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Pressure Vessel Design Question

  1. Mar 24, 2016 #1
    Hello,

    I am replacing an existing ASME Section VIII Division 1 column. The U-1 states it is designed to 240psig @ 650degF, but does not say anything about being designed for vacuum conditions. The SIS for the column states that it is safe to operate under full vacuum. The SIS is not a code document, but the U-1 is. This vessel is from the 1950s. Does anyone know if it didn't use to be a requirement to specify if a pressure vessel was rated for vacuum on the U-1? I have run into this before with a different column so am wondering which document to trust, the U-1 or the SIS.

    Thank you for your help!
     
  2. jcsd
  3. Mar 24, 2016 #2
    I use to make component parts for heat exchangers. All our testing was done with water/air pressure and compliant to ASME code U-1a. If its a system that was designed with support baffles it may be rated for vacuum also. We never did any vacuum testing but we did a lot of pressure testing and in 5 years I only ever seen one failure and it was catastrophic, it was an outer seam tie in that blew and we were trying to make it fail. I think it was well over 2,000 psi at failure if my memory serves me correctly. It pealed it open like a tin can and damaged the blast barriers and rattled the entire building.

    https://www.asme.org/about-asme/who-we-are/standards/asme-data-report-forms

    I also found this It may be useful.

    http://www.eng-tips.com/viewthread.cfm?qid=258334
     
    Last edited: Mar 24, 2016
  4. Mar 26, 2016 #3

    Baluncore

    User Avatar
    Science Advisor

    Pressure testing with a gas should be avoided whenever possible due to the enormous stored energy released on failure. It is also expensive because you must compress a significantly greater volume of air.

    Be safe by using cold water instead. If necessary for physical support, also submerge the vessel being tested in water. Pressure rise during the test is rapid and controlled with little energy being required. The only way you may know when the vessel fails is when the internal pressure suddenly drops. You may need to have a coloured dye in the vessel so you can find the crack. While such a failure is destructive, it is usually repairable.
     
  5. Mar 26, 2016 #4
    Testing should only be done on componet parts or designated test units. Under controled conditions and in compliance with state laws. This being a repair as long as its repaired to code the inspector that signs of on it will probably make any determination on that. I have built them new but i have no idea what is required for repair testing if any. And at 240 psi im not sure if you have to do a test or have it sent out for xray. But im thinking U-1a standards will apply.
     
    Last edited: Mar 26, 2016
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