Hydroexpansion of Tube to Tubesheet Joint

[htman]

Does anyone have any experience with hydroexpanding (instead of a plain roll) heat exchanger tube to tubesheet joints? We currently roller expand our joints and still have leakage problems which forces us to then add a strength weld. I am hoping that hydroexpanding will eliminate a strength weld.

Any input would be great!

Thanks

 

[insult2injury]

I've not used 'hydroexpanding'; however, I have used explosive expansion for these connections. If done correctly, the explosive expansion works very well. Note that it cannot be used for all tube materials.

I2I

 

[gr2vessels]

Did you try a better roller expander, say a new one? Can you train a new operator? The roller expansion process is still working well in most of the places, without strength weld reinforcement.
Sorry, no experience with hydroexpansion.
cheers,
gr2vessels

 

[LSUME]

htman
You may want to take a look at ASME publication82-JPGC-Pwr-1 "Hydro expanding: The Current State Of The Art" by S. Yokell.
Like gr2vessels stated roller expanding is generally adequate. There are several factors that can affect joint integrity such as: cleanliness, tolerances, material (tube & tube sheet), ligaments, groove width/ depth, etc. The majority of end users will specify the required joint connection: parallel pin roll, seal weld, strength weld, groove or no groove. Do your leak problems occur with retube jobs only? Is it a more common on a certain metallurgy ( eg. 90/10 tubes on SS TS)? I would do more research on cause.
I'm far from an expert on tube joint connections, but these are some of my observations.

 

[unclesyd]

We used Hydroexpansion for a number of years with excellent results. I can't answer you specific question about the leaking after rolling as we always use 3 grooves, expand to the back of the tube sheet, polish the tubes, and seal weld. This is for all alloys and CS. At one time we built 17 Hast C heat exchangers and hydraulic expansion saved the day. At one time during the initial fabrication we though we may have to go to explosive expansion. The problem was that the Hast C work hardened form the mechanical rollers, both the taper and parallel rollers. Hydraulic expansion was used on both new and in reworking bundles. We also expanded tube sleeves in a very large brand new Hast C bundle prior to commissioning.
The largest tube we have hydoexpanded is a 1 1/8 14 ga 304L SS.

 

[unclesyd]

Forgot to add we hydroexpanded tubes to baffles in large cooler that was part of refrigeration system. This was to help control a vibration problem. We have done this on several units.