Analysis of problems in the use of hard-sealed butterfly valves
The butterfly valve is a valve that uses a disc-type opening and closing member to reciprocate about 90° to open, close or adjust the flow of the medium. The butterfly valve is not only simple in structure, small in size, light in weight, low in material consumption, small in installation size, small in driving torque, simple and fast in operation, but also has good flow regulation and closing and sealing characteristics at the same time. It has been developed in the past ten years. One of the fastest valve varieties.
Butterfly valves can be divided into hard-sealed butterfly valves and soft-sealed butterfly valves according to the sealing form. Hard-sealed butterfly valves are widely used in generators, gas, steam, natural gas, city gas, cold and hot air, chemical smelting engineering and power generation environmental protection systems to transport various corrosion It is used to adjust and cut off the flow of the medium in the pipeline of the non-corrosive fluid medium. With the widespread use of hard-sealed butterfly valves, problems have arisen spontaneously. The problems of hard-sealed butterfly valves are analyzed as follows:
1. Since the multi-layer soft and hard stacked sealing ring is fixed on the valve plate, when the valve plate is normally open, the medium will form a positive scouring on its sealing surface. The soft sealing band in the metal sheet sandwich will directly affect the sealing performance after being scoured.
2. Due to structural conditions, this structure is not suitable for valves with a diameter below DN200, because the overall structure of the valve plate is too thick and the flow resistance is large.
3. Due to the principle of the triple eccentric structure, the seal between the sealing surface of the valve plate and the valve seat depends on the torque of the transmission device to press the valve plate against the valve seat. In the positive flow state, the higher the medium pressure, the tighter the sealing extrusion. When the flow channel medium flows back, as the medium pressure increases, the unit positive pressure between the valve plate and the valve seat is less than the medium pressure, the seal begins to leak.
