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Thread: Internal pressure and external pressure in pressure vessel

  1. #1

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    Internal pressure and external pressure in pressure vessel

    Dear all,

    Could you please explain to me about pressure in pressure vessel, when we should apply internal pressure? and when we should apply external pressure for our pressure vessel. What the dimension of PV should be our consideration? or there are other consideration?

    Thanks,
    Echo

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    No i'm a piping engineer, but now i should design tank with diameter 9m and high 13.5, the client want the tank based on ASME Sec VIII Div.1. I already read the ASME Sec VIII Div.1, except the wind and seismic, maybe the high also should be the consideration? or there is a high limitation to determining the pressure?

    Thanks,
    Echo

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    dear eko.
    please read PV handbook for your first book, then ASME Sect. VIII for next book.

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    dear eko
    ASME Sect. VIII is only for Horizontal Vessels and not for Vertical vessels. Use API 650 for the design or IS -803

    Recent Threads by deyprasen :


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      Quote Originally Posted by deyprasen View Post
      dear eko
      asme sect. Viii is only for horizontal vessels and not for vertical vessels. Use api 650 for the design or is -803
      you're wrong, read also asme bpvc sec. V111 div. 1 & 2..

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      Tanks = API 650up to 2.5 psi design pre , which is low
      API 620up to 15 psi design pre , which is also low

      Seismic and wind are treated differently in API ( See for instance appendix E in API 650 ..)
      ---------------

      Now = other vessels and COLUMNS as per ASME VIII
      design pressure to determine the thickness , a bit similar to your piping in B31.3

      based on = circumferential stress = P*R/ t
      Note = if you have external pressure there an other additional check stated in ASME

      longitudinal stress due to pressure = 0.5 * circumferential stress

      You have to check =

      stress = (longitudinal stress due to pressure) +/- (stress due to wind ) - (stress due to own weight )

      stress = (longitudinal stress due to pressure) +/- (stress due to earthquake ) - (stress due to own weight )

      They are textbooks in this site , go there and read atleast some basics, for instance =
      Pressure vessel design handbbok by Bednar
      or
      The pressure design manual by Moise
      or CAST book

      Also ASME VIII div & , in its appendix L , has some top good examples

      Above is implemented in software such as PV elite, or Compress but it important to understand what you are doing and before jumping onto a software

      take care and good luck

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      Quote Originally Posted by FATHI View Post
      Tanks = API 650up to 2.5 psi design pre , which is low
      API 620up to 15 psi design pre , which is also low

      Seismic and wind are treated differently in API ( See for instance appendix E in API 650 ..)
      ---------------

      Now = other vessels and COLUMNS as per ASME VIII
      design pressure to determine the thickness , a bit similar to your piping in B31.3

      based on = circumferential stress = P*R/ t
      Note = if you have external pressure there an other additional check stated in ASME

      longitudinal stress due to pressure = 0.5 * circumferential stress

      You have to check =

      stress = (longitudinal stress due to pressure) +/- (stress due to wind ) - (stress due to own weight )

      stress = (longitudinal stress due to pressure) +/- (stress due to earthquake ) - (stress due to own weight )

      They are textbooks in this site , go there and read atleast some basics, for instance =
      Pressure vessel design handbbok by Bednar
      or
      The pressure design manual by Moise
      or CAST book

      Also ASME VIII div & , in its appendix L , has some top good examples

      Above is implemented in software such as PV elite, or Compress but it important to understand what you are doing and before jumping onto a software

      take care and good luck
      hi,

      ASME SECTION VIII has three divisions, 1, 2, & 3 you have to specify where your requirement are applicable. it's not easy to say and reccommend any formulas without determining the application, it might be in ASME SEC VIII Div. 2 or Div. 1 check first.. the formulas you've mentioned here is absolutely wrong and incorrect. that is not the first step, you have to determine first the allowable stress of material to be used at design temperature and ambient temperature as per ASME SEC. II-D table 5A.. then use the formula mentioned in ASME SEC VIII depending in which division you are using.. whether DIV. 1 or 2.. take note thickness calculation formula for shell in this two division are different.. so be careful.

      Thanks,,
      Last edited by duazo2009; 08-06-2010 at 05:02 AM. Reason: ..

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      Quote Originally Posted by duazo2009 View Post
      hi,

      ASME SECTION VIII has three divisions, 1, 2, & 3 you have to specify where your requirement are applicable. it's not easy to say and reccommend any formulas without determining the application, it might be in ASME SEC VIII Div. 2 or Div. 1 check first.. the formulas you've mentioned here is absolutely wrong and incorrect. that is not the first step, you have to determine first the allowable stress of material to be used at design temperature and ambient temperature as per ASME SEC. II-D table 5A.. then use the formula mentioned in ASME SEC VIII depending in which division you are using.. whether DIV. 1 or 2.. take note thickness calculation formula for shell in this two division are different.. so be careful.

      Thanks,,
      Of course I have assumed
      design pressure + Design temperature both max and min + corrosion allowance + materials are known and should figure in the process data sheet , befor making a mechanical data sheet or any mechanical sizing

      Now you tell me or tell us where are the mistakes , by refering to the codes or text books
      I will be glad to learn and correct myself befor induced others in errors

      Thanks

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      CORRECTION =
      Of course I have assumed
      design pressure + Design temperature both max and min + corrosion allowance + materials are known and should figure in the process data sheet , befor making a mechanical data sheet or any mechanical sizing ARE ALL KNOWN AND HAV EBEEN ASSUMED OR SELECTED

      Sorry

    • #12

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      Quote Originally Posted by FATHI View Post
      Of course I have assumed
      design pressure + Design temperature both max and min + corrosion allowance + materials are known and should figure in the process data sheet , befor making a mechanical data sheet or any mechanical sizing

      Now you tell me or tell us where are the mistakes , by refering to the codes or text books
      I will be glad to learn and correct myself befor induced others in errors

      Thanks
      You Don't know what you're talking about..in designing a pressure vessel, design pressure and temperature should not be assumed.. in a certain equipment operating pressure and temperature are always given and there's a formula to calculate the design pressure and temperature, you have to clarify what kind of pressure is it whether it absolute pressure or gauge pressure... the way you're are expalaining, it seems that you don't know how to design... you are just refering to the entire codes but you don't know which section and paragraph it is found .. isn't it.. so my overall assesment regarding your reccomendation is absurd! and i repeat don't pretend that you know pressure vessel design.. thats all..

      Take note: data sheet will be made after finalizing the design which is the results of your calculations.

      Regards,

      Duazo2009, P.E.
      Last edited by duazo2009; 08-06-2010 at 12:41 PM.

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