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question safety valve

  • 1.  question safety valve

    SENIOR MEMBER
    Posted 28 days ago
    Hi,guys. it's necessary to install a safety valve, considering fire case, on a vaccum tower. or no need at all. why ?

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    Han Li
    project manager
    Hualu
    Xi'an
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  • 2.  RE: question safety valve

    SENIOR MEMBER
    Posted 27 days ago
    A quick response... it's been a while since I worked on this issue.  I'm digging deep.

    It may be that the design pressure of the tower is set by structural considerations and not bubble point of the contents. To get to that pressure would require a very hot temperature for the components when the tower is a vacuum tower. However, you may want to use the relief setting to limit the temperature because of the max temperature design of the column rather than the max pressure.

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    Steve Cutchen
    Investigator, retired
    US Chemical Safety Board
    Houston TX
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  • 3.  RE: question safety valve

    SENIOR MEMBER
    Posted 27 days ago
    as per ASME UG-125, if materials vapour pressure is less than tower design pressure base on vacuum tower design temperature. it is no need safe valve for tower.

    ---------------------------------
    Han Li
    project manager
    Hualu
    Xi'an
    ---------------------------------





  • 4.  RE: question safety valve

    SENIOR MEMBER
    Posted 26 days ago
    One subtlety which you may want to explore is cracked gases generated when the bottom of the tower sits at elevated temperatures for a period of time.  These cracked gases are estimated to allow proper sizing of the vacuum system and would have a high vapor pressure.  If sound engineering calcs demonstrate not enough gas is created in a reasonable fire fighting event then it may not be a credible scenario.

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    Thomas Doolin
    Houston TX
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  • 5.  RE: question safety valve

    SENIOR MEMBER
    Posted 26 days ago
    Overpressure due to external fire is not the only scenario to be considered in deciding on the need for pressure relief.  Other possible causes of overpressure are loss of cooling, overfilling with liquid, and inert gas regulator failure if a nitrogen blanket is used. I recommend you use some of the material available from the CCPS and in articles published in CEP magazine before making any decision not to install a pressure relief device on the column.

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    Barry Juran PE
    Consultant
    Philadelphia PA
    Chemical Process Engineer and Sr. Biopharm Specialist
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