ASME Div 2 Elastic-Plastic for Cast SA-395

[jiloebel]

Hi all,

We are looking to design a pressure vessel/Heat exchanger to Div 2, Part 5 Design by analysis. The geometry is complex, so based on recommendations we are trying to use the elastic-plastic method. The material intended to be used is SA-395, which isn't directly a Div 2 material, but is listed in UCD-23 in Div 1. The problem is that when trying to generate the stress-strain curve per Annex 3-D, there is are no parameters for a ductile iron in Table 3-D.1.

Several questions have come up for this:

1. Is SA-395 acceptable for use in Div 2, Part 5 since it is listed in UCD-23 in Div 1?
2. What parameters are to be used for cast ductile iron to generate the stress-strain curve in Annex 3-D?
3. For the elastic-plastic analysis, are thermal stresses to be included even though they are secondary stresses?

 

[TGS4]

1. Code Case 3090 covers this exact material (in the Grade 60-40-18) and the request for Design-By-Analysis. It needs to be ASME Section VIII, Division 1 construction, since the material is not permitted in Division 1.
2. All of the applicable parameters are provided in the Code Case.
3. Yes. The elastic-plastic methodology sorts this out so that you, as a user, do not need to. Follow the rules of ASME Section VIII, Division 1, Appendix 46 - you need to satisfy ALL of the failure modes listed in Part 5.

Happy to answer if you have more questions.

 

[jiloebel]

@TGS4

Thanks so much, I was hoping you would reply!

Just a quick point of clarity on what you said in point 1:

1. Code Case 3090 covers this exact material (in the Grade 60-40-18) and the request for Design-By-Analysis. It needs to be ASME Section VIII, Division 1 construction, since the material is not permitted in Division 1

I'm assuming you intended to say "the material is not permitted in Division 2"

I'm trying to get access to the Code case, it looks like we no longer have them in our Technical Specifications repository so hopefully that should clear it up for me.

As far as the elastic-plastic analysis, I've seen other posts and replies on this forum (from you and others), and my understanding is so long as ANY solution is obtained, regardless of stress levels, then the design is acceptable since it follows the LRFD methodology?

 

[jiloebel]

So, on the code case, I'm able to search for it and find the form but can't seem to view it. I see it should be in Supplement 7, but also that Supplement 7 will not be released until next month? I see the "last updated" date is today, maybe I'm missing something.

 

[TGS4]

Yes - I meant to write that the material is not permitted in Division 2.

You can look up the Code Case here - https://www.asme.org/codes-standards/publications-information/code-cases. If you are not able to access, please let me know, and I will upload the file here.

Yes - the criteria is numerical convergence.

 

[jiloebel]

@TGS4 , Looks like we replied at the same time. I found the case, but get an error when trying to view the files that I don't have access. If you are able to upload it here, that would be awesome!

 

[TGS4]

Here you go.

 

[jiloebel]

Got it, thanks!

Beta = 5.0... yikes!