Appendix 24 - Assistance 1

[ella0509]

Hello everyone.

We've got a pressure vessel design going through at the moment that utilises a clamp closure. I'm designing the ferrules and clamp to Appendix 24 (my 1st time) but I'm having some confusion over the notation.

I know that you have to do calculations for both operating and assembly conditions, but I'm confused as to when you need to use each value. For example, HG contains the W term which has two answers (Op and Assy). If I have two HG answers, then I have two MG answers. This intern gives me two Mo answers. MR is the same. MH is affected by Mo, and so on. If you have these multiple answers for all the notations then thats, fine, but I'm not entirely sure you do.

I would be grateful if someone that has experience of this Apendix could give me some guidance or examples to help me clarifiy......

Regards,
Lee

 

[prex]

In the site below, under 'Vessels -> ASMEVIII...' there are two sheets based onto App.24. You can consult the formulae: hope it will give you ideas on how to interpret code rules.

prex

http://www.xcalcs.com

Online tools for structural design

 

[ella0509]

Thanks prex - you get a star!!

The internet is a fine invention is it not......

Lee

 

[ella0509]

I fear I may have been too confident......

Has that xcalc program been validated. Tried to run my design with US units and there seems to be some possible unit conversion errors in it around the Mo / MH calculation point.

Anyhow back to my original question - why is MH2 not used in calculation number 16 (Hub Stress: Longitudinal) for the Gask Seating condition. MH1 is used in both operating and Gask Seat conditions - is this correct??

Again anyone with validated examples that I could run through the Excel Spreadsheet I've created would be great.

Thanks again,
Lee

 

[prex]

Hub stress for assembly condition is correctly calculated using MH2, as you might easily check, only the graphical formula is incorrect (it is now corrected).
Concerning the units problem, did you notice that the moments are expressed in kp-ft, not in lb-in?
Coming back to your original question, HG is indeed defined for both operating and assembly conditions; however the latter is not used in the formulae, so there is no need to calculate it.
Don't expect you'll find a certified example for such an odd calculation; come back if you want to discuss a bit more on the interpretation of code formulae.

prex

http://www.xcalcs.com

Online tools for structural design

 

[ella0509]

Thanks once again for your input Prex, its been most valuable.

I'd basically worked through both the code and the xcalc program and came to the same conclusions that you have just mentioned.

I've now basically got an Excel spreadsheet for the calculations. I'm relatively happy with the results, but because of my reservations with the Notation I've lost a little confidence in the answers. It was for this reson I was wanting some examples to plug the data in before I submit to the AI.

Regards,
Lee