Maximum allowable stress value for ASME-VIII-1 material
Maximum allowable stress value for ASME-VIII-1 material
(OP)
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
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





RE: Maximum allowable stress value for ASME-VIII-1 material
RE: Maximum allowable stress value for ASME-VIII-1 material
the code does not say
allowable stress at minimum tensiles
RE: Maximum allowable stress value for ASME-VIII-1 material
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: Allowable stress for API 5L materials in ASME VIII calculations. for a related discussion.
And finally,
jt
RE: Maximum allowable stress value for ASME-VIII-1 material
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RE: Maximum allowable stress value for ASME-VIII-1 material