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  • Collapse Pressure for Tubing under external pressure

    Discussion in 'The main mechanical design forum' started by Gandoff1927, Sep 21, 2016.

    1. Gandoff1927

      Gandoff1927 New Member

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      First off I am not an engineer but need to determine the collapse pressure of a 316L SS seamless pipe with the following dimensions. 1.687Ø O.D., 1.00Ø I.D., 27in. length. Environment is @ 200°f.
      Any help would be appreciated!
       
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    3. Dana

      Dana Well-Known Member

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      In theory it would be close to the burst pressure. In practice it will be less, could be a lot less, how much less depends on how "perfect" the tube is, i.e. dents, straightness, and how the ends are capped and/or supported.
       
    4. s.weinberg

      s.weinberg Well-Known Member

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      This is not something I know about (I mean, I could probably work punch the calcs for an ideal situation, but not something I have experience with), but I'm surprised that the crush pressure would be less than burst pressure.
      I know pipes are generally designed to hold stuff in, but my general impression is that round cross-sections are typically stronger in compression than tension, partially, but not fully due to the fact that cracks and such would tend to close, rather than open, as they would in tension.
       
    5. Erich

      Erich Well-Known Member

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      Steve, With compressive loads you have to consider buckling and other instability type situations. A minor dent in a thin walled tube would lead to collapse. I can stand on a perfect aluminum soda can. If I reach down and touch the sides it collapses immediately. That said, the OP's situation has a .34in wall thickness compared to a 1 in id. That qualifies has a thick tube in my book where instabilities are not important.
       
    6. Charles R. Solomon P.E.

      Charles R. Solomon P.E. New Member

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      First, become familiar with octhahedral shear stress theory. Then refer to any pre-2004 version of the Boiler and Pressure vessel code section 8 division 1 paragraph UG 28. Next, consult ASME B31-9 for pipe properties, and then assess potential defects using API 579. Or hire someone who knows what they are doing.....
       

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