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MAWP for Spherical Tank

03/19/2009 3:42 AM

Guys, need your help.

I want to calculate hydro test pressure for my sphere.

In what paragraph can i find the formula to determine MAWP for spherical tank.

Because according to ASME VIII-2 2007 para 8.2, it stated that hydro test pressure is 1.43 x MAWP.

But i can not find the formula for MAWP itself.

I have read about the hydro test pressure on ASME VIII-2 but the old 2001 edition. It stated that hydro test pressure is 1.25 x design pressure (Article T-3, para AT-300).

Can i follow the ASME 2001? Or is there any updated info for MAWP in ASME 2007?

Thank you very much Sir for your asnwer..

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#1

Re: MAWP Vessel According to ASME VIII-2 2007

03/19/2009 8:47 AM

MAWP = maxiumum allowable working pressure?
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#2

Re: MAWP for Spherical Tank

03/19/2009 9:11 AM

Hello Premium,

The MAWP, while it may be calculated using vessel parameters, is always stamped on the boiler plate on the vessel itself.

Mike

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#3
In reply to #2

Re: MAWP for Spherical Tank

03/19/2009 10:58 AM

Thanks for the response..

But, i need the formula to calculate the MAWP (maximum Allowable Working Pressure) for spherical tank according to ASME VIII div 2 edition 2007.

Can anyone show me in what paragraph i can find the MAWP calculation procedure?

Thank you for the response..

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XMech
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#4

Re: MAWP for Spherical Tank

03/19/2009 9:32 PM

There is no simple calculation for MAWP, unless, at a minimum, you choose the design pressure (which can be done unless the client specifically asks for the MAWP).

-----------------------

Excerpt from VIII-2 (2008a) 2.2.2.1:

d) Design Conditions

  1. Specified design pressure. The specified design pressure is the design pressure, see paragraph 4.1.5.2.a, required at the top of the vessel in its operating position. It shall include suitable margins required above the maximum anticipated operating pressure to ensure proper operation of the pressure relief devices. The MAWP of the vessel may be set equal to this specified design pressure. If the actual MAWP of the vessel is calculated, it shall not be less than the specified design pressure.

-----------------------

Please see this previous thread discussion:

http://cr4.globalspec.com/thread/30865

And NO!! you can not use the old edition test pressure. YOU MUST STICK WITH DESIGNING TO ONE EDITION.

And don't neglect - it is the greater of:

PT =1.43⋅MAWP

or

PT = 1.25·MAWP·(ST/S)

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#5
In reply to #4

Re: MAWP for Spherical Tank

03/19/2009 10:02 PM

Wow.. Welcome back Mr XMech.. One GA for you :-)

Thank you for answering.. I can understand it now..

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#6
In reply to #4

Re: MAWP for Spherical Tank

03/19/2009 10:34 PM

Sir..

If i want to calculate the actual MAWP according to ASME VIII-2 ed 2007, in what paragraph can i find the formula?

Thank you..

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#7
In reply to #6

Re: MAWP for Spherical Tank

03/20/2009 12:38 AM

There is no general formula for calculating MAWP - you have to find the weakest point of your vessel based on actual thickness used in construction. I would harbour a guess that you will find the limiting factor in your case will be connection of the structural legs to the shell, unless you have thickened the shell/provided a reinforcing pad - I believe from other conversations that you are going to use STD wall pipe for nozzles and have determined that the MAWP's for those are much higher than your design pressure - so those WILL NOT be the limiting factor of MAWP.

So let me reiterate - THERE IS NO SINGLE FORMULA FOR MAWP!!! - you must back calculate ALL areas of interest in your vessel using the actual thickness of material that you are going to fabricate from, and the MAWP will be the lowest pressure found at design temperature.

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