Expanding Tube to Tube Sheet Connections

Except for explosive expansion welding, I've never seen it done any other way than expand and weld. I would think expanding after welding would unnecessarily stress the weld. Often expansion is all that is needed for re-tubing condensers where some leakage is acceptable.

Are you re-tubing or sleeving?

- Weld first and expand-

There are possibilities of weld cracking during expansion.

You don't know whether the expansion is done to requirement or not (no testing is possible)

Removal of oil used during expansion difficult (hence weld integrity questionable)

Welding heat may affect expansion.

- Expand first and then weld

No oil so no defects

Tubes may be uniformly welded (maintaining uniform projection)

Weld cracks during expansion

welding may make expansion just a bit difficult (it will affect the tube shape and diameter)

So choice is left to you. Both the methods are used, based on the preferences and the processes developed for the same.

Ok thanks for your comments.

Despite the oil issue I think we should go for the expansion and then welding.

Pmoon it is a new exchanger with straight holes and no sleeves.

In fact there is another method available- which calls for pre-expand weld and then final expand.

Ah yes, the old expand-weld/weld-expand arguement

It always makes for a good discussion/heated battle.

The answer is - it depends.

One thing I will mention that has not been mentioned above is - there is a risk you can loose the seal from expanding first, then welding because of thermal expansion/yielding at temperature.

This discussion can lead the "chicken and egg" rhetoric.

Ask 5 different people this question and you will get 6 different answers.