70/30 Copper-Nickel Buttweld Pipe Fittings
70/30 Copper-Nickel / UNS C71500 / EN CuNi30Mn1Fe (CW354H, 2.0882) — the higher-strength copper-nickel for demanding seawater service. Tolerates higher velocities and temperatures than 90/10, with the same natural biofouling resistance. Used for condenser and heat-exchanger tubes, pump and valve bodies, brine heaters and high-flow seawater piping. ASME B16.9 and EEMUA 234. EN 10204 3.1/3.2.
½″–24″
Size Range
~4.5 m/s
Max Seawater Velocity
340 MPa
Min UTS (Annealed)
EN 10204
3.1 Std / 3.2 On Req.
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70/30 Copper-Nickel Grade Equivalents
| Common Name | UNS | EN Number | EN Name | Fitting Standard | ASME P-No. |
|---|---|---|---|---|---|
| CuNi 70/30 | C71500 | CW354H (2.0882) | CuNi30Mn1Fe | ASME B16.9 / EEMUA 234 | 34 |
| 70/30 Cupro-Nickel | C71500 | CW354H | CuNi30Mn1Fe | ASTM B466 / B122 (material) | 34 |
Material to ASTM B466 (seamless pipe) / B122 (plate). Fittings dimensionally to ASME B16.9 or EEMUA 234 for copper-nickel seawater piping. DIN 86019 / MIL-T-16420 also available for naval work.
Chemical Composition — UNS C71500 / EN CW354H
| Element | Specification |
|---|---|
| Cu | Balance (~68%) |
| Ni | 29.0–33.0% |
| Fe | 0.40–1.0% |
| Mn | 0.5–1.5% |
| Zn | ≤0.5% |
| Pb | ≤0.05% |
Higher nickel, higher strength. The ~30% nickel content raises strength and allows higher seawater velocity and temperature than 90/10. Controlled iron and manganese maintain resistance to impingement and erosion-corrosion.
Mechanical Properties — CuNi 70/30 (Annealed)
| Min. UTS | Min. YS | Elongation | Max Seawater Velocity | Max Service Temp |
|---|---|---|---|---|
| 340 MPa | 125 MPa | ≥30% | ~4.5 m/s | ~175°C |
Supplied in the annealed condition. 70/30 tolerates higher design velocity than 90/10; local turbulence at fittings should still be controlled by good hydraulic design.
Welding & Post-Weld Heat Treatment
No PWHT Required
Copper-nickel is a single-phase alloy and does not harden on welding, so no post-weld heat treatment is needed. Clean, oxide-free joints and full penetration are essential for seawater service.
Recommended Filler
ERCuNi (AWS A5.7) 70/30-type copper-nickel filler for GTAW and GMAW, matching the base composition for seawater resistance.
Preheat
No preheat required. Copper-nickel has lower thermal conductivity than copper, so standard heat input applies. Avoid interpass contamination.
Cleanliness
Remove all oxide, oil and marking ink before welding. Sulphur, lead and phosphorus contamination cause hot cracking in copper-nickel welds.
ASME P-Number
P-No. 34 (copper-nickel alloys). Separate WPS required — not covered by austenitic SS or nickel-alloy procedures.
Selection Guide — 70/30 vs 90/10 Copper-Nickel
| Grade | Nominal Ni | Max Seawater Velocity | Typical Use |
|---|---|---|---|
| CuNi 70/30 / C71500 | ~30% | ~4.5 m/s | Condensers, pumps, valves, high flow |
| CuNi 90/10 / C70600 | ~10% | ~3.5 m/s | Seawater mains, firewater, desalination |
| Super Duplex / S32750 | ~7% | High | High-pressure seawater, no velocity limit |
Key Application Areas
Condenser & Heat-Exchanger Tubes
Seawater-cooled condensers and heat exchangers where higher velocity and thermal duty demand the stronger 70/30 alloy.
Pump & Valve Bodies
Higher strength suits cast and wrought pump and valve components in seawater circuits.
Brine Heaters & Desalination
Brine-heater and high-temperature sections of MSF desalination plants.
High-Velocity Seawater Piping
Sections of seawater systems with elevated flow or turbulence beyond the 90/10 velocity limit.
Naval & Offshore
Naval seawater systems and offshore platform circuits requiring extra mechanical robustness.
Polluted / Turbulent Seawater
More aggressive polluted-seawater and turbulent conditions where 90/10 margins are marginal.
Available Fitting Types — 70/30 Copper-Nickel / C71500
Sizes typically ½″–24″. Larger sizes and EEMUA 234 dimensions available on enquiry.
Elbows — 90° & 45°
Long Radius (1.5D) and Short Radius (1D). ASME B16.9 / EEMUA 234. ½″–24″.
180° Return Bends
Long Radius. ASME B16.9. ½″–12″.
Equal & Reducing Tees
ASME B16.9 / EEMUA 234. ½″–24″.
Concentric & Eccentric Reducers
ASME B16.9 / EEMUA 234. ½″–24″.
Pipe Caps
ASME B16.9 / EEMUA 234. ½″–24″.
Collars / Stub Ends
EEMUA 234 composite flange collars for seawater piping. ½″–24″.
Crosses (4-Way)
ASME B16.9. ½″–8″.
Laterals (45° Y)
ASME B16.9. ½″–8″.
Flanges — All Types
Weld Neck, Slip-On, Blind, composite. EN 1092 / ASME B16.5. C71500. ½″–24″.
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Specify size, schedule, fitting type, standard (ASME B16.9 or EEMUA 234), and required MTR level (EN 10204 3.1 or 3.2 TPI). We respond within 1 business day.
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