Subsea Pipelines

Basics of Materials Selection
What is Materials Selection (SURF SURF)?
How it is Carried out?
Examples
Carbon Steel & Corrosion Resistant Material
Corrosion Resistant Alloys
Cost / Availability Trend SURF_Subsea Pipelines

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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

SURF_Subsea Pipelines

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Basics of Materials Selection Risers

Subsea Production System

Umbilicals Pipeline

Courtesy of Xodusgroup

SURF_Subsea Pipelines

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Basics of Materials Selection
Materials Selection – Subsea Pipelines
Selection Mechanism
Internal Corrosion
External Corrosion

#2 Strength Toughness

#1 Flow Assurance Operating & Design Data


Optimised Cost Based On
Procurement, Installation
Operation & Maintenance
Design & Regulatory Compliance

#3
Existing Track Record & Contractor Capability
Welding
NDT
Installability

SURF_Subsea Pipelines

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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
Halide ions To corrode or not to
Bacterial Activity corrode?!! Corrosion - Process

Fe M SURF_Subsea Pipelines

Fe2+ + 2eMn+ + ne6

Basics of Materials Selection
Several Relationships exist that predict corrosion rates based on
CO2
H2S
H2O
O2
Cl
pH level
Presence of Corrosion inhibitors
Flow velocity
Total System and Active Gas Partial Pressure
Many different corrosion rate models available SURF_Subsea Pipelines

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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 TOTAL - Corplus Intetech – ECE (Electronic Corrosion Engineer) Norsok - M 506 Honeywell - PREDICT IFE - KSC OLI - SCORE Scandpower - OLGA SURF_Subsea Pipelines

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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

Intetech - ECE Established Domains Qualification Testing


Experience



Operator Engineer

SURF_Subsea Pipelines

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Basics of Materials Selection
Selection Mechanism – How It Is Done
Internal Corrosion





Collection of Information
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

SURF_Subsea Pipelines

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Basics of Materials Selection Carbon Steels Sweet Corrosion

Sour Corrosion

Courtesy of Jacek Banas

SURF_Subsea Pipelines

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Basics of Materials Selection De Waard Milliams

SURF_Subsea Pipelines

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Basics of Materials Selection Oldfield Swales & Todd

0.0565 × V × CO CR = Re 0.125 × Pr 0.750

SURF_Subsea Pipelines

0.75

0.0565 × D × V CR = 0.125 0.125 Vk × d

0.875

× CO

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Basics of Materials Selection
Cumulated Thickness Loss (CTL)
Establish Corrosion Rate at various location
Plot Corrosion rate against Time
Calculate Area under worst Trace




CTL ATL (Acceptable Thickness Loss typically 3mm or 6mm) L Design life


Consider


or SURF_Subsea Pipelines

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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 Selection Courtesy 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 SURF_Subsea Pipelines

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Basics of Materials Selection

SURF_Subsea Pipelines

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Basics of Materials Selection

SURF_Subsea Pipelines

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Basics of Materials Selection 200 180 160 Other CRA and Austenitic Material

Temperature (°C)

140

13%Cr

120 22%Cr

25%Cr

No PLHT

100 Inhibited CMn

316L / 825

80 60 40 Uninhibited CMn

PLHT

20 0 0

10

20

30

40

50

60

70

Corrosion Resistance Index (PRENa)

SURF_Subsea Pipelines

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Basics of Materials Selection Courtesy 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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