ASTM B111 C70600 O61 Low Finned Tube For Heat Exchangers in Offshore Platforms
ASTM B111 C70600 O61 Low Finned Tube For Heat Exchangers in Offshore Platforms
An ASTM B111 C70600 O61 Low Finned Tube is a seamless, heat exchanger tube made from 90-10 copper-nickel alloy, in a lightly-drawn annealed temper, with integral low fins machined on its outer surface. This is a high-performance, corrosion-resistant, finned tube specifically engineered for efficient and durable service in seawater and other challenging cooling applications.
1. Base Tube: ASTM B111 C70600 O61 Seamless Tube
(1)Chemical Composition (ASTM B111 C70600)
The composition is specified in weight percent (wt. %). Values are maximum unless shown as a range.
| Element | Composition (wt. %) | Notes |
| Copper (Cu) | Remainder (≈86.5% min) | Basis metal. |
| Nickel (Ni) | 9.0 - 11.0 % | Primary alloying element; improves strength and corrosion resistance. |
| Iron (Fe) | 1.0 - 1.8 % | Critical element. Enhances resistance to impingement and erosion-corrosion in seawater. |
| Manganese (Mn) | 0.5 - 1.0 % | Acts as a deoxidizer and improves forgeability. |
| Lead (Pb) | 0.05 % max | Low level to prevent hot-shortness and maintain weldability. |
| Zinc (Zn) | 0.5 % max | Impurity limit. |
| Carbon (C) | 0.05 % max | Impurity limit. |
| Phosphorus (P) | 0.02 % max | Impurity limit. |
| Sulfur (S) | 0.02 % max | Impurity limit. |
| Other Elements (Total) | 0.15 % max | Sum of all other unnamed metallic impurities. |
Key Point: The Cu + Ni + Fe + Mn content must be ≥ 99.5%, ensuring high purity and consistent performance.
(2) Mechanical & Physical Properties
O61 (Light Drawn Annealed)
A. Tensile & Yield Strength
Values are typical minimums for the specified temper.
| Temper Code | Condition | Tensile Strength (min) | Yield Strength (0.5% Ext. under load, min) | Elongation (min) |
| O50 / O61 | Annealed / Light Drawn Annealed | 38 ksi (260 MPa) | 12 ksi (80 MPa) | 35 % |
| H55 | Drawn, Stress-Relieved (Hard Temper) | 52 ksi (360 MPa) | 45 ksi (310 MPa) | 15 % |
| H80 | As Drawn (Hard Drawn) | 60 ksi (415 MPa) | 50 ksi (345 MPa) | 5 % |
Note on O61 vs. O50: Both are annealed and very ductile. O61 has a light final cold draw, which may result in slightly higher strength and a smoother surface finish compared to O50, but they are often considered equivalent for procurement and design purposes.
2. Low Finned Tube
"Low Fin" (also called "Integral Low Fin" or "Karbate" style) means the fins are relatively short, closely spaced, and are machined or rolled directly from the wall of the original seamless tube. There is no bonding interface, eliminating the risk of fin separation.
Typical Fin Height: ~0.02 to 0.04 inches (0.5 to 1.0 mm).
Typical Fins per Inch: 19 to 40 fins per inch (fpi).
Fin Ratio: The ratio of total outside finned surface area to the inside bare tube surface area is typically between 2.5:1 to 4:1.
3. Key Advantages of This Specific Combination
- Enhanced Heat Transfer: The low fins provide a 2.5-4x surface area increase.
- Corrosion Resistance: C70600 alloy is famously resistant to seawater corrosion, making it ideal for marine and coastal service.
- Fouling Resistance: The CuNi alloy inhibits marine biological growth. The finned geometry can also reduce fouling compared to some bare tube arrangements.
- Material Integrity: Being integrally finned from a single piece, there is no risk of fin-to-tube bond failure.
- Ease of Installation: The O61 temper allows the tube ends to be easily expanded (rolled) into the tube sheets of the heat exchanger.
Primary Application of ASTM B111 C70600 O61 Low Finned Tube
This specific tube is engineered for enhanced heat transfer in corrosive environments, particularly seawater and brackish water cooling applications. Its design combines the corrosion resistance of 90-10 copper-nickel with the thermal efficiency of integral low fins.
Industry-Specific Applications
1. Marine & Offshore (Most Common Application)
- Main Central Coolers: Cooling jacket water for main propulsion diesel engines using seawater.
- Lube Oil Coolers: Cooling lubricating oil for engines, gearboxes, and thrusters.
- Charge Air Coolers (Intercoolers): Cooling compressed intake air for turbocharged diesel engines.
- HVAC Seawater Coolers: For shipboard air conditioning and refrigeration systems.
- Hydrogen Coolers: Cooling hydrogen in turbine generators on large vessels.
- Offshore Platform Coolers: For process cooling, power generation, and utilities.
2. Power Generation
- Auxiliary Seawater Coolers: Cooling closed-cycle cooling water, bearing lube oil, or transformer oil in coastal and nuclear power plants.
- Wind Farm Substation Coolers: Cooling critical electrical equipment in offshore substations.
3. Oil, Gas & Petrochemical
- Seawater-Cooled Process Coolers: In refineries and LNG plants located near coastlines.
- Oil Platform Utilities: Cooling systems for gas turbines, compression equipment, and process fluids.
4. Industrial & Desalination
- Desalination Plant Heat Rejection Sections: In multi-stage flash (MSF) and multi-effect distillation (MED) plants.
- Chemical Process Coolers: Where the cooling medium is seawater or corrosive brine.
Get in Touch
Have questions about our products or want to discuss a custom order? Our team is ready to help you.