CuNi 90/10 & CuNi 70/30 Weld Neck Flanges — ASTM B151, ASME B16.5, B16.47, ANSI, MSS SP-44, DIN 2633, EN 1092-1. Class 150–2500 | NPS ½" to 60".
A Copper Nickel Weld Neck Flange (CuNi WN Flange) is a forged flange featuring a long, tapered hub that is butt-welded directly to the pipeline. The hub's gradual transition from the flange thickness to the pipe wall thickness provides superior stress distribution across the joint — making it the preferred choice for high-pressure, high-temperature, and severe cyclic loading conditions in oil & gas, marine, and offshore applications.
Sunflex Metalloy manufactures CuNi Weld Neck Flanges in two grades: CuNi 90/10 (UNS C70600) and CuNi 70/30 (UNS C71500), conforming to ASTM B151 for forging bar stock and ASME B16.5 / B16.47 for flange dimensions and pressure ratings.
Offshore topsides, subsea manifolds, pig launchers, wellhead headers
Seawater cooling lines, ship hull fittings, fire mains, ballast systems
SWRO intake headers, MSF brine discharge lines, evaporator connections
Condenser cooling water lines, coastal intake/outfall piping systems
Offshore FPSO topsides, platform decks, subsea flowlines, process skids
Subsea tree assemblies, manifold connections, umbilical terminations
CuNi billets per ASTM B151 are heated to forging temperature and formed under multi-ton hydraulic presses. After forging, flanges undergo controlled heat treatment (annealing at 650–750°C for CuNi 90/10) to restore ductility and relieve residual stresses. CNC machining ensures ASME B16.5 dimensional tolerances.
XRF spectrometer verification of Cu, Ni, Fe, Mn chemical composition per ASTM B151 for every heat number batch.
Shell hydrostatic test at 1.5× rated working pressure per ASME B16.5 Table E1.1 with hold time verification.
Radiographic examination per ASME Section V, Article 2 / ASTM E1032 for critical pressure class flanges.
Volumetric UT per ASTM A388 / EN 10228-3 on all forgings to detect internal flaws before machining.
Surface examination per ASME Section V, Article 6 / ASTM E165 on flange face and bore after machining.
100% dimensional check per ASME B16.5 / B16.47 tables using calibrated instruments and CMM.
| Feature | Weld Neck (CuNi) | Slip-On (CuNi) | Threaded (CuNi) |
|---|---|---|---|
| Pressure Rating | ✅ Highest (Class 2500) | ⚠ Medium (Class 600) | ⚠ Low–Medium |
| Stress Distribution | ✅ Excellent (tapered hub) | ⚠ Good | ❌ Poor |
| Radiographic Inspection | ✅ Yes (butt weld) | ⚠ Limited | ❌ No |
| Cyclic Service Suitability | ✅ Excellent | ⚠ Moderate | ❌ Not recommended |
| High Temperature Service | ✅ Excellent | ⚠ Moderate | ⚠ Limited |
| Cost | Higher (justified by performance) | Lower | Lowest |
| Property | CuNi 90/10 (C70600) | CuNi 70/30 (C71500) | Test Standard |
|---|---|---|---|
| Tensile Strength (UTS) | 275 MPa (40 ksi) min | 380 MPa (55 ksi) min | ASTM B151 |
| Yield Strength (0.2% Proof) | 105 MPa (15 ksi) min | 170 MPa (25 ksi) min | ASTM B151 |
| Elongation (% in 50mm) | 30% minimum | 30% minimum | ASTM B151 |
| Brinell Hardness (HB) | ≤ 100 HB | ≤ 120 HB | ASTM E10 |
| Density | 8.94 g/cm³ | 8.94 g/cm³ | — |
| Modulus of Elasticity | 132 GPa | 152 GPa | — |
| Thermal Conductivity | 40 W/m·K | 29 W/m·K | — |
| Coefficient of Thermal Expansion | 17.1 × 10⁻⁶/°C | 16.2 × 10⁻⁶/°C | — |
| Pressure Class | Rating at -29°C to 38°C | Rating at 100°C | Rating at 150°C | Rating at 200°C |
|---|---|---|---|---|
| Class 150 | 19.6 bar (285 psi) | 17.7 bar | 15.8 bar | 13.8 bar |
| Class 300 | 51.1 bar (740 psi) | 46.6 bar | 43.8 bar | 40.8 bar |
| Class 600 | 102.1 bar (1480 psi) | 93.2 bar | 87.5 bar | 81.6 bar |
| Class 900 | 153.2 bar (2220 psi) | 139.8 bar | 131.2 bar | 122.4 bar |
| Class 1500 | 255.3 bar (3705 psi) | 233.0 bar | 218.7 bar | 204.0 bar |
| Class 2500 | 425.5 bar (6170 psi) | 388.3 bar | 364.5 bar | 340.0 bar |
| Element | CuNi 90/10 (C70600 / W.Nr. 2.0872) | CuNi 70/30 (C71500 / W.Nr. 2.0882) |
|---|---|---|
| Copper (Cu) | Remainder (~88–90%) | Remainder (~65–70%) |
| Nickel (Ni) + Cobalt | 9.0 – 11.0% | 29.0 – 33.0% |
| Iron (Fe) | 1.0 – 1.8% | 0.40 – 1.0% |
| Manganese (Mn) | 1.0% max | 1.0% max |
| Lead (Pb) | 0.02% max | 0.02% max |
| Zinc (Zn) | 0.50% max | 0.50% max |
| Carbon (C) | 0.05% max | 0.05% max |
| Sulfur (S) | 0.02% max | 0.02% max |
| Phosphorus (P) | 0.02% max | 0.02% max |
Iron content in CuNi 90/10 (1.0–1.8%) is critical for seawater corrosion resistance — it promotes formation of a protective oxide film on the alloy surface. NORSOK MDS C-600 specifies minimum 1.0% Fe for seawater service CuNi 90/10 components.
| NPS (inch) | OD Flange (mm) | Bolt Circle (mm) | No. of Bolts | Bolt Hole Dia (mm) | Flange Thickness (mm) | Hub Length (mm) |
|---|---|---|---|---|---|---|
| ½" | 89 | 60 | 4 | 15.9 | 11.1 | 35 |
| ¾" | 99 | 69 | 4 | 15.9 | 12.7 | 38 |
| 1" | 108 | 79 | 4 | 15.9 | 14.3 | 41 |
| 1½" | 127 | 98 | 4 | 15.9 | 17.5 | 52 |
| 2" | 152 | 120 | 4 | 19.1 | 19.0 | 57 |
| 3" | 191 | 152 | 4 | 19.1 | 23.9 | 67 |
| 4" | 229 | 190 | 8 | 19.1 | 23.9 | 76 |
| 6" | 279 | 241 | 8 | 22.4 | 25.4 | 89 |
| 8" | 343 | 298 | 8 | 22.4 | 28.6 | 102 |
| 10" | 406 | 362 | 12 | 25.4 | 30.2 | 114 |
| 12" | 483 | 432 | 12 | 25.4 | 31.8 | 127 |
| 14" | 533 | 476 | 12 | 28.6 | 35.0 | 140 |
| 16" | 597 | 540 | 16 | 28.6 | 36.6 | 152 |
| 18" | 635 | 578 | 16 | 31.8 | 39.7 | 165 |
| 20" | 698 | 635 | 20 | 31.8 | 42.9 | 178 |
| 24" | 813 | 749 | 20 | 35.1 | 47.7 | 203 |
All dimensions in millimetres. Tolerances per ASME B16.5 Table I. For Class 300–2500 and large diameter ASME B16.47 Series A & B dimensions, contact our technical team.
| Standard | Description | Applicability |
|---|---|---|
| ASTM B151 | Cu-Ni alloy rod, bar & shapes (UNS C70600 / C71500) | Forging raw material |
| ASTM B466 | Seamless Cu-Ni pipe & tube | Pipe schedule reference |
| ASME B16.5 | Pipe flanges NPS ½ to 24, Class 150–2500 | Dimensions & pressure ratings |
| ASME B16.47 | Large diameter flanges NPS 26–60 (Series A & B) | Large bore flanges |
| ANSI B16.5 | American National Standard — flanges | US project specifications |
| MSS SP-44 | Steel pipe line flanges | Pipeline applications |
| DIN 2633 | Weld neck flanges PN 16 per German standard | European projects |
| EN 1092-1 | Flanges and their joints — European standard | European CE-marked projects |
| BS 4504 | British Standard flanges for pipes & fittings | UK/Commonwealth projects |
| ISO 7005-1 | Metallic flanges — steel flanges | International projects |
| API 6A | Wellhead and Christmas tree equipment | Upstream oil & gas |
| API 6D | Pipeline valves — flanged ends specification | Pipeline applications |
| NORSOK MDS C-600 | CuNi material data sheet for offshore | Norwegian offshore projects |
| EN 10204 3.1 / 3.2 | Inspection documents — Mill Test Certificates | Material traceability |
| ASME Section V | Non-destructive examination procedures | NDT methodology |
| ASME Section IX | Welding and brazing qualifications | Welding procedure approval |
CuNi 90/10 (C70600) contains 90% copper and 10% nickel and is the most widely used marine grade — offering excellent seawater corrosion resistance at a lower cost. CuNi 70/30 (C71500) contains 70% copper and 30% nickel and provides higher tensile strength (380 MPa vs 275 MPa), superior resistance to high-velocity seawater erosion-corrosion, and better performance at elevated temperatures. CuNi 70/30 WN flanges are typically specified for naval condenser service, desalination plants, and high-velocity seawater lines above 3 m/s.
CuNi Weld Neck Flanges are manufactured from forging billets per ASTM B151 (Cu-Ni Alloy Rod, Bar and Shapes). The flange dimensions and pressure ratings follow ASME B16.5 (NPS ½ to 24") or ASME B16.47 (NPS 26 to 60"). Additional applicable standards include ANSI B16.5, MSS SP-44, DIN 2633, EN 1092-1 Type 11, BS 4504 PN 16/25/40, ISO 7005-1, API 6A, API 6D, and NORSOK MDS C-600 for offshore Norwegian projects.
Sunflex Metalloy manufactures CuNi Weld Neck Flanges from NPS ½" (DN 15) to NPS 60" (DN 1500). Sizes up to NPS 24" conform to ASME B16.5, while NPS 26" to 60" are manufactured per ASME B16.47 Series A (MSS SP-44) or Series B (API 605). Custom sizes outside standard tables are also available on request.
CuNi Weld Neck Flanges are available in all standard ASME B16.5 pressure classes: Class 150, 300, 600, 900, 1500, and 2500. The corresponding DIN/EN pressure designations are PN 10, PN 16, PN 25, PN 40, PN 63, PN 100, PN 160, PN 250, and PN 320. Pressure-temperature ratings per ASME B16.5 Table 2-1.1 (CuNi Group 3.3) apply.
Yes. We provide complete Mill Test Certificates (MTC) as per EN 10204 3.1 (manufacturer's own inspection) or EN 10204 3.2 (third-party independent inspection) for all CuNi flanges. The MTC includes chemical composition analysis, mechanical test results, heat treatment records, PMI results, hydrostatic test certificates, dimensional inspection reports, and NDE/NDT certificates as applicable to the order.
Absolutely. We welcome third-party inspection by all major internationally recognized agencies including Bureau Veritas (BV), DNV-GL, Lloyd's Register (LR), American Bureau of Shipping (ABS), SGS, Intertek, TÜV Rheinland, and RINA. We coordinate with the TPI agency to provide factory access, documentation, and witness testing during production and final inspection.
Send us your specifications — size, pressure class, grade, quantity, and delivery requirements. We'll respond within 24 hours with pricing and lead time.