LEADING COPPER NICKEL 90/10 & 70/30 COLLAR MANUFACTURER & EXPORTER — ISO 9001:2015 CERTIFIED
Manufacturer, Exporter & Supplier of Copper-Nickel 90/10 & 70/30 Collars
May 22, 2025 8 min read Sunflex Metalloy Engineering Team
Desalination plants — whether Multi-Stage Flash (MSF), Multiple-Effect Distillation (MED) or Seawater Reverse Osmosis (SWRO) — present a uniquely demanding corrosion environment: concentrated brine, elevated operating temperatures in thermal processes, continuous seawater intake, and decades-long design lives during which unplanned piping failure translates directly into lost fresh-water production. It is little surprise that Copper Nickel Welding Neck Collars and Stub End Collars are among the most widely specified flanged-joint components across the global desalination industry, particularly across the Gulf region where the majority of the world's large-scale MSF capacity is concentrated.
MSF plants operate by flashing heated seawater across a series of stages at progressively lower pressure, concentrating dissolved salts into an increasingly aggressive brine as the process proceeds. This brine, combined with elevated operating temperatures in the early stages, creates conditions considerably more corrosive than ambient seawater alone. SWRO plants, while operating at lower temperatures, still handle continuous high-volume seawater intake and concentrated reject brine streams. In both process types, any piping component that fails prematurely — including a flanged joint at a Welding Neck Collar or Stub End Collar — can force a costly unplanned shutdown of an entire train.
CuNi 90/10 (UNS C70600) is widely used throughout general seawater intake, cooling and lower-temperature brine handling piping in both MSF and SWRO plants, offering an excellent balance of corrosion resistance and cost across the majority of the plant's piping inventory. CuNi 70/30 (UNS C71500) is typically reserved for the highest-temperature brine heater and early-stage flash chamber piping in MSF plants, where its superior strength and higher erosion-corrosion threshold justify the additional material cost. Both grades are manufactured by Sunflex Metalloy as Welding Neck Collars, Stub End Collars and Composite Flanges to suit the full range of a desalination plant's piping specification.
The protective oxide film that Copper-Nickel alloys form in seawater remains stable across the elevated salinity and temperature conditions found in MSF brine circuits, a key reason why CuNi has displaced carbon steel and even many stainless steel grades in this application over the past several decades. This stability translates directly into the extended service life — often 25 years or more — that desalination plant operators require to justify capital investment in piping and associated flanged components including Welding Neck Collars and Stub End Collars.
MSF plants experience regular thermal cycling as stages start up, shut down and vary in load — placing cyclic stress on flanged joints. The extended hub length of long-pattern Welding Neck Collars and Stub End Collars (per ASME B16.9 or DIN 86037) provides a more gradual stress transition at the weld joint under these thermal cycling conditions compared to shorter pattern alternatives, making long-pattern collars a common specification choice for the highest-temperature sections of MSF plants.
Desalination authorities across the Gulf region — including major state utilities in Saudi Arabia, the UAE and Kuwait — typically reference a combination of ASTM/ASME material and dimensional standards alongside guidance published by the International Desalination Association (IDA) for material selection and corrosion allowance in desalination piping. Sunflex Metalloy's Copper Nickel Welding Neck Collars and Stub End Collars are manufactured to support compliance with these region-specific procurement requirements, with full EN 10204 3.1 Mill Test Certification and, where required, third-party inspection to satisfy Gulf desalination authority documentation standards.
For most desalination plant piping, Stub End Collars and Composite Flange assemblies offer the most cost-effective flanged connection, since the loose backing flange (commonly carbon steel or duplex stainless steel) never contacts the brine or seawater. Welding Neck Collars are typically specified where a more permanent, higher-integrity joint is required, such as at critical brine heater tube-sheet connections. Sunflex Metalloy's engineering team can support desalination EPC contractors in mapping the correct collar configuration and grade to each section of the plant's piping and instrumentation diagrams.
The brine heater and earliest flash stages of an MSF plant see the highest operating temperatures and most concentrated brine in the process, where CuNi 70/30's higher strength and erosion-corrosion resistance provide additional design margin compared to CuNi 90/10.
SWRO plants generally use less Copper-Nickel piping overall than MSF plants since much of the high-pressure membrane process uses duplex stainless steel or specialised polymer piping, but CuNi Welding Neck Collars and Stub End Collars remain widely used in SWRO seawater intake, pre-treatment and general cooling water piping.
Requirements vary by authority and project, but commonly include an EN 10204 3.1 or 3.2 Mill Test Certificate, dimensional inspection reports, and in many cases third-party witness inspection — Sunflex Metalloy supports all of these documentation levels.
Yes, Composite Flange assemblies (CuNi stub end with a loose backing flange) are widely used in desalination brine piping, since the wetted CuNi stub end handles the corrosive brine contact while a lower-cost backing flange material handles the structural bolting load.
Our engineering team is available to assist with collar selection, standard interpretation and custom specifications.
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