Yield and Tensile strength

[GeorgeEllwood]

Apologies for this simple question which someone can hopefully answer quickly.

I'm doing some rough analysis in ANSYS of a pressure vessel to work out approximately how thick the walls will be and hence the weight. I'm using PD5500 which gives limits of Fe= yield strength/1.5 or Fe = Tensile Strength/2.35 for this type of steel below 50°C.
Am I correct in thinking that I should find the Sress Intensity in my model and then check that it is below the figures I can find listed for Yield Strength/1.5 and Tensile Strength/2.35 of my material?

 

[TGS4]

I'm sure that PD-5500 has something equivalent, but in the ASME world, you need to look at ASME Section VIII, Division 2, Part 5.

By your question you seem to be new to pressure vessels. Correct? If so, gently put the FEA tool away, because what you are doing is significantly more dangerous than you can imagine.

In all Codes, there are design-by-rules formulae for finding the wall thickness of pressure equipment. The allowable stresses are, as you indicated, related to the yield and ultimate values. Use the allowable stresses and the formulae.

Am I correct in thinking that I should find the Sress Intensity in my model and then check that it is below the figures I can find listed for Yield Strength/1.5 and Tensile Strength/2.35 of my material?

No.

 

[GeorgeEllwood]

Hello,
Thanks for replying, you are correct I'm new to pressure vessels. The vessel in question is a very odd shape and isn't covered by any of the design by rules formulas. According to the book I've got that was written to accompany the british regulations it says to find the stress intensity, i.e the maximum difference between the principal stresses and to ensure that this is below the strengths listed for the material including the safety factors. That seemed to make sense to me but I haven't had a lot of experience with pressure vessels and wanted a double check from someone with more experience. I'm only looking for a rough answer to find out how approximately how much the vessel will weigh and the material costs before it goes out for design and manufacture.
Thanks
George

 

[TGS4]

To what Code will the new vessel be constructed?

 

[GeorgeEllwood]

It will be to PD-5500 it will be designed, built, manufactured and used in Britain.
Cheers
George

 

[TGS4]

If you are designing this to EN-13445, check out Annex C. If PD-5500, then check out Annex A.