The butterfly valve is an important device in water supply and drainage pipeline system. With the progress of industrial technology, different requirements are put forward for the structure and performance of the butterfly valve. Therefore, in the design and selection, the type, material and connection form should be selected reasonably according to the working conditions.
Sanitary butterfly valves have different structures such as single eccentricity, inclined plate type, midline type, double eccentricity, and triple eccentricity. The medium pressure acts on the valve shaft and bearing through the butterfly plate, so when the flow resistance of high-pressure small caliber is large, the diameter of the shaft and the thickness of the butterfly plate increase correspondingly. If the gate valve and ball valve or globe valve are used, it is more suitable to analyze the sealing and flow resistance than the actuated butterfly valve.
In recent years, the emergence of soft-sealed gate valves in the water system has improved the disadvantage that gate valves are easy to deposit sediment. Its flow resistance is relatively small, and it can be maintained online. It is very suitable for small and medium caliber, so it has been gradually applied.
The main advantages of metal sealed butterfly valve are reliable sealing, long service life, high-temperature resistance, not easy to damage and tear, and high pressure bearing capacity. Therefore, it has been widely used in recent years, especially in key parts of engineering systems. Butt-welded butterfly valves with rubber soft seals can be well sealed if they are well designed and manufactured, and large caliber can be easily changed online. However, rubber has the aging problem and can only be used in low-temperature conditions, so it is widely used in tap water and water supply system.
Metal-sealed butterfly valves abroad are also used in pumping stations, condensers, steam extraction systems and heat exchange systems of thermal power plants. Nuclear power plants are also used in pressure shell isolation, spray systems and brine, oil storage isolation in petroleum refining systems, steam supply valves, desulfurization systems and tail gas treatment, pyrolysis, and catalytic units. There are also petrochemical plants, cryogenic, slurry and papermaking systems.
Metal sealed butterfly valve is better for medium temperature and medium pressure. For places requiring high reliability, long service life and long-term unsuitable replacement of valves, metal-sealed butterfly valves should also be selected.
For normal temperature water valves, if it is not very demanding, long-term not to replace or replace inconvenient places, it is advisable to use butterfly valves with soft sealing structure. If rubber quality can be guaranteed, large-caliber butterfly valves for water should still be mainly rubber seat butterfly valves.
The emergence of new technology and new materials will improve the structural performance of tri-clamp butterfly valves, expand the scope of application of butterfly valves, and put forward updated requirements for the design and selection of butterfly valves.
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