Roller expansion of titanium tubes 1

[SHARMANA]

Hi everyone,
We have a requirement of retubing of titanium 0.6 thk tubes, tubesheets being alu bronze (SB171 C61400). Expansion joint is with double grooves. Is this combination of tube (harder material) with tubesheet (softer material) a recommended one? Is there any literature available for % of expansion in these case and recommended process of expansion.
Thanks.

 

[MJCronin]

You should search this site for similar questions before you post. Have you seen this one ?

https://www.eng-tips.com/viewthread.cfm?qid=324933

What was the original material of your tubes ?

What information did the titanium tube vendor give you ?

See page 25 and 26 of this guideline ....

https://www.timet.com/assets/local/documents/technicalmanuals/DesignandFabrication.pdf

Tell us more about your HX and the service ... Is this HX a Steam Surface Condenser -- part of a power plant ?

Is the liquid media seawater ?

Can you provide datasheets or drawings of the tubesheet ?

MJCronin
Sr. Process Engineer

 

[EdStainless]

In this case the grooves just reduce the contact area, don't use them. If they are already there fine.
Fortunately these will be thicker tubesheets.
A rough hole ID can be very helpful.
When they clean the tubesheet holes they will need to gauge every hole to find any that are too oversized or out of round.
These will either need to be abandoned or reamed out and sleeved.
This is actually done a lot in power plants.
Make the service provider supply references. And check with them.
You must build and test mock-ups to get the rolling torque correct. You will want to roll very near to the minimum that will work.
When you hydro and find leaks you can re-roll those just a little harder. But you have to be careful if you over-roll them you will have 7 tubes that leak (the original and all of its neighbors because you deformed the tubesheet).
You cannot use apparent wall thinning since it will be near zero and exceeding difficult to measure.
The whole trick is to never cause yielding in the tubesheet.
You will also need to roll as near the edges of tubesheet as you reliably can. I have seen them use 1/8" in from the front and 1/4" from the back.
I presume that this is a re-tube.
So you are going to be staking the Ti tubes between each support plate for vibration resistance?
I have seen Superferric SS tubes put into Muntz tubesheets (about 5x difference in yield strength), so your case isn't as difficult.


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P.E. Metallurgy, consulting work welcomed

 

[MJCronin]

SHARM ....

It is unfortunate that you are reluctant to share any specific information and have decided to drop this thread. This is a very typical MO from that ocean of third-world newbies out there...

More information = better answers

There is a complex and sad history about re-tubing of brine/seawater heat exchangers with titanium materials. The power plant industry has been developing methodologies and techniques since the 1970s. You must understand that your most significant challenge will not be the rolling methodology and integrity of the tubes

It will be something else ...

But your MBA boss seems to have convinced you not to take advantage of the free expertise available at eng-tips ...

I am sure that he will not blame you when the tubes leak ....

Ruined titanium 22 meter tubes are very expensive

Good Luck



MJCronin
Sr. Process Engineer

 

[MJCronin]

Good Luck SHARM,

Your biggest headache will not be tube rolling...

https://www.neotiss.com/images/publications/pdf/thin-wall-titanium.pdf

https://www.plymouth.com/wp-content/uploads/2017/03/Sel-Tubing-Mat-for-Pwr-Gen-_SW-Chem_-1.pdf

MJCronin
Sr. Process Engineer