lfbr000;
If twisted Hx tubing you mean damage caused by a circumferential rupture or failure where the tube whips around. This this could be caused by mechanical fatigue, stress corrosion cracking, fretting, etc.
I mean on a "KOCH" type heat exchanger with twisted tubes (aparently they dont have tube supports) what type of damage can you find in these tubes? Cracks, pits, erosion (proces) or any related to fabrication?
It is very much dependant on the process chemistry and the tube metallurgy. Be more specific on your application and you might get some good information.
We have used twisted tubes in several exchangers in different processes with good success. I don't beleive that a twisted tube has "common failure" modes that are any different that straight tubes. The problem is they are more difficult to inspect and obtain credible/repeatable results using typical tube examination techniques. This can be a very detrimental factor in an application where you know corrosion or tube damage is likely to occur.
I consider that the biggest factor for not using a twisted tube. If you have a process and MOC combination you know does not corrode the tube, then a twisted tube exchanger can be a suitable method to get more heat transfer out of a smaller foot print.
