3/8" tube leaks on our tubesheets

[designer73]

We are currently experiencing leaks on our tubesheets, they are drilled to 3/8 diameter, and have copper tubes in those holes, we are using aire_tool expanding guns and expanding tools, but we cant pin point why we are having so many leaks, any suggestions? mayeb a specific rolling pattern? any suggestions?

 

[gr2vessels]

Check out the tube hole diameter requirements in the TEMA. You'll find specific tolerancies for the tubes and holes in the tubesheet. Other than that, there might be many other reasons, one of them seems to be the lack of experience with the fabrication of heat exchangers. If the tubes, tubesheet and holes are fabricated to the correct specification, then you might have to hire someone who has worked with expander before.
If everything fails, then you might consider to weld the tubes in the tubesheet, if the current set-up allows that.
Cheers,
gr2vessels

 

[vpl]

Are the leaks occurring at the joint where the tubes meet the tubesheet?

Do they occur on all the tubes, some of the tubes, a few of the tubes? Is there a pattern (such as they occur on the first tubes installed but not the last ones?

Patricia Lougheed

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[designer73]

yes, the tubes are leaking at the joint where the tubes meet the tubesheet... and on some of the tubes. and no, there is no pattern.

 

[speco]

Designer73,

I'm not sure what is the customary tube hole configuration with such tiny tubes. Are the tube holes in the tubesheets gooved with a circumferential groove to lock in the tubes?

That's normally done in larger diameter tubes, sometime with two or even three grooves.

Regards,

Speco

 

[rmw]

What is the tubesheet material? How many times have the tubes been re-rolled? How thick is the tubesheet? How deep into the tubesheet are the tubes rolled? How much wall reduction are the tubes rolled to? What diameter are the tube holes? What gage (or wall thickness) is the tubes? Are they straight tubes or u-tubes? If straight tubes, what is the shell material; shell length?

What about the service? Is it steady state or are you stressing the Hx and pulling the tubes out of the tubesheet?

Lots and lots of variables here and we will need more details to help.

rmw

 

[designer73]

The tubesheet material is 3/4" thick and is SA516-70. They are rerolled couple of times when necessary(we know re-rolling is an issue/overexpansion). The tubes are rolled to full roll(thickness of the tubesheet). 12% wall reduction (to the expanders recommended reduction). The holes are drilled to .378 diameter. and the tubes are at a .028 wall thickness. They are straight tubes straighted from a spool of copper. (C12200 (H80), SB75). We hydro test them to 500psi

 

[unclesyd]

Are you rolling into an as drilled hole or is it reamed?

All of the small odd oil coolers we retubed we had to go to reamed holes, in fact all Hx's we fabricated or retubed the holes were always reamed to size.

 

[designer73]

YES, all of our holes are reamed.

 

[brandonb73]

We are a repair company and faced a similar problem. Every time we would re-roll a tube, the tube next to it would leak. This is because the roller pushes on the ligaments between the tubes. The only way we were able to fix it was to re-roll all the tubes.