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Sleeve valves were introduced in the 1960s, and became widely used at home and abroad in the 1970s. In the petrochemical plants installed in the 1980s, sleeve valves accounted for a large proportion. At that time, many people believed that sleeve valves could replace single- and double-seat valves and become the second generation of valve products. Today, this is not the case; single-seat valves, double-seat valves, and sleeve valves are all used equally. This is because the sleeve valve only improves the throttling mechanism, stability, and maintainability compared to single-seat valves; however, its weight, resistance to clogging, and leakage performance are on par with those of single-seat and double-seat valves. How can it then replace them? So, it can only be used together. 1. Why do rubber-lined butterfly valves and fluorine-lined diaphragm valves used in desalinated water media have a short service life? The deionized water medium contains low concentrations of acids or bases, which are highly corrosive to rubber. The corrosion of rubber is manifested as swelling, aging, and low strength; rubber-lined butterfly valves and diaphragm valves perform poorly, and the root cause of this is the fact that rubber is not resistant to corrosion. The back-gasket diaphragm valve was improved to a fluorinated diaphragm valve with better corrosion resistance, but the diaphragm of this fluorinated diaphragm valve cannot withstand folding up and down and gets damaged, resulting in mechanical failure and a shortened lifespan of the valve. The best solution now is to use a special ball valve for water treatment, which can last for 5 to 8 years. 2. Why is selection considered more important than calculation? Compared to calculation, selection is much more important and much more complex. Because the calculation is merely a simple formula-based process; what matters is not the accuracy of the formula itself, but whether the given process parameters are accurate. The process of selection involves many factors; a slight mistake can lead to an inappropriate choice. This not only results in waste of human, material, and financial resources but also leads to suboptimal performance, causing various issues related to use, such as reliability, lifespan, and operational quality.