HELP!!!Regarding Tee

What you are doing is making a "Stub-in" branch. You have a header pipe (or run pipe) and a branch pipe. This is allowed in the ASME 31 Code. There are two ways this is done. Both methods are commonlycalled a "Stub-in" but they are done in a different way.
One way is to cut the branch hole in the header pipe to the size of the outside diameter of the branch pipe. Then make the saddle cut of the branch pipe to fit the inside diameter of the header pipe. With this method the branch is inserted "into" the header pipe.
The second way is to cut the branch hole in the header pipe to the size of the inside diameter of the branch pipe. Then make the saddle cut of the branch pipe to fit the outside diameter of the header pipe. With this method the branch is sat "onto" the header pipe.
Both methods may be done with and without a reinforcing pad depending on the pressure and stress conditions.
With your case, considering the size of the header and the size of the branch I would recommend a full ring pad. The ring pad should be equal to (or greater than) the thickness of the header pipe and a minimum of 20" wide.

Just as there is with nominal pipe sizes and the actual pipe outside diameter there is a difference between the the nominal term for a pipe-to-pipe branch and the actual detail of execution.
It has been my experience that both are referred to as a "stub-in" but there are the two methods of the actual execution.
Your next question might be "When is one used versus the other?" The ASME B31.3 (and other) codes does not dictate when to use which. Most of the time the choice of the method ("in" or "on") is left up to the pipe fabricator (shop or field).

Riz_john,


I took this from eng-tip.com www.eng-tips.com/viewthread.cfm? ... 5&page=187 and I think it applies to your problem.


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Anything special that should be considered?

Well, yes, you will have to do the calculations shown in B31.1, paragraph 104.3.1.

The idea here is that if there is not enough "surplus" material surrounding the hole that you made to make the unreinforced fabricated branch connection (nee "stub-in"), you will have to provide a reinforcing pad (with a vent hole in it) to satify the requirements of B31.1. If you want to see some examples of how to do these calculations, look at Appendix H of B31.3 (unfortunately there is no such Appendix in B31.1) as it presents several "worked out" examples in a step-by-step format - really very informative.

If you have much internal pressure you should be prepared to provide additional reinforcement. If I were doing this retrofit, I would use sweep-o-lets (of the thickness appropriate for the pipe schedules)or at least weld-o-lets to make the branch connections (these welding fittings have "integral" reinforcing). I would also take some UT thickness measurements around the area to make sure how much of the original wall thickness is remaining after years(?) of corrosion. I would also perform MT or PT examination of the finished welds to make sure there are no cracks - also do a good VT to make sure there is no weld undercut.

Keep in mind that B16.9 welding tees are the first choice, then sweep-o-lets, then weld-o-lets, then fabricated REINFORCED branch connections, then fabricated UNREINFORCED branch connections. This is the reverse order in which we would expect to see fatigue failures.

I am sure some other of our colleagues can add some wisdom to this discussion.

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