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wazir shah
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Join Date: Jun 2014
Posts: 2

How to Calculate Allowable Stresses?

06/11/2014 8:11 AM

hello to all of you.....dear sir/maam i need your help in my current project....

i have designed a pressure vessel,

dia 3380 mm

shell thickness:10

length:19218 mm

i have to fix a nozzle in the pressure vessel.

nozzle is to be welded on pressure vessel.

what will be the allowable stresses?

how to calculate these forces????

nozzle:6",150#WN RF

shell:A285 GR C

flange:A181 GR I

line pipe:6" sch 80 (A106 GR A)

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Anonymous Poster #1
#1

Re: how to calculate allowable stresses??

06/11/2014 9:24 AM

By far the safest way to proceed is to STOP!

You don't seem to understand how many people could be hurt or killed by you not knowing what you are doing.
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Anonymous Poster #2
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Re: How to Calculate Allowable Stresses?

06/11/2014 9:53 AM

From your avatar, it appears you are a graduate of something. Let's assume it's a BSME degree, which would give you the analysis skills to work this problem, but you need to be mentored for what ever industry this pressure vessel is used within. They don't teach safety in university, nor design specific requirements/solutions/practices. This is part of the domain skill set you learn from others that mentor you.

You should not act like you can solve this if your design lead gave you the problem, but ask for help. If you don't you have failed the test.
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lyn
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#3

Re: How to Calculate Allowable Stresses?

06/11/2014 9:59 AM

Calculate stresses according to the applicable specifications to which the vessel is being built.

Know which specifications to consult would be a part of your learning experience.

Having someone give you the answer would defeat the purpose of your project.
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IdeaSmith
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Join Date: Mar 2012
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#4

Re: How to Calculate Allowable Stresses?

06/11/2014 10:00 AM

I cant think of a reason why a nozzle will be directly in the wall of a pressure vessel. What is the purpose of same and why not using a pressure vessel extension to place the nozzle with a valve as a seperator just in case.

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Tornado
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Technical Fields - Technical Writing - New Member Engineering Fields - Piping Design Engineering - New Member

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Location: Richland, WA, USA
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#5
In reply to #4

Re: How to Calculate Allowable Stresses?

06/11/2014 4:44 PM

Pressure vessel nozzles are generally attached directly to the vessel wall; that is the very meaning of nozzle.

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IdeaSmith
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#6
In reply to #5

Re: How to Calculate Allowable Stresses?

06/11/2014 9:06 PM

Ok, got it. Nozzle to me was something small and little to create a pressure differential. I get it that it might just be an outlet with a flange.

http://www.paulin.com/WEB_FE107_Experimental_Validation.aspx

Found the above with a quick search. Seems there is no easy answer for this one but a lot to read about.

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Tornado
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#7

Re: How to Calculate Allowable Stresses?

06/11/2014 11:35 PM

The allowable stress is simply the ultimate (or alternatively yield) stress of the material divided by the Code-mandated safety factor (based on whichever of the two). Not much calculation there.

The actual stresses (shear and moment loadings) on a nozzle can be calculated from structural formulas, notably involving cantilevers. FEA (finite element analysis) programs can help.

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texasron
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#8

Re: How to Calculate Allowable Stresses?

06/12/2014 7:35 AM

i have designed a pressure vessel,

No you have not! Please find someone who knows, I have graduate engineers from , lets say some countries, come here all the time and when they overextend their capabilities and background the results can fatal.

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JMCB
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Join Date: Jan 2014
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#9

Re: How to Calculate Allowable Stresses?

06/12/2014 8:46 AM

What pressures are you seeking to deal with
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MJCronin
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#10

Re: How to Calculate Allowable Stresses?

06/13/2014 7:39 PM

Waziir....

The best thing for you to do, as suggested above, is to stop and seek experienced advice on the design and specification of pressure vessels.

I have designed and specified many vessels, all in accordance with the ASME Section VIII pressure Vessel Code.

The most important thing for you to understand is that an engineering design code is a COMPLETE INTEGRAL DOCUMENT and that the complete design of a vessel incorporates the calculation methods, inspection methods, testing and ALLOWABLE stresses of that code.

In order for the vessel to be safe, you cannot pick and chose from various sources.

Furthermore, not anyone who can weld can produce safe vessels. The existing codes contain restrictions and requirements for weld materials, weld techniques and inspections that have been proven for nearly 100 years.

I suggest that you select a code, talk with experienced fabrications who can produce a safe vessel and make a purchase.

Let us know what your final decision is...

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Users who posted comments:

Anonymous Poster (2); IdeaSmith (2); JMCB (1); lyn (1); MJCronin (1); texasron (1); Tornado (2)

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