Copper-Nickel Alloys in Shipbuilding and Repair


Ship Systems

Seawater is used for cooling, tank cleaning and heating, ballasting, waste disposal, firefighting and by distillation as a source of fresh water for boiler feed water and sanitary hot and cold water. All require piping systems which essentially consist of pumps, valves, pipes and fittings. In cooling systems, heat exchangers are also required.

Applications for copper-nickel alloys include condensers, coolers and other heat exchangers, seawater desalination plant systems for compressed air, sanitary systems, bilge, ballast water, brine, fire mains and sprinklers, fuel oil, lube oil, warm water heating, grey and black water, hydraulic lines and tank heating.

Seawater Cooling Systems

The seawater system may consist of shell and tube heat exchangers supplied with seawater through a piping system; the power being supplied by electrically-driven centrifugal pumps. Flow is controlled by valves. The cooling system for the main engine is normally separate from that used for auxiliary units. The main engine systems in diesel-powered ships consist of heat exchangers, water jacket, lubricating oil and charge air coolers. Copper-nickel can be used for these applications.

The alternative centralized cooling systems involve one large seawater cooled titanium plate heat exchanger to cool fresh water which circulates through various heat exchangers in the engine room. Inhibitors can be used to control corrosion on the fresh water side. Therefore, copper-nickels are confined to the primary side and inlet pipes for their good resistance to seawater.

For steam ships, such as nuclear powered ships or LNG tankers, copper-nickel is a candidate material for the condensers and seawater systems. The use of scoop intake systems on steam turbine powered ships normally require 70-30 or 66-30-2-2 Cu-Ni alloys with high resistance to impingement corrosion.

Bilge and Ballast Systems

These are used to empty bilges and to fill or empty cargo and ballast spaces with seawater within the ship. The systems operate intermittently, often once per week. The pipes are not exposed to flowing seawater for lengthy times but could spend most of their life holding stagnant seawater. In oil tankers, the cargo pipes and pumps are often used for ballast purposes as the quantities of seawater are large and require massive pipes and pumps to handle the volume efficiently.

Copper-nickel alloys can be used in areas not exposed to polluted, stagnant water for prolonged times. They are particularly suitable for pressure and return lines of hydraulically-operated components, such as cargo and ballast pumps and control valves.

Sanitary Systems

Discharges from sanitary systems, cabin and galley drains are collected and passed through a sewage treatment plant before being discharged overboard. Copper-nickel piping can be used to supply water to these systems.

Fire Fighting Systems

Seawater is used for firefighting on ships and is distributed throughout the ship by a fire main served by its own pump. This system is often used for other purposes used frequently but for only comparatively short periods, such as for deck washing. 90-10 Cu-Ni is used for this application.

Inert Gas Systems

These are used on tankers to blanket cargo tanks with seawater-scrubbed flue gas. Seawater supply uses 90-10 Cu-Ni pipes. However, the effluent is acidic and is normally handled by other materials.

Cargo Tank Heating Coils

Where cargoes are too viscous to be pumped at ambient temperatures, tank heating systems are required. This is achieved by passing steam through a system of tank heating coils. 90- 10 Cu-Ni can be used for this task with appropriate cargoes, including asphalt and bitumen.

Feed Lines to Desalination Plant

Fresh water is normally produced by distillation in compact desalinators. These are often constructed in 90-10 Cu-Ni, the system pipe work being the same alloy. Hot fresh water is passed through the tubes of a heat exchanger in the desalinator, causing the seawater to boil. The resulting vapor is condensed and collected after passing through demister and deflector plates. Brine is discharged or re-circulated through the system in 90-10 Cu-Ni piping.

Hydraulic and Pneumatic Systems

Most ships have remote-controlled equipment, such as valves, which are operated by hydraulic or pneumatic pressure. These can be used for cargo handling systems, hatch covers and engine controls. For high-pressure systems, 90-10 Cu-Ni is a normal choice. For very high pressures, the 70-30 alloy may be used.

Chiller Systems

Chiller systems are required to meet the demands for top-quality fish and the post-catch refrigeration requirements of the fishing industry. They are also required to control temperature in the cargo holds, to provide both heating, ventilating and air conditioning (HVAC) and provision plants for cruise vessels and other passenger ships, and other marine type refrigeration needs. Water-cooled condensing units are designed and manufactured using cleanable, shell-and-tube condensers with copper-nickel tubes for seawater and copper for freshwater applications.

To improve condenser and condensing unit efficiencies, internally and externally enhanced tubes have been developed and are extensively being used to increase the heat transfer capabilities of the tubes in the condenser while minimizing the fouling impact.

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Copper-nickel alloys possess ideal requirements for ship and boat hulls. With both good resistance to corrosion and macrofouling, coatings are unnecessary, providing both savings in fuel, hull maintenance time and cost. Over the last 30 years, experience has been gained in constructing hulls using different product forms of copper-nickel alloys:

  • Construction of the hull from copper-nickel alloy plate onto steel or copper-nickel frames;
  • Construction of the hull from copper-nickel roll-bonded onto steel plate;
  • Cladding a fibreglass, wood or steel hull with copper-nickel alloy sheet or foil.

With tight restrictions on the use of organo-tin copolymer coatings and the quest for alternative antifoulants underway, copper-nickel as a boat hull material can offer many practical benefits. See Ship and Boat Hulls for more information.

Additional Links for Condenser Heat Exchange and Piping systems and Boat Hulls

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  1. Cu-Ni Alloys in Desalination Systems, B. Todd, Seminar Technical Report 7044-1919, CDA Inc., The Application of Cu-Ni Alloys in Marine Systems .
  2. Fabrication, .
  3. Product Forms, .
  4. Properties, .
  5. Seawater System Components, CDA, .
  6. Seawater System Design, CDA, .
  7. Standards, .
  8. Wolverine Engineering Data Books, Wolverine Tube, Inc., .