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Perormance matters

Copper-nickel Welding and Fabrication

Handling | Welding | PropertiesResistance to Corrosion and Bioouling | Important Applications

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cpp Dvp aii Puii 139,rvid uy 2013

cpp Dvp aii I Puii a7020-99/13,rvid uy 2013

ni Iiu Puii 12014,sd edii, uy 2013

cv p piu wd:TIG welding 90-10 copper-nickel straight pipe to a bend

(Courtesy Eucaro Buntmetall GmbH)

Copper Development Association is a non-trading organisation that promotesand supports the use o copper based on its superior technical perormanceand its contribution to a higher quality o lie. Its services, which include the

provision o technical advice and inormation, are available to those interestedin the utilisation o copper and copper alloys in all their aspects. The Associationalso provides a link between research and the user industries and is part o an

international network o trade associations, the Copper Alliance.

Copper Development Association Inc is a U.S-based, not-or-prot associationo the global copper industry, infuencing the use o copper and copper alloys

through research, development and education, as well as technical and end-usersupport. CDA is committed to promoting the proper use o copper materials insustainable, ecient applications or business, industry and the home.

The Nickel Institute is an international, non-prot organisation which promotesthe production, use and re-use (through recycling) o nickel in a socially and

environmentally responsible manner. They oer ree technical knowledge aboutnickel, its properties and uses to ensure optimum perormance, sae handlingand use. They are supported by most o the worlds producers o nickel and have

oces in Belgium, Canada, China, Japan and U.S.A.

Copper-nickel Welding and Fabrication

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Contents

coPPer-nIckel WelDIng anD abrIcatIon | 1

t d iu 2

1.0 Idui 3

2.0 th ay 4

2.1 Standards 42.2 Composition 4

2.3 Mechanical and Physical Properties 4

3.0 g Hdi 6

3.1 Cutting and Machining 63.2 Forming 7

3.3 Heat Treatment 73.4 Descaling 73.5 Painting 7

4.0 Wdi 8

4.1 Preparation or Welding 84.2 Tack Welding 84.3 Weld Preparations 9

4.4 Welding Consumables 94.5 Manual Metal Arc (MMA or SMAW) 104.6 Gas-shielded Tungsten Arc (TIG or GTAW) 10

4.7 Gas-shielded Metal Arc (MIG or GMAW) 114.8 Post-weld Treatment 124.9 Inspection 124.10 Mechanical Properties o Welds 12

5.0 cd P 13

5.1 Cutting 135.2 Welding 13

6.0 bzi 14

7.0 tu tuh ii 15

8.0 shhi d cddi oh suu 17

9.0 lii 19

10.0 Dii P 20

11.0 sw ci ri 21

11.1 Flow Rates 2111.2 Sand Abrasion 2111.3 Localised Abrasion 2111.4 Galvanic Behaviour 22

11.5 Handling Sulphides 23

12.0 biui ri 24

13.0 chi 25

14.0 biiphy 26

14.1 General 26

14.2 Fabrication 26

14.3 Piping Systems, Heat Exchangersand Condensers 26

14.4 Oshore Sheathing 2614.5 Boat Hulls 2714.6 Bioouling 27

15.0 uh Ii d advi 28

Dii:

Whilst this document has been prepared with care, Copper Development Association, Copper Development Association Inc and Nickel Institutecan give no warranty regarding the contents and shall not be liable or any direct, incidental or consequential damage arising out o its use. For

complete inormation on any material, the appropriate standard should be consulted.

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2 | coPPer-nIckel WelDIng anD abrIcatIon

t

Table 1 Designations in Standards or 90-10 and 70-30 Alloys

Table 2 UNS Chemical Composition (%) o 90-10 and 70-30 Alloys

or Welding Applications

Table 3 Typical Mechanical Properties o Annealed Copper-nickel

Sheet and Plate (taken rom EN1652:1997)

Table 4 Typical Physical Properties o Copper-nickels and Steel

Table 5 Welding Consumables - Specications

Table 6 Typical All-weld Metal Mechanical Properties (based on70-30 consumables)

Table 7 Bioouling Mass on Copper-nickel Sheathed Test PilingsAter 5 and 10 Years Exposure

iu

Figure 1 Examples o weld preparations or joining copper-nickel

plate

Figure 2 Examples o run sequence or welding copper-nickel clad

plate

Figure 3 Typical tube weld joint preparations or tube to tubesheet

abrication

Figure 4 Typical attachments or platorm sheathing

Figure 5 Copper-nickel boat landing stage

Figure 6 Galvanic series

Finished weld showing root penetration on pipe bore(Courtesy Eucaro Buntmetall GmbH)

Tables and Figures

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Copper-nickel alloys have a remarkablecombination o good resistance to bothcorrosion and bioouling in seawater. As

they are also readily welded and abricated,they are an obvious choice or pipesystems, heat exchangers and structures

engineered or marine use.

Copper-nickels have been specied or

seawater use or over 50 years; they arethe materials o rst choice or seawaterpipework and condenser/heat exchanger

service or many o the worlds navies,foating production storage and ofoadingvessels and merchant ships. They are used

in desalination, power plants and oshorere water systems, and or the sheathedsplash zone protection o oil and gas

platorm legs. In all such applications,their durability is proven.

Fabrication o copper-nickels is notdicult, although a higher degree ocleanliness is required than or steel. They

are ductile and easily ormed. Their

machinability is similar to that o

aluminium bronzes, phosphor bronzes andother copper alloys that do not havespecial ree-cutting additions. Copper-

nickels can be welded by most standardprocesses.

The core o this book is welding andabrication. General engineeringproperties, corrosion and bioouling

resistance and applications are includedonly where they infuence decisions on

abrication. It provides an inormedunderstanding o the two primarycopper-nickel alloys, to allow goodabrication and operation.

2

1.0 Introduction


TIG (GTAW) welding a 90-10 copper-nickel assembly

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3

2.0 The Alloys

There are two main grades o copper-nickelalloy used in marine service - 90-10 (10%nickel) and 70-30 (30% nickel).

The 70-30 alloy is stronger and has greaterresistance to seawater fow; but 90-10 will

provide good service or most applicationsand, being less expensive, tends to be morewidely used.

Both alloys contain small but importantadditions o iron and manganese, which

have been chosen to provide the bestcombination o resistance to fowingseawater and to overall corrosion.

2.1 sdd

Table 1 gives some o the more commoninternational designations or both alloys.

2.2 cpii

The chemical composition ranges or thetwo alloys vary between the dierent

standards. When materials are intended orwelding applications, the maximum limitsor some specic impurities need to berestricted because o their eects on hot

ductility, and thus on weldability. Exampleso preerred limits or Zn, C, Pb, S and P areshown in Table 2.

t 1 Dii i sdd 90-10 d 70-30 cpp-i ayay astm/Uns Iso cen

90-10 C70600C70620*

CuNi10Fe1Mn CW352H

70-30 C71500C71520*

CuNi30Fe1Mn CW354H

*C70620 and C71520 are intended or products that will be subsequently welded


t 2 Uns chi cpii (%) 90-10 d 70-30 ay Wdi appii

ay Uns n cumi.

ni mmx.

Zmx.

cmx.

Pmx.

smx.

Pmx.

ohmx.

90-10 C70620 >86.5 9-11 11.8 1.0 0.5 0.05 0.02 0.02 0.02 0.5

70-30 C71520 >65.0 29-33 0.4-1 1.0 0.5 0.05 0.02 0.02 0.02 0.5

t 3 typi mhi Ppi ad cpp-i sh d P ( en1652:1997)

ay 0.2% P sh mi.n/2*

ti sh mi.n/2*

ei mi.%

HdHV

90-10 100 300 30 90

70-30 120 350 35 100

* 1N/mm2 is equivalent to 145 psi

2.3 mhi d Phyi Ppi

Copper-nickels are stronger than copperbut lower in strength than steels. Theirductility, toughness and ormability are all

excellent. They do not embrittle at lowtemperatures and retain their mechanicalstrength and ductility down to cryogenic

temperatures.

Table 3 below gives typical annealed

mechanical properties or copper-nickel

plate; strength can be increased by coldworking but not by heat treatment. Heat

exchanger tubing is normally produced andordered in the light drawn rather thanannealed condition. For design purposes,

precise values should be taken romrelevant international standards based onproduct orm and size.

90-10 copper-nickel pipe abrication or

ship seawater system

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t 4 typi Phyi Ppi cpp-i d s

Ui 90-10 70-30 Pi c s

Density kg/dm3 8.90 8.95 7.85

Melting range C 1100-1145 1170-1240 1460-1490

Specic heat J/kgK 377 377 485

Thermal conductivity W/mK 40 29 50

Coecient o linear expansion 10-300C 10-6/K 17 16 12

Electrical resistivity at 20oC microhm/cm 19 34 30

Modulus o elasticity GPa 135 152 210

Modulus o rigidity GPa 50 56 81

Table 4 compares various physical

properties with those o steel. Additionally,the 70-30 alloy is essentially non-magneticand has a magnetic permeability very close

to unity. The 90-10 alloy has a higher ironcontent and can have a permeabilitybetween 1.01 and in excess o 1.2,

depending on the nal heat treatmentcondition. A ast cool rom the solution

heat treatment temperature o 750oC isnormally required to achieve a lowpermeability.

An example o a copper-nickel applicationdesigned to benet rom its abricabilityand corrosion properties is shown here.

It is a fanged strainer to be used as parto the seawater system or a 110m yacht.It is made rom 90-10 copper-nickel and

separates larger debris and hard oulingsuch as mussels, barnacles, stones andweeds which would otherwise enter,

block and cause obstructions in thesystem. The strainer has good resistanceto the seawater with an added benet o

deterring bioouling growth on its interior.


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53


3.0 General Handling

The precautions required or handlingcopper-nickels will be amiliar to anyabricator who routinely handles materials

like stainless steels and aluminium alloys,but may be new to those used to dealingwith only carbon steels.

Cleanliness is paramount: contaminationcan cause cracking and porosity during

heat treatment or welding and may aectthe corrosion resistance o the alloy.Ideally, abrication should be done in an

area devoted solely to copper-nickel alloys.Where this is impracticable, the standard ocare o the material should be well above

that necessary or carbon steels.

Sheets should remain in their

packing until needed and should beseparated - normally by protectivematerial - to avoid abrasion.

Plates and sheets are best stored

vertically in covered racks. Walking over sheets should be

avoided.

Plastic lm may be interposedbetween the sheet and rolls whenroll orming.

Grease and paint should be keptaway rom the surace, particularlynear edges o weld preparations; all

trace o marking crayons must beremoved beore making a joint.

Stainless steel brushes should beused, and tools such as grindingdiscs should not be interchangedbetween copper-nickel and other

materials. Openings o pipes and ttings must

be protected on completion o

abrication to prevent ingress o dirtetc. beore installation.

3.1 cui d mhii

Copper-nickels can be cut using mostconventional cutting processes, with the

exception o oxy-uel cutting. High-speedabrasive wheels work well or bevellingedges and trimming material. Band saws

or shears may be used or cutting, butallowance made or the alloys relativesotness and ductility. Plasma-arc cutting

is ast, accurate and economical. Laser andabrasive water jet cutting are also possible.

Although copper-nickels are not as readilymachined as ree-cutting brass, they aremuch easier to machine than materials,

such as stainless steels, which work hardenrapidly: they can be ranked with aluminiumbronze and phosphor bronze alloys. More

details and recommendations are givenin Recommended Machining Parameters forCopper and Copper Alloys, DKI Monograph i.18.

Plasma cutting copper-nickel plate(Courtesy Eucaro Buntmetall GmbH)

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64


3.2 i

Copper-nickels can be hot or cold ormed,although cold working is preerred; amaximum o 50% reduction is achievable

beore a ull inter-stage anneal becomesnecessary. A 20% cold reductionapproximately halves the as-annealed

elongation and doubles the proo strength.Hot working is carried out at 850-950C(90-10) or 925-1025C (70-30) but can lead

to hot cracking in inexperienced hands.

Tubes can be bent by a range o methods,

including rotary draw bending, 3-rollbending, compression bending and rambending (press bending). When bending

copper-nickel, a mandrel and wiper dieare also applied or support (mandrelbending). Care must be taken to get

smooth bends and avoid wrinkling, becauseliquid turbulence in service can lead toimpingement attack. Bends with a tube

bend radius o twice the tube diametercan be produced. Smaller radii requirepreabricated bends.

3.3 H t

The work piece should be clean and ree

rom any contamination beore and duringheating. Copper-nickels can embrittle iheated in the presence o contaminants

such as sulphur, phosphorus, lead andother low melting point metals, sourceso which include paints, marking crayons,

lubricating grease and fuids. Fuels usedmust be low in sulphur; normally, uel oilscontaining less than 0.5% by weight o

sulphur are satisactory.

Oxidising atmospheres cause surace

scaling and thereore urnace atmospheresshould be between neutral and slightlyreducing and must not fuctuate between

oxidising and reducing conditions. Flameimpingement must be avoided.

For a ull anneal, soaking times o 3-5minutes per mm thickness are appropriate.

The recommended temperatures are:

90-10 750-825C 70-30 650-850C.

Stress relieving is seldom applied but, irequired, the recommended temperatures

are:

90-10 250-500C

70-30 300-400C.

3.4 Di

Surace oxide lms on both alloys can bevery tenacious. Oxides and discolouration

adjacent to welds can be removed withvery ne abrasive belts or discs. I picklingis required, a hot 5-10% sulphuric acid

solution containing 0.35g/l potassiumdichromate is satisactory. Beore pickling,oxides can be broken up by a grit blast.

The pickled components should be rinsedthoroughly in hot, resh water and nallydried in hot air.

3.5 Pii

Painting copper-nickel is strictlyunnecessary as the alloys inherently resist

corrosion and bioouling. However, it issometimes desirable, perhaps or aestheticreasons, or to reduce the exposed metal

area in a bimetallic couple, and so reducethe risk o galvanic corrosion.

A thorough roughening by grit or sandblasting is crucial beore paint is applied.Compared with treating steel, a ner

particle size and less pressure should beused. Above the water line on boat hulls,epoxy ollowed by polyurethane coatings

can be applied. Leading paint supplierswill normally preer to recommendappropriate paint specications based

on their proprietary products or specicapplications.

Rotary draw bending copper-nickel pipe using a mandrel(Courtesy Eucaro Buntmetall GmbH)

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Copper-nickels can be readily welded byall conventional processes and, since theyhave a simple metallurgical structure, donot require preheat or post-weld heat

treatment. However, it is essential thatrequirements or preparation, particularlycleanliness, are careully ollowed and that

welders undergo a period o amiliarisationwith the particular characteristics othese alloys i they are not to encounter

problems. Automatic welding, includingorbital welding o pipe, may also beappropriate.

In some applications, insurance andinspection bodies may require qualication

o both welders and welding proceduresto appropriate standards. A weldingprocedure specication (WPS) should be

prepared in all cases.

Since the predominant application o

copper-nickels is in the orm o relativelythin-walled pipe, the tungsten inert gas(TIG), otherwise known as the gas-shielded

tungsten-arc (GTAW), welding processis requently used, both or joiningpipe sections and or attaching ttings

and fanges. The most widely availablewelding process is the manual metal arc(MMA), otherwise known as shieldedmetal arc (SMAW), using fux-coated stick

electrodes; this process is quite suitable orwelding copper-nickel alloys and has theadvantage o using relatively inexpensive

equipment. For thicker materials, above6mm, the TIG (GTAW) process can be usedor the root run beore completion o the

weld by the MMA (SMAW) process. Thegas-shielded metal arc (MIG), otherwisegas-shielded metal arc (GMAW) process,

using a continuous wire eed, is aster and

can be closely controlled with modernsophisticated equipment. Relevanteatures o these three processes ollow.

4.1 Ppi Wdi

I stored correctly, material to be weldedshould be in a generally clean condition.Dirt o any kind must be removed alongwith residual oil and grease. Particularattention should be given to sources o theelements that can cause cracking or micro-ssuring in the weld, which can originaterom crayon or paint identicationmarkings, temperature indication markers,and other contaminants. (Fittings o otheralloys, such as gunmetal - copper-tin-zincalloy - are also a source o detrimentalelements and should not be welded tocopper-nickel alloys.)

The joint area should be thoroughlycleaned beore welding starts. Particularattention should be paid to the weldpreparation and an adjacent area at least10mm wide, preerably wider, either side o

the preparation, which can be degreasedwith an uncontaminated organic solventapplied with a ne abrasive pad or a cleancloth. The area should be dried with cleancloths. Their appearance ater use is anindicator o cleanliness: they should be reerom any residue.

4.2 t Wdi

Because o their high coecient othermal expansion relative to carbon steel,copper-nickels have a greater potentialor distortion when welded. Weld xtures

can help, but their use is limited to sub-assemblies. Thereore tack welds shouldbe made to maintain a uniorm gap andalignment between the parts being welded.They must be positioned at about hal thespacing usual or carbon steel and arepreerably quite short. The TIG (GTAW)process is oten used or tacking but,where it is available, MIG (GMAW) spotwelding is a convenient and well controlledtechnique or the purpose. Tacks shouldbe wire brushed or ground to clean metalwhere they are to be incorporated into thejoint weld metal.

753


4.0 Welding

TIG welding 3rd weld run in joint with pulled T piece(Courtesy Eucaro Buntmetall GmbH)

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4.3 Wd Ppi

It is possible to weld copper-nickel up to3mm thick with a square butt preparation.However, autogenous welding should

not be attempted, since this will result

in porous welds due to the absence oeective deoxidisers in the alloys. Above

this thickness, a bevelled preparation mustbe used; the included angle o the V shouldbe larger than or carbon steel - typically,

70 or more - because the molten weldmetal is not as fuid as with carbon steels,and manipulation o the electrode or

torch is necessary to ensure usion withthe side walls. Figure 1 shows some weldpreparations.

Although it is possible to weld in all

customary welding positions, it is desirableto weld down-hand, which allows higherdeposition rates and may demand less

skill. It will oten be impracticable to turnlarge or complex structures into this mostavourable position or welding, but it isworth the eort o manipulating sub-

assemblies or down-hand welding, wherepossible.

There is no need to pre-heat the base metalbeore tacking or welding unless this isnecessary to ensure that the base metal is

dry. To avoid microssuring, the interpasstemperature is maintained below 150C.

4.4 Wdi cu

While consumables are available that

deposit weld metal similar in compositionto the 90-10 copper-nickel alloy, weldsmade with them may not have adequate

corrosion resistance or all applications.Consumables or the 70-30 alloy, on theother hand, oer superior deposition

characteristics and the corrosion resistanceo 70-30 weld metal is at least comparableto each o the base metal alloys. These

consumables are thereore recommendedor both types o alloy.

For welding copper-nickel to steel, nickel-copper consumables containing about65% Ni are used as the weld metal canabsorb more iron dilution rom the steel

without cracking than copper-nickel weldmetals.

These consumables are available asfux-coated electrodes and bare wires torecognised specications rom most o

the major suppliers - see Table 5. These

contain an addition o titanium to reactwith atmospheric nitrogen and oxygen,

which would otherwise create porosity. Iweld metal porosity persists despite theuse o the correct ller material, the most

likely causes are inadequate shielding othe weld pool and improper weld jointcleaning. Other possible causes include an

excessively long arc, moisture on the weldpreparation or the use o coated electrodeswhich are not ully dry.

864


t

t

t: up to 3mm, A: 0-1.5mm

t: 3-15mm, A: 1-3mm, B: 1.5-2.5mm, C: 70-80

A

B

A

C

Figure 1 Examples o weld preparations or joining copper-nickel plate

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9753


t 5 Wdi cu - spifi

Welding Process Form Type AWS Spec BS Spec

MMA(SMAW)

Flux-coatedelectrode

Cu-30% Ni A5.6 ECuNi In drat

65% Ni-Cu A5.11 ENiCu-7 BS EN ISO 14172E Ni 4060

TIG (GTAW)

MIG (GMAW)

Wire in

straightlengths or

spools

Cu-30% Ni A5.7 ERCuNi BS EN ISO 24373

S Cu 7158

65% Ni-Cu A5.14 ERNiCu-7 BS EN ISO 18274S Ni 4060

aWs - American Welding Societybs - British Standards Institution

Manual metal arc welding o a boat hull

4.5 mu m a (mma smaW)

Flux-coated electrodes are designedto operate with direct current,electrode positive.

No special electrode baking ordrying treatment is required unlessthey have been exposed to the

atmosphere or some time. In thiscase, they should be dried in anoven, eg 1-2 hours at 250C.

The electrode size should beslightly smaller than that selectedor a carbon steel electrode under

comparable conditions, taking intoaccount the need or manipulation.

Any weaving should not be more

than three times the electrodediameter.

A long arc should be avoided, since

this results in weld porosity throughreaction with the surroundingatmosphere.

Start/stop positions can be unsound:

reversing the electrode direction toremelt initially deposited weld metalor the crater at the end o a run can

help to avoid problems. Slag must be removed between runs

by chipping and brushing to leave a

clean surace or the next run.

4.6 g-hidd tu a (tIg gtaW)

Unlike the MMA (SMAW) process, separatecontrol o heat input via the arc and llermaterial addition gives TIG (GTAW) adegree o fexibility, which is an advantage

when welding shaped joints or insertingroot runs in thicker joints. It is the processo choice or welding thin-walled pipe in

the workshop or under conditions where astable gas shield can be assured.

Filler material should beincorporated and simple usion othe base metal avoided.

A backing gas, normally argon, must

be used when making a root run in apipe weld.

Argon is a suitable shielding gas. The arc should be kept as short

as possible to ensure that the

shielding gas protects the weld pooladequately.

Direct current should be used.

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4.7 g-hidd m a (mIg gmaW)

The higher capital cost o equipment andthe need to buy complete spools o llerwire make MIG (GMAW) more appropriate

or extensive welding operations. Theprocess is less used or copper-nickels thanthose discussed earlier.

MIG (GMAW) can be operated over a rangeo currents to provide various transer

modes:

Dip (or short circuiting) transfer- Low heat

input, used or thinner sections. Modernpower sources and electronic systemspermit close control o metal transer.

Pulsed-arc transfer - A technique whichprovides a combination o low overall heat

input and adequate usion to the basemetal. It is suitable or a range o materialthicknesses.

Spray transfer - Relatively high heat inputand suitable only or thicker materials -

say, above 6mm thickness - and down-hand welding.

Because o the range o transer conditionswhich are possible with the gas-shieldedmetal arc process, welding parameters canvary widely. In all cases these should be

set or the equipment, and the positionand thickness o the material, by careulwelding procedure trials directed towards

stable transer conditions and welds ogood appearance.

Argon or a mixture with helium isthe preerred shielding gas. The spooled ller wire must be

kept dry and not exposed tocontamination.

Attention should be paid to the

eectiveness o the wire eedingsystem when welds have to be madesome distance rom the welding

equipment, since ller wire isrelatively sot.

Low riction liners are essential or

the eed hose.TIG (GTAW) welding 90-10 copper-nickel assembly. Note bafe or backing gas supply at rootrun stage (Courtesy Eucaro Buntmetall GmbH)

TIG (GTAW) weld process


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75


4.8 P-wd t

No heat treatment is necessary aterwelding. All traces o spatter should beremoved rom joints, including slag rom

the manual metal arc process, and the weldarea may be cleaned, or example with arotating fap wheel or stainless steel brush,

to leave a bright nish.

4.9 Ipi

Welds should be inspected visually ordeects such as cracks, undercut, lack o

usion and penetration, and weld contour.Liquid dye penetrant inspection is a simplemethod or detecting surace deects.

For critical applications, more advancedinspection techniques (e.g. radiography)may be specied, but these are not usually

required or general abrications.

4.10 mhi Ppi Wd

A 70-30 copper-nickel ller material isrecommended or welding the 90-10 and

70-30 copper-nickel alloys. Because othe higher nickel content, the weld metalis stronger and more noble galvanicallythan the 90-10 copper-nickel base metal.

When evaluating the results o test welds,a transverse bend test is not appropriatebecause deormation is concentrated in

the relatively sot material adjacent tothe weld. A longitudinal bend test shouldbe used instead. Table 6 shows typical

properties o 70-30 all-weld-metalsdetermined rom test pieces orientedparallel to the weld axis.

t 6 - typi a-wd m mhi Ppi bd 70-30 cu( ud di pup)

Wdi p0.2% Pshn/2

tishn/2

ei5d*%

HdHV

TIG (GTAW) 200 385 40 105

MMA (SMAW) 270 420 34 120

* d is the diameter o the test piece gauge length

Pipe assembly showing both cold pulled T pieces and welded saddle connections(Courtesy Eucaro Buntmetall GmbH)

Butt weld showing area which had been cleaned ater welding(Courtesy Eucaro Buntmetall GmbH)

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5.0 Clad Plate

Thicker plate sections - eg tubesheets

and water boxes - can be constructedeconomically using steel plate which hasbeen roll-clad with 90-10 or 70-30 copper-

nickel. This type o material can haveadvantages, but is not so readily availableas solid copper-nickel plate.

Clad plate should be handled with the careappropriate to copper-nickel alloy, not that

or structural steel.

5.1 cui

Unlike solid copper-nickel plate, it ispossible to use oxyacetylene equipment

or cutting clad plate i the ratio o steel toclad thickness is 4:1 or greater (20% clador less). The clad side o the plate is placed

ace down so that cutting starts rom thesteel side and the slag stream rom thebacking steel is a cutting agent or the

cladding. This is not necessary or plasma-arc cutting, but trials may be needed tond the most suitable settings or either

cutting procedure. The cut ace must be

ground or machined to clean metal beorewelding.

5.2 Wdi

When designing weld procedures or

clad plate, it is necessary to treat thecladding and backing material as separatecomponents and to avoid the respective

weld metals being mixed. Otherwise,

cracking is likely rom the copper in carbonsteel weld metal or the iron in copper-

nickel weld metal. The region beside theinterace between the backing material andthe cladding is welded with 65% nickel-

copper ller material, which can cope withiron pick-up rom the carbon steel side.When the clad plate thickness is less thanabout 10mm, 65% nickel-copper ller

metal is oten used or the complete weld.

When it is possible to weld rom either

side on plates 12mm and thicker, the usualprocedure is to weld the steel side rstwith a steel ller metal. The alloy side is

prepared or welding by back-gouging tosound metal and welded with a rst passo 65% nickel-copper alloy ollowed by

70-30 copper-nickel. Figure 2 shows thesequence.

When access is possible only rom the steelside, the joint is prepared to give access tothe copper-nickel cladding, so that it can

be welded like a solid alloy. The weld jointin the steel backing is then made with the

65% nickel-copper ollowed by the steelller runs.

With a preparation rom the cladding side,

the joint is partially lled with steel weldmetal and completed with a combinationo 65% nickel-copper ller and 70-30

copper-nickel ller.

1

2

3

4

2A

3

2

11A

CuNi clad

carbon steel

CuNi clad

carbon steel

bevel optional

CuNi clad

carbon steel

CuNi clad

carbon steel

1.55mm min

30 to 450

Weld joint and bead

sequence or cladplate 6-8mm thick:

Run 1 -

copper-30% nickel

ller

Backgouge carbon

steel to sound

metal; bevel

Runs 2, 3, 4 -

65% Ni-Cu ller

Weld joint and bead

sequence or clad 12mmthick and over:

Runs 1, 2, 3 (or as

needed to ll) - steel

ller

Backgouge clad to sound

metal; bevel

Run 1A - 65% Ni-Cu ller

Run 2A - Cu-30% Ni ller

Figure 2 Examples o run sequence or welding copper-nickel clad plate

0 - 1.5mm

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6.0 Brazing

Copper-nickel alloys are readily brazed byall processes, although torch brazing is themost common. Since the process relies

on wetting the suraces to be joined bythe brazing alloy, absolute cleanliness isessential. Fluxes alone are not capable o

removing all contamination, particularlythose containing lead or sulphur, andoils, paint, etc, which should be removed

careully with solvents and degreasingagents. Oxides and dirt can be eliminatedwith emery paper or a chemical cleaning

process.

I parts have been cold ormed, they may

contain signicant internal stresses, whichpromote intergranular penetration bymolten ller material during brazing -

resulting in cracking at the joint. Removalo stresses by ull annealing is notnecessary; heating to 600-650C or a ew

minutes is sucient or adequate stressrelie and this can be done simply with anoxy-uel torch, taking care that the part is

heated uniormly.

While phosphorus-bearing brazing alloys

are oten recommended or joiningcopper alloys, they are not suitable orcopper-nickels because the nickel reacts

with phosphorus to orm a brittle nickelphosphide phase. Silver-based brazingalloys (silver solders) should be used. They

oer a useul combination o meltingrange, fow characteristics and mechanicalproperties. They also perorm well in

brazed joints where copper-nickels areexposed to seawater. Alloys containing

cadmium are no longer recommendedbecause o health hazards in application,but there is a range o silver-copper-zincalloys which are suitable and sae.

For brazing pipe and ttings, pre-placedbrazing alloy rings are preerred over

manual eeding, giving better control oquality and minimal use o fux (residues owhich must always be removed ater the

joint has been made, usually by washingwith hot water). The larger the pipe size,the more dicult it is to achieve uniorm

heating around the diameter to reach the

brazing temperatures. Some organisationslimit brazing to pipe diameters up to and

including about 50mm.Furnace brazing is possible, and better

where signicant numbers o assembliesare to be joined.

Exothermic, endothermic or dissociatedammonia atmospheres are suitable,together with inert gas. Because o the

high vapour pressure o some brazing

alloy constituents, vacuum brazing is lesssuitable.

Capillary brazing o a sleeve to a pipe using a silver solder(Courtesy Eucaro Buntmetall GmbH)

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7.0 Tube to Tubesheet Fabrication

In heat exchangers and condensers, tubesare joined to tubesheets to prevent leakagebetween the tube side and shell side. Oten

the easiest and least expensive methodis to expand the tube mechanically intothe drilled hole in the tubesheet, usually

by roller expansion. Ideally, the tubesheetshould be harder and less galvanicallynoble than the tubes. A mechanically

expanded joint may be acceptable when:

service temperatures are under

about 200C tubesheets are suciently thick toallow rolling-in a suitable length o

tube design pressures are relatively low a weld joint is not needed to support

the tube bundle a mechanical joint is not used or

severe services where a leak could

present a catastophic saety hazard.

When a tube-to-tubesheet (T/TS) weld

is made in a copper-nickel construction,it is most oten made by an automatic

gas-shielded tungsten arc (TIG or GTAW)

process, either with or without ller

metal. Manual welding can be used onspecial designs and is oten the standardmethod or weld repairing; ller metal

addition is essential here, to avoid weldporosity. While the TIG (GTAW) process iswell adapted to make T/TS welds with thin

wall tubes, other welding processes may bebetter suited or large diameter and thickerwall tubes. Alternative welding processes

include MMA (SMAW), MIG (GMAW) orplasma arc. Explosive welding is another

joining option, although it is seldom usedin copper-nickel construction.

There are many dierent T/TS weld joint

designs used in industry and each has itsparticular advantages and disadvantages.Figure 3 illustrates the common welds that

can be made on the tubesheet ace - fushtube, recessed tube, trepanned tube sheet,added-ring and ace-side llet weld.

Selection o the particular automatic TIG(GTAW) weld joint conguration to useinvolves considerations such as:

joint crevice leak path sizerequirement

ller metal requirements tubesheet heat sink structural fexibility

available equipment tube dimensions and llet size.

Successul T/TS welding depends criticallyon the accurate machining o holes, jointpreparation on the tubesheet and cleaning

all suraces prior to welding. Accurately

machined holes are particularly importantto make sure the tungsten electrode isalways positioned correctly in the weld

joint.

The tubesheet should be cleaned

immediately ater drilling and positionedso that, during cleaning, the contaminantsdrain rom the tubesheet and do not

accumulate on one surace. Compressedair should not be used to blow o thecleaning solution unless equipment is

installed to remove moisture and oilcontamination rom the air. Dry nitrogen is

oten a good alternative to compressed air.

Tube to tubesheet welding o a large heat exchanger using automatic TIG (GTAW) welding heads(Courtesy Arc Machines Inc)

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Prior to T/TS welding, it is oten desirableto expand the tube into the tubesheet, orexample by a light roll to ensure the tube

is centred in the hole or good tracking inautomatic welding. A hard roll prior towelding increases the chance o producing

a weld deect rom escaping gas as theweld is being made. Ater welding onthicker tubesheets, the tube is oten given

a hard roll stopping about 25mm short othe back side.

The completed T/TS weld should beinspected visually or deects. A liquidpenetrant inspection is also quite standard.

Other inspections might be imposed - aleak test and, in some T/TS designs, aradiographic inspection can be made o

selected areas. Deects such as cracks orporosity should be ground out and repairedby TIG (GTAW) with ller metal. Large heat exchanger

Figure 3 Typical tube weld joint preparations showing nished weld on the right side. 1st and 3rd columns are solid copper-nickel tubesheet; the2nd and 4th columns are clad plate (ex Reynolds et al - see Bibligraphy)

Flush tube weld Cladding Cladding

Trepanned tubesheet llet weld

Added-ring weld

Fillet weld

Recessed tube weld

Explosive tube weld

A1 A2

Tube wall Tubesheetligament

Tube wall Tubesheetligament

B1 B2

C

D1 D2

E1 E2

F1 F2

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8.0 Sheathing and Cladding o Oshore Structures

The corrosion rate o steel in the splashzone varies with location and season butis generally 0.5-1.5mm/yr. This increases

dramatically at the higher suracetemperatures ound in hot riser pipes -fuid conduits that extend rom a sea foor

well or pipeline to the platorm structureat the sea surace. At temperatures o over90C, steel corrosion rates can reach 8mm/yr.

Splash zone sheathing is normally 3-5mmthick. The sheathing should span at least

rom below mean tide level to well intothe atmospheric zone. Potential galvaniccorrosion on the adjacent steel is addressed

by painting the top section; the bottom,submerged junction will be protected bythe cathodic protection normally applied to

the structure.

Attachment o the alloys has involved

straps and xings, but the normal methodis welding. Both 90-10 and 70-30 alloyscan be welded to steel - careully, because

o alloy mixing. The sheet is pre-ormed tohal cylinders and longitudinal joints are

lapped so that the alloy is welded to itsel.Horizontal butt welds between sectionscan be made direct to the steel and areoten a 3-bead method such that the cappass experiences minimum dilution rom

the steel. Occasionally, where the steelhas a rough surace or it is not consideredappropriate to weld the alloy sheathing

direct to the steel riser or other structure,horizontal steel bands are initially weldedto the steel and the sheathing welded to

the band.

Structural members sheathed in 90-10 copper-nickel during construction o thePhase 1 Morecambe gas eld platorms

(Courtesy Centrica Energy Upstream, East Irish Sea)

90-10 copper-nickel splash zone protection on a platorm in the Morecambe Field, UK.The sheathing has been in service over 25 years

(Courtesy Centrica Energy Upstream, East Irish Sea)

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Sheathing thus involves a combination osimilar and dissimilar metal welds, whichare made according to the principles

already discussed: nickel-copper weldingconsumables or part or all o jointsbetween the copper-nickel alloy and steel

to avoid the possibility o weld cracking,and 70-30 copper-nickel or the copper-nickel to copper-nickel welds. Figure 4

shows an outline o a typical sheathingassembly used on oshore platorm legswith an indication o the types o joint

involved and the weld procedure.

For oshore renewable power, the

combination o high corrosion resistanceand a natural low adherence by biooulingcan also be used where personnel transer

rom the boats to the structures. Figure 5shows a prototype landing stage (patentpending) designed or access to oshore

wind turbine towers. Larger diameterpipe sections are made rom steel with a

complete outer cladding o around 5mmthick 90-10 copper-nickel, whereas theladder rungs are straight copper-nickelsection. Welding o the clad pipes involves

procedures similar to those o clad platedescribed in Section 5.0.

Figure 5 - Copper-nickel boat landing stage(Courtesy o KME Germany GmbH & Co. KG)

Figure 4 Typical attachments or platorm sheathing

Typical circumerential

butt joint

Typical longitudinal

lap joint

Typical circumerential

llet joint

Structural steel

Copper-nickelRoot runs 65% Ni-CuCapping runs 70Cu-30Ni

Copper-nickel 1 run 70Cu-30Ni50mm

Copper-nickel

Structural Steel

Root andcap runs65% Ni-Cu

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9.0 Linings

Copper-nickel sheet can be a convenientand economic alternative to solid alloyor clad plate or lining a vessel. An earlyexample was the construction o a waterbox in which the lining was abricated asa separate component rom 1.2mm thick90-10 copper-nickel sheet, made to tclosely into a carbon steel shell. It wasthen attached to the shell by a patterno MIG (GMAW) spot welds, using anautomatically timed sequence. It wasnecessary to ensure that the lining ttedclosely in the shell and was in intimatecontact with it when the welds were made.Seal welds around the fanged openingcompleted the lining process. Automaticspot welding allowed welds to be madewith a 70-30 copper-nickel alloy ller wirewith reproducibly low iron dilution.

In recent years, techniques have beenextensively developed or lining vesselsand ducting with corrosion-resistantalloys, particularly in the power generationindustry. Spot welds are usually used tominimise bulging due to the dierent

thermal expansion o the backing materialand the lining, or rom the pressurevariations. The lining is attached as sheetsor strips by a careully designed weldingprocedure. It is important that the backingmaterial surace is thoroughly cleaned,usually by grinding and blast cleaning with

abrasives to produce an uncontaminatedsurace. The nal surace should be closelyinspected and any areas o localisedthinning must be repaired beore liningstarts.

Two welding procedures are commonlyadopted or lining:

Each sheet is llet welded to thebacking material and a third,covering bead deposited to completethe joint.

Each strip is tack welded to thebacking material, overlapping theadjacent sheet by a ew centimetres.A seal weld is then made directlybetween the strips.

With both procedures, it is advisable to use65% nickel-copper ller material, although70-30 copper-nickel ller can be used orthe seal weld in the second procedure.

The number and pattern o spot welds isdetermined by the area o sheet or strip

between the welds. The reproducibilityo the technique also makes it ideal orthe repetitive sequence o tack welds.Fillet and seal welds are best made by theMIG (GMAW) process since it operates atrelatively high speeds and can be closelycontrolled. Details and regions o complex

shape may be welded by the TIG (GTAW)process: although slow, it is fexible andacilitates manipulation o the weldingtorch.

Throughout abrication o a lining, caremust be taken to avoid surace damage tothe copper-nickel sheet; on completion,any weld spatter and discoloration mustbe removed. Welds should be examinedvisually or deects and the absence oporosity or cracks breaking the surace owelds can be conrmed by a penetrantinspection technique.

Proprietary processes are also available;an example is the lining o steel pipe with90-10 copper-nickel as shown below. Inthis instance, diameters up to 2.5m can beproduced with the pipe manuactured romcarbon steel plate and a 90-10 copper-nickel liner sheet. There is no necessity ora metallurgical bonding between the twolayers as the pipe orming process createsa tight mechanical t and the weld designprovides a ull seal.

Large diameter steel pipe manuactured with 90-10 copper-nickel inner liner(Courtesy o KME Germany GmbH & Co. KG/Bergrohr GmbH)

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10.0 Desalination Plants

90-10 copper-nickel brine piping or a desalination plant

The multi-stage fash (MSF) process o

desalination involves large heat exchangersproducing up to 57,000m3 o water perday. Copper-nickel alloys are widely usedto abricate piping, waterboxes, evaporatorshells, tube plates, etc. The 90-10 nickelalloy is usually used in such abrication,although a 70-30 copper-nickel with2% iron and 2% manganese (C71640,CW353H) is also widely used or heatexchanger tubing.

About 40 waterboxes are needed in atypical unit. The normal construction isclad plate with 2-3mm o 90-10 copper-

nickel on a mild steel plate. These haveperormed very reliably in many plantsor both raw seawater and de-aeratedbrine. Many hundreds are in service, withthousands o tonnes o clad plate.

Some large plants use 90-10 clad plateor the main shell. An economic choiceor small standard units is solid 90-10copper-nickel with external carbon steelreinorcements. Being able to weld thealloy directly to the steel is a key actor inthis abrication.

Both 90-10 and 70-30 alloys are used or

tubesheets and can be welded direct toa carbon steel shell. When copper-nickelclad tubesheets are used, the claddingshould be thick enough to allow or a rollerexpanded joint - 8-10mm normally.

Piping o 90-10 copper-nickel is used orboth natural seawater and hot de-aeratedbrine service. Large pipes up to 1.37mOD are abricated rom plate; seamlesspipe is used or sizes up to about 400mm.Standard ttings like tees, bends, reducers,saddle joints and fange connections areavailable or the smaller sizes. These

can be welded to the pipe so that pipingsystems can easily be assembled. Diametersbelow about 50mm OD are normally joinedby brazing with silver solders.

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11.0 Seawater Corrosion Resistance

The resistance to seawater corrosion ocopper-nickel alloys results rom the

ormation o a thin, adherent, protectivesurace lm which orms naturally andquickly on exposure to clean seawater.The lm is complex and predominantly

cuprous oxide with the protective valueenhanced by the presence o nickel andiron. The initial lm orms airly quicklyover the rst couple o days but takes

up to three months to ully mature. Thisinitial exposure is crucial to the long-termperormance o copper-nickel.

Once a good surace lm orms, the

corrosion rate will continue to decreaseover a period o years. For this reason, ithas always been dicult to predict the lieo copper-nickel alloys based on short-

term exposures. Normally, corrosion rateso 0.02-0.002mm/year are anticipated.

11.1 w r

With increasing seawater fow rate,

corrosion remains low due to the resilienceo the protective surace lm. However,when the velocity or a given geometry

is such that the shear stress action othe seawater on the lm is sucient to

damage it, impingement attack can result.General experience has shown that 90-10copper-nickel can successully be used

in condensers and heat exchangers withvelocities up to 2.5m/s; the 70-30 alloy canbe used up to 3m/s. For pipeline systems,

higher seawater velocities can saely beused in larger diameter pipes as indicatedby BS MA18 Salt Water Piping Systems in

Ships, which suggested a maximum designvelocity o 3.5m/s in pipes o 100mmand larger or 90-10 copper-nickel, and

4m/s or the 70-30 alloy. Although these

guideline values are now considered to beconservative, they work well because they

take into account eects rom things likebends which cause areas o high local fowrate. Nevertheless, extreme turbulence has

to be avoided - rom elements like tightradius bends, partial blockages and areasdownstream o partially throttled valves.

Minimum fow rates o more than 1m/s areusually preerred to avoid sediment build

up.

The seawater velocities considereduntil now have been or continuous

fow. Firemains are normally used ortest purposes and res, at intermittentvelocities as high as 12-15m/s. Experience

has shown that these high fow rates areacceptable in such short-term operations.

The hydrodynamics around oshorestructures are somewhat dierent topipework systems. Experience to date or

ship hulls has shown minimal corrosion

ater 14 months at 24 knots (12m/s) or the90-10 alloy. The highest recorded velocityis 38 knots (19m/s) or a patrol boat which

showed no measurable thickness loss ater200 hours at maximum operating speed.The upper service velocity or hulls is still

to be established.

11.2 sd ai

The eect o sand abrasion in seawateris dicult to quantiy. Sand loadings o

less than 200ppm rarely damage goodprotective lms on copper-nickel alloys.

Very ne sand (under 0.05mm) is tolerableup to about 1000ppm. Larger diametersand particles tend to be increasinglyabrasive to the lm in the 200-1000ppm

range. The 70-30 alloys have somewhatgreater resistance to sand. For sandloadings o 1000ppm and or larger

particles o sands in the 200-1000ppmrange, a 2% manganese, 2% iron, 30%nickel, copper-nickel alloy, C71640

(CW353H), has better resistance in thewaters rom shallow estuaries and romintakes o desalination plants along the

Arabian Gul.

11.3 lid ci

Copper-nickels have good inherentresistance to chloride pitting and crevice

corrosion. Crevice corrosion is seldomound. The mechanism is a metal ionconcentration cell type totally dierent to

that o stainless steels. Any corrosion isoutside the crevice and shallow.

Section through copper-nickel tube showing protective mature surace oxide lm

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Copper-nickels are not susceptible tochloride or sulphide stress corrosioncracking or hydrogen embrittlement and,

unlike brasses, do not suer crackingdue to ammonia in seawater service. Butammonia can cause higher corrosion

rates, although copper-nickels are moreresistant than many other copper-basedalloys. Copper-nickel tubing is resistant to

chlorination at the dosing levels used tocontrol bioouling. Excessive chlorinationcan be detrimental, as it reduces erosion-

corrosion resistance.

Dealloying is not common with copper-

nickel alloys. Denickelication o the 70-30alloy has been encountered occasionallyin renery overhead condenser service,

where hydrocarbon streams condense attemperatures above 150C. This appears tobe due to thermogalvanic eects resulting

rom local hot spots. The solution has beento remove the deposits which lead to thehot spots, either by more requent cleaning

or by increasing fow rates. Ammoniain seawater can produce a type o

dealloying which looks similar to hot spotcorrosion. This happens at around ambienttemperature, but only under heat transerconditions. It can be controlled by adding

errous sulphate to the seawater.

11.4 gvi bhviu

Copper-nickel alloys lie mid-way inthe galvanic series (Figure 6): they arecompatible with other copper alloys but

more noble than zinc, aluminium and steeland less noble than stainless steels, nickel

alloys and titanium. The 70-30 alloy isslightly more noble than the 90-10 alloy.

Figure 6 Galvanic series

Volts: saturated calomel hal-cell reerence electrode

Alloys are listed in the order o the corrosion potential they exhibit in fowing sea water(2.5-4m/sec, 10-27oC)Alloys indicated by in the chart may become active and exhibit a potential near

-0.5 volts in low-velocity or poorly aerated water, and in shielded areas

+ 0.2 0 - 0.2 - 0.4 - 0.6 - 0.8 - 1.0 - 1.2 - 1.4 - 1.6

MagnesiumZinc

BerylliumAluminium alloys

CadmiumMild steel, cast iron

Low alloy steelAustenitic nickel cast iron

Aluminium bronze

Naval brass, yellow brass, red brassTin

Copper

Pb-Sn solder (50/50)Admiralty brass, aluminium brass

Manganese bronzeSilicon bronze

Tin bronzeStainless steel types 410, 416

Nickel-silver90-10 Copper-nickel

80-20 Copper-nickel

Stainless steel type 430Lead

70-30 Copper-nickel

Nickel-aluminium-bronzeNickel-chromium alloy 800

Silver braze alloys

Nickel 200Silver

Stainless steel types 302, 304, 321, 343Nickel-copper alloys 400, K500

Stainless steel types 316, 317Alloy 20 stainless steels cast and wrought

Nickel-iron-chromium alloy 825

Nickel-molybdenum alloy BTitaniumNickel-chromium-molybdenum alloy C

PlatinumGraphite

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11.5 Hdi suphid

Sulphides are present in polluted watereither rom industrial efuent or whenthe water conditions support the growth

o sulphate reducing bacteria. Theycan also be produced in stagnantconditions by decomposition o organic

matter. Sulphides can interere withsurace lm ormation on copper-nickelalloys, producing a black lm containing

cuprous oxide and sulphide. This is not as

protective as lms ormed in clean waterand higher general corrosion rates and

pitting can result. . Exposure to sulphidesshould be restricted wherever possible andparticularly during the rst ew months o

contact with seawater while the normalprotective oxide lm is maturing.

The sulphide lm can be gradually replacedby an oxide lm with subsequent exposureto aerated conditions, although high

corrosion rates can be expected in theinterim. However, i an established cuprousoxide lm is already present, then periodic

exposure to polluted water can be toleratedwithout damage to the lm.

For condensers and piping systems, tting

out and commissioning are the likelieststages or sulphides to be a hindrance.Whether in a ship, platorm topside or

power plant, aerated, clean seawatershould ideally be circulated at start up orlong enough to orm a good protective

lm. This lm provides a high degree ocorrosion protection against subsequentsulphides. Where it is not possible to use

clean seawater, circulating the systeminitially with resh water containing erroussulphate additive will encourage eective

lm ormation. Low levels o chlorinationhave also been ound to mitigate corrosionattack in sulphide polluted seawater.

Chlorination treatment and erroussulphate treatment should be staggered iboth are used in the same system as there

is a tendency or a precipitated foc to ormi they are dosed at the same time.

An alternative method o adding errousions is to use a driven iron anode. This

is more to maintain a protective layerthan to orm one, and reduces biooulingresistance.

Other pretreatment compounds havebeen used with variable success. Sodium

dimethyldithiocarbamate has been usedby the British and German navies. TheUK Ministry o Deence have addressed

preconditioning in Protection o Seawater

System Pipework and Heat ExchangerTubes in HM Surace Ships and Submarines

Deence Standard 02-781, Issue 2. It is alsorelevant to other marine industries.

Ater brie exposure to sulphides during

normal operation, clean water shouldbe restored as soon as possible. Normalshipping harbour turn around times -

which oten involve exposure to pollutedwater - have rarely led to signicantproblems.

Metal suraces can be exposed to sulphidesunder deposits or sediment caused bysulphate reducing bacteria, or example

where deposits are not removed romtubing. The remedy is proper scheduledcleaning - oten water fushing or

cleaning with non-metallic brushes at 2-6month intervals. Sponge ball cleaningis an alternative. Such procedures are

also necessary to restore optimum heattranser.

Where there is long-term exposure tode-aerated, sulphide containing seawater,or regular alternating exposure to sulphidepollution and aeration, copper-nickel is

generally not recommended.

Inlet/outlet maniolds or seawater course ltration unit in 90-10 copper-nickel

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75

12.0 Bioouling Resistance


Copper-nickels natural properties have ahigh resistance to marine macroouling.This quality can be exploited to reduce

cleaning o pipework or condensers,decrease wave drag and reduce oulingremoval costs o platorm structures.

Optimum bioouling resistance requiresthe alloy to be reely exposed or electricallyinsulated rom less noble alloys.

In oshore sheathing, neoprene orconcrete have been used to insulate the

sheathing rom the cathodically protected(CP) structures. However, it is now knownthat some ouling reduction is obtained

even when CP is applied. Table 7 showsthe results o 10-year studies at LaQueCorrosion Services in North Carolina. The

isolated pilings show negligible build up.When directly connected to the steel,with or without cathodic protection, the

ouling rate was only 44% o that on theplain steel piling. Similar results havebeen ound in service. A light scraping

action can readily remove any biooulingattachment which does orm.

Long-term exposure o copper-nickelto quiet or stagnant seawater can leadto a thickening o microouling (slimes)sucient to allow some colonisation o

macrooulants. As these will not be asrigorously attached as on many othersubstrates, experience has shown that they

will periodically slough away or can beremoved by a light scraping.

tl 7 biofouling m on coppr-nikl shhd t Piling afr 5 nd 10 Yr expour

Pii biui m/2

P a cvd

b ( hhd)

5 year removal 18 100

10 year removal 12 100

c iud

5 year removal 0.36 1.9


Diy wdd



ru iud



Exposure panels (let to right in above picture): steel, 90-10 copper-nickel sheathed steel,copper-nickel - all three protected with aluminium anodes - and reely exposed copper-nickel.

Ater 12 months exposure at Langstone Harbour, UK, there was no macroouling on the reelyexposed panel.

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13.0 Checklist

h i i d iui:

Source copper-nickel rom a reputable supplier and to international standards

Maintain a high level o cleanliness during the abrication o copper-nickels

Use 70-30 copper nickel consumables or similar welds in 90-10 and 70-30 copper nickel

Use 65% nickel-copper consumables or copper-nickel-steel dissimilar welds

Ensure maximum velocity limits or the alloys are not exceeded

Avoid velocity raisers - eg sharp angled bends in pipe systems

Avoid use o polluted water during commissioning

Add errous sulphate to enhance the protective lm ormation i extra saeguard

required

Electrically insulate copper-nickels rom less noble alloys when highest resistance to

bioouling is required.

The 70-30 copper-nickel hull o the Asperida ater 12 years in service

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75


14.0 Bibliography

14.1 g

Copper-nickel Alloys: Properties and Applications. NiDI/CDAPublication TN 30. 1982

90-10 Copper-nickel. CDA Publication No 118. 1997

90/10 and 70/30 Alloys Technical Data. CDA Publication TN 31. 1982

Guidelines or the Use o Copper Alloys in Seawater. A Tuthill. Nickel

Institute Publication 12003

The Application o Copper-nickel Alloys in Marine Systems. Technical

report (compendium) available rom CDA Inc

The Corrosion o Copper and its Alloys: A Practical Guide orEngineers. Roger Francis. NACE International. 2010

Copper Alloys or Marine Environments. CDA Publication No 206. 2012

The Corrosion Perormance o Metals or the Marine Environment: A

Basic Guide. Edited by C Powell and R Francis, European Federationo Corrosion/NACE. Maney Publishing. 2012

Many additional papers are also downloadable romwww.coppernickel.org web pages.

14.2 ii

Joining Copper-nickel Alloys. R E Avery. CDA Inc Seminar Technical

Report 7044-1919. The Application o Copper-nickel Alloys in MarineSystems. 1992

Brazed Copper-nickel Piping Systems. CDA Inc Application DataSheet 701/5

Fabrication o Copper-nickel Alloys or Oshore Applications.

D E Jordan, C Powell. Welding in Maritime Engineering. October1998. Croatia

Machining Brass, Copper and its Alloys. CDA Publication TN 44. 1992

Recommended Machining Parameters or Copper and Copper Alloys,

DKI Monograph i.18. 2010

Pipelines o Copper-nickel Alloys-Part 2. Basic Principles or Design,Fabrication and Testing. DIN 85004

Welding Copper-nickel Clad Steel. CDA Inc Application Data Sheet

Copper Advantage: Guide to Working with Copper and Copper Alloys.

Copper Development Association Inc Publication. 2010.

14.3 Pipi sy, H exh d cd

Protection o Seawater System Pipework and Heat Exchanger Tubesin HM Surace Ships and Submarines. DEF Stan 02-781. Issue 2. UKMoD

The Selection o Materials or Seawater Cooling Systems - A PracticalGuide or Engineers. R Francis. NACE International. 2006

The Design and Installation o 90-10 Copper-nickel Seawater PipingSystems. Nickel Institute Publication 11007

Heat Exchanger and Piping Systems rom Copper Alloys -

Commissioning, Operating and Shutdown. M Jasner et al. KMEpublication. 1998

Successul Welding o Tubes to Tubesheets. D Reynolds, J Kratz,J Kieer. 2nd Symposium o Shell and Tube Heat Exchangers.Houston. September 1981

14.4 oh shhi

Review o Splash Zone Corrosion and Bioouling o C70600 Sheathed

Steel during 20 Years Exposure. C Powell and H Michels. Eurocorr2006. Maastricht

Metallic Coatings or Corrosion Control or Marine Structures.D Peters, H Michels, C Powell. International Workshop on Control orMarine Structures and Pipelines. Galveston 1999

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14.5 b Hu

The Asperida, a Copper-nickel Sailboat ater more than Thirty Yearsin Seawater. H Michels and K Geremia. Paper 5238 Corrosion 2005NACE International

Corrosion and Bioouling Protection o Ship Hulls Using Copper-

nickel. Proceedings o International Conerence on Marine CorrosionPrevention - A Re-appraisal or the Next Decade. C Powell. October1994. London. Royal Institute o Naval Architects

Copper-nickel Sheathing Costing Study - Phase 3. MARAD Report770 87026. US Dept o Transportation. August 1987

CA 706 Copper-nickel Alloy Hulls: The Copper Mariners Experienceand Economics. Monzolillo, Thiele and Tuthill. The Society o Naval

Architects and Marine Engineers. 1976

Use o Copper-nickel Cladding on Ships and Boat Hulls. CDA

Publication TN 36. 1985

14.6 biui

Long Term Exposure Trials Evaluating the Bioouling and CorrosionResistance o Copper-nickel Alloy Sheathing Materials. S Campbell

and C Powell. 12th International Congress on Marine Corrosion andFouling. July 2004. University o Southampton

Bioouling Resistance o Cupronickel - Basics and Experience.

W Schleich and K Steinkamp. Stainless Steel World 2003 Conerence.

Maastricht. November 2003

Preventing Bioouling with Copper Alloys. CDA Publication 157. 2002

Seawater Corrosion Resistance o 90-10 and 70-30 Copper-nickel

- 14 year Exposures. K Erd and Anderson. Material Perormance.November 1975

The Interrelation o Corrosion and Fouling o Materials in Seawater.

K Erd. NACE Corrosion-75. Toronto. 1975

Controlling Bioouling on Ferry Hulls with Copper-nickel. L Boulton,C Powell. 10th International Congress on Marine Corrosion andFouling. Melbourne 1999

Many o these papers are available to download rom the ollowing

websites:

www.copperalliance.org.uk

www.copper.orgwww.coppernickel.org

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15.0 Further inormation and advice

Copper Development Association (CDA)5 Grovelands Business CentreBoundary Way

Hemel Hempstead HP2 7TEUKFax: +44 1442 275716

Email: [email protected]: www.copperalliance.org.uk

Copper Development Association Inc (CDA Inc)260 Madison Avenue

New YorkNew York 10016-2401USA

Phone: +1 212 251 7200Fax: +1 212 251 7234Email: [email protected]

Web: www.copper.org

Nickel Institute (Toronto Oce)Brookeld Place161 Bay St, Suite 2700

Toronto, OntarioCanada M5J 2S1Phone: +1 416 591 7999Email: [email protected]

Web: www.nickelinstitute.org

Nickel Institute (Brussels Oce)Avenue des Arts/Kunstlaan, 13

B-1210 BrusselsBelgiumPhone: +32 2 290 32 12Fax: +32 2 290 32 20

Email: [email protected]: www.nickelinstitute.org

90-10 copper-nickel welded abrication with fange connections

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Notes

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Copyright2013.

CopperDevelopmentAssociation

Copper Development Association

5 Grovelands Business CentreBoundary Way

Documents

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