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STP-NU-037-2013 pdf free

The value of Sm is defined as“the lower of two stress intensity values, Sm (time-independent) and S,(time- dependent).”Finally, the stress S, is defined as the“expected minimum stress -to-rupture strength” and pertains to base metal, although the definition is provided in the paragraphs of NH-3221 dealing with criteria for weldments. At 100,000 hr, Skmin and S, should be equivalent.
With respect to the assessment of the consistency in the current operating condition allowable stresses, the current S values in ASME II-D Tables lA and 1B should agree with the So values in ASME II-NH Table 1-14.2, as mentioned above, since they are intended to be identical. However, no direct comparisons are possible between the stresses based on the criteria in ASME Section II-D and Section II-NH without knowing the criteria that controls the stress allowables for specific temperatures and times in the two Codes. Both Codes include the minimum stress-to rupture strength criterion, although ASME II-D Tables 1A and 1B call for a factor of 0.80 on stress while ASME II NH calls for a factor of 0.67 on stress. On the other hand, if 0.80 Semin controls the S values in the ASME II-D tables, then 0.80 S, for 100,000 hr in ASME II-NH Table 1-14.6 should agree with the S and So values. If FawgSReavg controls the S values in the ASME II-D tables and the So values in ASME II-NH, then 0.80 S, for 100,000 hr in ASME II-NH Table 1I-14.6 should be greater than the S and So values.
This report (1) provides an evaluation of the consistency of the stress allowable in ASME INH with the ASME II-D values for each of the five materials currently covered by ASME II-NH; (2) briefly reviews the databases that were used to establish or recommend stress allowables; and (3) reviews the expansion of the databases for the materials.STP-NU-037 pdf free download.

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