Try to get a hold of AWS Welding Journal 2000, Vol. 79. There is a three-page article in there titled Improving the Reliability of Tube-to-Tubesheet Joints written by Harry W. Ebert.

Ebert discussed four types of tube-to-tubesheet joints:

1. Roll or expand only (without grooves)    - strength is poor    - leak resistance is poor    - tube replacement is very easy    - application is limited (i.e. low pressure water or air)2. Roll or expand only (with grooves)    - strength is limited (can be improved by explosive expansion)    - leak resistance is limited (can be improved by explosive expansion)    - tube replacement is easy    - applicable for low stresses and low consequences of leakage3. Roll or Expand and Seal Welded (with grooves)    - commonly used by the oil industry    - strength is limited (can be improved by explosive expansion)    - leak resistance is good (can be improved by explosive expansion)    - fabrication problems are frequent    - tube replacement is more difficult    - applicable where stresses are not too high and where risks of leakage is low4. Strength Weld (no grooves required)    - full strength    - leak resistance is good (maximum leak resistance can be achieved if two pass welds are used)    - some fabrication problems, esp. if there are grooves    - tube replacement is more difficult, esp. if there are grooves    - applicable where mechanical and thermal stresses are high and leakage is unacceptable