ASME Section II Part D Stress Values

[Charan5]

Hello,

I am looking for ASME stress value tables for SA 210 A1 material and I know these are based on certain criteria according to ASME Section II Part D, Appendix 10. However, when I see allowbale stress values for SA 210 A1 at 100-650 F, it is 17100 psi. And this value is not matching to min tensile 60 ksi and min yield 37 ksi per above criteria, unless I am missing Ry value.

 

[rumandcola]

The ASME allowable stresses are well below tensile and yield stresses. This value has a safety factor worked into it.

 

[gr2vessels]

The ASME VIII incorporates a safety factor of approx 3.5 in limiting the allowable design stresses, hence 60,000psi / 3.5 = 17100 psi. 60,000 psi is the listed minimum tensile strength and the 17100 psi is the allowable design stress for this material.
Cheers,
gr2vessels

 

[jte]

Just to be clear, ASME VIII Div. 1 sets its base allowable Tensile stress S as the lowest of ultimate at temp divided by 3.5, two thirds yield at temp, or time dependent (i.e. creep) limited values.

Be sure to apply this allowable stress appropriately, and don't confuse it with allowable compressive stress.

jt

 

[Charan5]

Thamk you very much for the feedback, and it is clear in Appendix 1. Appendix 10 is something different.

 

[Charan5]

Hello,

One more thing, I am wondering, is it okay to arrive allowable stress based on tensile stress values, even if the yields are much less than code minimum and 2/3 of yields is higher than tensile based stress values. For eg.60/3.5=17100 psi and 2/3*27Fy=18000 psi. Is this detrimental as long as the material is not stressed to yields for permanent deformation.

 

[jte]

Charan-

What exactly are you playing with? Do you have competent oversight / mentoring?

jt

 

[Charan5]

Hello Jte,

I am not sure about your question. I am fully aware of the ASME Section I and VIII, and this is a situtation where we have tubes are chromized and in the process the stress values are reduced. Trying to justify the tubes for pressure containment using the allowables within code limits.

 

[jte]

So you have a material which is modified and thus no longer listed in II-D which you are using for a Section I or Section VIII component?

jt

 

[Charan5]

That's correct. You might know, codes does not require the materials to meet every Section II propeties after fabrication, like bending, heat treatment etc. So, once you alter the material properties, it is up to the designer how to interpret and apply these values within certain boundary. Unfortunately code is not clear in defining the limits for every case.

 

[TGS4]

That's an interesting interpretation you have, Charan5. Do you have an official ASME Interpretation to back up that claim? Perhaps a reference to a particular Code paragraph that I am not familiar with could also enlighten me.

Where is this "vessel" going to be installed? What is your jurisdiction's thoughts on this?

 

[Charan5]

Hello TGS4,

Some interpretations I-83-01 & I-95-03 which talks about similar cases. We have not checked with Jursidiction and it's in US.

 

[metengr]

I am not sure about your question. I am fully aware of the ASME Section I and VIII, and this is a situtation where we have tubes are chromized and in the process the stress values are reduced. Trying to justify the tubes for pressure containment using the allowables within code limits.

Typically boiler tubes (Section I) may be chromized for corrosion resistance only, and the diffusion distance for chromizing is such that the argument could be made that bulk properties are unaffected. This is a post fabrication issue that the Code does not address. How and why would one decide on altering the allowable stress values?

The bulk properties are normally unaffected by this process unless you operate in the creep regime and there have been isolated cases where local creep damage has occurred immediately under the chromized layer (where chrome has combined with carbon to produce a lower creep strength ferrite zone). In this case, the orientation of the lower creep strength zone is not oriented in the direction of primary membrane stresses.

 

[jte]

Definitely an interesting thread. In addition to the interpretations Charan has provided, I'd also suggest that VIII-1-83-299 and VIII-1-07-04 deal with similar issues.

Question: In a brazed construction, does the fabricator have to demonstrate that the material properties after brazing are not below the minimum specified values?

Reply: No, provided the requirements of Section IX are met.

Question: Must a stainless steel component which receives a significant amount of cold forming during fabrication, and is not subjected to a final solution anneal, satisfy the mechanical properties of Code approved Section II, specification in its final formed shape?

Reply: No.

jt

 

[twistobar]

JTE, I agree those are interesting interpretations, bit I submit that they are not calling for modified allowable stresses to be used in the design and Section II allowable stresses should still be valid with the Interpretations.
Regards,

... a man's got to do what a man's got to do...

 

[jte]

twistobar-

Agreed.

jt

 

[Charan5]

Thanks for all feedback.

 

[GenB]

gentlemen, where will I find the ASME stress related x 3.5,
why is 3.5 and not 4?
please advise.

 

[jte]

GenB-

Because the code committee, for various reasons, changed the factor against ultimate from 4 to 3.5 starting with the 1999 Addenda. Factors against yield, time dependent, and compressive did not change.

I'm sure you'll find much more on this if you search the forum. If you have a specific question, I'd suggest starting your own thread.

jt