Custom Carbon Steel Heat Exchanger U Tube Bundle for Oil Refinery | ASME U Stamp Manufacturer
Yuhong Group Co., Ltd. specializes in the design and fabrication of custom heat exchange equipment, pressure vessels, and air-cooled heat exchangers. Our product portfolio includes complete shell-and-tube heat exchangers, replacement tube bundles, U-bend tubes, finned tubes, and core components such as tube sheets, baffles, channel covers, and flanges. This description covers our custom carbon steel U-tube bundle assemblies — engineered for oil refinery services and manufactured under ASME U Stamp certification.
Product Overview
The U-tube bundle is the primary heat transfer component in shell-and-tube heat exchangers. Unlike fixed tubesheet designs, the U-tube configuration features tubes bent into a U-shape with both ends secured into a single tubesheet. This allows each tube to expand and contract independently under thermal cycling, eliminating the need for expansion joints or floating head mechanisms.
Our custom carbon steel U-tube bundles are designed, fabricated, and inspected in accordance with ASME Boiler and Pressure Vessel Code Section VIII, Division 1, and bear the ASME U Stamp — certifying compliance under authorized inspector supervision. Additional design and fabrication criteria follow TEMA Standards (Tubular Exchanger Manufacturers Association) where applicable.
Key Design Parameters
- Design pressure: Up to 206.8 bar (3,000 psi)
- Design temperature: Up to 450°C (tube side)
- Tube diameter: 3.2 mm to 76.2 mm (⅛" to 3")
- Bundle diameter: Custom, typically 500 mm to 3,000 mm
- Tube length: Up to 20 m
Main Components and Material Specifications
| Component |
Material Standard |
Grade / Specification |
Key Properties |
Typical Dimensions |
| U-Bend Tubes |
ASME SA179 / ASTM A179 |
Cold-drawn seamless low-carbon steel |
Tensile ≥325 MPa; Yield ≥180 MPa; Elongation ≥35%; Hardness ≤72 HRB |
OD: 3.2 - 76.2 mm; WT: 0.71 - 3.40 mm |
| Tubesheet |
ASME SA516 Gr.70N |
Normalized carbon steel plate |
Tensile 485-620 MPa; Yield ≥260 MPa |
Thickness: Custom, typically 40-150 mm |
| Baffle Plates |
ASME SA36 / SA516 |
Carbon steel structural plate |
High-strength structural carbon steel |
Custom-cut to bundle diameter |
| Tie Rods & Spacers |
ASME SA36 / SA193 |
Carbon / alloy steel |
Per design requirements |
Custom lengths |
| Channel / Cover |
ASME SA516 Gr.70 |
Carbon steel plate |
Per ASME VIII Div.1 |
Custom dimensions |
Note: Material grades may be varied per client specification and process conditions. Alternative tubesheet materials include ASME SA266 Gr.2N, SA336 F5/F11/F22, and SA350 LF2 CL1 for low-temperature service.
Inspection and Testing Requirements
All tube bundles undergo mandatory inspection and testing in accordance with ASME Section VIII Division 1 and the documented Quality Control System:
| Test / Inspection |
Standard / Method |
Purpose |
| Raw Material Inspection |
ASME SA-20 / MTR verification |
Verify chemical composition and mechanical properties |
| Tube Flattening Test |
ASME SA179 / ASTM A179 |
Verify ductility and soundness of seamless tubes |
| Tube Expansion Test |
ASME SA179 |
Verify tube-to-tubesheet joint integrity |
| Non-Destructive Examination (NDE) |
Ultrasonic Testing (UT), Penetrant Testing (PT) |
Detect surface and subsurface defects in tubesheet forgings and welds |
| Hydrostatic Test |
ASME Section VIII UG-99 (1.3* MAWP minimum) |
Verify pressure integrity of tube-to-tubesheet joints and tube wall strength |
| Dimensional Inspection |
Per fabrication drawing and TEMA tolerances |
Verify tube layout, baffle spacing, and overall bundle geometry |
| Welding Procedure & Performance Qualification |
ASME Section IX |
Qualify all welding procedures (PQR) and welders (WQR) |
| Final Documentation |
ASME Form U-1 / U-2 Data Report |
Certified record for National Board registration |
Note: All testing is witnessed by the ASME Authorized Inspector and available for third-party inspection upon request.
Application Scenarios in Oil Refineries
Custom carbon steel U-tube bundles are specified for a wide range of refinery process units where thermal differentials are significant and tube-side fouling requires periodic bundle removal for cleaning:
- Crude Oil Preheaters — Preheat crude oil before atmospheric distillation using recovered heat from product streams
- Refinery Condensers — Condense overhead vapors from distillation columns
- Feed Water Heaters — Preheat boiler feed water using waste heat
- Reboilers — Provide heat input for fractionation tower bottoms (thermosyphon or kettle type)
- Gas Coolers — Cool refinery fuel gas, hydrogen, and other process gas streams
- Intercoolers / Aftercoolers — Cool compressed process gas between compressor stages
- Heat Recovery Units — Recover thermal energy from refinery off-gas and product streams
The removable bundle design allows for mechanical cleaning, visual inspection, and bundle replacement without disturbing shell-side piping — critical for refinery turnarounds and maintenance planning.
Technical Advantages and Customization
Thermal Expansion Management
The U-tube design inherently accommodates differential thermal expansion between tube and shell sides. Each tube bends independently, eliminating axial stress that would otherwise require expansion joints in fixed-tubesheet designs. This is particularly valuable in refinery services where temperature differences can exceed 100°C between inlet and outlet.
Single Tubesheet Construction
With only one tubesheet, the design reduces shell-side leakage paths compared to floating head designs, and simplifies the tube-to-tubesheet joint inspection.
Removable Bundle for Maintenance
The tube bundle can be withdrawn from the shell for cleaning, retubing, or replacement — reducing downtime during planned maintenance.
Custom Engineering Capabilities
- Custom tube layout and baffle spacing to match process thermal and hydraulic requirements
- Material selection per client corrosion and temperature specifications (carbon steel, alloy steel, stainless, duplex, titanium)
- Tube-to-tubesheet joints: roller-expanded, strength-welded, or expanded-and-welded per design
- Full material traceability with certified Mill Test Reports (MTRs)
- ASME U Stamp with National Board registration
- Optional coatings, cladding, or corrosion allowance per client specification
Frequently Asked Questions / Technical Considerations
Q: Why specify a U-tube bundle instead of a fixed tubesheet design for refinery service?
A: U-tube bundles eliminate thermal stress caused by differential expansion between tubes and shell — a common failure mode in refinery units with large temperature differentials. The single tubesheet design also reduces the number of potential leak paths.
Q: What is the minimum U-bend radius?
A: Per ASME and TEMA standards, the minimum centerline bend radius is typically 2* the tube outside diameter (R ≥ 2* OD). This ensures bend quality and prevents excessive wall thinning. Our CNC mandrel bending maintains wall thinning ≤ 12% (ASME limit: ≤ 17.5%).
Q: What documentation is provided with an ASME U Stamp bundle?
A: Each U-tube bundle is supplied with the ASME Manufacturer's Data Report (Form U-1 or U-2), certified Material Test Reports (MTRs) for all pressure-retaining components, NDE reports, hydrostatic test records, and welding procedure / welder qualification records.
Q: Can the bundle be designed for sour service (wet H₂S)?
A: Yes. For refinery sour service applications, material selection follows NACE MR0175 / ISO 15156 requirements with appropriate hardness controls and weld procedure qualifications. Carbon steel grades can be specified with HIC-resistant properties upon request.
Q: What is the typical lead time for a custom U-tube bundle?
A: Lead times range from 45 to 150 days depending on bundle complexity, material availability, and shop load.
