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Quotes - Engineering - Sales| PRODUCT | STYLE | TEMA TYPE | BUNDLE |
| U-Tube Heat Exchanger | U-Tube, single tubesheet | BEU / AEU / BKU | Removable |
High-Temperature U-Tube Heat Exchangers
Unlimited Differential Expansion
When shell and tubes run at very different temperatures they try to change length by different amounts. In a fixed tubesheet exchanger that difference has nowhere to go, so it becomes stress in the shell, the tubesheet and the tube joints. The standard remedy is a bellows expansion joint in the shell, which works and which introduces the most fatigue-sensitive component in the whole assembly.
A U-tube bundle removes the problem rather than accommodating it. Each tube is fixed at one end and free at the bend. It grows, the bend radius shifts slightly, and no load is transmitted anywhere. Tubes can even run at different temperatures from one another without consequence.
Cycling is the real test. Steady high temperature is manageable in several designs. What separates them is repeated heating and cooling: startup, trip, blowdown, batch operation. Those cycles fatigue an expansion joint and they fatigue a fixed tube joint. A U-bundle simply moves.
Thermal fluid systems have their own rules. Film temperature, not bulk temperature, degrades hot oil, so tube-side velocity and heat flux are selected to keep the film within the fluid supplier's limit. Get that wrong and the fluid cokes on the tube wall, which shows up as fouling that cleaning will not fix.
Typical Construction
- Expansion accommodation: Unlimited; no expansion joint required
- Typical fluids: Thermal oil, hot water, steam, process gas, molten media
- Film temperature control: Velocity and flux selected to the fluid supplier's limit
- Thermal cycling: Tolerated by design; each tube expands independently
- Materials: Carbon steel, low alloy, 304L/316L, higher alloys as required
- Insulation: Jacketed or lagged; personnel protection where specified
- Supports: Sliding and fixed saddles sized for shell growth
- Gaskets: Selected for sustained temperature, not just design point
- Codes: ASME Section VIII Division 1, TEMA R, B or C
- Bundle: Removable for shell-side cleaning and inspection
High-Temperature U-Tube Heat Exchangers
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High-Pressure U-Tube
High-pressure U-tube heat exchangers. Why the U-tube wins above the range of a floating head seal, D-type front heads, heavy tubesheets and hydrostati
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Corrosion-Resistant U-Tube
Corrosion resistant U-tube heat exchangers in duplex, Alloy 20, Hastelloy, AL-6XN and titanium. Alloy selection by attacking species, plus NACE limits
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Sanitary U-Tube
Sanitary U-tube heat exchangers in 316L with tri-clamp connections, drainable geometry and removable bundles. Built for 3-A duty and CIP circuits.
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Startup Is Usually the Governing Case
The worst thermal condition an exchanger sees is rarely steady operation. It is the moment hot fluid meets a cold bundle, or cold fluid hits a hot one after a trip. Those transients produce differential expansion far beyond anything in the process datasheet.
Tell us how the unit is started, how fast, and what happens on a trip. A U-tube bundle tolerates all of it, but the shell supports, the nozzle loads and the gasket selection still have to be designed for it.
Support Design at Temperature
A hot shell grows, and if both saddles are fixed the shell will find another way to relieve the load, usually through the nozzles and into the piping. Standard practice is one fixed saddle and one sliding, with slotted holes sized for the calculated growth.
This is a detail that gets lost between the exchanger supplier and the installing contractor more often than any other. We will state the expected growth and the required support arrangement on the drawing so it does not have to be inferred.
