ASME VIII Div 1 Procedure for noncircular cross section vacuum chamber subjected to external load 3

[LearningENG-]

Hi All,

I'm currently working on designing a vacuum chamber as a insulation for a cryostat. Due to design requirements, at least one side of the chamber should be flat so I can't choose a cylindrical chamber. I'm hoping to design the chamber as per Figure 13-2(a) (3) or a "D" shaped chamber. The problem is I can't find any procedure for calculating the allowable stress under external pressure for these two kinds of chambers. It seems this code only shows how cylindrical chamber or rectangular chamber (as shown in figure 13-2(a) (1) and (2)) should be calculated under external pressure.

Does anyone have an idea of where/how I should start to calculate the chamber I hope to design?

TIA,
XS

 

[SnTMan]

LearningENG-, you have two choices here;

1) Design per Code rules, or as you noted, a vessel per sketch (a)(1) or (2)
2) Design the vessel you prefer by other means. This is what is meant by reference to U-2(g). This could be recognized structural theory, FEA analysis, or methods of your own devising. Whether you are required to stamp the vessel can have a bearing on the alternative chosen.

I personally do not know of any canned analysis for your chosen design, but I'd note that most people in the business tend to select designs for which rules exist, particularily for small quantities.

Best of luck,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[LearningENG-]

Hi Mike,

Thanks for your reply. In this case I think I'll go as per sketch (a)(1) since, like you said, the design procedure is clear and I only need to make one.

Regards,
XS

 

[SnTMan]

LearningENG-, if you are subject to any kind of schedule or budget constraints, that is probably the best way to go

I guess I did overlook one other alternative, the proof test (UG-101). Again, not likely the best option for small quantities.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[marty007]

This is what is meant by reference to U-2(g). This could be recognized structural theory, FEA analysis, or methods of your own devising.

Note in 2019 ASME VIII-1 U-2(g) was revised, and now provides only three methods for the design of geometry where VIII-1 does not contain rules:
[ol a]
[li]Mandatory Appendix 46 (Use of VIII-2 rules)[/li]
[li]Proof test in accordance with UG-101[/li]
[li]Other recognized and generally accepted methods, such as those found in other ASME, EN, ISO, national, and industry standards or codes. This option shall provide details of design consistent with the allowable stress criteria provided in UG-23[/li]
[/ol]

Methods of your own devising are no longer acceptable...

-Marty

 

[SnTMan]

marty007, thx, good to know.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[LearningENG-]

Thanks Marty for your clarification.

XS