Sealing Principle of Tri-eccentric Sealed Butterfly Valve

Release time:

2024-07-08

(1) Structural characteristics. The rotary center of the valve plate (i.e. the center of the valve shaft) forms a dimension a offset with the sealing surface of the valve plate and a B offset with the center line of the valve body: the center line of the sealing surface of the valve body and the center line of the valve seat (i.e. the center line of the valve body) form an angle B offset.

(2) Sealing principle. Because on the basis of the double eccentric sealing butterfly valve, the center line of the seat is offset by the center line of the valve body to form a B angle, the offset result is that when the eccentric sealing butterfly valve is fully opened, the sealing surface of the valve plate will be completely separated from the sealing surface of the valve seat, and a double eccentric seal will be formed between the sealing surface of the valve plate and the sealing surface of the valve body. The same clearance y of butterfly valve is shown in Figure (19). As the offset of angle B makes the valve longer, the tangent of the rotation path of the sealing surface of the valve plate and the sealing surface of the valve seat form an angle 1 and angle 2 on the large and small semicircle of the valve plate with short radius rotation. When the valve plate opens and closes, the sealing surface of the valve plate gradually disengages from the sealing surface of the valve seat and gradually tightens the sealing surface of the valve plate so as to be thorough. The mechanical wear and abrasion between the two sealing surfaces of the butterfly valve seal pair are eliminated when the valve plate is opened and closed.

When this kind of butterfly valve is opened from 0_to 90_, the sealing surface of the valve plate will immediately detach from the seat sealing surface at the moment of opening. When it is closed from 90.0, only at the moment of closing, the sealing surface of the valve plate will contact and tighten the seat sealing surface. Because of the formation of angle 1 and 2,

When the butterfly valve is closed, the sealing specific pressure between the two sealing faces of the sealing pair can be changed from the elasticity of the valve seat of the conventional butterfly valve to the driving torque of the valve shaft, which not only eliminates the aging, cold flow and elastic failure of the elastic material of the elastic valve seat in the conventional butterfly valve.

The specific pressure between the two sealing surfaces of the sealing pair decreases and disappears, and the specific pressure of the sealing pair can be adjusted arbitrarily by changing the driving torque, which greatly improves the sealing performance and service life of the tri-eccentric butterfly valve.

(3) The main reasons for the failure of sealing performance of sealing pairs. Cavitation and erosion of the medium on the two sealing surfaces of the sealing pair.

(4) The characteristics of tri-eccentric sealed butterfly valve.

1) The design of sealing pair is complex, the manufacture is difficult and the cost is high.

2) The sealing performance is very good.

3) Long service life and high pressure.