Buying copper nickel alloy tube for a real project is rarely as simple as "send me a quote for 90/10". Once the line list crosses heat exchangers, cooling-water headers, fire-water mains and a refinery overhead condenser, the grade, temper, dimensional standard and testing scope all start to diverge. A heat-exchanger bundle on a North-Sea platform has very different requirements from a chemical-plant overhead condenser, even if both are nominally "seamless Cu-Ni".

This walkthrough condenses the questions our engineers field every week from EPC buyers, refinery procurement teams and shipyard subcontractors. It is built around three service environments — refinery & petrochemical, marine & offshore, and heat-exchanger tube bundles — and shows how the same alloy family is specified differently for each.

Copper-nickel alloys (the "Cu-Ni" family, UNS C70600 for 90/10 and UNS C71500 for 70/30) are the default choice for seawater, brackish water, condensate and a wide range of refinery side-streams. The reason is that nickel alloyed into copper stabilises a thin, self-repairing oxide film on the inside of the tube. In practical terms this gives:

• Very good resistance to flowing seawater up to about 3.0–3.5 m/s (90/10) and 3.5–4.5 m/s (70/30).
• Resistance to biofouling far better than carbon or stainless steel, which reduces cleaning intervals.
• No stress-corrosion cracking in chloride service, unlike many stainless grades under residual tensile stress.
• Stable thermal conductivity, which makes it ideal for condenser and cooler tube sheets.

Most procurement mistakes in Cu-Ni start with the grade decision. Both grades are corrosion-resistant; they are not interchangeable. The decision is driven by water velocity, temperature and the presence of pollutants (sulphides, ammonia, hydrocarbons).

Rule of thumb used by our refinery and shipyard buyers: if the line is salt-water service at moderate velocity and ambient temperature, 90/10 is the economic default. If you face higher velocities, hotter side-streams, polluted water or a low-margin design, 70/30 earns its premium back in longer inspection intervals.

The standard listed on the purchase order controls everything: dimensional tolerances, mechanical properties, testing scope and traceability. The most common pairings we see in refinery and marine projects are:

• ASTM B466 / B466M — seamless and welded Cu-Ni pipe (UNS C70600, C71500). The default for process piping and shipbuilding.
• ASTM B111 / B111M — seamless Cu-Ni tube for condensers and heat exchangers. Almost always cited for U-tube bundles.
• ASTM B395 — U-bend tube specifically; covers the additional bend-zone testing.
• EEMUA 144 / EEMUA 234 — the European offshore norm for 90/10 piping. Many North-Sea and Middle-East operators require it.
• EN 12451 / EN 12452 — European standards for copper alloy tubes in heat exchangers and condensers.
• JIS H 3300 — Japanese standard, used in shipyards building to IACS rules.

If your RFQ only says "Cu-Ni 90/10 to ASTM" without naming a product form, you will get a quote — but it may not match the dimensional schedule on your isometric drawings. Always pin down B466 vs B111 vs B395 up front.

A Cu-Ni line on a real project is never just tube. The leak-tight boundary of a cooling-water header, for example, consists of the tube, the matching pipe fittings (butt-weld elbows, tees, reducers in Cu-Ni or aluminium-bronze), the pipe flanges on the equipment connection, the gaskets, the stud bolts and the isolation industrial valves.

This is where most Cu-Ni RFQs lose time: a 90/10 tube is ordered to B111, a bronze elbow is ordered to a different factory, the flanges arrive in the wrong facing (RF vs FF), and the site is left mixing weld procedures on receipt. The cost of the mismatch is not the price of the parts — it is the schedule slip and the rework on tie-ins.

For refinery and petrochemical packages, a typical Cu-Ni bundle covers: condenser tubes (B111/B395), tube sheets, transition pieces to clad flanges, butt-weld fittings in matching Cu-Ni or aluminium-bronze (B466), flanges to ASME B16.5 with raised-face or composite bonding, gaskets (typically non-asbestos or spiral-wound for the higher classes), stud bolts in B7/B8 with PTFE or graphite gaskets, and the matching industrial valves for block, drain and vent duty.

Roughly half of the Cu-Ni volume on a refinery project is not straight pipe — it is U-bend heat-exchanger tube. The U-bend geometry introduces three things the straight-tube spec does not cover:

• Additional flattening and ovality checks across the bend zone.
• Stress-relief heat treatment of the bend region (most specs require it).
• Hydrostatic test of the finished U-tube, not just the straight stock.

A clean U-bend in 90/10 or 70/30 is also where the difference between "we made it" and "we made it correctly" shows up. Surface scoring from poor mandrel lubrication, micro-cracks on the extrados and residual ovality in the bend zone are the three most common receiving-inspection rejections. Specifying ASTM B395 with the right bend radius (typically 1.5× the tube OD, sometimes 2× for thicker walls) and asking for a bend-zone surface-finish report before shipment prevents most of them.

A Cu-Ni delivery is high-value and corrosion-critical, so the MTC review is not a formality. The five checks our inspectors run on every consignment:

1. Heat number on the tube matches the MTC, and the MTC matches the PO line item.
2. Dimensional check: OD, wall thickness and ovality against ASTM B111/B395 table.
3. Surface finish: no scoring, dents or pitting visible on 100% of the bundle ends.
4. Mechanical properties: tensile and, where required, hardness on a sample per heat.
5. Hydrostatic or eddy-current test certificate matches the standard cited on the PO.

If any of these fails, the lot is held and the supplier is asked to re-test or ｒｅｐｌａｃｅ before the bundle is released to site. The cost of holding 8 tonnes of tube is negligible compared to a forced outage caused by a leaking condenser.

A short list of mistakes our team has walked buyers through in the last 12 months:

• Specifying "Cu-Ni" without naming UNS C70600 or C71500. Different mills default to different grades.
• Quoting B466 (pipe) on a heat-exchanger line that should be B111 (tube). The dimensional tolerances are not interchangeable.
• Buying flanges in the wrong facing (RF vs FF) for a Cu-Ni stub end. RF is the safe default for water service.
• Forgetting to specify the gasket and stud-bolt material. A Cu-Ni flange with the wrong gasket will leak on first heat-up.
• Mixing 90/10 and 70/30 in the same cooling-water circuit to chase price. Galvanic bimetallic couples accelerate pitting on the 90/10 side.

Putting it all together, a clean RFQ to a mill or distributor should contain, at minimum:

• UNS grade (C70600 or C71500) and temper (typically O61 / annealed for condenser service).
• Product form: pipe, tube or U-bend, and the ASTM/EN/JIS standard to apply.
• Size schedule: OD × wall × length or bend radius for U-tubes.
• Quantity by item, with a 5–10% allowance for wastage and site rework.
• Testing scope: hydrostatic, eddy-current, hardness, intergranular corrosion if applicable.
• MTC format: EN 10204 3.1 is the default; 3.2 is required by some refinery clients.
• Delivery terms and packaging: end caps, wooden crate, seaworthy wrapping for ocean freight.

A 10-line RFQ that captures these points is worth more than a 30-line RFQ that lists the same boilerplate every refinery in the world uses. The technical clarity is what gets you a clean quote and a clean delivery.

For EPC contractors and refinery procurement teams, the question is rarely "which Cu-Ni tube should I buy". It is "can one supplier hold the entire cooling-water, fire-water and heat-exchanger tube bundle on a single MTC chain, with matching fittings, flanges, gaskets and valves, and deliver on the project schedule?" That is the question we built our bundled-supply model around.

If you have a line list for a refinery, marine or offshore package — even at the early RFQ stage — sending it through before the spec is finalised usually saves 2–4 weeks of clarification cycles later. Our engineering team is set up to review the spec, flag the wrong-grade or wrong-standard items, and return a clean technical-and-commercial quote in one pass.