Copper Nickel Pipeline Systems: The Ultimate Guide

Copper Nickel Pipeline Systems are used by many industries using seawater such as shipping, offshore oil and gas production, power plants and coastal industrial plants.

Seawater is mainly used for cooling purposes, but it is also found in oil field water injection, desalination plants, and fire-fighting.

This book will provide a basic overview of the Copper Nickel Pipeline Systems. 

Chapter 1 What are Copper Nickel Pipeline Systems?

Copper-nickel (Cu-Ni) pipeline systems are an assembly of copper nickel pipes, copper nickel pipe fittings, copper nickel flanges and valves that connect processing systems for handling seawater.

90-10 Cu-Ni and 70-30 are the two copper nickel alloys primarily used in these pipeline systems. The reasons for using them are exactly three: corrosion and biofouling resistant, high strength and low-cost fabrication.

copper nickel pipe system

The use of 90-10 Cu-Ni is primarily used in submarines due to its high strength. The remaining applications of Cu-Ni are with 70-30 Cu-Ni.

While both materials are useful, and designs have to factor in velocity and temperature, the current trend is towards the use of 90-10 Cu-Ni rather than other alloys such as aluminum brass , stainless stell or others, the reasons for this are:

• Cu-Ni alloys have better weldability and higher strength.
• Cu-Ni alloys has high stress corrosion resistance. Cu-Ni alloys do not usually require any stress relief heat treatment after fabrication.
• Cu-Ni alloys has a proven track record of reliability. In fact, only 9 cases of premature failure have been reported in the last 20 years

You can also check the copper nickel alloy chemical composition here.

The Cu-Ni alloys have proven themselves over the years in military operations, that is why all navies use Cu-Ni  90-10 to be specific for most of their pipeline systems.

There are also proven economic factors that limit the use of other materials, and these are:

1. Carbon steel and cast iron are low cost materials, while they are stronger, they require considerable life-time maintenance, as well as being magnetic.
2. Cu-Ni is low cost fabrication materials; low maintenance cost too, easy to manipulate and design and easy to fix under times of pressure.

Cu-Ni are corrosion and biofouling resistant which make them the ultimate choice of material for any seawater application.

However, they are used primarily for the pipeline systems, casings and equipment interiors can be made of other materials, and usually are.

Thus Cu-Ni pipeline systems are a symbiotic part of a whole system where many materials are used together.

Planning pipeline systems require expertise since heat and pressure differences between different materials can impede integrity, so while a Cu-Ni pipeline system might be perfect, it has to be part of a perfect system to provide the best performance.

Conclusions

Cu-Ni pipeline systems are perfect for all seawater processing systems. They provide the strongest, most resistant, and economical solution to handling long life corrosion and biofouling in a complex system. Fabrication is cheap and easy, maintenance is low cost and easy, and they provide the highest economic ratio to quality and reliability over all other materials.

Chapter 2 Effect of Velocity

All seawater piping systems must deal with velocity. This is the most important aspect of any sweater piping system and system design, as well as quality of fabrication, is of utmost importance.

When designing systems for velocity several mechanical attributes come into play, and these include the size, dimensions, and a number of pipes and valves used within a system.

Velocity influences not only the costs of manufacture but also the behavior of corrosion as well as how much maintenance a system will require.

The main differences in how materials react to corrosion are:

High corrosion of around 0.1mm-0.2mm/annum: Carbon Steel, it is cheap and abundant and strong, but it will wear out very quickly when compared to other alloys, as well as requires constant maintenance.

The flow rate will either increase the corrosion or decrease it based on the mass flow of oxygen on the surface of the material. Corrosion includes pitting, that focuses continuous and exaggerated erosion within the pitted area. Zinc coating (galvanizing) will prolong the lifetime of the carbon steel surface by around 6 months at the most.

So if you use the composite weld neck flange , the material outer flanges , or named as backing flanges ( DIN 86037 standard and EEMUA 145 ), is carbon steel with galvanized.

Friction in pipes due to the flow of the fluid

Stainless steel alloys are less liable to fall for corrosion, but they are susceptible to pitting and localized crevices in low pressure systems, so they are not considered ship worthy of pipe systems.

Nickel base including Inconel^TM Alloy 625, Hastelloys^TM C-276, C-22, and titanium are impervious to pitting or crevice corrosion in low velocity seawater and are impervious to attack under high pressure systems as well. However, the cost of these materials makes them economically unsound for most systems.

The Cu-Ni alloys provide both the velocity proof attributes as well as an economically viable solution, which is why they are considered to be the best choice for most sweater piping systems.

the attributes of materials commonly used in seawater systems.

Velocity is the major issue when designing piping systems. Most designs are made around standard pipe diameters and thicknesses.

When designing a system, it is important to remember that effect that certain parts have on velocity. The velocity may increase due to turbulence caused by small radius elbows, orifices, partly throttled valves, misaligned flanges, etc.

All designs must be carefully tested both in the development stage and after fabrication. All systems must decrease turbulence to the minimum.

Effect of Temperature

Many studies have shown that the higher temperature rates tend to increase corrosion in non-Cu-Ni systems. While in Cu-Ni systems the film forms on the surface of the alloys at the following recorded rates:

• 1 day at 15°C
• A week or more at 2°C 

Chapter 3:Main Components in Copper Nickel Alloy Pipe Line

3.1. Copper Nickel Pipes

Since there are only two standards Cu-Ni piping in use, the same treatment of the alloys is expected by fabricators as well as maintenance engineers of the systems.

Copper Nickel Pipes

Here are the globally accepted guidelines for handling Cu-Ni piping guidelines for good surface film formation:

• Maintain a clean environment at all times, and assure that all lubricants, dirt, and debris are cleared from the system on a daily basis.
• Use filters to avoid solid state matter invading the system.
• Always use clean and unpolluted sea water or fresh water for all hydrotesting. If polluted water was introduced into the system, flush it out, rinse clean the system, blow dry it and start again.
• When introducing a new system with intermittent flow, such as a fire fighting system, use sea water that has minimum levels of matter in the suspension. After which you must flush clean the system within 4-5 days with oxygenated water to avoid putrefaction.
• To protect against sulfides in the water, add ferrous sulfate or install simulated iron anodes to improve film formation.
• Make sure you constantly maintain your system after installation. Mature film formations take up to 3 months to form in seawater, but time-frames can change with hotter temperature climates.
• Sea water pumping systems that have high levels of matter suspended in the water should be maintained at a minimum flow rate above 0.5-1m/s; this will prevent deposits forming on the surfaces. However, if the sea water is contaminated with sand, the flow rate should be lowered by 1-1.5m/s.

3.1.1 Guidelines for Prevention of Erosion Corrosion:

Control Flow rate

• Never exceed maximum designed flow rate.
• Typical standard flow rates for Cu-Ni alloys are:

• For short duration processing, you can reach flow velocities of 10-15 m/s.

3.1.2 Guidelines for Shutdown and Standby Conditions:

3.1.3 Guidelines for Chlorination:

Sea water cooling systems add chlorine to control fouling. Chlorine is either electrolytically generated or added as sodium hypochlorite.

Cu-Ni alloys are not affected by moderate doses of chlorine at normal flow rates, but under turbulent conditions, a safe operating velocity should be considered when the chlorine dosing is too high.

Acceptable levels of residual chlorine content:

• For continuous dosage, 0.3 ppm with a maximum of 1 ppm
• For intermittent dosage, a level of 0.5 ppm
• Don’t chlorinate simultaneously.

3.1.4 Connection Guidelines:

• When there is a mismatch of pipe ends don’t exceed the half of wall thickness, it must be less than 2 mm.
• Maintain the preferred maximum depth of excessive weld root penetration. This is dependent on the pipe diameter. For example, DIN 85004 is:

3.1.5 Guidelines for Correct Piping Design and Installation:

• Streamline the system; this will reduce the pumping power and thus the probability of erosion.
• Make systems run piping as directly as possible
• Copper nickel elbow radius r greater or equal to 1.5d, or angled branches are preferable when considering the effects sudden of r/d-ratio for elbows has on pressure changes.
• Copper nickel stub end flanges are preferable and cut the gasket flush with the inner surface of the pipe.
• Design velocity should be reduced by 0.25-0.5 m/s when rolled-over type flanges are used.
• Try to minimize the number of valves to control the flow.
• Make sure you design the system so that operators can easily measure and control flow rates.
• When purchasing valves, make sure you have the weld geometry data that reveals the effect of the pressure drop in the system.
• It is best to maintain a downstream distance of 5 x ID from elbows to pumps and valves.

3.2 Copper Nickel Flanges

Flanges are used to connect pipes that you will want to disconnect in the future. There are two types of flanges:

Copper Nickel Flanges

• Solid flanges ( main 5 style in copper nickel field )
  • Copper Nickel Weld Neck Flanges
  • Copper Nickel Slip On Flanges
  • Copper Nickel Socket Weld Flanges
  • Copper Nickel Threaded Flanges
  • Copper Nickel Blind Flanges

• Weld-neck collars with loose flanges.
  • Composite Weld Neck Flanges
  • Composite Slip On Flanges

Advantages:

• Flanges can be disconnected
• Flanges can be used for large diameters
• Flanges allow for connecting different materials together
• Flanges provide good galvanic insulation
• Flanges allow for quick assembly and is-assembly in fire-hazardous areas.

Disadvantages:

• Flanges and/or weld neck collars are welded to the pipe
• Flanges require large spaces
• Flanges cost more and raise the assembly costs and time
• Flanges lead to auxiliary flange fittings

3.2.1 Solid Copper Nickel Flanges

Copper nickel solid flanges are always fabricated using 90-10 copper-nickel.

They are mostly used in tanks and vessels where the environment is hostile, usually in moist atmospheres.

Advantages:

• Very good in corrosive atmospheres.

Disadvantages:

• Flanges raise the price of fabrication
• Flanges must be in a fixed-position with the bolt-hole circles exactly lined up.
• The flange is fixed and cannot be turned.

3.2.2 Weld-neck stub ends with a loose flange

Composite Weld Neck Flanges

Weld-neck stub ends are made of 90-10 Cu-Ni alloy with a loose carbon steel flange with galv. These are found in dry atmospheres where only the inside of the system is exposed a corrosive medium.

Advantages:

• Fabrication is cheap
• Flanges are loose, so they can be turned.

Disadvantage:

• Are not good in corrosive atmospheres.

3.3 Copper Nickel Pipe Fittings

Copper Nickel Pipe Fittings

Copper nickel pipe fittings are a wide range of products that are used to complete a pipeline system. They come in many shapes and sizes and include the following:

• Copper Nickel Elbows: These are used to change the direction of flow.
• Copper Nickel Tees: These are used to channel the medium into more than one direction.
• Copper Nickel Reducers: These are used to change the flow rate of the medium in the system.

3.3.1 Copper Nickel Elbows

Copper Nickel Elbow

Copper nickel elbows are one of the most common copper nickel pipe fittings. They  come in many sizes and radius. They differ for specific systems. Most elbows come in a pre-defined standard form, the bend refers to the inside radius, and these are 1.0xD, 1.5xD in copper nickel pipe fittings field.

Copper nickel elbows flow behavior and their pressing properties depend decisively on the bending radii and the bending angles.

3.3.2 Copper Nickel Tee

Copper nickel tee is the most common copper nickel pipe fitting. It is used to combine or divide the flow of seawater.

Copper Nickel Equal Tee

Copper nickel tee come a variety of connection options that include copper nickel butt-weld tee, female thread and socket weld tee.

Copper nickel tees are used to connect pipes of different diameters or change the direction in a pipe run, or both.

The design of a pipeline system may include tees with copper nickel alloy equal tee or copper nickel reducing tee size of their three connections, although copper nickel equal tees are the most common.

3.3.3 Copper Nickel Reducers

Copper nickel reducers are used to meter the flow as a function of direction and not design.

Copper Nickel Concentric Reducer

These fittings will most probably cause more turbulence in the system when the dimension is expanded.  We calculate the maximum taper angle a for non-turbulent flow as:

• &alpha; = 2φ<40°
• &alpha; – Taper angle
• φ – reduction / expansion angle

Generally, turbulence rarely induces damage. That is why reducers in accordance with DIN, EEMUA or ANSI are applied with an expansion angle up to 19°.

They are two types reducers , copper nickel concentric reducers and copper nickel eccentric reducers.

3.4 Valves and Pumps in Cu-Ni Systems

General

valve

Valves are the main parts of a pipeline system that are affected by corrosion.

This is due to the number of moving parts within the valve, and the resistance these produce within the flow.

Valves have three main components:

• The body
• The seat
• The shaft (or stem)

Some valves are used for throttling flow, and as such create turbulence. We shall look at the three components and how valves effect flow.

Valve Bodies

Good valve bodies are made of Cu-Ni components; this assures that both the body and the internals are well kept and secure from corrosion.

In Table 2 you can see the effect of velocity in the various Cu-Ni and other cast alloy valves. Note that Cu-Ni gives the best corrosion resistance results.

Valve Seats and Stems V

Since valves are the more expensive parts of a seawater piping system, design features must be considered for practical uses as well as financial ones. The design of the valve determines the cost based on weight and complexity in design. In most cases, the body is not made of a Cu-Ni alloy, but a harder material such as cast iron.

Care must be made to assure that these valves maintain their life expectancy over time. Since the cost of a “pure” Cu-Ni valve is higher than a hybrid metal valve, it is imperative to consider all the aspects of life expectancy before integrating a hybrid valve rather than a Cu-Ni valve.

A butterfly valve will cost less than a globe valve. However, a globe valve gives better flow characteristics.

Figure 1. Valve design

In some occasions, valves will be lined with a rubber fitting, even when using Cu-Ni alloy valves, internal turbulence has to be factored into the equation and linings are considered to be effective when dealing with surface adherence in the face of water under pressure.

The membrane valve is a great solution provider for good performance in seawater applications. The robber lining can be damaged when operators use the valve for severe throttling. The complex design of the globe valve tends to increase turbulence within the body that is why these valves should be 70-30 Cu-Ni.

Pump Casings

Pump casings can suffer damage caused by the difference in water speed due to the distance between the impeller and the casing. Experience has proven that longer lasting casings are made of chromium-containing 70-30 Cu-Ni. These casings outperform all other materials, including the standard 70-30.

In most cases, 70-30 casings perform satisfactorily, but due to the increase in pump speed, these too have a life span of only 18 months. The only way to reduce such failures is to either redesign the pump design to reduce seawater velocity over the surface of the casing or change the casing material to chromium-containing 70-30 Cu-Ni.

3.5 Strainers

simplex strainers

Strainers are divided between duplex strainers and simplex strainers. They are used widely on marine pipeline systems. Strainers filter out detrimental materials from the pipelines.

In most cases, the primary filter (trash rack) is a strong mesh or grid of metal that catches large objects and prevents them from blocking or clogging the system.

duplex strainers

These trash racks are made of painted steel to protect them from corrosion.

After the trash racks come a system of screens either stationary or traveling. They are set in the intake area of the system, followed by fine filters distributed within the system, usually by design.

Filters are also used to remove air from the system.

Air is a catalyst to corrosion when the Cu-Ni alloys meet air and seawater at the same time.

Design should include air release valves, in high area’s and near water boxes.

Actually, such strainers and copper nickel pipes are hard to transport , because of the big dimension and heavy weight.

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3.6 Gaskets

Gaskets operate like any other gasket; you must cut the gasket flush with the inner surface of the pipe.  The gasket must be an exact fit since turbulence can occur when you have either small or large gaskets. This turbulence adds to pitting and corrosion around the gasket seal, and this can lead to erosion of the gasket.

Gasket

When using a ring gasket, which is the most common in seawater pipeline systems make sure the surfaces are flush with each other. Also, as with all material handling, make sure the inner surfaces are clean. The integrity of the seal will affect its mechanical capabilities, so maintenance of the seal’s cleanliness before assembly is key to a successful fabrication process.

3.7 Bolting (Fasteners)

Fasteners as expected from this alloy are resistant to sea-water corrosion and widely used for onshore and offshore marine applications. Steel are most commonly used alloys for producing marine fasteners.

Bolting

Conclusion

Seawater piping systems must be designed form a holistic view point, only by looking at the greater picture can you build up the details and focus on issues to create a comprehensive and corrosion free system.

Chapter 4:Joining Methods

There are a number of methods for copper nickel joining parts in a piping system. Here is the list of the most common methods used, we will present the pros and cons of each method.

You can also view an in-depth article on welding and brazing in our article on Copper Nickel Welding Guide.

• Welded joints
• Brazed joints
• Flange connections
• Threaded unions
• Press joints
• Connections with pipe couplings

4.1 Butt Welded joints

The most common method of welding for piping systems is the butt weld joint, in general welding is when two parts are fused together by the melting the two surfaces and applying the molten material to meld the two together.

You can check copper nickel butt weld pipe fittings on our website , there are five main butt weld copper nickel pipe fittings. Elbow, reducer,tee,saddles and end cap.

Pros:

• Strength and stability of the welded join is similar to that of the joined parts material
• Conservation of space
• Cheaper fabrication using no extra fittings

Cons:

• A solid join, cannot be disconnected
• Assembly time is longer
• When different materials need to be joined, the welding process becomes more complex
• Sometimes the galvanic insulation is poor
• Welding must be performed in a clean and fire-hazard free environment

4.2 Brazed joints

Brazing is the application of molten material to glue two material surfaces together.

In copper nickel field , only eemua 146 have brazed forged fittings to be used.

If you want to know more about brazing weld method , you can feel free to check our other article < Copper Nickel Welding Guide > to get more info.

Pros:

• Assembly of Small diameters up to RA 38 are fast
• Conservation of space
• Capacity or high-pressure stress
• Brazing is more versatile when joining different types of material

Cons:

• More expensive to fabricate
  • A solid join, cannot be disconnected
  • Outside diameters greater than 76mm will have problems with obtaining sealed joints
  • Outside diameters greater than 76mm are more expensive to process
  • X-raying the joint for inspection purposes is not possible
  • The process only works for overlapped joints
  • Galvanic insulation is usually poor
  • You will need auxiliary fittings for joining
  • Brazing must be performed in a clean and fire-hazard free environment

4.3 Threaded unions

When you need to section to be fixed together but with the ability to disengage them in the future, you would prefer to use the threaded union approach.

Threaded union fittings are attached through welding, brazing, pressing and clamping, depending on the purpose and design.

In copper nickel field , eemua 146 and ansi b16.11 have the fittings to be used by threaded unions.

The normal threaded type is BSPT and NPT.

Pros:

• The assembly process is quick
• The joined components can be disconnected
• An assembled part can be taken apart without risk in a fire-hazardous area.
• These joins do not need any X-ray or ultrasonic testing
• You can join different materials easily

Cons:

• The material cost of assembly is high
• You need to consider assembly and disassembly spacing
• You can only use this for outer pipe diameters up to 76mm
• Galvanic insulation is poor
• There are two sealing categories that complicate the connection:
  • Metallic sealing effect
  • Soft sealing effect

4.4 Socket Weld Joints

Socket Weld is also very common joint style in copper nickel field. Especially in EEMUA 146 standard and ANSI B16.11 standards. The normally size is from 1/2” – 2”.

Pros:

• The assembly process is quick

Cons:

• The material cost of assembly is high

4.5 Metallic sealing effect

Metallic seals are used when aggressive, and the highly corrosive medium is present, as well as environments with extreme temperatures are present.

This type is not used in copper nickel.

Metallic seals come in a few forms, and they include:

• 24°/25° sealing taper
• Cone-shaped sealing
• Sealing with a wedge ring
• Sealing with a cutting ring
• Sealing by means of a collar

4.6 Soft sealing effect

A soft seal uses an O-ring to seal the connection between surfaces. While this is an easier system, it requires constant maintenance checks of the integrity of the seal.

4.7 Press joints

Press joints are used when permanently joining two pipe sections together. The joint is a mechanically crimped fitting that houses an O-ring into the pipes.

Pros:

• The assembly process is quick
• An assembled part can be taken apart without risk in a fire-hazardous area.
• These joins do not need any X-ray or ultrasonic testing

Cons:

• The process requires more materials, raising the cost
• The process requires more tools for pressing the metal to form the seal
• The join stress capacity is low
• It is a fixed join
• Assembly can only go up to 108mm outer pipe diameter
• Galvanic insulation is poor
• It is not advised to join different pipe materials

4.8 Joining with pipe coupling

A pipe coupling join is a non-fixed solution and allows for sections of pipe to be joined that can be disconnected at any time. The joint is made by clamping with a joining device. The coupling is usually stainless steel with an inner rubber seal.

Pros:

• The assembly process is quick
• An assembled part can be taken apart without risk in a fire-hazardous area.
• These joins do not need any X-ray or ultrasonic testing
• Galvanic insulation is good
• You can join different types of materials

Cons:

• Expensive assembly process
• The join stress capacity is low
• You need to invest in joining sockets

Chapter 5. Standards

5.1. Copper Nickel Pipes Standard

5.1.1 European Standard ( EEMUA 144 and DIN 86019 )

5.1.2.American Standard

5.1.3 Japanese Standard

5.2 Seamless and Welded Copper Nickel Butt Welded Pipe Fittings

5.2.1 European and American Standards

5.3 Copper Nickel Flanges

• EN1092-3 Flanges and their joints-Circular flanges for pipes, valves, fittings, and accessories

References

1. “Chlorination of Seawater – Effects on Fouling and Corrosion.” D. B. Anderson and R. B. Richards, Journal of Engineering for Power, July 1966.
2. Protection of Seawater System Pipework and Heat Exchanger Tubes in HM Surface Ships and Submarines in Sea water systems; UK Ministry of Defence Standard 02-781 Issue 2- May 2009.
3. Living with the Threat of Microbiologically Influenced Corrosion in Submarine Sea Water Systems-the Royal Navy Perspective; by Lt. G.J.E. Nicklin RN, MoD, UK. ©
4. British Crown Copyright 2008/MOD 9th International Naval Engineering Conference and Exhibition (INEC 2008) April 2008 Hamburg.
5. Copper Nickel Piping for Offshore Platforms, CDA Inc Application Data Sheet 708/5.
6. Materials Selection for High Reliability Sea water systems; B.Todd; CDA Inc Seminar Technical Report 7044-1919. The Application of Copper Nickel Alloys in Marine Systems.
7. Schleich. Typical Failures of CuNi 90/10 Seawater Tubing Systems and How to Avoid Them. Eurocorr 2004 Paper 124.
8. British Standard BS MA 18. Salt Water Piping Systems in Ships.
9. DIN 85004-2: 1996 Copper Nickel Piping Systems, Part 2: General Guidelines for Construction, Fabrication, Testing.
10. Fabrication.
11. Heat Exchangers and Piping Systems from Copper Alloys Commissioning, Operating, and Shutdown. KME Publication.
12. Cu-Ni Seawater Piping Systems. G. Wildsmith. Proceedings of Marine Engineering with Copper Nickel. London April 1988.
13. The Design and Installation of 90-10 Sea water Piping Systems. Nickel Development Institute Publication 1107.
14. Reference Section/Seawater Piping.
15. Application of Copper-Nickel Alloy UNS C70600 for Seawater Service; by W.Schleich; Paper 5222 Corrosion 2005. (©NACE).