At present, as a kind of component to cut off or control flow rate in pipeline system, stainless steel butterfly valve has been widely applied in petroleum, chemical industry, metallurgy and power. For current well-known butterfly valve technology, sealing type of stainless steel butterfly valve adopts multi-level sealing. Rubber and PTFE are used as sealing materials. Limited by structure, stainless steel butterfly valve is not suitable for industry having high temperature, high pressure, corrosion and abrasion.
Stainless steel butterfly valve is a kind of more advanced three-eccentric metal sealing butterfly valves. Body and seat are connected structure. The sealing face of seat is bead welded with alloy materials having high temperature resistance and corrosion resistance. Multi-level soft lap is fixed on disc. Compared with traditional butterfly valve, stainless steel butterfly valve has high temperature resistance, convenience for operation without friction during on-off. When valve closes, torque of transmission mechanism is increasing to compensate sealing, and sealing and service life of butterfly valve are highly improved.
Some problems still exist when using stainless steel butterfly valve:
1. For multi-level soft lap sealing ring being fixed on disc, when disc is normally opened, media form positive washing on sealing face of disc. Soft sealing strip in interlayer of metal sheets has direct influence on sealing after being washed.
2. Limited by structure, the butterfly valve is not suitable for being used as valve whose diameter below than DN200, because disc is too thick, having high flow resistance.
3. Due to the principle of three-eccentric structure, sealing of sealing face between disc and seat depends on toque of actuator pressing disc to seat. When media flow positively, the higher media pressure is, the tighter sealing is. When media inside pipe flow negatively, with the increasing media pressure, unit positive pressure between disc and seat is lower than media pressure, then, media begin to leak.
Feature of high performance three-eccentric double sealing butterfly valve is that the sealing of seat consists of soft T-type sealing ring and multi-level stainless steel plate. The sealing face between disc and seat is an oblique cone. The surface of oblique cone on disc is bead welded with alloy materials having temperature resistance and corrosion resistance. Spring fixed between pressing plate of regulating ring and adjustable bolts on pressing plate are assembled together.
The structure can effectively compensate elastic deformation caused by tolerance between axle sleeve and body or media pressure, figure out the sealing of valve during two-way interchange of media transmission. Sealing ring combines advantage of metal hard sealing and soft sealing. It has zero-leakage performance no matter under low temperature and high temperature.
Experiment shows that when flow direction of media is the same as rotate direction of disc, the pressure of sealing face is caused by torque of actuator and media pressure on disc. When forward direction media pressure increasing, extrusion of oblique cone surface of disc and sealing face of seat is tighter and tighter, and sealing is better and better. When media flow reversely, sealing between disc and seat depends on torque of actuator pressing disc to seat. With reverse media pressure increasing, unit positive pressure between disc and seat is lower than media pressure. Stored deformation of spring on regulating ring after being loaded can compensate tight pressure between disc and sealing face of seat for automatic compensation. Unlike current butterfly valve whose disc is installed with multi-level sealing ring, the sealing ring of stainless steel butterfly valve is directly installed on body. Adding regulating ring between disc and seat is an ideal two-way hard sealing method. Stainless steel butterfly valve will take place of gate valve, globe valve and ball valve.
