Product Definition and Manufacturing Route
ASME SB111 is the ASME designation matching ASTM B111/B111M, the specification for seamless copper and copper-alloy tube for condensers, heat exchangers and similar service. The C70600 grade within it is the 90 % copper, 10 % nickel alloy, sometimes written 90/10 CuNi, and it is supplied as a cold-finished seamless tube with a smooth bore and a uniformly annealed structure.
Production begins with an induction-melted and continuously or semi-continuously cast billet that is inspected for internal soundness before it is cut to length. The billet is extruded at temperature into a hollow shell, then reduced to final size by cold pilgering and drawing over a mandrel, with intermediate annealing steps that restore ductility between passes. The finished tube is straightened, cut to length, degreased, descaled and dried, and the bore is purged during final annealing so that no carbonaceous film is left on the inner surface. That last step matters: a carbon film on the bore of a copper-nickel tube is a well-documented cause of early localised corrosion in seawater service, and a properly controlled bright or inert-gas anneal is the way to avoid it.
Standard Condenser and Heat Exchanger Tube Sizes
| Outside diameter | Common wall thickness | Typical use |
|---|---|---|
| 5/8 in (15.88 mm) | 18 BWG to 20 BWG | Compact condensers and oil coolers |
| 3/4 in (19.05 mm) | 18 BWG to 16 BWG | General condenser and cooler duty |
| 1 in (25.4 mm) | 18 BWG to 14 BWG | Large condensers and seawater heaters |
| 1-1/4 in (31.75 mm) and above | As agreed for the design pressure | Process heat exchangers and special circuits |
Wall thickness is chosen against the design pressure after allowance for tube-sheet rolling and for the corrosion allowance needed over the design life. Where larger diameters are required, the same alloy is ordered as seamless pipe under ASME SB 466, which shares the C70600 composition and temper requirements with SB111.
Mechanical and Thermal Data
| Property | Requirement or typical value |
|---|---|
| Tensile strength, min (annealed) | 40 ksi (275 MPa) |
| Yield strength at 0.5 % extension under load, min | 15 ksi (105 MPa) |
| Elongation in 2 in (50 mm), min | 30 % |
| Thermal conductivity | Approximately 45 W/(m·K) at room temperature |
| Coefficient of thermal expansion | Approximately 17 × 10-6 per °C over the normal service range |
| Density | 8.94 g/cm³ |
The alloy is used up to a maximum metal temperature of about 315 °C in oxidising environments, and its strength is unaffected by heat treatment, so the annealed temper remains the reference condition for design. Where the tube is to be expanded into a tube sheet, the annealed temper is also the condition that gives reliable and repeatable rolling.
Applications of 90/10 Copper-Nickel Seamless Tube
Main and auxiliary condensers on ships and in coastal power stations.
Multistage flash and reverse-osmosis desalination plants, including brine heaters.
Oil coolers, air coolers and jacket water coolers on engines in marine and offshore service.
Seawater piping spools and instrumentation lines where a seamless bore is required.
Heat recovery and refrigeration condensers using brackish or chloride-bearing cooling water.
Inspection, Testing and Installation Points
Eddy-current examination of the full tube length to ASTM E243 is the standard non-destructive test for seamless copper-alloy tube.
Hydrostatic testing is performed when specified, and the test pressure is calculated from the tube dimensions and the allowable stress of the alloy.
Flattening and expansion tests demonstrate ductility; a reverse-bend or flare test may be added for tube destined for heavy rolling.
Dimensions, wall thickness and length are verified against the tables of ASME SB111, and the straightened tube is checked for a permissible bow.
Tube-sheet holes are reamed and cleaned, and copper-nickel ferrules or impressed-current protection are used at the water-box end to control inlet-end erosion.
During storage and erection the tube ends are kept capped and tubes are stored away from carbon steel to prevent tramp iron pickup.
FAQ
Q: Why does a seamless tube matter in a condenser?
A seam-free bore removes the weld line that can act as a corrosion path and as a stress raiser in a rolled joint. Condenser and heat exchanger tube specifications are written around seamless product for exactly that reason.
Q: What is the maximum seawater velocity for 90/10 tube?
Design guidance for clean seawater is generally in the region of 2.5 to 3 m/s in the tube, and lower where the water carries sand, entrained air or sulphides. Excessive velocity is what causes inlet-end and impingement attack rather than general corrosion.
Q: How is the tube protected against fouling?
The alloy forms a copper-rich corrosion product film that marine organisms do not colonise readily, so chemical dosing requirements are lower than for steel or titanium circuits. Ferrous sulphate dosing is used in some designs to reinforce the protective film in the inlet region.
Q: Can tubes be re-rolled after service?
Removing a used tube and installing a replacement is normal maintenance practice. Re-rolling a tube that has already been expanded once is avoided because the wall thins at the rolled zone.
Q: Which test certificates accompany the tubes?
The usual package is a mill certificate with heat-number traceability, chemical and mechanical results, eddy-current test report, dimensional record and the pressure test record where applicable.
Q: Is the alloy suitable for steam or high-temperature process fluid?
The tube side may carry steam or hot process fluid, but the temperature limit depends on the fluid and the environment. Above roughly 315 °C in oxidising conditions the alloy loses ground to other materials and an application review is needed.
