ASME SA209 Embedded Fin Tube With AL1060 Fin For Boiler Economizers and Air Heaters

1. Base Tube Material: SA209

Composition:

Carbon (C) 0.10–0.20%
Manganese (Mn) 0.30–0.80%
Phosphorus (P) ≤ 0.025%
Sulfur (S) ≤ 0.025%
Silicon (Si) 0.10–0.50%
Molybdenum (Mo) 0.44–0.65%
Copper (Cu) ≤ 0.25% (if present)
Chromium (Cr) ≤ 0.30%
Nickel (Ni) ≤ 0.40%
Vanadium (V) ≤ 0.03%

Properties:

• Good high-temperature strength and creep resistance.
• Improved resistance to oxidation and corrosion compared to plain carbon steels at elevated temperatures.
• Good weldability.

2. Fin Material: AL1060

Properties:

Excellent Thermal Conductivity: (~230 W/m·K) - The primary reason for using aluminum fins.

Good Corrosion Resistance: Forms a protective oxide layer.

High Formability/Ductility: Easily shaped during manufacturing.

Low Density: Lightweight.

Low Strength: Softer than alloyed aluminums, but sufficient for many fin applications.

High Electrical Conductivity.

3. Fin Type: Embedded (G-Fin)

Manufacturing Process: 

• A groove is machined (often by knurling) into the outer surface of the steel base tube.
• A strip of aluminum fin stock (AL1060) is fed into the groove.
• High-pressure rollers or dies force the tube wall material over the edges of the aluminum strip, cold-working and mechanically locking the fin base securely into the groove. This creates a continuous, tight, mechanical bond along the entire length of the fin.

Key Features:

• Strong Mechanical Bond: The fin is physically locked into the tube wall, offering excellent resistance to fin loosening due to thermal cycling or vibration.
• No Solder/Braze: Eliminates issues like flux corrosion, braze alloy melting point limitations, or potential voids in the bond line.
• Direct Metal-to-Metal Contact: Provides low interfacial thermal resistance (good heat transfer efficiency).
• Fin Integrity: The AL1060 fin material itself remains unaltered (not melted), retaining its full thermal conductivity and corrosion resistance.
• Fin Density: Allows for relatively high fins per inch (FPI).
• Appearance: Typically has a clean, metallic look with a visible seam where the tube metal is rolled over the fin base.

Key Advantages:

• High heat transfer efficiency.
• Excellent fin bond strength and durability under thermal cycling.
• Good high-temperature capability of the base tube.
• Corrosion resistance of fins (AL1060) and base tube (SA209).
• No low-melting-point braze alloys to limit operating temperature.

4. Application

• Marine & Offshore Systems
• Desalination Plant Heat Exchangers
• Sulfuric Acid (H₂SO₄) Coolers
• Sour Gas (H₂S) Reboilers
• Steam Condensers in Geothermal Plants
• Flue Gas Waste Heat Recovery
• Ammonia (NH₃) Evaporators
• Heat Recovery Ventilators (HRVs)

5.Typical Applications:

• Heat Recovery Steam Generators (HRSGs): Economizer and evaporator sections.
• Boiler Economizers: Recovering heat from flue gases.
• Air Heaters (Ljungström type or tubular): Preheating combustion air.
• Process Gas Heaters/Coolers: In refineries, petrochemical, and chemical plants.
• High-Temperature Finned Tube Bundles: Where both elevated temperature resistance and efficient extended surface are required.