Subsea PipelinesSubsea Pipelines
Basics of Materials Selection
� What is Materials Selection (SURFSURF)?
How it is Carried out?� How it is Carried out?
� Examples
� Carbon Steel & Corrosion Resistant Material
� Corrosion Resistant Alloys
� Cost / Availability Trend
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Basics of Materials Selection� Materials Selection
� Mechanisms for Choosing Suitable Materials � Corrosion Resistance – Internal External Corrosion� Mechanical Properties – Yield Strength and Toughness� Easy of Fabrication/Installation – Weldability Formability Inspection
� Establishing Cost of Selected Materials � Carbon Steel + Corrosion Inhibition� Corrosion Resistant Materials� Bimetallic Materials� Fabrication & Installation Costs
� Operation � Maintenance Costs
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Basics of Materials Selection
Subsea Production SystemRisers
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Courtesy of Xodusgroup
Pipeline
Umbilicals
Basics of Materials Selection� Materials Selection – Subsea Pipelines
� Selection Mechanism� Internal Corrosion Strength Flow Assurance� External Corrosion Toughness Operating & Design Data
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� Optimised Cost Based On� Procurement, Installation � Operation & Maintenance � Design & Regulatory Compliance
� Existing Track Record & Contractor Capability � Welding� NDT� Installability
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Basics of Materials Selection
� Material Selection
� Corrosion
� Subsea Pipelines -Saline Muds, Seawater & Process Fluids
� Wet Acid gases (CO2 H2S) or O2� Wet Acid gases (CO2 H2S) or O2
� Halide ions
� Bacterial Activity
� Corrosion - Process
Fe Fe2+ + 2e-
M Mn+ + ne-
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To corrode
or not to
corrode?!!
Basics of Materials Selection
� Several Relationships exist that predict corrosion rates based on� CO2
� H2S
� H O� H2O
� O2
� Cl-
� pH level
� Presence of Corrosion inhibitors
� Flow velocity
� Total System and Active Gas Partial Pressure
� Many different corrosion rate models available
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Basics of Materials Selection
� Internal Corrosion – Carbon Steels & Low Alloy Steels
� De Waard Milliams or Flow Chemistry
� Shell - HydroCor
� BP - Cassandra� BP - Cassandra
� TOTAL - Corplus
� Intetech – ECE (Electronic Corrosion Engineer)
� Norsok - M 506
� Honeywell - PREDICT
� IFE - KSC
� OLI - SCORE
� Scandpower - OLGA
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Basics of Materials Selection
� Internal Corrosion – Corrosion Resistant Alloys
� Flow Chemistry
� Honeywell – SOCRATES� Selection of Corrosion Resistant Alloys Through Environment Specification� Selection of Corrosion Resistant Alloys Through Environment Specification
� Intetech - ECE
� Established Domains
� Qualification Testing
� Experience
� Operator
� Engineer
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Basics of Materials Selection
� Selection Mechanism – How It Is Done
� Internal Corrosion
� Collection of Information
� Design & Operating Data� Design & Operating Data
� Flow Assurance & Production Profiles
� Default Selection – Carbon Steel
� Determine corrosion rates using known Algorithms
� Establish if Inhibition is possible
� Calculate Corrosion Allowance
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Basics of Materials SelectionCarbon Steels
Sweet Corrosion Sour Corrosion
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Courtesy of Jacek Banas
Basics of Materials Selection
De Waard Milliams
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Basics of Materials Selection
750.0125.0PrRe
0565.0
×
××=
OCV
CRO
k
CdV
VDCR ×
×
××=
125.0125.0
875.075.00565.0
Oldfield Swales & Todd
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kdV ×
Basics of Materials Selection
� Cumulated Thickness Loss (CTL)
� Establish Corrosion Rate at various location
� Plot Corrosion rate against Time
� Calculate Area under worst Trace � Calculate Area under worst Trace
� CTL
� ATL (Acceptable Thickness Loss typically 3mm or 6mm)
� L Design life
� Consider
� or
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Basics of Materials Selection
Courtesy of FEESA
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Basics of Materials Selection
Courtesy of FEESA
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Basics of Materials SelectionCourtesy of IFE
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Basics of Materials Selection
� Decision
� If or > 1
� Carbon Steel is Risky; Select CRA
� CS + CRA
� Solid CRA
� CRA – Clad or Lined
� CRA - Plastic Liner
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Basics of Materials Selection
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Basics of Materials Selection
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Basics of Materials Selection
140
160
180
200
Tem
pera
ture
(°C
)
13%Cr
Other CRA and Austenitic Material
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0
20
40
60
80
100
120
0 10 20 30 40 50 60 70
Corrosion Resistance Index (PRENa)
Tem
pera
ture
(°C
)
Uninhibited CMn
316L / 825
25%Cr
Inhibited CMn
22%Cr No PLHT
PLHT
Basics of Materials SelectionCourtesy of Arcelor Mittal
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Basics of Materials Selection
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Basics of Materials Selection
� Q&A
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