PetroStreet

What are the factors that a U-tube bundle is selected over fixed tube one?
I know about accommodating expansion during high temperature applications, bundle is removable, what else?

Clean service or easily cleaned conditions on both tube side and shell side is also an important consideration when selecting U-tube bundle.

There is a cost advantage as well. U-tube exchangers are often cheaper because of only one tubesheet (fixed has two). There are no expansion joints needed (which are expensive + failure-prone). Fabrication is simple, so if service allows, it can save you on budget.

U-tubes are more flexible, better at absorbing vibration.
Less risk of tube-to-tubesheet joint failure, fatigue cracking. Important in high velocity services, two-phase flow

Fixed tubesheet exchangers often need expansion joints which is a weak component, quite expensive, and has got a risk of failure.
U-tube avoids this completely which means more reliable long-term operation.

I would like to summarize here that one can select:
U-TUBE when:
High differential Temperature / thermal cycling
One side clean (usually tube side)
Need removable bundle
Budget matters
Want to avoid expansion joints
and FIXED TUBESHEET when:
Both sides need cleaning
Low temperature difference
Simpler maintenance needed