what are 3 eccentrics of a triple eccentric butterfly valve?
basically the 3 eccentrics of a triple eccentric butterfly valve is shaft eccentricity, disc eccentricity and sealing surface eccentricity.
1) The offset of the valve plate relative to the centre line of the valve body;
(2) The offset of the valve shaft relative to the centre line of the valve body;
3) the offset of the valve body centre line relative to the axis of the cone angle of the valve seat.
Three eccentric triple eccentric butterfly valve features
enhanced sealing high performance: three eccentric triple eccentric butterfly valve sealing is achieved through the valve sealing surface between the extrusion, the greater the closing torque, the higher the sealing level, can achieve ‘zero leakage’.
Zero friction: reduce the friction of the valve in the switching process, so that the service life of the valve is greatly increased.
High flow rate: Due to the superiority of three eccentric structure, the flow diameter of the valve increases, and the valve has a high flow rate.
Short stroke: when the valve opens and closes, the valve shaft only needs to rotate between 70-90°, which shortens the opening and closing time of the valve, and can realise fast closing.
Wide range of use: three eccentric metal-sealed triple eccentric butterfly valve 9 has a wide range of temperature and pressure, the temperature can be from -196-650 ℃, pressure from PN10-PN160 (ANSI CL 150 ~ CL900).
Long service life: three eccentric metal seal triple eccentric butterfly valve is a metal-to-metal sealing valve, wear-resistant performance is good, long time work without deformation, in addition, in the opening moment, the valve seat and sealing ring that is detached, no friction, so the valve has a very long service life.
Regulating performance: three eccentric metal sealed triple eccentric butterfly valve has a regulating function, often used as a regulating valve.
The working principle of the 3 eccentric triple eccentric butterfly valve
The “three eccentricity” of the three-eccentric triple eccentric butterfly valve means that the stem axis simultaneously deviates from the center of the disc and the center of the body, and the rotation axis of the valve seat has a certain Angle with the valve body channel axis.
The structure is characterized by the eccentric position of the valve stem axis in the double eccentric (the valve stem axis deviates from the center of the butterfly plate and the center of the body) at the same time, the conical axis of the sealing surface of the butterfly plate is skewed to the cylindrical axis of the body. That is to say, after the third eccentricity, the sealing section of the butterfly plate is no longer a true circle, but an ellipse, and the shape of the sealing surface is therefore asymmetrical, with one side inclined to the center line of the body and the other side parallel to the center line of the body.
The biggest feature of this design is that it fundamentally changes the sealing structure of triple eccentric butterfly valve
It no longer relies on the elastic deformation of the seat to achieve the seal effect (position seal), but completely relies on the contact surface pressure of the seat to achieve the seal (torsion seal). When the valve is opened, the disc sealing surface will be completely detached from the seat sealing surface, forming a gap between the two.
When the valve is closed, the control plate rotates with the valve stem and deflected into the sealing surface of the valve seat to seal it. Because the contact surface pressure is proportional to the medium pressure, when the medium pressure increases, the sealing force between the valve seat sealing surface and the butterfly plate will also increase accordingly, thus solving the problem of zero leakage of the metal seat in one stroke, and making the valve resistant to high pressure and high temperature.
When the triple eccentric butterfly valve pipeline fluid pressure into the seat sealing box slot, based on Posson’s principle of force, so that the seal in the pipeline pressure action. The resultant force generated by the expansion force of the ring squeezes the sealing surface of the valve seat towards the butterfly plate to seal the valve. When the positive 1-direction medium pressure increases, the more tightly the inclined cone surface of the butterfly plate and the sealing surface of the valve seat are squeezed, the better the sealing effect is.
When countercurrent, the seal between the valve plate and the seat depends on the torque of the driving device to press the valve plate against the seat. With the increase of the reverse medium pressure, when the unit positive pressure between the valve plate and the valve seat is less than the medium pressure, the deformation energy stored by the spring of the adjustment ring after loading can compensate the tight pressure of the valve plate and the sealing surface of the valve seat, and play an automatic compensation role.
