When a process stream carries seawater, brackish cooling water, or a corrosive hydrocarbon, the tube material you choose decides whether the heat exchanger runs for thirty years or fails in three. Copper-nickel alloy tubes have been the default choice for marine condensers, desalination plants, and offshore piping for more than a century, and the reason is simple: nothing else in this price range balances corrosion resistance, thermal conductivity, fouling tolerance, and fabricability quite as well.

But the phrase "copper-nickel" covers a family of alloys, and the wrong grade can quietly erode both your budget and your schedule. This guide walks through what 90/10 and 70/30 alloys actually do, which standards apply, and how EZ Steel Industrial packages the tubes with complementary pipe flanges and heat efficiency tubes so you can source a full piping system from one supplier.

Why copper-nickel, and why now

Modern refinery and shipyard operators are running condensers and charge coolers harder than ever. Seawater intake temperatures are climbing, biofouling pressure is increasing in warmer coastal waters, and the shift toward LNG and offshore wind demands materials that survive chloride-rich, sour, and moderately sour service. Copper-nickel answers each of those pressures:

• A natural protective oxide film that resists pitting and crevice corrosion in seawater — without the need for chemical dosing.
• Strong resistance to macrofouling; barnacles and mussels struggle to anchor on a surface that releases small amounts of copper ions.
• Excellent thermal conductivity, which means thinner tube walls and more compact exchanger bundles.
• Easy to weld, braze, bend, and roll into U-tubes using standard workshop tools.

90/10 versus 70/30: the choice that actually matters

Almost every copper-nickel tube you will ever specify falls into one of two compositions. Both are covered by the same family of ASTM, EN, GB, and JIS standards, but their service envelopes are different.

A simple rule of thumb

If the tube bundle sits in clean or moderately polluted seawater at moderate velocity, 90/10 is the cost-effective workhorse and is what most shipyards default to. If velocities climb above 3.5 m/s, if the water carries sand or entrained gases, or if the process side is hotter and more aggressive, step up to 70/30. EZ Steel Industrial keeps both grades on the shelf, in straight lengths and as heat efficiency tubes bent to your radius.

Where these tubes actually work

Marine and shipbuilding

Seawater cooling, fire-fighting mains, sanitary drains, and ballast piping on commercial vessels are still the largest single market for copper-nickel. The combination of biofouling resistance and easy field bending makes 90/10 the standard pick. For navy hulls and LNG carriers where higher flow rates are common, 70/30 tubes are increasingly specified.

Power plant condensers

Once-through and helper condensers in coastal and offshore power stations run on seawater at scale. Copper-nickel tubes handle the steady flow and the periodic shutdown cycles that pit stainless steel, and they tolerate chlorine dosing that would attack aluminium brass. The tubes can be supplied as straight lengths for pull-through replacement or as pre-bent U-tubes for new builds.

Petrochemical and refinery service

Overhead condensers, debutanizer reboilers, and amine regenerator overheads often use copper-nickel because it tolerates trace H2S and chlorides that stress stainless steel. Match the grade to the chloride level and the velocity, and 70/30 tubes give refinery operators a long, predictable service life between turnarounds.

Desalination

Multi-stage flash and multi-effect distillation plants have used copper-nickel evaporator tubes for decades because the alloy resists the brackish, deaerated, hot brine on the process side. 70/30 is the dominant choice here thanks to its higher strength at temperature.

Standards you should see on the MTC

A reputable copper-nickel tube ships with a mill test certificate that references the producing standard. The most common ones EZ Steel Industrial supplies against are:

• ASTM B111 / B111M — seamless condenser tubes for the North American market.
• ASTM B466 / B467 — seamless and welded pipe for marine and process piping.
• EN 12451 — seamless copper and copper alloy tubes for heat exchangers (Europe).
• GB/T 8890 — the Chinese national standard for heat-exchanger and condenser tubes.
• JIS H 3300 — Japanese standard covering C7060 and C7150 grades.
• EEMUA 144 and EEMUA 234 — the marine specifications most shipyards and offshore operators reference for 90/10 and 70/30 respectively.

When you request a quote, ask for the standard and the UNS number on the certificate. That single line of paperwork will tell you whether the mill quoted to the right specification or substituted a near-neighbour.

Pairing copper-nickel tubes with the rest of the system

A heat exchanger is only as reliable as the connections feeding it. EZ Steel Industrial supplies copper-nickel tubes alongside the supporting components you need to finish a piping run, so you are not chasing mismatched flanges, gaskets, and bolts from three different vendors.

Pipe flanges and copper-nickel flanges

Pipe flanges are usually supplied in carbon steel, stainless steel, or a copper-nickel alloy matched to the tube. For seawater service, our copper nickel flanges in 90/10 (C70600) keep the galvanic series consistent with the tube and avoid the bimetallic corrosion traps that show up when a steel flange is dropped into a copper-nickel line.

Gaskets, stud bolts, and nuts

Spiral-wound gaskets with graphite or PTFE filler, paired with B7 / B8 stud bolts, cover the bulk of refinery and shipyard service. RTJ gaskets are available for higher-pressure hydrocarbon service.

Heat efficiency tubes: U-bends and finned tubes

For shell-and-u-tube exchangers, EZ Steel Industrial delivers pre-bent U-tubes to the radius you specify, with full heat treatment, hydrostatic testing, and NDT as required. When heat transfer is the bottleneck rather than pressure containment, finned tubes in copper-nickel or copper-nickel-clad aluminium dramatically increase the surface area without changing the pressure ｄｒｏｐ.

A practical selection workflow

1. Define the service fluid. Seawater, brackish water, or a process stream? Each fluid has its own chloride, oxygen, and velocity profile.
2. Check velocity and temperature. Use the seawater velocity limits in the table above as a starting point, then check against the EEMUA publication that matches your application.
3. Pick the grade. 90/10 for general service, 70/30 for higher velocity, higher temperature, or more aggressive chemistry.
4. Confirm the standard. Specify ASTM, EN, GB, or JIS on the purchase order so the mill test certificate is unambiguous.
5. Specify the form. Straight tube, U-bend, finned tube, or clad composite — and the OD × wall thickness the exchanger designer has called for.
6. Plan the connections. Match the flanges, gaskets, and bolting to the tube material and the service fluid at the same time.

Common questions engineers ask before ordering

Can I weld 90/10 to 70/30 in the same system?

Yes. Use a copper-nickel filler such as ERCuNi or a matching 70/30 filler for the joint. Avoid joining copper-nickel directly to steel without a flange or a dielectric ｕｎｉｏｎ — the galvanic step is too large and the steel side will pit.

Do I need to treat the water?

For most seawater service, mechanical filtration to remove debris and occasional sponge-ball cleaning is enough. Continuous chlorination is acceptable up to about 1.5 ppm residual; above that, consider switching to a higher-nickel alloy or titanium.

What about biofouling inside the tubes?

The same copper ion release that keeps the outside of the tube clean also helps the inside. Combined with sponge-ball cleaning, most operators run a full year between outages without significant fouling.