High-strength Tubes For Efficient Heat Transfer
Low alloy u-bent tubes are seamless tubes designed for heat exchangers, offering excellent corrosion resistance and thermal efficiency.
High-strength Tubes For Efficient Heat Transfer
Low alloy u-bent tubes are seamless tubes designed for heat exchangers, offering excellent corrosion resistance and thermal efficiency.
Low Alloy U-Bent Tubes are seamless or welded tubes crafted from low alloy steel, bent into a U-shape for use in heat exchanger tubes and boiler tubes. Conforming to standards like ASTM A213 (T5, T9, T11, T22, T91) and JIS G3462, these tubes are engineered for high-pressure and high-temperature applications in industries such as petrochemical, power generation, oil and gas, and chemical processing. Their corrosion resistance and ability to act as a thermal expansion absorber make them ideal for enhancing pipeline durability in demanding environments.
Manufactured using cold-drawing or hot-rolling processes, Low Alloy U-Bent Tubes feature outer diameters from 6.35mm to 50.8mm, wall thicknesses from 0.8mm to 6mm, and bend radii from 1.5D to 1500mm, customizable to client specifications. Post-bending heat treatment, such as stress relief annealing at 650-720°C or normalizing at 850-950°C, ensures optimal mechanical properties and prevents cracking. Surface treatments like pickling, passivation, or 3LPE coating enhance corrosion resistance, while plastic caps protect tube ends during transport.
These tubes undergo rigorous testing, including hydrostatic, eddy current, flaring, flattening, and hardness tests, to meet ASTM A450/A450M and TEMA standards. With tensile strengths ranging from 415 MPa (T11) to 620 MPa (T91) and yield strengths from 205 MPa to 440 MPa, they are designed for temperatures up to 650°C and pressures up to 10 MPa. The U-bend design minimizes thermal stress, eliminates the need for expansion joints, and reduces installation costs, making them ideal for compact heat exchanger systems.
The low alloy steel composition, typically containing 1-5% chromium (Cr) and 0.5-1% molybdenum (Mo), provides superior corrosion resistance and creep strength compared to carbon steel, while being more cost-effective than stainless steel. Common grades like T11 and T22 are suited for boiler superheaters, while T91 is used in high-temperature, high-pressure applications like power plant reheaters. The seamless construction ensures leak-free performance, and their ability to handle abrasive fluids makes them suitable for pneumatic conveying systems.
Addressing challenges like pipeline wear, corrosion, and thermal stress, Low Alloy U-Bent Tubes offer a robust solution for engineers seeking reliable heat exchanger tubes. Their high strength-to-weight ratio, durability, and low maintenance requirements make them a preferred choice for critical applications in harsh industrial environments, ensuring long-term performance and efficiency.
Engineered for heat exchanger efficiency, low alloy U-bent tubes combine strength, heat resistance, and cost-effectiveness for industrial applications.
High & low yield stainless steels
Alloy steels with Cr, Mo, Ni
Carbon steels for cost efficiency
Mechanical strength
Corrosion resistance
Heat resistance
Simplifies fluid routing in piping systems, reducing the need for additional fittings while enhancing installation flexibility.
Designed for high-pressure, high-temperature service in boilers and condensers.
Withstands aggressive media in refineries and process plants.
Efficient heat transfer in refrigeration and food processing equipment.
Reliable for offshore, refinery, and gas plant heat exchanger units.
Low alloy U-bent tubes deliver long service life with excellent heat transfer, high mechanical strength, and adaptability for critical industries.
| Element | Composition (%) |
|---|---|
| Carbon (C) | 0.05-0.15 |
| Manganese (Mn) | 0.30-0.60 |
| Phosphorus (P) | ≤0.025 |
| Sulfur (S) | ≤0.025 |
| Silicon (Si) | 0.50-1.00 |
| Chromium (Cr) | 1.00-1.50 |
| Molybdenum (Mo) | 0.44-0.65 |
| Property | Value |
|---|---|
| Tensile Strength, min (MPa) | 415 |
| Yield Strength, min (MPa) | 205 |
| Elongation, min (%) | 30 |
| Hardness, max (HBW) | 163 |
| Element | Composition (%) |
|---|---|
| Carbon (C) | 0.08-0.12 |
| Manganese (Mn) | 0.30-0.60 |
| Phosphorus (P) | ≤0.020 |
| Sulfur (S) | ≤0.010 |
| Silicon (Si) | 0.20-0.50 |
| Chromium (Cr) | 8.00-9.50 |
| Molybdenum (Mo) | 0.85-1.05 |
| Vanadium (V) | 0.18-0.25 |
| Niobium (Nb) | 0.06-0.10 |
| Property | Value |
|---|---|
| Tensile Strength, min (MPa) | 620 |
| Yield Strength, min (MPa) | 440 |
| Elongation, min (%) | 20 |
| Hardness, max (HBW) | 250 |
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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