ASME VIII Div 2 and Pipe Support design? Is it allowed?

[Corduroy]

Hi,

Just wondering if you can use ASME VIII Div 2, which is a Pressure Vessel code to design pipe supports. Basically use the FEA comments in the code and apply this to a design of pipe supports.

Thanks.

 

[fegenbush]

If you are using the parameters and techniques in Div 2 to drive your FEA, I think you are in the clear. It is also possible to use a manual technique. WRC 107 is one possible choice in this category.

 

[prex]

No, you can't.
Pressure vessels are shell (two dimensional) structures mainly made from plate, so 'sections' to be checked are rectangular ones (through thickness) with a plastic to elastic bending modulus ratio of 1.5.
Support structures are basically linear (one dimensional) structures, making wide use of standard beams. Now standard beams have a plastic to elastic bending modulus ratio quite lower than 1.5, it can be as low as 1.1 .

prex
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[jtseng123]

wholly confused !!??

 

[fegenbush]

I should clarify my answer. For design of the interaction between the pipe support and the shell of the vessel, there are many techniques available (none of them particularly easy) to determine the appropriate arrangement. For the stresses in the pipe supports themselves (shear, bending, and torsion of the members) something akin to the AISC Steel Construction Manual would be appropriate.

 

[TGS4]

Both prex and fegenbush are correct.

In accordance with ASME B31.3, Article 302.4.1, the pipe must be protected against overstress, damage, collapse, or buckling due to superimposed loads from supports... Unfortunately, B31.3 does not address how to do this exactly. However, it provides some additional guidance in 304.7.2, which provides using FEA in accordance with ASME Section VIII, Division 2, Part 5 (with some additional provisos).

Depending on whether you decide to use an elastic (allowable stress basis) or elastic-plastic (LRFD) analysis, I would follow the rules of ASME Section VIII, Division 2 (per 304.7.2) for the pipe, and the rules of the local jurisdictional structural Code for the attached structural steel.

This is how pressure vessel appurtenances such as ladders and platforms are designed. So too should you design piping appurtenances accordingly.

If you read and understand the limits and boundaries of the respective Codes, there is no confusion.

 

[Corduroy]

Thanks all for the replies.

Just to clarify. Are you guys saying that ASME VIII is not reconmended to be used for pipe supports? and only pressure vessels? I ask this because I can't find any reference to pipe supports in the code.

Also, MSS SP58 is the only code that I know of, for the design of pipe supports. Am I correct in saying his? Is there any other and specifically that mentions FEA?

ASME B31.3 does reference pipe supports, however it directs you to MSS SP58.

Thanks again for your replies.

 

[TGS4]

Corduroy - the answers to your questions have already been given above.

ASME Section VIII, Division 2, Part 5 can and should be used when using FEA to evaluate the effects of the pipe supports on the pipe. The references in ASME B31.3 (302.4.1 and 304.7.2) are appropriate. VIII-2, Part 5 is NOT specific to pressure vessels, but can be used with any pressure equipment (including process piping, power piping, tanks, etc - see API-579-1/ASME FFS-1 Notes in Table B1.4).

You could apply MSS SP-58 using FEA, applying the stress limits in Article 4. However, one could argue (and this is on a jurisdiction-by-jurisdiction basis) that the local Structural Code could apply. However, if you choose MSS SP-58, then you are on your own to figure out how to apply FEA to the stress limits in Article 4.

 

[Corduroy]

Thank you for replying. I only asked for clarification, because Prex said above "No, you can't" and then you said Prex was correct. Hence the request for clarification.

I'm not convinced that VIII-2 is for pipe supports, because a pipe support is not a pressure vessel, it doesn't have a "shell structure". Where MSS SP58 is all about pipe supports.

 

[TGS4]

I never said that VIII-2, Part 5 is for the pipe support itself. However, an important part of the design of the pipe support is its effects on the pipe. You use VIII-2 for the pipe, and MSS SP-58 (or an applicable Structural Code) for the support.

That said, the rules in VIII-2, Part 5 are applicable to just about any structure. They are essentially the same rules as exist in AISC, especially for the LRFD (elastic-plastic analysis method) approach. A stress is a stress, and the piece of metal doesn't know whether or not it is in a pressure vessel or a bridge. Just figure out what your allowable stress is, or what your load factor should be and analyze it...