Hello friends.

This is my first post on CAESAR II discussion forums. If this query or similar query has been discussed before, please provide me reference of discussions.

Background:-
PENG's book states that Code (B31.3) SIF are only one half of the theoretical SIF(SIF due to circumferential shell bending stress) and hence the calculated stress range is only one half of the theoretical stress. The reason stated is that the SIF's are based on girth welded pipe as unity and since girth weld also has a SIF of almost 2 in comparison to a polished tube, so the SIF of other components has been reduced to half.
To account for this, the allowable stress range has been adjusted accordingly. However, because only the local peak stress and shell bending stress are halved, the difference between code stress and theoretical stress affects only the final fatigue evaluation.

Query:- The "f" factor will account for final fatigue evaluation and since the "f" factor's value is coming from fatigue curve of a girth welded pipe only so we can assume that allowable stress(Stress range ) has been accounted accordingly.
Is my understanding correct?

Neeraj
"The harder I work, the luckier I become"

Guess not, as far as I know the basic concept of those two factors are not related whatsoever.

As Mr.Peng stated, using Code SIF is fine as long as your stress is within the stress range.(which will be reduced by "f" or not)

About the theoretical SIF, you may find this post interesting.

http://65.57.255.42/ubbthreads/ubbthreads.php?ubb=showflat&Number=5545&page=1&fpart=1

Hello Caesar III.

Thanks for sharing your experience and providing a reference to superb post.

My query is answered. Code's SIF are actually half the theoretical SIF value but Code's allowable stress(allowable stress range) is quite less is comparison to Section III(nuclear piping) where theoretical SIF's(or rather stress indices) are used.

"f" factor is not related to this SIF's.

Thanks

Could not stop myself from sharing an excellent article on Code SIF by Mr. Ron Haupt:-
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http://www.sstusa.com/pipe-stress-article-piping-sif.php
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Thanks