Maximum allowable stress value for ASME-VIII-1 material 2

[starrproe]

Recently, We came across a case where a LAS forging material(SA 336-F5) used for body flange in Shell and tube exchanger had the yield and tensile strength values reported (In the test certificates) above the mimimum values specified in the code(Tables 1A / 1B) by around 10%.
The manufacturer is trying to use these higher strength values to deduce that the maximum allowable stress values at design temp.(319C) can also be accordingly adjusted and hence, is arriving at a lower thickness than that would otherwise have been required.

My query is -Does Code allow / restrict taking credit of such higher strength values while performing calcs?
Is there any code interpretation on the issue?

Any help would be highly appreciated.

Regards,
Starrproe

 

[boilerone]

I don't think this is going to be allowed. For example, what if in the future this particular part needs to be replaced? How can you make sure they check the original document and know that the material needs to be a higher strength one not just go with SA 336-F5?

 

[vesselfab]

the allowable stress values are listed

the code does not say

allowable stress at minimum tensiles

 

[jte]

starrproe-

No, test values cannot be used for new construction. In a FFS situation, yes. There are several reasons to use minimums, in my opinion concerns with future repairs and alterations are at the top of the list. When the time comes to replace a part of the shell, will the folks know that “ordinary” steel of the same spec and grade is insufficient and that they actually have to compare test results? Probably not. I’ve seen too many vessels with weak or lost paper trails to have any confidence that folks evaluating repair options 15 years from now will recognize the trap which has been set for them.

See also thread794-168056 for a related discussion.

And finally,

Subject: Section II, Part D (2001 Edition); Yield Strength of SA-724, Grade C
Date Issued: July 1, 2002

Question: Is it permissible to use values from material test reports in lieu of the design values
shown in Section II, Part D?

Reply: No.

jt

 

[CodeRef]

All the above responses deserve stars, but jte found the interpretation.....so a star for him...

FAQ731-376

 

[starrproe]

Thanks a lot to you all for your valuable conribution.