CuNi 90/10 & CuNi 70/30 Orifice Flanges — ASME/ANSI B16.36, ASME B16.5. Class 300–2500 | NPS 1" to 16". Supplied in pairs for flow measurement.
A Copper Nickel Orifice Flange is a specialized flange pair used with a differential pressure (DP) flow measurement orifice plate. Unlike standard flanges, orifice flanges have precision-drilled and tapped ports (typically 1/2" NPT) on each flange face for connecting differential pressure taps (upstream and downstream) to a DP transmitter, gauge, or flow meter.
Sunflex Metalloy manufactures CuNi Orifice Flanges in CuNi 90/10 (UNS C70600) and CuNi 70/30 (UNS C71500) per ASTM B151, conforming to ASME/ANSI B16.36 and ASME B16.5 dimensional standards. Supplied in matched pairs with jack screws, stud bolts, nuts, and gaskets.
Ship seawater cooling circuits, air conditioning sea water lines
Ballast water systems, bilge, fire main and general service piping
Low-pressure intake and outfall piping, auxiliary seawater circuits
Utility seawater headers, non-critical process piping on platforms
Cooling water distribution headers in coastal power generation facilities
Jetty seawater supply systems, port utility piping installations
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.
Orifice Flanges are always supplied in pairs. Jack screws must be used to open the flanges for plate removal — never lever the flanges apart as this damages the seating faces. The differential pressure tap orientation (horizontal or vertical) must be specified at time of order to ensure correct tapping hole position for the installation.
| 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) |
Orifice Flanges are dimensionally identical to standard ASME B16.5 flanges of the same pressure class and size, but with the addition of: (1) two precision-drilled and tapped differential pressure ports on the pipe bore face of each flange at 180° apart; (2) two or four jack screw holes for controlled flange separation during plate removal; (3) identification markings (U/S and D/S for upstream and downstream). The flange pair is always supplied matched and tested together.
Yes — CuNi Orifice Flanges are the recommended choice for seawater flow metering. The CuNi 90/10 alloy provides the same outstanding seawater corrosion resistance as the rest of the CuNi piping system, ensuring the metering accuracy is maintained over the full service life without corrosion-induced bore distortion that would affect the beta ratio and flow coefficient.
Sunflex Metalloy supplies CuNi Orifice Flanges complete with: matched flange pairs (upstream and downstream), carbon steel or CuNi jack screws, stud bolts and nuts (per ASME B18.2.1 / ASTM A193 B7 or CuNi studs as specified), spiral wound gaskets (for RF facing), and the orifice plate if specified. DP transmitter isolation valves and manifold connections can also be coordinated through our supply.
The beta ratio (β = orifice bore d ÷ pipe bore D) is determined by the flow measurement engineer based on the required differential pressure range, flow rate range, and fluid properties per ISO 5167-2 / AGA Report No. 3. Sunflex Metalloy can machine the orifice plate to the specified beta ratio if provided the calculation sheet, or supply blank orifice plates for the customer's instrument engineer to machine to the required bore.
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