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paresh_career001
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SCL As Per Old and New Code (ASME SECTOIN VIII DIV 2)

04/20/2009 1:07 PM

I have done FEA of MANWAY NOZZLE designed as per ASME SECTOIN VIII DIV 2...and have taken SCL (stress classification line) for the result evaluation. i have done it in two ways:

1. I have taken SCL at 7 postions by Edition 2004 Add. 2006 ( Max. shear stress theory) and then

2. I have taken SCL at same positions by Editon 2007 (Von mises theory) ....now i have found that STRESS VALUES AS PER ED. 2004 gives higher value than ED. 2007. USUALLY WHAT HAPPENS IS ED. 2007 GIVES HIGHER ALLOWABLE STRESS THAN ED.2004...

My question is why this happen? is there any technical reason behind it?........MY FEA OF NOZZLE IS QUIET SAFE IN BOTH THE NEW AND OLD CODE........

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Abdel Halim Galala
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Engineering Fields - Piping Design Engineering - New Member Egypt - Member - Member since 02/18/2007

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#1

Re: SCL As Per Old and New Code (ASME SECTOIN VIII DIV 2)

04/21/2009 1:56 AM

Each code/standard has its own factor of safety (depends on his point of view of the recommended theory of failure), which affects directly at the value of the Allowable Tensile Strength of material, S. For example, more than 10 years ago, S of ASME A516-70 related to rules of ASME VIII, Div.1 changed from 17500 psi to 20 000 psi (at amb. temp.) up till now.

Therefore, the organizations issuing codes/standards have to review their rules, empirical formulas, factors of safety, acceptance criterias, ... etc., and may be in conjunction with improving of method of production, fabrication, quality control,... etc. and may be by adding some additional requirements or tests to the material through production phase or during fabrication phase.

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paresh_career001
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Location: Gujarat, India
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#2
In reply to #1

Re: SCL As Per Old and New Code (ASME SECTOIN VIII DIV 2)

04/21/2009 3:05 AM

thank you sir..but i want to know why SCL results of new code with max. shear stress theory is more than the new one....? though it is oveserved that von mises gives more stress than max.shear stress... does not it? please correct me if i m wrong....

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