The size of a stainless steel valve should be accurately selected for a desulfurization butterfly valve according to the required flow rate (the Cv value). The diameter and opening angle of a stainless steel valve should be calculated according to the required flow rate (Cv value) and other technical parameters. If the diameter of the stainless steel valve is too big, the stainless steel valve will operate for a long time with a small opening, and the medium pressure will increase. In this way, the valve core and valve stem of the stainless steel valve are susceptible to the impact of the medium; the stainless steel valve will vibrate, and the valve core rod will even break under the long-term impact of the medium.
A butterfly valve has simple structure, small sizes, light weights and consists of several parts. In addition, the stainless steel valve can be opened and closed quickly by rotating 90 degrees, which is easy to operate and has excellent fluid control characteristics at the same time. When a butterfly valve is in the fully open position, the medium flows through the valve body and the thickness of the butterfly plate becomes the resistance. Therefore, the pressure drop generated by the valve is particularly small, which has better flow control characteristics. A butterfly valve has two types of seals, namely elastic seals and metal seals. For elastic sealing valves, the sealing ring can be embedded in the valve body or connected to the periphery of the butterfly valve plate.
A butterfly valve with metal seals usually has a longer service life than that with elastic seals, but it is difficult to seal them completely. Metal sealed butterfly valves can adapt to high operating temperatures, while elastic sealed butterfly valves have a disadvantage of temperature limitation. If a butterfly valve is required for flow control, it is important to accurately select the size and type of stainless steel valves. The structure principle of a butterfly valve is particularly suitable for manufacturing stainless steel valves with large diameters. Butterfly valves are not only widely used in ordinary industries such as petroleum, natural gas, chemical industry and water treatment, but also in cooling water systems of thermal power plants.
Medium temperature for desulfurization butterfly valves should not exceed 150℃. The medium temperature can reach 150℃ in the short term, and the temperature should be controlled within 120℃ in the long term. Otherwise, the F46 lining of each part of the stainless steel valve is easy to soften and deform, resulting in failure and great leakage of the stainless steel valve. If the temperature of the medium is lower than 180°C for a short time and less than 150°C for a long time, fluoroplastic can be selected. The fluoroplastic lined with PFOS is more expensive than that lined with F46. There should not be negative pressure. The use of negative pressure in the pipeline should be avoided for stainless steel valves lined with fluorine. If there is negative pressure, the fluorine lining layer in the inner cavity of the stainless steel valve is easily sucked (protruding) and falls off, causing the stainless steel valve to fail to be opened and closed. Pressure and pressure difference should be controlled within the permitted range, especially for regulating valves lined with fluorine and bellows sealed globe valves. Because the bellows is made from tetrafluoroethylene material, the pressure and pressure difference are very great, which easily cause the bellows to break. If the working pressure and pressure difference are great, the fluorine lined regulating valve with bellows seals can be replaced with tetrafluoride packing seals. The media for the desulfurization butterfly valve must not contain hard particles, crystals, impurities, etc. to prevent the fluorine lining layer or PTFE bellows of the valve core and valve seat of the stainless steel valve from wearing during the opening and closing operation. For media containing hard particles, crystals and impurities, the valve core and valve seat can be made from Hastelloy.
