API 579/ASME FFS-Level III

[usecheijk]

Hi,
I have a doubt about alternating stress correction in API 579: ¿What about alternating stress correction in order to take into account mean stress (throught Goodman criteria for example)?, I didn't see this in Annex B1 of API 579

Thanks

Jack

 

[TGS4]

The S-N curves provided in Annex B1 already include a mean stress correction, with the assumption that the mean stress is equal to 2/3 yield (equal to the allowable stress). There is no need to adjust the curves further, except if you are in locations with welds. In which case, I would recommend the use of Structural Stress in B1.5.5.

Does this answer your question?

 

[usecheijk]

Thanks TGS4, very useful your answer.

But what happen if mean stress is not equal to 2/3 yield?

Jack

 

[TGS4]

There is no provision in the Code to adjust for that situation. The 2015 Edition of API-579/ASME FFS-1 will likely provide some guidance on that aspect.