Cupronickel (CuNi) is a copper alloy containing nickel and other strengthening elements such as iron and manganese. The copper content in copper-nickel alloys typically ranges from 60% to 90%. (Monel is a term for a nickel-copper alloy with a minimum nickel content of 52%.)
Cupronickel or nickel alloys are silver in colour, despite having a higher copper content. Cupronickel has excellent corrosion resistance to salt water and is thus used in heat exchangers, piping, condensers in seawater systems, and marine hardware. It is also used in high-quality boat propellers, shafts, and hulls. Other applications for copper-nickel alloys include military equipment, chemical, electrical, and petrochemical industries.
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Usage of Copper-Nickel Alloys
Copper-nickel alloys have a wide range of applications, making manufacturing easier and more convenient. In addition to machine parts and repairs, these alloys have a long history of being corrosion-resistant, making them an excellent choice in outdoor environments.
Applications for Copper-Nickel Alloys.
Desalination of water
Copper-nickel alloys are widely used in multiple-effect distillation (MED) and multi-stage flash (MSF) desalination plants. Due to cost considerations, these alloys are preferred in corrosion conditions in various sections or areas of the plant.
An MSF plant employs a process that typically consists of a series of tube or plate heat exchangers capable of achieving temperatures of 120 C in the brine heater while decreasing as the brine and distillate pass through the plant for heat recovery, followed by heat rejection sections.
Long exposure to hot de-aerated seawater and brine is required for both the brine heater and the heat recovery sections. On the other hand, the heat rejection section employs natural seawater—the exteriors of the tubing handle water vapour and other non-condensable gases.
Offshore Petroleum and Gas
Copper-nickel alloys are widely used in cooling, seawater, and firewater/deluge systems on platforms and FPSOs (Floating Production Storage and Offloading vessels). They are most popular in warmer climates because of their excellent resistance to chloride crevice corrosion and stress corrosion cracking.
Electricity generation entails critical heat transfer processes such as heat exchangers, coolers, steam generators, condensers, pipework, valves, tanks, and fittings in nuclear and fossil-fuelled power plants. Copper-nickel alloys are ideal for these applications because they can be used successfully in various environments, including clean seawater with high total dissolved solids, brackish water, freshwater, and cooling tower water.
Shipbuilding and Repair
Aeons ago, the 90-10 and 70-30 copper-nickel alloys were developed for naval condensers and seawater piping. It is a testament to their toughness in harsh conditions that they are still used in many of the world’s most important navies. They are also used on FPSOs and commercial ships.
Seawater is used for tank cleaning and heating; cooling; ballast; waste disposal; firefighting; and as a source of fresh water for boiler feed water and sanitary cold and hot water through distillation. Pumps, pipes, valves, and fittings are all piping system components. Heat exchangers are also required for cooling systems. Onboard desalination plants, compressed air systems, sanitary systems, bilge, ballast water, brine, fuel oil, lube oil, fire mains and sprinklers, warm water heating, hydraulic lines, grey and black water, and tank heating are all applications for copper-nickel alloys.