What a C70600 CuNi 90/10 Condenser Tube Is
UNS C70600 is a copper-nickel alloy containing approximately 90% copper and 10% nickel, with controlled additions of iron and manganese. The alloy was developed for primary forming of wrought products and is the standard tube material for seawater-cooled condensers, heat exchangers and distillers. Its industry name is cupronickel 10, its EN symbol is CW352H, its EN chemical designation is CuNi10Fe1Mn, the German material number is 2.1972 and the British Standard designation is CN102. The combination of a stable protective film, high thermal conductivity and immunity to chloride stress corrosion cracking is what keeps 90/10 tube in service for decades in power stations, ships and desalination plants.
Chemical Composition and Equivalent Designations
| Designation system | Reference |
|---|---|
| UNS number | C70600 |
| EN symbol | CW352H |
| EN chemical designation | CuNi10Fe1Mn |
| DIN material number | 2.1972 |
| British Standard grade | CN102 |
| JIS designation | C7060 |
| Product standards | ASTM B111, ASTM B466, ASME SB111, DIN 86019, EEMUA 144, EEMUA 234 |
The balance of the composition is copper, with nickel, iron and manganese making up the specified range. Iron is deliberately retained at around 1.3% to stabilise the protective corrosion film in fast-flowing seawater, and manganese supports the same mechanism while acting as a deoxidiser.
| Element | Typical content, % |
|---|---|
| Copper | balance |
| Nickel | 9.0 - 11.0 |
| Iron | 1.0 - 1.8 |
| Manganese | 0.5 - 1.0 |
| Carbon, lead, sulphur, phosphorus, zinc | residual limits in the low hundredths or less |
Mechanical and Physical Properties
| Property | Metric | Imperial |
|---|---|---|
| Tensile strength, ultimate | 303 - 414 MPa | 43,900 - 60,000 psi |
| Tensile strength, yield, temper dependent | 110 - 393 MPa | 16,000 - 57,000 psi |
| Elongation at break | approx. 42% | approx. 42% |
| Elastic modulus | 140 GPa | 20,300 ksi |
| Shear modulus | 52.0 GPa | 7,540 ksi |
| Poisson ratio | 0.34 | 0.34 |
| Machinability, free-cutting brass = 100% | 20% | 20% |
Annealed tube is the normal delivery condition for condenser service because it must be rolled into a tube sheet without cracking. Light drawn tube is used where higher stiffness is needed for unsupported spans.
Condenser Tube Dimensions and Wall Thickness
Condenser tube sizes follow ASME B36.19 outside diameters, and wall thickness is selected from the standard series according to design pressure, tube sheet support spacing and expected erosion. The following selection covers the sizes most frequently ordered for surface condensers and shell-and-tube exchangers.
| Size, in. | Outside diameter, mm | Wall thickness, mm |
|---|---|---|
| 1/2 | 21.3 | 1.65 |
| 3/4 | 26.7 | 1.65 |
| 1 | 33.4 | 1.65 |
| 1 1/4 | 42.4 | 1.83 |
| 1 1/2 | 48.3 | 1.83 |
| 2 | 60.3 | 2.11 |
| 2 1/2 | 73.0 | 2.11 |
| 3 | 88.9 | 2.41 |
Applications in Power, Desalination and Marine Plant
Industrial plant: condenser tubes, condenser plates, heat exchanger tubes, evaporator tubes, distiller tubes, valve bodies, pressure vessels and ferrules.
Marine service: tube sheets for salt water duty, salt water piping systems, salt water fittings, baffles, propeller sleeves, hull fittings and hot water tanks.
Automotive and transport: power steering tube and brake lines where corrosion resistance and formability are both required.
Process industry: pump impellers and components for oil refining equipment and weld torch tips.
Plumbing and HVAC: flanges, water boxes and general seawater-cooled exchangers.
Installation, Rolling and Service Practice
Tube sheet holes are reamed and cleaned so that the rolled joint seals without over-expansion; excessive expansion work-hardens the tube ends and invites stress corrosion.
Expansion is followed by flaring or, where a fully leak-tight joint is required, by seal welding with a matching copper-nickel filler.
Iron contamination from tools, wire brushes or steel scaffolding must be removed, because embedded steel particles become pitting sites in seawater.
Seawater velocity is held within the design range for the tube size; smooth, gradual transitions at inlets reduce local turbulence and erosion.
Chemical cleaning agents and ammoniacal condensates are avoided where oxygen is present, as both can attack the protective film.
Frequently Asked Questions
Q: What is the difference between C70600 and C71500 condenser tube?
C70600 contains about 10% nickel and C71500 about 30%. The 70/30 grade offers higher strength and greater resistance to velocity and polluted water, while C70600 is the cost-effective choice for clean seawater in moderate service.
Q: Which temper should be ordered for condenser tubes?
Annealed tube is standard because it rolls into the tube sheet cleanly. Light drawn tube is used where the tube must span an unsupported run without excessive sag.
Q: How is C70600 tube tested before delivery?
Chemical analysis, tension testing, eddy-current examination, flattening and expansion tests, and hydrostatic or pneumatic pressure testing where specified. Grain structure and microscopical examination are added for critical service.
Q: Why is iron added to 90/10 copper-nickel?
Iron stabilises the protective oxide film that forms in seawater and raises resistance to erosion-corrosion. Keeping iron in the specified 1.0% to 1.8% range is a key quality variable for tube performance.
Q: Can C70600 tubes be welded into a tube sheet?
Yes. Seal welding after expansion is common practice in high-integrity condensers, and the alloy welds readily by gas tungsten arc welding with a matching filler.
Q: What causes premature failure of condenser tubes?
Over-expansion during installation, iron contamination, ammonia in the steam condensate, sulphide-polluted cooling water and local high-velocity turbulence at inlets are the usual causes, together with inadequate cleaning during shutdowns.
