U-tube heat exchangers use tubes bent into a U-shape, eliminating the need for a floating head and allowing free thermal expansion. However, the U-bend region is susceptible to erosion, vibration fatigue, and stress corrosion cracking, making tube replacement a key maintenance activity.
AQ Process Systems sources and exports pre-bent U-tubes in all standard metallurgies, matched to the original bend radii. We also supply tube sheets, baffles, tie rods, channel components, and complete re-tubed bundles for U-tube exchangers used in refineries, petrochemical plants, and power stations.
All U-tubes are supplied with post-bend heat treatment (where required by material specification) and dimensional inspection to ensure correct bend radius and leg length for your specific tube layout.
| Component | Specification | Description |
|---|---|---|
| U-Tubes | ||
| U-Bend Tubes | CS, SS 304/316, duplex, Ti, CuNi, Inconel | Pre-bent to OEM radii | Pre-bent U-tubes matched to original bend radius, leg length, and material, with post-bend heat treatment. |
| Straight Tube Sections | For partial re-tubing | Matched OD & wall | Straight tubes for replacing the straight-leg portion when the U-bend is not accessible. |
| Complete U-Tube Bundles | Re-tubed assemblies | Hydro-tested | Complete re-tubed U-tube bundles with new tubes, baffles, and supports, ready for installation. |
| Tube Sheet & Baffles | ||
| Tube Sheets | SA 516, SA 240, clad | Single tube sheet (U-tube type) | Replacement tube sheets, drilled to OEM tube layout pattern with correct tube pitch and ligament. |
| Baffle Plates | CS or SS | Segmental, double-segmental | Shell-side baffle plates, drilled and trimmed to the correct tube layout and shell diameter. |
| Tie Rods & Spacers | SS or CS | Complete sets | Baffle support tie rods and spacer tubes, maintaining correct baffle spacing throughout the bundle. |
| Tube Support Plates | At U-bend zone | Anti-vibration | Support plates in the U-bend region preventing tube vibration and fretting wear. |
| Channel & Gaskets | ||
| Channel Covers | CS or SS | Flanged (TEMA A) or bonnet (TEMA B) | Stationary-end channel cover or bonnet, providing access to tube ends for inspection and plugging. |
| Channel Gaskets | Spiral wound, kammprofile | ASME B16.20 | Channel cover and shell flange gaskets, replaced during every bundle pull or channel opening. |
| Pass Partition Plates & Gaskets | CS or SS plates | Graphite or PTFE gaskets | Tube-side pass partition plates and their gaskets for multi-pass channel configurations. |
| Nozzles & Protection | ||
| Nozzle Connections | Flanged | CS or SS | Inlet/outlet | Shell-side and tube-side nozzle connections, replacement or upgrade for corroded nozzles. |
| Impingement Protection | Rods, plates, or baskets | Shell inlet zone | Impingement protection devices at the shell inlet nozzle, preventing direct jet impingement on tubes. |
Parts are matched to OEM material specifications and dimensional tolerances. Please provide the equipment manufacturer, model number, and serial number (if available) for precise part identification. Mill Test Certificates (MTC) supplied with all tube materials per EN 10204 3.1.
U-tubes are most vulnerable at the bend region due to several factors: thinning of the outer wall during bending, residual stress from the bending process (which can cause stress corrosion cracking in susceptible materials like SS 304/316 in chloride environments), erosion from high-velocity tube-side flow at the bend, and vibration fatigue if the U-bend zone lacks adequate support. Post-bend stress relief heat treatment and proper support plates mitigate these risks.
Replacing inner U-tubes is difficult because they are nested, removing an inner tube requires removing all outer tubes first. Typically, only the outermost rows can be individually replaced. For significant tube failures, a complete re-tube is usually more practical and cost-effective. Leaking tubes can be plugged (at both ends in the single tube sheet) as a temporary measure.
We supply U-tubes bent to any required radius, from tight bends (minimum 1.5x tube OD) to large-radius bends. Each tube is bent to the specific radius required by its row position in the tube layout. Bending is performed cold (for most carbon steel and stainless steel) or hot (for thick-walled alloy tubes), with post-bend heat treatment as required by ASME or material specification.
Yes. We supply factory re-tubed U-tube bundles with new tubes (bent and installed), new baffles and tie rods, and new tube-to-tubesheet joints (expanded and/or welded). Bundles are hydrostatically tested and ready for lift-in installation during your turnaround.
U-tube exchangers have only one tube sheet (vs two for fixed-tubesheet), and the bundle can be pulled for cleaning and inspection. This makes maintenance easier and reduces the gasket inventory. However, the inner tubes cannot be mechanically cleaned or individually replaced. The spares inventory for U-tube exchangers focuses on tubes, baffles, and channel gaskets, whereas fixed-tubesheet exchangers need expansion joints and two sets of tube sheet gaskets.
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