Forces on a pressure vessel containing a vacuum

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Discussion Overview

The discussion revolves around calculating the forces acting on a pressure vessel that contains a vacuum, specifically addressing non-cylindrical or non-spherical shapes. Participants explore resources and methodologies for understanding external pressure effects on such vessels.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant suggests that the problem should be viewed as an external pressure issue, noting that the internal vacuum or external atmospheric pressure does not change the fundamental calculations.
  • Another participant references the ASME boiler and pressure vessel code as a valuable resource, although they express uncertainty about its coverage of external pressure for non-standard shapes.
  • A later reply emphasizes that ASME code primarily addresses cylindrical or spherical vessels and that for flat plates, the relevant calculation focuses on the differential pressure (dP) across the plate, regardless of whether the pressure is below atmospheric.
  • Participants mention "Roark's Formulas for Stress and Strain" as an additional resource for flat plate calculations.

Areas of Agreement / Disagreement

There is some agreement on the importance of considering external pressure, but participants express differing views on the applicability of ASME code to non-cylindrical or non-spherical vessels, indicating a lack of consensus on the best approach for these shapes.

Contextual Notes

Participants acknowledge limitations in the resources available and the specific applicability of codes and formulas to different vessel shapes, which may affect the calculations discussed.

harry_harrin
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Hi,

I'm trying to work out how to calculate the forces acting on a vessel containing a vacuum. The vessel is not cylindrical or spherical. Can anyone suggest any websites or textbooks that might be useful?

Thanks
 
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I think that should be looked upon as a external pressure problem. The fact that its a vacuum inside or 1 atm with 2 atm outside doesn't matter.
The construction of pressure vessels is given in the ASME boiler and pressure vessel code manual section VIII. (I am not sure anymore if external pressure is covered but I believe it is)
Those are not that easy to get your hands on but a large university should have it in their library.
 
Thats great, Thanks very much for your help jaap
 
Hi harry. ASME code is an excellent resource, but regarding external pressure, ASME is focused on cylindrical or spherical parts.

If you have flat plates, either circular or rectangular, it doesn't matter if there is a vacuum on one side or positive pressure. The calculation is done depending on dP across the plate, so you don't need to concern yourself with whether or not the pressure on either side is below atmospheric - only the dP across the plate is pertinant.

For flat plates, also look for "Roark's Formulas for Stress and Strain".
 
that was really useful, thanks for that
 

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