Marine & Ship-Building Copper-Nickel Tube Buyer's Guide: EEMUA 144/234, MIL-T-16420K, GB/T 26291 & DIN 86019 Piping from a Mill-Direct Source

A practical B2B guide to selecting, qualifying, and sourcing copper-nickel tube for ship systems — covering the standards that shipyards and class societies actually accept, the alloy choice between 90/10 and 70/30, and the procurement workflow that prevents costly rework at the yard.

For shipyards, naval architects, and offshore procurement teams, copper-nickel (Cu-Ni) tube is the default alloy for seawater cooling, fire-fighting, ballast, bilge, and sanitary systems on commercial vessels, naval ships, and offshore platforms. The reason is straightforward: Cu-Ni alloys form a thin, self-healing protective oxide film in seawater that resists biofouling, erosion, and general corrosion far better than carbon steel, stainless steel, or aluminum in long-term marine service. But "copper-nickel tube" is not a single product — it is a family of alloys (90/10 and 70/30) governed by a layered set of standards (EEMUA 144, EEMUA 234, MIL-T-16420K, GB/T 26291, DIN 86019, ASTM B466, BS/EN 2871) that vary by region, vessel flag, and classification society. Specifying the wrong standard, alloy, or dimensional class is one of the most expensive errors in a ship-piping package — it can stop a vessel from being signed off by the class surveyor and force a yard-side rework.

This guide, written for B2B buyers, gives you a single reference to make those calls correctly. It is built around the products on the marine & ship-building copper-nickel tube line at EZ Steel Industrial, and it draws on the broader copper & nickel alloy catalog the mill carries, so the same mill-direct relationship can be extended to related components such as pipe fittings and industrial valves for a complete seawater system.

1. The Standards That Actually Govern a Marine Cu-Ni Pipework System

A marine Cu-Ni system is almost never bought under a single standard. The tube itself is qualified to one standard, the flanges to another, the fittings to a third, and the welding procedure to a fourth. The four families you will encounter most often are:

• EEMUA 144 / 145 / 146 — the European (originally UK Engineering Equipment and Materials Users Association) family for offshore 90/10 Cu-Ni. EEMUA 144 covers the tube, EEMUA 145 the composite and solid flanges, and EEMUA 146 the fittings. They are widely accepted by major class societies for offshore platforms and high-spec commercial vessels.
• EEMUA 234 — extends the family to 70/30 Cu-Ni for higher-velocity and higher-strength seawater service. Often specified together with EEMUA 144 because the same fabricator can supply both.
• MIL-T-16420K — the US military / naval specification for Cu-Ni tube used on US Navy and many allied naval vessels. The (SH) suffix indicates a shock-resistant grade, which is mandatory for combatant ship piping.
• GB/T 26291 — the Chinese national standard for marine Cu-Ni tube, used on Chinese-built commercial ships and increasingly accepted on export vessels built in China.
• DIN 86019 — the German standard, harmonized with EEMUA on the 90/10 chemistry and widely used across European yards.
• ASTM B466 / B466M — the US specification for seamless Cu-Ni pipe and tube, and the reference chemists quote when they want UNS C70600 (90/10) or C71500 (70/30).
• BS 2871 / EN 12451 / EN 12449 — British and European copper-alloy tube standards. EN 12449 is the dimensional reference that EEMUA 144 pulls most of its OD sizes from.

2. 90/10 vs 70/30 Copper-Nickel — Which Alloy, and Why

The "10" and "30" refer to the nominal nickel content of the alloy. Both are excellent in seawater, but they are not interchangeable.

For most commercial ship seawater systems, 90/10 is the default and is what the EEMUA 144 / DIN 86019 / MIL-T-16420K family is written around. 70/30 earns its higher cost in three situations: where seawater velocity will exceed 90/10's corrosion-erosion limit (pump discharge lines, fire-fighting pump manifolds), where the class society rules call it out by name (some naval and high-spec offshore specs), and where higher strength is needed to reduce wall thickness and weight on a length-critical system. EEMUA 234 is the standard to specify if you go this route.

3. Size Range, Pressure Classes, and How to Read an EEMUA 144 Schedule

EEMUA 144 covers Cu-Ni tube from DN15 (1/2") up to DN500 (20") and separates the supply into two pressure classes — 16 bar and 20 bar — with a different wall thickness for each. The split is the same for both alloys, so when you compare 90/10 and 70/30 on the same drawing you compare like-for-like mass. The actual size tables run on the OD list from BS EN 12449:2012 Table 16(1) up to 450 mm, with the remaining larger sizes (500 mm and above) taken from BS MA 60 (the withdrawn but still-referenced ships' pipework summary). Most yards, in practice, draw their 90/10 schedule from DN15 to DN300, and step up to 70/30 for the larger lines or where a heavier wall is required for mechanical reasons.

A common error is to specify "EEMUA 144" without stating the pressure class, then end up with a wall that is too thin for the design pressure of the line. Always state both the standard and the pressure class on the RFQ — for example, "EEMUA 144, 16 bar, 90/10, DN100".

4. Welding, Bending, and Field Fabrication on a Yard

Cu-Ni tube is welded with TIG/GTAW as the default, using a matching filler — ERCuNi (Cu-Ni 90/10) filler for 90/10 base metal and ERCuNi for 70/30 base metal, typically supplied as 1.6 mm or 2.4 mm rod. No preheat is required and no post-weld heat treatment is needed. Backing gas (typically argon or argon/helium) is mandatory on the root pass to prevent oxide formation on the inside surface — this is the single most common cause of in-service pitting. Bend radii follow the rules in EEMUA 144 Annex or, in US practice, MIL-T-16420K.

5. Inspection, Testing, and What the MTC Must Show

A mill-direct Cu-Ni tube shipment for marine service should be released with EN 10204 3.1 (or 3.2 for class-witnessed lots) Material Test Certificate, and the certificate should record at minimum:

• Heat analysis chemistry with all EEMUA 144 / 234 elements (Cu incl. Ag, Ni incl. Co, Fe, Mn, Zn, Pb, S, P, C) and the residual "other named elements" cap at 0.3% max
• Mechanical test results: tensile strength, 0.2% yield strength, elongation
• Dimensional report: OD, wall, length, ovality — against the table in the standard and the tolerance class ordered
• Non-destructive test: 100% eddy current (per EEMUA 144 / ASTM E243) for seamless tube, plus hydrostatic test as a default
• Surface condition: bright-annealed, free of heavy oxide, with plastic end caps fitted
• Marking: manufacturer, standard, grade, size, heat number, inspector stamp

For naval / MIL-T-16420K (SH) service, the certificate scope expands to include impact testing at low temperature, more detailed NDT, and often a class-witnessed 3.2 certificate rather than 3.1.

6. System-Level Spec: Pairing Cu-Ni Tube with the Rest of the Seawater Loop

A seawater system on a ship or platform is more than tube. The same Cu-Ni material logic applies to the fittings, flanges, and valves in the loop, and a mill-direct supplier that can deliver the full package in one shipment saves a yard weeks of receiving inspection. The components you should expect to source together:

• Cu-Ni tube per EEMUA 144 / 234, MIL-T-16420K, GB/T 26291, DIN 86019, or ASTM B466 — seamless ≤ 419 mm, seam-welded > 419 mm
• Cu-Ni flanges per EEMUA 145 or ASME B16.5 (composite or solid)
• Cu-Ni fittings (elbows, tees, reducers) per EEMUA 146 — these sit on the pipe fittings shelf in the same product family
• Compatible valves (typically bronze or Ni-Al-bronze bodied, Cu-Ni or stainless trim) — sourced from the industrial valves line
• Gaskets — non-asbestos compressed fiber or PTFE for Cu-Ni flanges; avoid graphite-only on thin-wall tube because of the higher seating stress
• Stud bolts and nuts — typically stainless steel A2-70 / A4-80 with PTFE or graphite coating, never bare carbon steel

7. A Six-Step Procurement Workflow That Prevents Rework at the Yard

The cleanest B2B RFQ-to-delivery path for a marine Cu-Ni tube package looks like this. Each step is one the mill and the buyer's QA team should agree on in writing before the PO is cut.

8. Common Sourcing Pitfalls — And How to Avoid Them

Five errors we see most often on B2B marine Cu-Ni tube orders, with the practical fix for each.

• Pitfall 1 — "EEMUA 144" without a pressure class. Forces the mill to default to 16 bar; you may end up with a wall that is too thin for the design pressure. Fix: write "EEMUA 144, 20 bar, 90/10" on the RFQ.
• Pitfall 2 — Mixing UNS numbers across standards. 90/10 is C70600 in ASTM and CW352H in EN — same alloy, different designation. A drawing that says "UNS C70600 to ASTM B466" and a delivery note that says "CW352H to EN 12451" describe the same chemistry, but a strict QA reviewer may flag it. Fix: state both designations or pick one and let the mill cross-reference.
• Pitfall 3 — Ordering seam-welded tube below 419 mm. EEMUA 144 calls for seamless below 419 mm and seam-welded above. Some lower-cost suppliers will deliver welded tube in the seamless range, which class surveyors will reject. Fix: add "seamless only, ≤ 419 mm" to the RFQ.
• Pitfall 4 — Skipping the impact test on (SH) naval orders. MIL-T-16420K (SH) requires Charpy impact at a specified low temperature. A 3.1 certificate without impact data is a class-witness hold. Fix: require "3.2 certificate with impact test results" in the QA terms.
• Pitfall 5 — Not extending the supplier scope to fittings and flanges. A tube shipment in 90/10 paired with carbon-steel fittings creates a corrosion-couple system and an instant class objection. Fix: buy the pipe fittings and flanges from the same mill, in the same alloy system, on the same PO.