Author:Site Editor Publish Time: 2018-12-31 Origin:Site
The axial center of the valve stem is simultaneously deviated 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 axis of the valve body passage, which is called triple offset butterfly valve.
The triple offset butterfly valve is widely used in metallurgical, electric power, petrochemical, and industrial pipelines such as water supply and drainage and municipal construction with medium temperature ≤ 425 °C for regulating flow and load-carrying fluid.
The range of three offset disc valves can withstand pressures up to 2500 lbs, temperature resistance down to -196 °C, up to 700 °C, seals up to 0 leakage, and control ratios up to 100:1. That is to say, in all kinds of harsh and critical process control pipelines, whether it is an on-off valve or a control valve, as long as the selection is right, the disc valve can be safely used now, and the cost is low.
Three offset butterfly valves to withstand high temperatures, hard seals must be used, but the leakage is large; for zero leakage, a soft seal must be used, but it is not resistant to high temperatures. In order to overcome the contradiction of the double offset butterfly valve, the butterfly valve was subjected to the third eccentricity. The structural feature is that the conical axis of the sealing surface of the disc is deflected to the axis of the main cylinder at the same time as the offset position of the double offset stem, that is, after the third eccentricity, the sealing section of the disc is not In addition, it is a true circle, but an ellipse, and its sealing surface shape is also 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 third eccentricity is that it fundamentally changes the sealing structure, no longer a positional seal, but a torsion seal, that is, it does not rely on the elastic deformation of the valve seat, but completely relies on the contact surface pressure of the valve seat to achieve the seal. The effect solves the problem of zero leakage of the metal valve seat in one fell swoop, and the contact surface pressure is proportional to the medium pressure, and the high pressure and high temperature are also solved.