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

# 1# 2

� 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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