How to Know the thickness of SS304 plates for a high vacuum chamber?

[Donodt]

TL;DR

What is the calculation of the thickness of stainless steel plates for a vacuum chamber if the chamber measures 400mx450x250. at a vacuum pressure of .06 mbar

What is the calculation of the thickness of stainless steel plates for a vacuum chamber if the chamber measures 400mx450x250. at a vacuum pressure of .06 mbar

 

[berkeman]

Welcome to PF.

I hope you're not building a rectangular vacuum chamber...

And those dimensions are in meters?!

 

[Baluncore]

There is really no difference between a high-vacuum chamber and a common or laboratory vacuum chamber. They must both be designed to withstand an external pressure of one atmosphere, with a margin sufficient to eliminate the possibility of collapse. It is important to consider the external mounting forces on the tank, and the mass of equipment that might be operated inside the chamber.

Flat plates should be avoided in the construction. All surfaces must be curved in at least one dimension. The minimum weight solution would be a sphere, but that is difficult to fabricate because it has a double-curved surface, so a circular chamber with conical ends will be easier to fabricate.

The design problem is dependent on what will be inside the vacuum chamber. If there is room for internal baffles, or support plates, like in a vacuum reservoir, or a fuel tank, then the design can be simplified and the weight significantly reduced. An alternative topology is to fabricate ridges or fins on the outside surface of the chamber.

If the pressure difference is cycled often, then fatigue analysis will be needed. The fuselage of an aircraft has a lifetime determined by the number of flight cycles.

1. What is the purpose or application of this chamber?
2. What are the real dimensions, and the units?
3. What access to the chamber is required?
4. How many cycles of evacuation will occur?

 

[Vanadium 50]

From a mechanical point of view, that's correct. However, for high vacuum, you have a restricted choice of materials. You could use, e.g. plastic for a rought vacuum chamber, but not for a good vacuum because it outgasses like crazy.

Mechanically, 15 psi is not hard to do. But as the vacuum needs to get better and better, the problem gets tougher because of the material restrictions.

 

[Baluncore]

From a mechanical point of view, that's correct. However, for high vacuum, you have a restricted choice of materials.

True, but the OP has clearly specified grade 304, stainless steel, which I believe is hermetic, even to hydrogen.

The access ports and seals will be an important design consideration, but those are as yet unspecified, and are independent of the shape and dimensions of the chamber.

One problem with electrically conductive, high-vacuum chambers, comes while trying to locate the last pore in a TIG weld. With glass vessels, you can hunt the pores using a high-voltage brush, not so with metals.