Roller Expanding Duplex Tubes in a 304ss Tubsheet

[uglyspec]

Hello,

Has anyone had success roller expanding 2205 duplex tubes in a 304ss tubesheet? (tube yield is approx. 60k / tubesheet yield approx. 30k)

Tubeside gas has some hydrogen content.

Thanks!

 

[SnTMan]

You're not gonna be happy. If you can get a good roll on a given tube, rolling subsequent tubes will likely loosen it. I'd say you need to weld.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[metengr]

Do the 304 tubesheet holes to accept the duplex tubes contain serrations? If not, welding is the only option. You would be best served by requesting a tube to tubesheet mockup to evaluate pull out strength, and decide your best option going forward.

 

[SnTMan]

...or, is it feasible to change TS material?

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[uglyspec]

Metengr - Tube holes would be double grooved. I was also going to strength weld the tube joint.

SnTMan - I could change the tubesheet to 2205 duplex but it would exceed the job budget.

If the roll quality is that poor, is it even worth rolling?

 

[SnTMan]

Likely not. Don't know what kind of unit you've got, but if you are counting on any strength from the joint, review Appendix A. You will likely need to qualify the joint.

If you just need leak-tight welding should do it.

RE The Budget: I always want to say things like "OK, so a 2205 TS is not in budget. Is forever chasing roll-leaks (and not getting anywhere) in budget?"

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[EdStainless]

Thin wall tubes? And no grooves, use small serrations.
If the tubes are heavy wall switch to 2205 tubesheet.
It can be done but the rolling window is very tight, slightest over-roll and they will leak, and nearly no chance to re-roll.
Of just roll to contact and then seal weld.
I agree with Tinman, chasing leaks will cost a lot more than changing tubesheets.
Today 316 and 2205 are close in price. Suck it up and do it right.

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P.E. Metallurgy, Plymouth Tube

 

[SnTMan]

uglyspec, made my last post before noticing...

If you are welding anyway, probably no need to change TS material. Roller expanding likely not worth the effort. You should be OK I'd think.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[EdStainless]

Even if they are welding they will need to roller expand some.
The design likely is relying on the tubesheet supporting the ends of the tubes.
I have seen some ugly fatigue failures in tubes that were not rolled (ones that were missed in a bundle).

We see people rolling Sea-Cure tubes (75ksi Yield, 90ksiUTS) into Muntz metal tubesheets (20ksi Yield, 50ksiUTS) but these are thin tubes (0.0208" wall) and it takes great care (more labor and control than normal).

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P.E. Metallurgy, Plymouth Tube

 

[metengr]

The duplex tube to 304 ss tubesheet joint can be designed as a light roll/strength weld joint and achieve good results. Again, make sure you have a tube to tubesheet weld joint qualified using a mock-up.

 

Hydrogen is very slippery.
You will need a well-developed welding procedure; i.e., more than just enough to pass a WPQR, and close control of quality throughout the job.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."