Question:

AutoPIPE supports CSA N289.3 calculations for ASME Section III, NB Code. However, CSA N289.3 states that “The seismic fatigue usage factor shall be determined from Equations 11 and 14 in NB-3653.2 and NB-3653.6 of the ASME BPVC, Section III, Division 1. This fatigue factor is added to the fatigue usage factor associated with Levels A and B load ranges to obtain the cumulative fatigue usage factor.”

It appears that AutoPIPE calculates a separate fatigue usage factor under Level C but does not automatically combine it with the Level A and B fatigue usage factors to determine the cumulative usage factor required by CSA N289.3.

Could you please confirm whether this understanding is correct?

Answer: 

After reviewing code sections (NB-3653.2 and NB-3653.6 of the ASME BPVC, Section III, Division 1). There is no specific mentions of service level C being added to service level A or B. 

After some additional checking in AutoPIPE there doesn't appear to be a path in the program to incorporate level A and B usage factor with N289.3. In fact, Equation 10 doesn't even allow for the same load combination in equation 10 for N289.3 other than level A or B. 

Finally, Level A/B and Level C usage factors are summed up in the output report "Cumulative Usage".

Usage Factor Summary Table

This table summarizes all the critical Load Set pairs with corresponding number cycles.

Stress Summary Table

The final cumulative usage factor from the fatigue report is added to the stress summary table as shown.