At present, butterfly valve is extremely widely used in many fields such as petroleum, chemical industry, metallurgy, hydroelectricity etc. to act as a kind of part to achieve the ON/OFF and flow control of the pipe system. In the known technology of butterfly valve, the butterfly valve usually adopts sealing structure with rubber, polytetrafluoroethylene etc. as its sealing materials. Because of the limitation of the structural features, it’s not suitable for high temperature, high pressure, corrosion and wearing-resistance industries. Nowadays, there is a kind of advanced butterfly valve which is tri-eccentricity metal hard sealing butterfly valve, whose body and base is an integrated unit. The sealing surface of the valve base is made of build-up welding high temperature resistance, corrosion resistance alloy material. With multilayer of overlapping seal ring fixed on the valve plate, this kind of valve has the advantage of high temperature resistance, easy to operate, free of friction for opening and closing as compared to the traditional butterfly valve. It also has the advantage of improved sealing property and prolonged service life by the compensation of seal with the increase of moment of force of the transmission mechanism when closing.

Nevertheless, this type of butterfly valve still has the following problems in use:

Ⅰ. Since multi-layers of soft and hard overlapped seal rings are fitted on the valve plate, the medium scours the facade of the sale surface when the valve plate is ON. The sealing property will be directly affected after the soft gasket between the sheet metal is scoured.

Ⅱ As restricted by its structure condition, the structure is not suitable for the valve with clear opening below DN200, because the integral construction of the valve plate is too thick and the flow resistance is big.

Ⅲ. The sealing between the sealing surface of the valve plate and valve base relies on the moment of force of the transmission mechanism which forces the valve plate press on the valve base because of the principle of the tri-eccentricity construction. The higher the pressure of the medium is, the more tight the sealing squeezing becomes in the drag flow situation. It begins to leak when the pressure between the valve plate and valve base is less than that of the medium at the situation that the pressure of medium is increasingly increased under the counterflow of medium in the pipe.

The high performance tri- eccentricity tow-way hard sealing butterfly valve features: The described sealing ring of the valve base is composed of multilayer sheet stainless steel on both sides of the T shape sealing ring. The sealing surface of the valve plate and valve base is oblique circular cone construction with build-up welding high temperature resistance, corrosion resistance alloy material on the surface; the construction which assembles the spring fixed between the governing system pressure plate with the adjusting bolt on the pressure plate.

The construction effectively compensates the tolerance zone between the bushing and valve body and the elastic deformation of the valve stem under the pressure of medium. It also solves the existent sealing problem of the valve during the interchangeable two-way medium transportation. It adopts multilayer sheet stainless steel on both sides of the soft T shape sealing ring which has double advantages of both the hard metal sealing and soft sealing. It has the sealing property of zero leakage either at low temperature or at high temperature.

The pressure on the sealing surface is generated by the moment of force of the transmission mechanism and the pressure of the medium to the valve plate when the test certification pond is in the drag flow condition (the medium flow is on the same direction as the rotation of the butterfly plate). The more tight the squeezing becomes between the oblique circular cone surface of the valve plate and the valve base sealing surface, the better the sealing effect becomes when the pressure of the forward direction medium increases. The sealing between the valve plate and valve base relies on the moment of force of the driving device which forces the valve plate to press on the valve base in the counterflow condition. When the positive intensity of pressure is less than that of the medium with the increase of the reverse medium pressure, the stored deformation energy of the spring of the governing system after loading can compensate the tightening pressure of the sealing surface of the valve plate and valve base to act the automatic compensation role. So the new practical type is not installed with soft hard multilayer sealing ring on the valve plate just as the existing technology, but is installed directly on the valve body. Addition of a governing system between the pressure plate and valve base is a very ideal two-way hard sealing mode. It can replace gate valve, stop valve and globe valve.