Fatigue analysis with AutoPIPE Harmonic analysis command :
AutoPIPE does not have cyclic type of stress, therefore need to add a new code combination with H1 by itself for the RPM of the harmonic from a rotation compressor:
Combination Name = H1
Description = Harmonic Load case #1 for RPM = xxx .
Combination method = 1 Sum
Category = Occasional,
Case = H1.
Now, change the default "Allowable Stress" setting from "Automatic" (typical 1.33 *Sa) to 6500 psi. In this case, because a compressor is high cycle fatigue, API-618 mentions using a value of 26000 psi peak to peak. Therefore, use half of that which is 13000 psi peak to peak or to consider some SIF values typically would suggest using 13000/2 = 6500 psi for the Stress allowable.
Therefore, 26000/2 for peak to peak, /2 assuming a weld stress factor = 2, because the piping codes are typically based on SIF while fatigue values are typically based on stress concentration factors and there is a factor of 2 between SIF and stress concentration factors
AutoPIPE nuclear has a full fatigue analysis engine, however AutoPIPE Standard and Advance does not. This shortfall will be fixed in a future version of the application by enhancement CAE-CR-3268: Add fatigue analysis for ASME piping codes.
"Fatigue" load case