| Applies To | |
| Product(s): | AutoPIPE |
| Version(s): | ALL; |
| Area: | Reporting |
| Date Logged & Current Version | Oct 2023 23.00.00.230 |
Problem:
In a model set up Service Level A and B summaries. For equation 10, the Service Level A summary includes only Service Level A load cases, and the Service Level B summary includes only Service Level B load cases along with the corresponding number of cycles in each case. For the Service Level A summaries, the output shows which load case pair from my Level A summary the results come from. Therefore, this summary is based on only the load cases I have included in my Service Level A summary.
However, for my Service Level B summary, the results also show that only the load cases included in the Service Level B summary definition are used. However, ASME NB-3654, "Consideration of Level B Service Limits", explicitly states that
"All load sets, including Level A and Level B Service Loadings, shall satisfy the fatigue requirements of NB-3653.1 through NB-3653.6 and the thermal stress ratchet requirement of NB-3653.7".
Therefore, I don't think that the full ranging required for Service Level B (i.e. including ranging with the Service Level A load cases as well) is being included in the calculation.
Furthermore, the output gives separate fatigue summaries for each stress summary, which are then summed to give the Cumulative Usage Factor (CUF) at each location (i.e. total CUF = CUF for Level A + CUF for Level B at each node). This shows that for the Level B summary, only the Level B cases are being considered, which seems to contradict NB-3654. I suppose a workaround would be to include the Service Level A cases in the Level B summary as well. However, this means that the CUF will be incorrect as the Level A cases will contribute to both the Level A and B summaries (although the result will be available for just the Service Level B part of the CUF).
Lastly, the help says that there is a limit of 50 equation 10 entries per stress summary. If I have to combine my Level A and B summaries, I will have more than 50 transients to consider.
Is there a way to include more than 50 cases per summary?
Solution:
The stress summaries are completely independent of each other, so they only consider the load cases you provide. You should include your Level A and B load cases in Level B stress summary to satisfy NB-3653.1 through NB-3653.6.
The limit on Eqn 10 is 50, so you will have to conservatively combines some transients. This should be possible if you have a number of very similar transients as you have stated, and may have been something to consider when defining them.
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See Also
ASME BPV-III-1-ND, AutoPIPE Nuclear Piping Code FAQ