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.   

See Also

Bentley AutoPIPE

External Links

Bentley Technical Support KnowledgeBase

Bentley LEARN Server

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