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Ferritic / Duplex / AusteniticSteel Grades

for Condenser Tubesreported by

Dr. Winfried HeimannChristian Behrle

FerriticFerritic / / DuplexDuplex / / AusteniticAusteniticSteel Grades Steel Grades

forfor CondenserCondenser TubesTubesreportedreported byby

Dr. Winfried HeimannDr. Winfried HeimannChristian BehrleChristian Behrle

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• Dr. Winfried Heimann• was heading varios division of R+D, quality control and application engineering in Thyssen Edelstahlwerke and

ThyssenKrupp Nirosta• was being Senior Manager with Outokumpu Stainless• after retirement he is acting as Consultant in this field

• Christian Behrle• is heading the Technical Department for R+D in Fischer-group• specialised in SS-tubes for desalinations• DME – Member of the Board• Member of IDA• Member of EDS

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Typical Relation of Corrosion Resistance und Mechanical Strength of some Stainless Steel Grades

Mechanical Strength

Cor

rosi

onR

esis

tanc

e

Austenitic grades Superferritic grades

Ferritic-Austenitic(Duplex)-Grades

Ferritic grades

1.4565

1.4404

1.4547

1.41621.4362

1.4410

1.4539

1.4521

28 Cr + Mo+ Ni

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EN10088

ASTMA 240

Cr%

Ni%

Mo%

Others PRE1

1.4162 S32101 21 1,5 0,3 N 26 19

1.4362 S32304 23 4,8 0,3 N 26 25

1.4410 S32750 25 7 4,0 N 43 85

1.4521 S44400 18 <0,5 1,90 Ti + Nb 24 22

1.4404 316 L 17 10 2,1 - 25 21

1.4547 S31254 20 18 6,1 N + Cu 43 87

1.4565 S34565 24 17 4,5 N + Mn 46 >87

1 PRE= %Cr + 3,3%Mo + 16x%N (Pitting Resistance Equivalent)2 Critical Pitting Temperature acc. ASTM G 150

Ref.: Mikael Willför, Outokumpu: Materials selection for thermal plantsDME-Workshop 2008, Duisburg

Stainless Steel Grades for Seawater Desalination Plants

Duplex stainless steel grades Austenitic stainless steel grades

CPT2

°C

Ferritic stainless steel grades

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EN10088

ASTMA 240

Yield Strength Rp0,2MPa

EN(ASTM)

Tensile Strength

RmMPa

EN(ASTM)

ElongationA5%

EN(ASTM)

1.4162 S32101 (530) (700) (30)

1.4362 S32304 450(420) 650(600) 20(20)

1.4410 S32750 550(550) 750(750) 20(15)

1.4521 S44400 320(275) 420(415) 20(20)

1.4404 S31603 240 530 40

1.4547 S31254 320(310) 650(690) (35)

1.4565 S34565 420 800 30

Mechanical properties of Stainless Steel Cold rolled Strip Minimum Values

Duplex stainless steel grades Austenitic stainless steel gradesFerritic stainless steel grades

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Ferritic grades17Cr 28Cr2Mo 1-4Mo

0-2Ni(Superferritics)

Duplex grades Austenitic grades1.4404 1.4547

1.4565(Superaustenitics)

Density g/cm³ 7,7 7,7 7,8 8,0 8,1

Modulus of Elasticity GPa

220 200 200 200 195

Thermal Conductivity

W/mK

23 17,5 15 15 12

Thermal ExpansionRT - 300°C

10-6/K

11 10 14,0 17,0 16,5

Specific HeatJ/kg°C

430 500 500 500 450

Physical Properties of Stainless Steel grades(Average values according to EN 10088 or ASTM A240)

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Corrosion of Materials in Sea Water Desalination Plants

Forms of corrosion

• General corrosion

• Pitting and crevice corrosion

• Erosion corrosion

• Galvanic corrosion

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Corrosion Resistance of Stainless Steelin Sea Water

• Stainless Steels have negligible thinning in sea water

• Chromium oxide film (passive layer) forms immediatelyon steel surface with exposure to air

• Oxygen levels as low as 20 ppb are still sufficient torepair itself after being damaged

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Corrosion Resistance of Stainless Steelin Sea Water

•

Pitting and Crevice Corrosion•

Under certain conditions the protective surface filmon stainless steels can break down locally:

oxyginated waterhigh chloridetoo high chlorination levellow pH-value

pitting and crevice corrosion

more resistant grade has to be selectedacc. to PRE = %Cr + 3,3% Mo + 30 (16)% Nranking of alloys can be carried out

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Critical Pitting and Crevice Corrosion Temperaturesof Stainless Steel Grades

According to ASTM G 48

1.4404

1.4404

1.4439

1.4439

1.4462

1.4462

1.4539

1.4539

1.4410

1.4410

1.4565

1.4565

PittingCrevice Corrosion

100

80

60

40

20

0

Tem

pera

ture

[°C

]

PRE (%Cr + 3.3 %Mo + 30 %N)

25 35 45 55

1.4547

1.4547

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Critical Pitting Temperature of Stainless Steel Grades(Values determined according to ASTM G 150)

0

20

40

60

80

100

1.4301 1.4162 1.4404 1.4362 1.4436 1.4462 1.4539 1.4410 1.4547 1.4565

[°C]C

ritic

al P

ittin

g Te

mpe

ratu

re

Duplex Stainless Steel Grades Austenitic Stainless Steel Grades

Ref.: Outokumpu StainlessCorrosion HandbookNinth Edition, 2004

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20 Cr / 6,6 Mo

1.4529

1.44041.4438

20 Cr / 6,1 Mo

1.44621.4439 1.4539

90unweldedTIG-welded,without fillerTIG-welded,overalloyed filler(THERMANIT® 625)Laser-welded tubes (0,3x30)mm, minimum value

80

70

60

50

40

30

20

10

025 30 35 40

Test according to ASTM G48

PRE = % Cr + 3.3 • % Mo

Crit

ical

Pitt

ing

Tem

pera

ture

1.4565

%Cr + 3,3x%Mo on the CPT (Critical Pitting Temperature) of welded and unwelded Stainless Steels

°C

Influence of PRE (Pitting Resistance Equivalent)

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Erosion Corrosion in Sea Water Desalination Plants

Erosion corrosion is the most common failure, e.g. in the heat rejection

• Copper alloys, brasses and bronzes are prone to impingement attack, at sea water velocities above 3m/s.

• In sea water polluted with solids copper based alloys suffersevere erosion corrosion even at very low flow rates (< 0,5 m/s)

• Stainless steels and especially high alloyed grades like Duplex and Superaustenitics are much better resistant to erosion corrosion thancopper based alloys.There is no risk of erosion corrosion with special stainless steelsat velocities up 20 m/s even up to 40 m/s with high nitrogen containingSuperaustenitic steel UNS S34565.

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Corrosion Resistance of Stainless Steelin Sea Water

• Erosion and Erosion Corrosion

• The passive layer is maintained atvery high flow rates and

• Sea water velocities in excess of 40 m/s canbe accommodated (in praxis usually below 10m/s)

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AusteniticMn-Steels

Ferritic Cr-SteelsDuplex Stainless Steels

Superaustenitic SteelsUNS S34565

1000

100

10

10 20 40 60

Flow velocity [m/s]

Cor

rosi

onra

te [g

/m²d

]

AusteniticSteel

Corrosion of Stainless Steelsin Contaminated (Solids) Flowing Sea Water

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Galvanic Corrosion in Sea Water Desalination PlantsMulti-metal systems: Stainless steels, titanium, copper aloys

• Titanium is cathodic to most of other metals.

• Stainless steels are towards the more noble end of the galvanic series.

• Superaustenitic stainless steels are compatible with titaniumbecause their free corrosion potential is close together.

• Galvanic corrosion occurs when using titanium or stainless steeltubing together with copper based alloy tube sheets, increasingcorrosion attack to the tube sheet to a point where cathodicprotection is required in the water boxes.

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Chlorination – Performance of Stainless Steel• Chlorination is used to control microbiological films. To prevent the build-up of biofilms and remove settled biological species.

• Practice of chlorination is the addition of a hypochloride solutionto the sea water

• Chlorination can be either continuous orintermittent (Chlorine is added for shorter periodse.g. twice a day 15 minutes)

• Chlorination level- continuous: 0,1 - 0,4 ppm- intermittent: several ppm

total amount of chlorine is less than with systemsusing continuous systems

• The objective: Keep the residual chlorine level < 0,5 ppm

• Stainless steel perform well up to 2ppm

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Condenser tubes UNS S34565

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Welding root planedWelding root sag < 0,2 mm

Welding root sag< 0,15 mm

Laser welding

Tungsten inert gas welding - TIG

Weld shape of TIG and Laser welded Stainless Steel –thin walled tubes, welded from 1,5 mm cold rolled strip

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Tube assembly specimenMethodes of joining:• Welding to the tube plate• Rolling into the tube plate

Corrosion Tests in Simulated MSF DesalinationPlant EvironmentsTests carried out by Cortest Laboratories, Sheffield

Material: • UNS S34565, laser welded tube with

0,35 mm wall thickness,20 mm and 30 mm diameter

• UNS S31603, S31803, S32760, and S34565,plate material

Test Environment:• Alloy C276 autoclave• Syntetic sea water heated to 90°C• Three oxigen levels, 750, 150, and 65 ppb

Test Duration: 30 days

Experimental Test Program

Ref.: NACE Corrosion 2001, Paper No. 01484NACE Corrosion 2002, Paper No. 02190

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Corrosion Tests in Simulated MSF DesalinationPlant EvironmentsTests carried out by Cortest Laboratories, Sheffield

Ref.: NACE Corrosion 2001, Paper No. 01484NACE Corrosion 2002 Paper No 02190

Results:• UNS S34565 thin walled, laser welded tubing did not

corrode in any of the tests• No corrosion occurred at the welds of any

tubeplate material studied.UNS S34565, S32760, S31603

• Some corrosion was observed at non welded joints.Greatest on S32760 and least on S34565.

• The extend of corrosion on the non-welded assemblieswas not great. In particular for the S34565 the corrosion isinsignificant at the lowest oxigen level tested of 65 ppb.

Conclusions:• UNS S34565 thin walled laser welded tubes when welded to S34565, S32760 or S31603

tubeplates would be suitable for MSF plant evaporators.

• UNS S34565 thin walled laser welded tubes when rolled into S34565 tubeplatewould be suitable for MSF plant evaporators.

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Stainless Steel grades for Condenser Tubesfor MSF-Desalination Plants

Superaustenitic stainless steels: 1.4565 (S34565)

Superduplex stainless steels:1.4410 (S32750)1.4501 (S32760)

Superferritic stainless steels:Seacure(S44660)1.4592 (S44735)

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Stainless Steel grades for Condenser Tubesfor MED-Desalination Plants

Austenitic stainless steels:

1.4404 (S31603)

Duplex stainless steels:

1.4162 (S32101)1.4362 (S32304)

Ferritic stainless steels:

1.4521 (S44400)

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Stainless Steel thin walled Tubes for Desalination Plants

MSF Plants:• Heat recovery stages• Heat reject stages• Brine heater• Vacuum systems

MED Plants• Evaporator shell

• Condenser tubes

• Tube and Tube support plates• Vacuum ejectors

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Technical Data:

Capacity:Operating Temperature:Raw Water:Destillate :Effectiveness:

MED - HTE Multi Effect DistillationHorizontal Tube Evaporation

2 x 12.000 m³ / d<65°C

Brackish Water< 5µS/cm

>95 %

MultiMulti--EffektEffektDestillation PlantDestillation Plant

AVR, NLAVR, NL

1,4 Million MetersCondenser Tubes of 1.4565

(UNS S34565)Producer: Fischer Edelstahlrohre GmbH

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Source:VA TECH WABAG

Stainless Steels in the Sea-Water-DesalinationCondenser Tubes made of 1.4565

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Stainless Steels in the Sea-Water-DesalinationTechnology Heat-Exchanger Tubes

made of 1.4565

Windpowered seawater desalination Plant

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MSF and MED condenser tubing

Historically titanium and copper alloys• Poor availability of titanium• Environmental impact of toxic copper ions

Trends and options• Decreasing use of copper alloys• Use of corrosion resistant stainless steels

Duplex stainless steelsAustenitic and superaustenitic stainless steelsFerritic and superferritic stainless steels

• Reduction of wall thickness, e.g.heat exchanger tubes with 0,3 to 0,1 mm, UNS S34565 Ref. AVR Rotterdam

Ref.: DME-Seminar Materials and Corrosion inDesalination Plants, June 2007Heike Glade, BremenJan Olsson, Outokumpu Stainless

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Reference ListFischer Edelstahlrohre GmbH

Rügen Evaporator-Condenser Tubes of UNS S34565 in Operation since 1998 at about 80°C

St. Martin Testing of Condenser Tubes of UNS S34565 since 1998

Rotterdam MED-Plant of AVR Rotterdam, NLin Operation since Dez. 1999,1,4 Mio m Tubes of UNS S34565

Al-Taweelah A1 Condenser tubes of 316 L (1.4404) / MED

Creek Island Evaporator-Condenser Tubes of UNS S34565 will start up in 2009 at about 80°C

South Korea Evaporator-Condenser Tubes of UNS S34565 Installation in a MED test plant

Sharjah U.A.E. Layyah Station for Power Generation & Water Desalination – Intake Pump Cooling Coil