Seamless Tubes For High-performance Heat Exchangers
U-bent heat exchanger tubes ensure efficient heat transfer and corrosion resistance in demanding applications.
Seamless Tubes For High-performance Heat Exchangers
U-bent heat exchanger tubes ensure efficient heat transfer and corrosion resistance in demanding applications.
U-Bent Heat Exchanger Tubes are seamless or welded tubes bent into a U-shape, designed to optimize heat transfer in heat exchanger tubes and boiler tubes. Conforming to standards like ASTM A179, A192, A213, and ASME SA213, these tubes are critical for industries such as petrochemical, power generation, chemical processing, and HVAC, where corrosion resistance and pipeline durability are essential. The U-bend configuration acts as a thermal expansion absorber, minimizing stress and eliminating the need for additional expansion joints.
Available in materials like low-carbon steel, stainless steel (304, 316, 347H), and alloy steels, U-Bent Heat Exchanger Tubes are manufactured through cold-drawing or hot-rolling processes, followed by precise mandrel bending to maintain uniform wall thickness and prevent ovality. Outer diameters range from 6.35mm to 50.8mm, with wall thicknesses from 0.8mm to 3.4mm and bend radii from 1.5D to 1500mm. Post-bending heat treatment, such as solution annealing (1010-1193°C for stainless steel) or stress relief (≥650°C for carbon steel), enhances mechanical properties and corrosion resistance. Surface treatments like pickling, passivation, or galvanization further improve durability.
These tubes undergo rigorous testing, including hydrostatic, eddy current, flaring, flattening, and dimensional inspections, to comply with ASTM A450/A450M or TEMA standards. With tensile strengths ranging from 325 MPa (carbon steel) to 515 MPa (stainless steel), they are designed for operating temperatures up to 650°C (stainless steel) or 450°C (carbon steel) and pressures up to 9.8 MPa for high-pressure applications. The U-bend design ensures compact layouts, reducing installation costs and space requirements in heat exchangers and condensers.
The U-Bent Heat Exchanger Tubes excel in applications requiring high thermal conductivity and resistance to corrosive fluids, such as water, steam, or chemical solutions. Their seamless construction minimizes leak risks, while their ability to absorb thermal expansion enhances system longevity. Compared to straight tubes, U-bent tubes reduce the need for additional fittings, making them ideal for complex heat exchanger designs. Optional end finishes, such as plain, beveled, or capped ends, ensure compatibility with various tube sheet configurations.
Addressing challenges like pipeline wear, corrosion, and thermal stress, U-Bent Heat Exchanger Tubes provide a reliable solution for engineers seeking efficient heat exchanger tubes. Their versatility, durability, and low maintenance requirements make them a preferred choice for high-performance heat transfer systems in demanding industrial environments.
Engineered to meet diverse industrial needs with robust materials and versatile designs.
U-bend tubes are widely used in heat-exchanger systems. Heat-exchanger equipment on the basis of seamless stainless U-tubes is essential in strategically important and critical fields — nuclear and petrochemical machine building.
a...................The difference in length between two straight pipe
sections
c..............The tangent spacing of the outer wall of the elbow
Da............nominal steel pipe outer diameter
E..............The distance between the outer diameters of the two straight
ends
f...............the distance between the ends of the two straight ends
l............... straight tube length
Lg............. straight pipe section plus total length of pipe
Rm...........nominal bending radius
S.............nominal wall thickness
Smin.......The minimum wall thickness at the back of the elbow
t...............the bend deviates from the horizontal distance
So...........Standard minimum wall thickness
| Item | Condition (when) | Tolerance |
|---|---|---|
| Ovality | Nominal bend radius ≤ 2 x nominal OD | less than or equal to 12% |
| 2 x nominal OD < Nominal bend radius ≤ 4 x nominal OD | less than or equal to 10% | |
| Nominal bend radius > 4 x nominal OD | less than or equal to 5% | |
| Nominal bend radius ≤ 2 x nominal OD | 0.75 x nominal wall | |
| Minimum wall thickness | 2 x nominal OD < Nominal bend radius ≤ 4 x nominal OD | 0.8 x nominal wall |
| Nominal bend radius > 4 x nominal OD | 0.9 x nominal wall | |
| Nominal bend radius ≤ 8" (200mm) | +/-3/64"(1mm) | |
| Bending Radius | 8" (200mm) < Nominal bend radius ≤ 16" (400mm) | +/-1/16"(1mm) |
| Nominal bend radius >16" (400mm) | +/-5/64"(1mm) | |
| Distance between legs | - | Max 1/16"(1.5mm) |
| Wall thinning of bending area | - | Max 17% |
| Difference between leg lengths at the ends | Leg length ≤ 16' (4.88m) | +1/8"(3mm) |
| Leg length > 16' (4.88m) | +3/16"(5mm) | |
| Deviation from plane of bend | - | ≤ 3/16"(1.5mm) |
| Flattening on bend | - | ≤ 10% nominal diameter |
| Straight leg length | ≤5m | +1/8"(3mm) |
| >5m | +3/16"(5mm) | |
| Total tube length including radius | ≤6m | +3/16"(5mm) |
| >6m | +5/16"(8mm) |
U-Tube heat exchangers are known for their distinctive U-shaped tubes that offer several advantages and also come with certain limitations.
The U-tube heat exchanger features a single tubesheet with both ends of the tubes secured to it. This design allows the tubes to expand and contract freely, avoiding thermal stress and offering excellent thermal compensation. A double tube pass is utilized, providing a lengthy process path, high flow rates, and superior heat transfer performance with robust pressure resistance. The tube bundle is removable from the shell for convenient maintenance and cleaning, presenting a simple structure and low cost.
Limitations imposed by the elbow's curvature radius restrict the arrangement of heat exchange tubes. This results in a larger inner tube spacing within the tube bundle and a lower utilization rate of the tube sheet. The shell-side fluid is prone to short-circuiting, which can impede heat transfer. When a tube leaks or sustains damage, only the U-shaped tubes on the outer part of the bundle can be readily replaced. Damage to the inner heat exchange tubes is not as easily repairable and may require blocking off. Furthermore, the damage to a single U-shaped tube equates to the loss of two tubes, leading to a higher scrap rate.
U-bend tubes are used to transfer heat between fluids.
Transfers heat between fluids, allowing return flow at 180° in a compact space.
Used in heat exchangers, chemical & petrochemical, food processing, and refrigeration industries.
Applied in heat exchangers at Oil & Gas, petrochemical plants, refineries, and power plants.
Handles aggressive fluids like sodium hydroxide + sodium hypochlorite safely.
Allows pipeline expansion without buckling; flexible or sliding options available.
Enhances heat transfer when the outside coefficient is lower than the inside, improving efficiency.
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