Common knowledge on the selection of various valves

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Basic knowledge on selecting ball valves: Features of ball valves include a simple structure, rapid opening and closing, easy operation, small size, light weight, few components, low fluid resistance, and good sealing performance. Selection criteria for ball valves: 1. Suitable for media at low temperatures (below 150 degrees), high pressures, and high viscosity ； 2. It cannot be used for flow regulation ； 3. Used in applications requiring rapid opening and closing ； 4. Ball valves are generally recommended for use in systems that require two-position control, high sealing performance, resistance to wear, use in channels with reduced diameters, fast opening and closing actions, high-pressure shutdown (large pressure difference), low noise levels, situations involving vaporization, low operating torque, and low fluid resistance ； 5. Also suitable for light structures, low-pressure shut-off, and corrosive media ； 6. The ideal valve for use with low-temperature and cryogenic media; for piping systems and devices handling such media, low-temperature ball valves equipped with valve caps are recommended ； 7. Most ball valves can be used in media containing suspended solid particles; depending on the sealing material, they can also be used for powdered and granular media ； 8. When selecting a floating ball valve, its seat material must be able to withstand the entire load exerted by the ball and the operating mechanism. Ball valves with large diameters require significant force to operate; for ball valves with a diameter of DN200 or more, a worm gear drive should be used ； 9. For high-pressure, large-diameter ball valves with a diameter of DN200 or more, fixed-ball ball valves should be used ； 10. In corrosive media such as acids and alkalis in chemical processing systems, all-stainless-steel ball valves made of austenitic stainless steel with polytetrafluoroethylene as the valve seat seal ring are recommended. 11、 Q1（4）1F-16 ≤ 150℃ Water, oils ； Q41F-16C Water, oils ； Q41F-16P: Nitric acid, citric acid solution at room temperature, lysine, organic acids. Q41F-16R: Acetic acid, citric acid solution at temperatures above 50°C. 12. General selection sequence: QQ11F-16-----Q41F-16------Q41F-16PC-----Q41F-16P------Q41F-16R------Q41F-16C (P, R). Basic knowledge on selecting check valves: Check valves are classified into lift-type and swing-type based on their structural design. Selection criteria: 1. To prevent backflow of the medium, check valves should be installed on equipment, apparatus, and pipelines ； 2. Check valves are generally suitable for clean media and should not be used with 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 presents 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 where water hammer is likely to occur; the diaphragm helps to eliminate the water hammer that results from backflow of the medium. They are generally used in low-pressure, normal-temperature pipelines, especially in water supply pipelines. The operating temperature of the medium usually ranges from -12 to 120°C, and the operating pressure