Low-Carbon Cold Drawn ASTM A179 Seamless U-Bend Tube For Power Plant Boilers

ASTM A179 U-bend tubes are seamless cold-drawn low-carbon steel tubes that have been thermally or mechanically bent into a U-shape for use in heat exchangers, condensers, and boilers. The U-bend design allows for thermal expansion and efficient heat transfer in confined spaces.

Key Features of ASTM A179 U-Bend Tubes:

1. Material Composition (Same as ASTM A179 Straight Tubes)

Note: Small amounts of residual elements (Cu, Ni, Cr, Mo) may be present but are not specified.

2. Mechanical Properties

Cold-Drawn Process: Ensures a smooth surface finish and tight dimensional tolerances.

Heat Treatment: Typically supplied in the annealed or stress-relieved condition for better ductility.

Key Characteristics of ASTM A179 material:

✅ Excellent Thermal Conductivity (due to low carbon content)
✅ Good Weldability & Formability (suitable for bending and flaring)
✅ Smooth Internal Surface (minimizes fouling in heat exchangers)

3. U-Bend Specifications

Bending Process:

Cold bending (for tighter radii)

Induction/heat-assisted bending (to prevent cracking)

Bend Radius: Typically 1.5x to 3x the tube OD (e.g., for a 19mm tube, bend radius ≈ 28.5–57mm)

Wall Thinning: ≤ 10–15% (post-bending)

Surface Finish: Smooth, free from cracks or deformities

4. Advantages of U-Bend Tubes

✅ Compact Design – Saves space in heat exchangers.
✅ Thermal Expansion Handling – Absorbs stress from heating/cooling cycles.
✅ Reduced Leak Points – Fewer welded joints compared to straight tubes.
✅ Efficient Heat Transfer – Smooth inner surface minimizes fouling.

5. Comparison: U-Bend vs. Straight Tubes

6. Common Defects & Quality Checks

Cracking at the bend (due to improper bending technique)

Excessive wall thinning (must be within 10–15%)

Ovality (deformation) – Should meet ASTM tolerances

7. Testing Methods:

Hydrostatic Test (checks for leaks)

Eddy Current Test (detects surface defects)

Dimensional Inspection (OD, wall thickness, bend radius)

Applications of ASTM A179 U-Bend Tubes:

ASTM A179 U-bend tubes are primarily used in heat exchangers and condensers where efficient heat transfer, compact design, and thermal stress resistance are critical. Their seamless, cold-drawn, low-carbon steel construction makes them ideal for moderate-temperature and pressure environments.

1. Heat Exchangers (Most Common Use)

Shell & Tube Heat Exchangers – U-bend tubes allow for thermal expansion and reduce the need for expansion joints.

Compact Design – The U-shape minimizes space requirements while maximizing heat transfer efficiency.

Fluid Types:

Water, steam, oil, refrigerants, and chemicals.

Industries:

✔ Power Plants (condensers, feedwater heaters)
✔ Oil & Gas (refineries, petrochemical processing)
✔ HVAC & Refrigeration (chillers, evaporators)

2. Condensers

Used in power plant condensers to convert steam back into water.

Advantages:

High thermal conductivity (due to low carbon content).

Smooth inner surface reduces fouling.

3. Boilers & Feedwater Heaters

Low-pressure boilers (not for high-temperature/pressure applications like A192/A213 tubes).

Feedwater heaters (pre-heat water before entering boilers).

4. Industrial Process Equipment

Chemical Processing – Heat transfer in reactors, distillation columns.

Food & Beverage – Pasteurizers, sterilizers.

Pharmaceuticals – Clean steam systems, heat recovery.

5. Marine & Offshore Applications

Shipboard condensers & coolers (due to corrosion-resistant treatments).

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