At what pressure should the flanges of vacuum vessels be designed?
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At what pressure should the flanges of vacuum vessels be designed?
The most important criterion when selecting flanges for vacuum vessels is their airtightness. Flanges with too low a grade are prone to deformation during welding, which leads to a decrease in sealing performance; therefore, flanges with a pressure rating of 1.6 Mpa or higher must be used. Ensure that the plane has sufficient stiffness during welding. The ability to maintain stiffness at low pressures is insufficient. Moreover, the factors affecting vacuum equipment are difficult to identify visually. Therefore, its performance must be ensured through \"hardware\" in terms of both the flange and the sealing material.
Theoretically, with the same internal and external pressures, it is easier for the internal pressure to cause leaks, while a vacuum is less prone to leakage
When standard pressure vessel flanges are used for the flanges of vacuum vessels, and the vacuum level is below 600 mmHg, the nominal pressure class of the flanges should be no less than 0.6 MPa； When the vacuum degree is greater than or equal to 600 mmHg, the nominal pressure class of the flange should be no less than 1.0 MPa. For details, see Clause 7.1.5 of HG/T20583-2011.
I’m not sure where your theory comes from. When the internal and external pressures are equal, the forces acting on the flange are the same. As for whether leakage occurs or not, internal pressure causes the medium to be pushed outward, while external pressure essentially refers to the degree of vacuum; leakage happens when air enters the vacuum system, thereby reducing the vacuum level
Your choice must be one with a pressure rating of over 1.6 Mpa; you’re referring to the pipe flange, right?
Don’t forget that internal pressure exerts an outward pulling force and bending moment on the flange, which accelerates leakage; external pressure does not have such effects
It is recommended to use a pressure of over 1.6 MPa; flanges with male and female surfaces should be used. Over time, vacuum equipment will experience slight leaks, resulting in a decrease in vacuum level that does not meet the process requirements
A container that can handle 1.6 MPa would be way too thick
Check the temperature; I’ve seen ones at 0.25 MPa.