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Topic
Materials for Demanding Topside
Offshore Application
Presented by
Vikram Pandit
Sandvik’s objective is zero
harm to our people, the environment we work in, our
customers and
our suppliers.
SAFETY FIRST
PROTECTIVE
EQUIPMENT
ASSEMBLY
POINT
EMERGENCY
EXIT
EMERGENCY
NUMBER
ALARMFIRST AID
KIT
HERITAGE
Founded 1862 in
Sandviken, Sweden
Göran Fredrik Göransson
redesigned the Bessemer
furnace to mass-produce steel
A breakthrough and an innovation
started the company 150 years ago
3
Outline
• Atmospheric corrosion
• The SMT grades
• Field testing
• Material selection
• Summary
Atmospheric corrosion• The atmosphere might look clear and bright, but it hides a lot of
nasty things
• All these chemical species can, especially in combination with water, cause corrosion of metals
Species Chemical name Outdoor / ppbv Indoor / ppbv
O3 Ozone 4-42 3-30
H2O2 Peroxide 10-30 5
SO2 Sulphur dioxide 1-65 0.3-14
H2S Hydrogen sulphide 0.7-24 0.1-0.7
NO2 Nitrogen dioxide 9-78 1-29
HNO3 Nitric acid 1-10 3
NH3 Ammonia 7-16 13-260
HCl Hydrochloric acid 0.2-3 0.05-0.2
HCHO Formaldehyde 4-15 10
HCOOH Formic acid 4-20 20
Atmospheric corrosion
• Many of the mentioned air pollutants are of no great concern to stainless steel
• Some will work as oxidisers and other will lower pH• O2, O3 and H2O2 are oxidising species
• NO2, SO2, HNO3 and HCl will form acids in water
• Detrimental, especially in combination with chlorides
Atmospheric corrosion
• Certain atmospheric environments are especially corrosive• Within or close to industries there can be an increased amount of air
pollutants such as acids or chlorides
• Close to the seacoast salt spray and salt deposits in combination with very humid air can cause localised corrosion and stress corrosion cracking
• Can give effect many kilometres inland
• More severe in tropical regions
• Installations at sea same situation as above• Platforms
• Cargo ships
Atmospheric corrosion
• Atmospheric corrosion is a little bit different compared to wet corrosion
• Usually complicated interactions and mechanisms between the metal and the air pollutants
• Condensation and evaporation can give highly concentrated environments
• Large temperature differences between day and night can give a lot of condensation
• Droplet formation under the tubes
• Plenty of oxidising chemical species
Atmospheric corrosion
Cl-Cl-
Cl-
O2
O2
O2
CO2
Cl-Cl-
Cl-
O2
O2
O2
CO2
SO2
SO2
Evap
ora
tion
Mo
re s
evere
co
nd
itio
ns
Atmospheric corrosion
• If condensation takes place or the tubes are exposed to sea spray the underside of the tubes will be especially vulnerable
• If the tubes are exposed to rain they may get washed clean
• If the tubes are protected from rain, salt accumulation can increase the corrosion rate
The SMT H&I grades
Grade Cr Mo N PRE
316L 17 2.1 - 24
3R60 (316/316L) 17.5 2.6 0.04 26
Sanicro 41 (825) 20 2.6 - 29
2RK65 (904L) 20 4.5 - 35
Sanicro 28 27 3.5 - 39
254 SMO (6Mo) 20 6.1 0.2 43
SAF 2507
(SDSS)
25 4 0.3 43
Material selection• Standard grade for H&I tubing is 3R60 (Dual Grade Certified 316L)
• This grade will work in almost all indoors and inland installations
• Care has to be taken if local conditions are “non-standard” Hydrochloric acid plant
• Sulphuric acid plant, etc
• Is the tube hot?• Good because no condensation
• Bad if exposed to sea spray or similar
• For light weight constructions• Duplex grades (thinner wall thickness)
• Coiled tubing (less couplings)
Material selection• For temperate coastal regions 3R60 can be
a solution indoors or in protected areas
• If the H&I installation is exposed to salt spray etc. 3R60 will stain and possibly experience pitting as well
• If the tubes get warm (>60C) chloride stress corrosion cracking is a real threat to system integrity
• Sanicro 41(Alloy 825) has poor resistance to chloride induced corrosion and will behave only slightly better than 3R60
• Chloride induced stress corrosion cracking is not an issue with Sanicro 41
• 2RK65 (904L) has sufficient resistance towards chloride induced corrosion for this environment and should be the material of choice
Field exposure Swedish West Coast
Alloy 825 (Sanicro 41)316L
904L (2RK65) Super Duplex (SAF 2507)
Material selection• In tropical coastal regions 3R60 is not recommended
• Field exposure and experience from platforms in Brazil shows that 316L tubes will stain and pit extensively under these conditions
• High risk for chloride induced stress corrosion cracking if the tubes are hot
• 2RK65 is at its limits under these conditions
• Staining and some pitting
• No risk for SCC
• SAF 2507 shows no corrosion after field testing in tropical climates
• Specified by Petrobras for platforms
• An alternative is 254 SMO
• Easier to bend
• Specified by Statoil for all their platforms in the North Sea
Field exposure Florida, US
Alloy 825 (Sanicro 41)316L
904L (2RK65) Super Duplex (SAF 2507)
Lower deck installation test (18 months)
316L Super Duplex (SAF 2507)
STRESS CORROSION CRACKING
316L
•Austenitic stainless steels (300
series)
•Temp > 60 °C
•Tensile stress
•Corrosive media like Chlorides,
H2S etc
• Sudden Failure
STRESS CORROSION CRACKING resistance
aa
Temperature,°C (°F)
0 (32)
50(120)
100(210)
150(300)
200(390)
250(480)
300(570)
0.0001 0.001 0.01 0.1 1 10Cl–, weight-%
SCC
No SCC
N08028/Sanicro 28SAF 2205
AISI 304/304L
AISI 316/316L
904L
SAF 2507No cracking
SAF 2304
Results of SCC tests with constant load in 40% CaCl2, pH = 1.5 at 100°C, aerated solution
aa
1.00.2 0.4 0.6 0.8Stress/Tensile strength
SAF 2507
100
200
300
400
500
600Time to failure, h
AISI 316L
SAF 2205
The SMT gradesGrade Cr Mo N PRE Environment
316L 17 2,1 - 24 Inland
3R60 (316/316L) 17,5 2,6 - 26 Coastal temperate, protected
Sanicro 41 (825) 20 2,6 - 29 Coastal temperate, protected
2RK65 (904L) 20 4,5 - 35 Coastal temperate
Sanicro 28 27 3,5 - 39 Coastal tropical?
254 SMO (6Mo) 20 6,1 0,2 43 Coastal tropical
SAF 2507
(SDSS)
25 4 0,3 43 Coastal tropical
Material selection– Minimum weight• Large installation
• 20 km tubes
• Max working pressure 350 bar
• Other diameter 12.7 mm
• Solution 1• 3R60 12.7 x 1.63 mm
• Max pressure 351 bar
• Weight = 0.453 kg/m
• Weight installation = 9070 kg
• Solution 2• SAF 2507 12.7 x 0.89 mm
• Max pressure 354 bar
• Weight = 0.261 kg/m
• Weight installation = 5220 kg
Material selection– Coiled tube• Installation 5 km
• Solution 1• Normal length tubes, 6 m
• Fittings ~ 1000
• Fittings ~ 20 € / piece
• Cost of fittings 20000 €
• Solution 2• Coiled tube
• Number of fittings drastically reduced
• Much less scrap
• Save a lot of money!
Summary• 316L has limitation when it comes to
offshore and marine/ sea water application
• Pitting and Stress Corrosion Cracking is the main problem with this grade esp. in Chloride environment
• In coastal areas higher alloyed grades are recommended
• Temperate climates: 2RK65 (904L)
• Tropical climates: SAF 2507 or 254 SMO (6Mo)
• Low weight installations calls for high strength tubes
• Super Duplex
THANK YOUPlease feel free to contact me for any further information-
Vikram Pandit
Vikram.pandit@sandvik.com
+91 9372342108
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