Obround Large Openings - ASME VIII Div.1 1

[FredricS]

Hi,
I have to design a vertical pressure vessel with a lateral obround large opening.
The shell mantle has about 70" OD and the attachment is conical with a square base. The connection between the shell and the opening has a large side of 69.7"(in the diameter direction), and a small side of 56".
I've carried out a feasibility analysis considering the specification given in ASME Div.1 (Mandatory Appendix 13), by means of this code requirement I've found the minimum code thickness of the sheet-metal to built up the cone.
To validate the connection between this opening and the mantle is required a FEA analysis of the vessel. In order to satisfy all code requirements I'm checking that the requirements given in ASME Div.2 (Appendix 4) are satisfied.

Do I miss some code requirements during this procedure?

Thank you in advance for your help and your suggestions.

 

[TGS4]

If you're going to perform the FEA by virtue of going through U-2(g), please ensure that you are using the latest version of Division 2 (e.i. 2007 Edition with 2009 Addenda). The reference the you gave (Appendix 4) is for the 2004 Edition with 2006 Addenda at the latest. Division 2 has CHANGED substantially since 2006.

And no, I don't think that you've missed anything.

 

[FredricS]

Thank you TGS4 for your information inherent the changes of the Division 2.

I'm quite new about Division 2 but, I need to know if is it possible to use a smaller thickness than required by Appendix 13 after performing FEA analysis?
Another point is that to understand how to evaluate the FEA compliance to the Division 2 specification. For a 3D FEM model may I use the mean Von Mises stress instead the Primary Stress to verify the compliance to the code? If it is not possible how is the fastest way to perform it?

Thanks

 

[TGS4]

A few things.

1) U-2(g) may NOT be used to override mandatory requirements that are in Division 1. If there are rules in Division 1, then you HAVE to follow them.

2) This is a topic unto itself. Do yourself a favour - search through the archives on this site for discussions about FEA for Pressure Vessels. Then, hire a qualified consultant. Ask them LOTS of questions, and make sure that you completely understand what and why they're doing what they're doing. This is too complex a topic to teach for free on-line.

(As an aside, my company just completed a "training" programme whereby we had an engineer in our office, and we were training him how to do FEA for pressure vessels. The process took one (1) year. I am self-taught, but the process took about three (3) years. Don't fool yourself into thinking that it can be done quicker - it can't.)

 

[MrBTU]

TGS4 - thank you for that insight. It seems that more and more we are being pushed towards FEA for "off sheet" U-2(g) calcs in order to justify designs, and from reading the guidelines and looking at some of the rejected FEA's, it is clear that garbage in = garbage out. It takes a competent press vessel designer to do the FEA, not just a software jockey. I guess we need to start the 3 year process....