Analysis of the differences between soft-sealed butterfly valves and hard-sealed butterfly valves

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Butterfly valves, also known as flap valves, have a wide range of applications. They are typically installed on pipes in engineering systems such as those for gas, natural gas, liquefied petroleum gas, hot and cold air, as well as in chemical processing industries, to transport various corrosive and non-corrosive fluid media, and they serve to regulate and stop the flow of these media. There are many types of butterfly valves, and different types serve different purposes. Classified by their sealing method, butterfly valves can be divided into soft-sealed butterfly valves and hard-sealed butterfly valves. Although the two types of butterfly valves differ by only one character, there are significant differences between them in terms of structural materials and application areas. This article analyzes the differences between soft-sealed butterfly valves and hard-sealed butterfly valves. The main difference between soft-sealed butterfly valves and hard-sealed butterfly valves lies in their sealing surfaces: in soft-sealed butterfly valves, one side of the sealing pair is made of a metallic material, while the other side is made of an elastic non-metallic material, usually rubber or PTFE. The combination of such sealing materials gives soft-sealed butterfly valves good sealing performance, but they are not resistant to high temperatures, are prone to wear, and have a short service life. The sealing surfaces of a hard-sealed butterfly valve are made of metal on both sides. The metal-to-metal sealing gives hard-sealed butterfly valves average sealing performance, but they are resistant to high temperatures, pressure, and wear, and also have a relatively long service life. The sealing seat of soft-seal butterfly valves is made of rubber or PTFE, offering excellent sealing performance and the ability to achieve zero leakage; however, its service life is relatively short, it cannot withstand high temperatures, and it is not suitable for use in pipelines carrying highly corrosive media. The sealing seat of a hard-sealed butterfly valve is made of metal, resulting in relatively poor sealing performance; however, it is wear-resistant and has strong compressive strength, making it suitable for use in pipelines carrying highly corrosive media. Apart from the difference in the sealing surface, the differences between soft-sealed butterfly valves and hard-sealed butterfly valves also include: 1. Soft-sealed butterfly valves are mostly of the centerline type. Hard-sealed butterfly valves are mostly of single-eccentric, double-eccentric, and triple-eccentric types. 2. Soft-sealed butterfly valves are suitable for normal temperature environments. Hard-sealed butterfly valves can adapt well to low-temperature, normal-temperature, and high-temperature environments. 3. Soft-sealed butterfly valves are suitable for low-pressure and normal-pressure environments. Hard-sealed butterfly valves are suitable not only for low and normal pressure conditions but also for medium and high pressure environments. 4. As mentioned above, soft-sealed butterfly valves have better sealing performance than hard-sealed butterfly valves. However, in order to enable hard-sealed butterfly valves to function in a wider range of operating conditions, three-eccentric hard-sealed butterfly valves with special manufacturing processes were invented, allowing them to maintain good sealing properties even in high-pressure and high-temperature environments. 5. Soft-sealed butterfly valves are suitable for two-way opening, closing, and regulation in ventilation and dust removal systems, as well as in industries such as water treatment, light industry, petroleum, and chemicals. Hard-sealed butterfly valves are commonly used in heating, gas supply, as well as in environments involving gas, oils, acids, and alkalis