allowable stress use in calculation

[19750412]

Hi all, I need a help in below matter. I try to find on forum an answer but I can’t.
The whole vessel is designed acc. to ASME VIII Div.1.During calculation I found that some nozzle did not fulfill requirements of WRC107, (the stress are exceeded at reinforcing pad edge for Pm+Pl+Q (total)). I have informed our client about that and in answer I get information that I should use for calculation of this nozzle allowable stress from Div. 2., ( for shell and pad also). In the answer my client said laconically that such solution is allowed by ASME, but any specific point has been mentioned.
Reading of UG-23 I can’t find such statement and in my point of view is not allowed.
I have also the question, whether I can use multiplication factors given in UG-23 (e) to calculate local stresses in shell based on WRC 107, when this specific point of ASME defined discontinuities which do not comply with nozzle construction.
Thanks in advance for help.

 

[TomBarsh]

ASME Section VIII Division 1 addresses allowable combined local membrane stress plus bending stress, PL + Pb, in UG-23(c); the permissible stress is 1.5 x the basic allowable tensile stress. However, Division 1 does not address secondary membrane plus bending stress, Q, which would represent the "surface" stresses for your WRC-107 analysis. It is for this stress that many designers refer to the Division 2 allowable stress factors based on paragraph U-2(g) in Division 1. For Q stress Division 2 permits 3.0 times the basic allowable tensile stress.

Related to this, recently UG-23(e) was revised to address discontinuity stresses. Here also the allowable is taken as 3 times the basic allowable tensile stress.

 

[19750412]

Thanks for your help.
Of course all this I found in ASME Div.1 and is more or less clear for me. But I probably do not precisely describe my problem. My client said that for shell and pad material which is SA-516 60 I should use in calc. allowable stress in design temp. given in table 2A Sec. II Part D instead of this given in table 1A of same section. (for this mat. Acc to div. 1 Sa 117.9 MPa, acc. to div. 2 Sa 134 MPa). And this makes me confused.

 

[jamesl]

Your client is wrong. You use Div.2 methodology, not Div.2 allowable stresses.

 

[TGS4]

To follow-up on what jamesl wrote, the paragraph that you were referred to - U-2(g)

This Division of Section VIII does not contain rules to cover all details of design and construction. Where complete details are not given, it is intended that the Manufacturer, subject to acceptance of the Inspector, shall provide details of design and construction which will be as safe as those provided by the rules of this Division.

In order to prove to the Inspector that your design is as safe as it would otherwise be in Div. 1, the generally-accepted engineering principle says use the Div. 1 allowable stresses. So, yes, your client is wrong.

 

[19750412]

Thanks All for help. I was thinking exactly as jamesl said. To be on safe said we can use Div. 2 methodology not allowable stress.