selection criteria: 1. To prevent backflow of the medium, stainless steel check valves should be installed on equipment, devices, and pipelines ； 2. Stainless steel check valves are generally suitable for clean media and are not appropriate for media containing solid particles or high viscosity ； 3. Generally, vertical lift check valves should be used on horizontal pipes with a nominal diameter of 50 mm ； 4. The direct-acting lift check valve can be installed in both horizontal and vertical pipes ； 5. For the inlet pipeline of the water pump, a foot valve is recommended; such valves are generally installed only on vertical pipes at the pump inlet, with the fluid flowing from bottom to top ； 6. The lift-type type has better sealing performance than the swing-type, but it creates greater fluid resistance; the horizontal type is suitable for use in horizontal pipes, while the vertical type is suitable for use in vertical pipes ； 7. The installation location of the swing check valve is not restricted; it can be installed on horizontal, vertical, or inclined pipelines. When installed on a vertical pipeline, the flow direction of the medium should be from bottom to top ； 8. Swing check valves are not suitable for use in small-diameter applications; they can operate at very high pressures, with a PN rating of up to 42 MPa. Moreover, their diameter can also be quite large, reaching over 2000 mm. Depending on the material of the housing and seals, it can be used with any working medium and in any operating temperature range. The media include water, steam, gases, corrosive substances, oils, pharmaceuticals, etc. The operating temperature range of the medium is between -196 and 800°C ； 9. It is suitable for low-pressure, large-diameter applications, and the installation location is limited ； 10. The installation location of the butterfly check valve is not restricted; it can be installed on horizontal pipelines as well as on vertical or inclined pipelines ； 11. Diaphragm check valves are suitable for pipelines prone to water hammer; the diaphragm helps to eliminate the water hammer that occurs when the fluid flows in reverse. They are generally used in low-pressure, normal-temperature pipelines, especially in water supply pipelines. The operating temperature of the fluid typically ranges from -12 to 120°C, and the operating pressure