Three common structural forms of electric butterfly valve
The electric butterfly valve can be divided into capsule type, membrane type and composite type according to the structure.
1) When the air chamber volume is the same, the more the curvature, the smaller the stiffness of the butterfly valve. However, if the curvature is too large, the lateral stability of the butterfly valve is poor. The effective area of the bladder type electric butterfly valve has a large change rate, and the stiffness of the butterfly valve is high. Therefore, the method of increasing the auxiliary air chamber is usually used to reduce the stiffness of the butterfly valve. When the pressure is high, increasing the volume of the auxiliary air chamber has a more obvious effect on the stiffness of the butterfly valve, but this effect decreases with the increase of the volume. For bladder type electric butterfly valve, proper rigidity of butterfly valve can be obtained by properly selecting change rate of effective area of butterfly valve and volume of auxiliary air chamber. The capsule type electric butterfly valve has a long service life due to the small change of membrane curvature during operation.
2) The change rate of the effective area of the membrane electric butterfly valve is smaller than that of the capsule type, so a lower stiffness of the butterfly valve can be obtained without an auxiliary air chamber. It controls the change rate of effective area by changing the shape and size of the piston, so as to obtain a more ideal anti S-shaped elastic characteristic curve. The bladder type electric butterfly valve is difficult to achieve. In addition, from the perspective of the sealing form of butterfly valve, the membrane electric butterfly valve can adopt the pressure self sealing type, which is simple in structure and low in cost. Generally, the service life of membrane electric butterfly valve is not as long as that of bladder type. At present, membrane electric butterfly valve is still widely used in automobiles.
3) From the structural point of view, the composite electric butterfly valve is a type between the first two. It combines the advantages of the above two types of electric butterfly valves, has a lower stiffness of the butterfly valve, but the manufacturing process is complex.