U-Tube vs Floating Head Exchangers

Into the second tubesheet, the floating head cover and backing ring, the rear shell cover, and the machining that lets all of it seal while it moves. None of those parts add heat transfer surface; they exist so the tubes can be straight. On a clean tube-side duty you are buying a rear assembly that will be gasketed, bolted and then never opened. The shell cover alone is often the heaviest single component handled during maintenance. A U-tube bundle has one tubesheet, one head and a shell that needs nothing behind it.

If chemical cleaning restores the clean-condition pressure drop and outlet temperature, you do not need rodding and a U-tube serves the duty. Scale, biological film and most organic deposits respond to circulated chemicals. What does not respond is hard, bonded material such as coke, polymer or calcium sulfate laid down above it's solubility limit, and fibrous or particulate plugs that physically block tubes. If you have chemically cleaned an existing exchanger and still see high tube-side pressure drop afterward, that is the signature of a mechanical cleaning requirement, and it points to floating head.

Yes, because the floating head gasket sits inside the shell, so a leak mixes the two streams internally with nothing dripping outside. The first sign is usually a chemistry change: conductivity rising in condensate, process fluid appearing in cooling water, or a tube-side outlet temperature that no longer matches the shell-side heat balance. On a U-tube unit every gasketed joint is at the front head on the outside, so a leak shows as a visible weep at the flange. For hazardous or corrosive shell fluids that external visibility is the argument HeatX makes most often.