materials used in sea water system

7/27/2019 Materials Used in Sea Water System

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Materials Used in Sea Water SystemMaterials Used in Sea Water System


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Material Selection

Materials Used in Sea Water SystemMaterials Used in Sea Water System

Introduction

Sea Water &Corrosion

Composites

Ni Base alloys

Titanium Alloys

Copper alloys


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Cooling purpose

Oil field water injection

Fire-fighting

Desalination plants

Main use of sea water

4- Oil and gas production

Industrial Applications

1- Shipping

2- Offshore

3- Power plants and

coastal industrial plants


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Causes of Abrupt failures of water cooling system usually

related to:

- Corrosion - Scales

Biological Proliferations

Fouling

A- System design

B- Equipment and material selection

C- Maintenance


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Main materials used in sea water system

1- Steel alloys (high alloy steel 254 SMO and cast iron )

2- Stainless steel (316 L & duplex stainless)

3- Copper alloys (Cu-Ni& 5% Ni Al bronze)

4- Titanium alloys (Pure Ti &23 (Ti-6Al-4VELI))

5 - Composite material

seawater-cooled

condensers

offshore and marine

applications

valves and pumps

offshore and marine

applications

oil gas and piping

system

6 Ni Base alloys Sea water services


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Corrosion data on materials in high velocity test

Alloy Corrosion rate Seawater Velocity

Grey cast Iron 13 38

Carbon steel 9.5 40

Monel Alloy 400 0.010 43

Monel alloy K-500 0.010 43

Stainless steel 0.005 43


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Economic Factors for materials selection

1-A low initial cost system

Carbon steel and Cast iron require considerable maintenanceover the life of the plant.

Such a system is a reasonable choice in areas where labor costs are low

and material is readily available

2-A high initial cost system

Alloy materials

if correctly designed and fabricated, will

require minimum maintenance and will

function reliably

Rising labor costs in most industries and need for high reliability incapital intensive plant has produced a trend to this type of system


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Seawater piping systems

Minimum first cost - high

maintenance

cost system Component

High reliability - low

maintenance

cost system

Galvanized steel Pipe Copper-base

90-10 Cu-Ni

Steel Flanges - Cast or forged 90-10

Cu-Ni

- Steel welded overlayed

with Cu-Ni

- Gunmetal

60/40 brass/naval brass Tubeplates - Nickel aluminium bronze

- 90-10 Cu-Ni

Aluminium brass Tubes - 70-30 Cu-Ni

(particularly 2% Fe + 2% Mn)

- 90-10 Cu-Ni

Cast iron or leaded Gunmetal Pump casing - Cast Cu-Ni

- Nickel aluminium bronze

- Admiralty Gunmetal

- Ni-resist Type D2

Gunmetal Pump impeller - Monel Alloy 410

- Alloy 20 (CN7M)

- Stainless steel (CF3 and CF8)- Nickel aluminium bronze

Naval brass Pump shaft - Monel Alloy 400 or 500

- Stainless steel (type 316)

- Nickel aluminium bronze

Cast iron Strainer body - Ni-resist iron type D2

- Nickel Aluminium Bronze

- Cast Cu-Ni

- Gunmetal

Galvanized iron Strainer Monel alloy 400


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Component Concentration(mg/l)

% of total salt

Chloride 18,980 55.04

Bromide 65 0.19

Sulfate 2,649 7.68

Bicarbonate 140 0.41

Fluoride 1 0.00

Boric acid 26 0.07

Magnesium 1,272 3.69

Calcium 400 1.16

Strontium 13 0.04

Potassium 380 1.10

Sodium 10,556 30.61

Total 34,482 99.99

Composition of sea water


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Effect of sea water on corrosion resistance

Chemical Effect

Carbonates and Sulfates

Chlorination Effects

pH

Geographical Variations

Temperature Effects

Velocity Effects

Salt Precipitation, Deposits and

Bio-fouling and Sediments Effects

Fouling

Bioforms

Localized Variations

Dissolved Oxygen

Characteristics

Design Effects

Crevice Geometry and SurfaceFinish Effects


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Sea water velocity

Corrosion data on materials in high velocity test

Alloy Corrosion rate Seawater Velocity

Grey cast Iron 13 38

Carbon steel 9.5 40

Ni-Cu Alloy 400 0.010 43

Ni-Cu alloy K-500 0.010 43

Stainless steel 316 0.005 43

Gun metal (85/5/5/5) 1.30 40

Nickel Aluminium Bronze 0.80 38-42


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Types of corrosion

Mode of Corrosion Copperbased

alloys

StainlessSteel 316

Stainless Steel 6Mo and Duplex

TitaniumAlloys

General Corrosion Resistant/Su

sceptible1

Resistant Resistant Resistant

Crevice Corrosion Susceptible Susceptible Susceptible (>25C) Resistant (60C)

Resistant Resistant3

Corrosion Fatigue Susceptible Susceptible Susceptible Immune

Galvanic attack Susceptible Susceptible Resistant Immune

Microbiological

Corrosion (MIC)

Susceptible Susceptible Susceptible Immune

Weld/HAZ Corrosion Susceptible Susceptible Susceptible Resistant

Erosion Corrosion Susceptible Resistant Resistant Highly Resistant

1. Dependent on Pollution level/sea water chemistry2. Grades 7,11,12, 16,17,20,21,24, 28,29 resistant to at least 200C

3. Standard Grade 5 has finite susceptibility, Grade 23 (ELI) has improved K1SCC values


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Titanium alloys

Titanium is as strong as steel, yet 45% lighter. The high strength,

low density and corrosion resistance of titanium contribute

positively towards cost reduction. Weight saving is of great

importance for offshore platforms

Titanium requires no corrosion allowance so equipment can

be designed to satisfy the minimum requirements formechanical strength and handling

The number and variety of applications of titanium and titanium alloys

offshore continues to increase. From no more than a few hundreds of kilos

in chlorination systems and heat exchangers twenty years ago, total

consumption now approaches three thousand tons.


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Titanium alloys applications in sea water systems

Titanium alloy grade Application

23 (Ti-6Al-4VELI) Taper Stress Joints

Drilling Riser

Fire Water Systems

Sea Water Lift Pipes

Ballast Water Systems

Anchor System Pipework

Penetrations and Manholes

Penetration Sleeves

Fresh Water Pipework

Sea Water Pipework

Seawater systems, fire, ballast and

produced water Pipework

Gravity Based System

Booster Lines

23

2 (Commercially Pure)

2

2

2

2

2

2

2 (110 tons)

2 (300 tons)

2(500 tons)

9 (Ti-3Al-2.5V)


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Composites

Composites are fast taking over as superior alternative to other

traditional materials even in high pressure and aggressive environmental

situations. Composites have become attractive candidates for

applications in oil gas, piping system, topside applications, down-holetubing in sub-sea, and others

Composite piping system Composite handrails and

grids/gratings

Composite coil tube


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Composite Piping System (Glass Reinforced Epoxy (GRE) )

Glass Reinforced Epoxy (GRE) piping system offers complete solution for offshore

environment against highly corrosive fluids at various pressures, temperatures, adversesoil and weather conditions (especially in oil exploration, desalination, chemical plants,

fire mains, dredging, portable water etc.)

Composite Pressure RisersComposite riser is the pipeline that connects the rig of the water surface to the well

bore at the seabed

Caissons at offshore

platforms

Composites

C i i l li i


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Composite material applications

No Application

1 Composite Grids/ Gratings2 Hand rails & Ladder Components

3 Aqueous Piping System

4 Water & fuel storage tanks, Vessels

5 Low pressure composite valves

6 Spoolable type thermosetting tubes

7 Sump Caissons and pull tubes

8 Cable support systems

9 Modular paneling for partition walls

10 High pressure accumulator bottles

11 Flexible & Floating Risers, Drill pipe

12 Sub sea structural components

13 Boxes, housings and shelters

14 Fire water pump casing & sea water lift pump casing

15 Tendons

16 Offshore bride connecting between platforms

17 Blast & Fire protection


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Ni Base alloys

Nickel with no other significant alloying elements (UNS NO2200)

Chromium-free nickel alloys (UNS NO4400 & UNS NO 10001)

readily losing its passivity and suffering pitting and

crevice corrosion. General corrosion rates as high as8 mpy are possible in polluted seawater.

little used in seawater

67 nickel- 33 copper (UNS NO4400) and

70 nickel - 28 molybdenum (UNS NO 10001)Alloy 400 has been widely

used in seawater

The alloy possesses

excellent resistance to high-

velocity seawater

Care should be exercised whenspecifying alloy 400 for thin-wall

products such as exchanger tubes

Its general corrosion rate in quietly moving

seawater ranges from approximately 0.1- 1.0 mpy.

Pits in alloy 400 tend to self-stifle


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Nickel-chromium alloys, with and without molybdenum.

625 (NO6625), alloy C-276 (N10276),

and alloy C-22 (NO6022)

Alloying elements such as, chromium

and molybdenum make the alloys

possess superior crevice corrosion

resistance compared with lesseralloyed nickel alloys.

It is considered for seawater

service where there is a potential

for crevice corrosion

Nickel Aluminum Bronze

This alloy has a good combinations of

mechanical properties and corrosionresistance

It has been used in wide variety of

marine applications including

valves and fittings, ship propellers,

pumps, pump shafts, valve stemsand heat exchanger waterboxes

Ni Base alloys


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Nickel Aluminum Bronze

This alloy has a good

combinations of mechanical

properties and corrosionresistance

It has been used in wide

variety of marine applications

including valves and fittings,

ship propellers, pumps, pumpshafts, valve stems and heat

exchanger waterboxes

Ni Base alloys


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Copper-tin, copper-aluminium and copper-zinc alloys

Nominal composition per centAlloy Copper Tin Zinc Aluminium Other

Admiralty

Gunmetal88 10 2 - -

LeadedGunmetal

85 5 5 5 -

Leaded

Gunmetal +

nickel

86 7 2.5 - 2.5% Lead

2% Nickel

Nickelaluminium

bronze

85 - - 10 5% Iron5% Nickel

Aluminium

brass

76 22 2 0.02% Arsenic

Typical compositions of alloys commonly used in seawater systems

Copper alloys system in piping


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Typical compositions of alloys commonly used in seawater systems

Alloys of nickel and copper

Nominal composition per cent

Alloy Copper Nickel Iron Other

90-10 Cu-Ni Remainder 10 1.5 1.0 Mn (max)

70-30 Cu-Ni Remainder 30 0.6 1.0 Mn (max)

70-30 Cu-Ni (high

iron)Remainder 30 2.0 2.0 Mn

70-30 Cu-Ni+Cr Remainder 30 0.7 1.6 Cr

Ni-Cu Alloy 400 31.5 66 1.35 0.9 Mn

Cast Ni-Cu AlloyBS 3071

30.5 66 1.35 1.6 Si

Ni-Cu Alloy K 500 31.5 66 1.35 1.9 Mn 2.8 Al

0.5 Ti

Cast Ni-Cu Alloy

BS 3071 NA3 29 64 2.0 4.0 Si


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Copper alloys system in piping

Two copper-base alloys have been widely used for seawater

handling, namely aluminum brass and 90-10 Cu-Ni

When using non-ferrous piping the

system must be designed on the basis of

water velocity in order to avoid

impingement attack

Copper 0.75 m/sAluminum

brass2.5 m/s

90-10 Cu-Ni 3.0 m/s

70-30 Cu-Ni 3.5 m/s submarine

Piping


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Copper alloys system in Piping

The current trend is towards the use of 90-10 Cu-Ni

1- Its better weldability. Although aluminum brass can be welded using aluminum

bronze filler

2- Its high stress corrosion resistance. 90-10 Cu-Ni does not normally require any stress

relief heat treatment after fabrication. Aluminum brass requires stress relief to avoid

the possibility of stress corrosion cracking to which it is susceptible in seawater

3- Its good experience. Some reports showed that, only nine cases of premature

failure over a period of 20 years. This is a remarkable result considering the

large tonnage of the alloy in use throughout the world.


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Copper alloys system in valves

Many corrosion problems in seawater systems occur in

valves. Often such problems are due to the use of steel or castiron valves with non-ferrous piping. Although the life of such

valves in a steel or cast iron pipe system is short (i.e., two to

three years) when fitted in a alloy system, it may be less thana year due to the galvanic effects from the piping.

The three main components of a valve are :1- The body

2- Valve seats

3- The shafts or stems


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1- The body

The basic low cost valve used in ferrous pipe systems has a cast iron bodywith 60-40 brass internals. Depending on design, corrosion rates of several

millimeters per year can occur on the body. The body cathodically protects

the internals (until a layer of graphitic corrosion product forms) and the

valve will function for two to three years.

Upgrading of valve body materials to give higher reliability requires the use of

alloys with good corrosion resistance. Such materials are copper base alloys such

as nickel aluminum bronzes, Admiralty and leaded gunmetals and cast Cu-Nis. Allthese alloys are characterized by good resistance to static seawater (necessary for

shut-down conditions) and to flowing seawater.


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2- Valve seats and stems

The material of Valve seats should have high resistance to fast flowing seawater

such as, stainless steels, nickel-base alloys and Monel alloy 400.

Dezincification of a 60-40 brass stem from a bronze valve

Experience shows that when manufacturersupgrade the body material they often use the

same materials for seats and stem as in a cast

iron valve, i.e., 60-40 brass. Under these

conditions the life of the valve internals is

extremely short because, having lost the

cathodic protection of the ferrous body, they

fail by dezincification in a few months

C ll i l


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Materials for seawater valves in non-ferrous pipe systems

Type of valve Body materialBall, disc, or

seat material

Stem

material

Butterfly

valves

Gunmetals

5% nickel aluminium bronze

Rubber-lined cast iron (provided a

seal is fitted at the stem)

Cast 70-30 Cu-Ni

5% nickel

aluminium

bronze

Cast 70/30 Cu-Ni

Cast Monel alloy

Stainless steel

(Type 316)

Ni-Cu alloys

400 or K500

Stainless

steel

(type 316)5% nickel

aluminium

bronze

Globe, gate, orball valves

As above, except that rubber linedvalves should be avoided

As above As above

Membrane

valves

Rubber lined cast ironRubber

(membrane)

Not critical

as there is

no seawatercontent

INTERACTIONS WITHIN THE SYSTEM


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INTERACTIONS WITHIN THE SYSTEM

1- Make the "key" component of a more noble material. For example, use copper-base

alloy trim in a cast iron valve body.

Galvanic Effects

Wherever possible, components of similar galvanic potential should be used for

construction of the system. Where this is not possible, the following guidelines

should be used:

2- Ensure that the material of lower potential is present in a much larger area

than the more noble material so that the accelerated corrosion of the anode is

spread over a large area.

3- Paint the more noble material. This can be beneficial as it reduces the cathode

area even when the paint film is incomplete. An imperfect paint film on the

anode would intensify attack at breaks in the paint.


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Thank You Very Much

materials used in sea water system

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