CuNi 90/10 & CuNi 70/30 Blind Flanges — ASTM B151, ASME B16.5, B16.47, MSS SP-44, API 6A. Class 150–2500 | NPS ½" to 60".
A Copper Nickel Blind Flange (CuNi BL Flange) is a solid, disc-shaped flange with no center bore — used to close the open end of a piping system, pressure vessel nozzle, or valved connection. It is bolted against a mating flange to create a pressure-tight seal, making it an essential component for pipeline termination, isolation, and pressure testing.
Sunflex Metalloy manufactures CuNi Blind Flanges in CuNi 90/10 (UNS C70600) and CuNi 70/30 (UNS C71500) per ASTM B151, conforming to ASME B16.5, ASME B16.47, MSS SP-44, API 6A, DIN 2527, EN 1092-1 Type 05, and BS 4504 standards.
Termination of offshore pipelines, pig launcher kicker lines, dead-end branches
Blanking unused hull penetrations, isolating seawater system sections during maintenance
Isolating membrane trains, blanking unused nozzles in pressure vessel arrays
Temporary isolation of pipeline sections for online inspection or repair work
Blanking condenser water box openings during tube cleaning and maintenance operations
Closing spare nozzles on manifolds, blanking unused riser connections on topsides
All CuNi flanges are forged from ASTM B151 billets, heat treated (annealed) to restore ductility per ASTM B151 requirements, then CNC machined to ASME B16.5 / B16.47 dimensional tolerances. Full quality records and heat treatment certificates accompany every delivery.
XRF-based Positive Material Identification per ASTM B151 for Cu, Ni, Fe, Mn chemistry verification on every heat number.
Shell hydrostatic testing at 1.5× rated pressure per ASME B16.5 / API 598 with hold time verification and certified results.
Volumetric UT per ASTM A388 / EN 10228-3 on all forgings to detect internal flaws before and after machining.
Surface DPT per ASME Section V / ASTM E165 on flange faces and bore after final machining operations.
100% dimensional check per ASME B16.5 / B16.47 tables using calibrated vernier, micrometers, and CMM instruments.
Tensile, yield, elongation, and Brinell hardness per ASTM B151 on test coupons from each production heat.
CuNi Blind Flanges subjected to full pipeline pressure (for hydrostatic testing) must be designed to withstand the maximum allowable pressure at test temperature. Flange thickness verification per ASME VIII Div.1 Appendix 2 may be required for elevated pressure classes.
| Property | CuNi 90/10 (C70600) | CuNi 70/30 (C71500) |
|---|---|---|
| Tensile Strength (UTS) | 275 MPa (40 ksi) min | 380 MPa (55 ksi) min |
| Yield Strength (0.2%) | 105 MPa (15 ksi) min | 170 MPa (25 ksi) min |
| Elongation (50 mm GL) | 30% minimum | 30% minimum |
| Brinell Hardness (HB) | ≤ 100 HB | ≤ 120 HB |
| Density | 8.94 g/cm³ | 8.94 g/cm³ |
| Modulus of Elasticity | 132 GPa | 152 GPa |
| Element | CuNi 90/10 (C70600) | CuNi 70/30 (C71500) |
|---|---|---|
| Copper (Cu) | Remainder (~88–90%) | Remainder (~65–70%) |
| Nickel (Ni) + Co | 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 |
Every CuNi flange is manufactured with full heat traceability. Chemical composition is verified by OES (Optical Emission Spectrometry) on each heat and confirmed by XRF-based PMI prior to dispatch. MTC provided per EN 10204 3.1 (standard) or 3.2 (third-party witnessed) per project requirements.
| Standard | CuNi 90/10 Designation | CuNi 70/30 Designation |
|---|---|---|
| UNS (ASTM) | C70600 | C71500 |
| DIN / W.Nr. | CuNi10Fe1Mn / 2.0872 | CuNi30Mn1Fe / 2.0882 |
| EN (CW No.) | CW352H | CW354H |
| BS | CN102 | CN107 |
| MIL Spec | MIL-T-16420 (Comp B) | MIL-T-16420 (Comp A) |
| NORSOK MDS | C-600 (CuNi 90/10) | C-601 (CuNi 70/30) |
Marine and offshore piping systems always include blind flanges on dead-end connections, spare nozzles, and future tie-in points. CuNi Blind Flanges are specifically preferred because they provide the same corrosion resistance as the mating CuNi pipe system — avoiding galvanic compatibility issues and ensuring the same service life as the rest of the pipeline. Using CuNi blind flanges with CuNi pipe ensures metallurgical compatibility and prevents accelerated galvanic corrosion at the joint.
Yes — this is one of the primary applications. CuNi Blind Flanges are bolted onto the open end of a pipeline section while it is pressurised with water for hydrostatic testing per ASME B16.5, ASME B31.3, or project hydrostatic test procedures. The blind flange must be rated for the full hydrostatic test pressure (typically 1.5× design pressure), and the thickness must be verified if test pressure approaches the maximum allowable working pressure.
ASME B16.47 Series A corresponds to the MSS SP-44 standard and has larger outside diameters and thicker flanges than Series B. Series B corresponds to the API 605 standard and has more compact dimensions. For NPS 26" to 60" CuNi Blind Flanges, customers must specify whether Series A or Series B is required as the bolt hole patterns and ODs differ significantly.
Yes. Sunflex Metalloy can supply CuNi Blind Flanges with machined and tapped center connections (typically ½" NPT or ¾" NPT threaded) for pressure gauge connections, thermowell installations, or drain/vent connections. These are specified as 'Blind Flange with Center Connection' and the tapped hole specification must be provided at time of order.
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