Tie-in on expansion loop

[SWMechanical]

I am doing a piping design. One of the branchs has to come off from the expansion loop of the header. Does anybody know if it is good to have a tie-in on the expansion loop?

Thanks,

 

[BigInch]

We'd do a lot better and waste a lot less time, if we just answered the question. (Mayda) For all the examples that you can make up that work, I can make up an infinate number that don't. The facts actually are that no details of the piping config under discussion were given and you have no basis for a made up solution with a 50 ft distance between anchors, and an apparently symetrical loop, showing me that it can work, just as there is no basis for any examples that won't work. Without any other basis to go on, except the FACTS that the OP has stated, its not a good idea and it can't be justified by anything presented here. End of FACTS. Now, being that the OP question has been answered at least once, if not twice, I'll leave you guys to hash out the rest of the infinite possibilities by yourselves. Careful with the lunar gravitational constant.
Enjoy.

I have not failed. I've just found 10,000 ways that won't work."-Edison “If Edison had a needle to find in a haystack, he would proceed at once to examine straw after straw until he found the object of his search. I was a sorry witness of such doings, knowing that a little theory and calculation would have saved 90% of his work.- Tesla

 

[IFRs]

Ceaser gives idealized results. Field conditions are seldom ideal - friction can vary, pipe may squirm, internal stresses from welds or seams may unbalance a pipe's stress distribution, pipe has manufacturing tolerances, field hands may bend, stress, rotate, hammer pipe, etc. It is a great tool but don't kid yourself that it is all knowing. In general, as many have posted, adding a tap to a loop is bad parctice. Then again, maybe the loop was intended for 600 degree service and the service is ambient. Maybe the lines were designed for 600 psi and the service is 100. Only a fully informed and highly qualified and experienced engineeer or team can justify violating industry standard practice.

 

[Gator]

But if you put a flexhose into the loop it might work! Sorry, just making fun of one "design" I once saw.

 

[StressGuy]

I'll have to take some middle ground here, myself. I do agree with the notion that the first response to such a proposal would be "Can we connect that somewhere else?".

In doing so, it needs to be made clear to the owner/project team that you are going to have to effectively reanalyze the whole header (at least back to the loop anchors) in order to assess the impact of the new branch on the loop.

But, I've seen enough existing units that have been stuffed so full of pipe from various expansions and debottlenecking efforts, that the loop may be the only exposed place left to connect to. If so, then it does need to be considered very carefully.

Things get even more complicated if the tie-in is a "hot tap."

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

"All the world is a Spring"

All opinions expressed here are my own and not my company's.