Criteria of the ASME Boiler and Pressure Vessel Code for Design by Analysis in Sections III and VIII

[Umar107]

Can anyone please share a copy of this document "Criteria of the ASME Boiler and Pressure Vessel Code for Design by Analysis in Sections III and VIII, Division 2 1969" on the following address

umararshad91@gmail.com

 

[TGS4]

It's included as an Appendix to ASME PCC-1. What is your interest in such an old document?

 

[Umar107]

I was trying to understand the concept of secondary stresses and why do we use the limit of 3S for secondary stresses in elastic stress analysis. Thanks @TGS4, found the document.

 

[Umar107]

@TGS4,
I need some guidance regarding the stress classification in an elastic stress analysis of pressure vessel. As per my understanding, bending stresses at gross structural discontinuity (shell head interface) will be secondary(hence 3S criteria) while primary stresses will be away from any discontinuity (1.5S criteria for membrane plus bending) . Right?

What if we have mechanical loading at nozzles, how would we classify the stresses around nozzles. In PV elite, wrc107 consider the bending stresses at nozzle shell interface as secondary and uses a 3S criteria. Is it the correct procedure?

I need a detailed case study for better understanding of this topic. If you can please share a reference that would be great help. Thanks

 

[DriveMeNuts]

"WRC 429 1998 - 3D Stress Criteria - Guidelines for application" provides a good explanation of different stress limits and stress categorisation.

With respect to bending stresses in the shell local to nozzles under mechanical load:
ASME VIII Div 2 Table 5.6 classifies the bending stress due to both internal pressure and mechanical load as secondary.
EN 13445-3 Table C-2 categories the bending stress due to internal pressure as secondary and due to mechanical loads as Primary. However there is a note saying that if the user can accept small deformations (e.g. regarding functionality or esthetical requirements), then the bending stresses can be considered secondary.

 

[TGS4]

Understanding stress categorization is a topic well beyond the capability of covering in an online discussion on eng-tips. I would refer you to the guidance given in ASME Section VIII, Division 2, Part 5, Paragraph 5.2.1.2:

For components with a complex geometry and/or complex loading, the categorization of stresses requires significant knowledge and judgment. This is especially true for three-dimensional stress fields. Application of the limit load or elastic–plastic analysis methods in 5.2.3 and 5.2.4, respectively, is recommended for cases where the categorization process may produce ambiguous results.

 

[Umar107]

@TGS4,Thanks for your response Sir.
I want to learn elastic analysis better before moving towards limit load and elstic plastic analysis. Can you please share a good case study where stress classification is addressed?
Another thing, How can we apply limit load and elastic plastic method in ASME NC. I can't find load multipliers in NC. If there is a case study about it that would be great help.

 

[Umar107]

@DriveMeNuts
Thanks for your response. I also think it's the true interpretation of table 5.6.

 

[TGS4]

There are a number of scholarly articles written on the subject. I would recommend looking at ones presented at the ASME PVP Conference as a good place to start. And you have already been recommended WRC 429. The example problem manual for Div 2 is another good resource. ASME PTB-3.

 

[DriveMeNuts]

I think it is very wise to learn the elastic stress categorisation method before moving on to non-linear material methods.
Elastic analysis is a good learning tool for learning about various failure modes. It can also be used to assist in verifying a non-linear analysis.
If I hadn't learnt elastic design, then it would be more difficult for me to interpret an elastic-plastic result. The plot potentially could just be a pretty colourful picture consisting of rubbish-in equals rubbish-out.