Base Tube ASME SA179

• Type: Seamless, cold-drawn low-carbon steel tube.
• Key Properties: Excellent thermal conductivity, good internal corrosion resistance (for clean fluids), smooth internal bore (minimizes pressure drop), high-pressure capability, easily weldable.
• Typical Applications: Primarily used in heat exchangers, boilers (economizers, superheaters), condensers, and other pressure vessels involving water, steam, oil, or gas on the tube side.

Key Properties:

• Exceptional Thermal Conductivity: ~230 W/m·K (significantly higher than steel, the primary reason for using Al fins).
• Good Corrosion Resistance: Forms a protective oxide layer, suitable for many ambient air/atmosphere applications. Note: Performance depends heavily on the specific environment.
• High Formability: Easily wound into the groove.
• Lightweight: Reduces overall tube weight.
• Cost-Effective: Pure aluminum is generally less expensive than high-alloy options.
• Softer/Lower Strength: Compared to alloys like 3003 or 5052. This can make fins slightly more susceptible to physical damage during handling or cleaning but is usually sufficient for most applications.

Fin Type & Attachment:

• "L Type" Fin: Refers to the cross-sectional shape of the fin strip before and during winding. The strip has an "L" profile.
• "Wound" Process: Describes the manufacturing method.

Attachment Mechanism (L Type Wound):

1. A precision helical groove is machined into the outer surface of the SA179 base tube.
2. An AL1060 strip, pre-formed into an "L" shape, is fed under tension into this groove.
3. As the tube rotates, the foot of the "L" (the short leg) is mechanically forced and locked into the groove.
4. The long leg of the "L" stands perpendicular to the tube surface, forming the fin.

Key Advantages of L-Type Wound:

• Strong Mechanical Bond: The cold-working process during winding creates a tight, gas-tight, interference fit. The fin is securely locked into the groove.
• Excellent Heat Transfer: Direct and substantial metal-to-metal contact between the fin foot and the tube groove ensures low thermal resistance.
• No Solder/Braze/Glue: Eliminates potential failure points, contamination risks, and high-temperature processes that could affect base tube properties.
• Good Durability: Resistant to thermal cycling stresses.
• Suitable for High-Pressure Tubes: The base tube remains seamless and its pressure integrity is unaffected by the external finning process.​

Typical Applications:

• Air Cooled Heat Exchangers (ACHEs): For process cooling (oil & gas, chemical, power plants).
• Heat Recovery Steam Generators (HRSGs): Economizer sections.
• Finned Tube Boilers.
• Deaerators.
• Drying Ovens & Kilns.
• HVAC&R Coils: Less common than copper tubes here, but used in specific industrial applications.
• Any application requiring efficient heat transfer from a pressurized fluid inside a tube to air/gas outside.

Key Considerations:

• Galvanic Corrosion: The carbon steel (SA179) tube and aluminum fin (AL1060) are far apart on the galvanic series. In corrosive environments (especially salt spray, coastal, or high humidity), galvanic corrosion can occur at the interface. Protective coatings (e.g., paint on fins, sometimes epoxy inside tubes) or careful environmental control are often necessary.
• Fin Protection: AL1060 fins are relatively soft. Care must be taken during handling, installation, and cleaning (e.g., avoid high-pressure water jets directly perpendicular to fins) to prevent bending or damage.
• Temperature Limits: While the fin attachment is robust, the AL1060 fin material itself has lower strength and melting point (~650°C) compared to the steel tube. Continuous operating temperatures are typically limited to around 200-250°C for aluminum fins to avoid excessive softening/creep. SA179 tube can handle much higher temperatures internally.