Ruggieri Pipeline Integrity

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Fracture Assessm ents of Mar ine

Pipelines and Subsea Componentsin Host i le Environm ents:

Cri t ical Concerns and Recent

Developments

Claudio Ruggieri

NAMEFFractur e Mechanics and Struc tural Integr i ty Research Gro upFacul ty of Engin eering

Universi ty of So Paulo - Brazi l


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Outline

Chal lenges in Pipeline Safety Standards:Link ing Design and Operation

Current Pract ices and Standards for Defect

and Safety As sessments of Pipel ines

Innovat ive App roaches as More Rat ional andYet More Eff ic ient Integr i ty AssessmentProcedu res for High Perfomance Pipel ines

Some Key Cr i t ical Concerns Dr iv ing FurtherResearch and Development


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Going Farther and Deeper......

Increasing Demand forFossil Fuels, Including

Natural Gas, is Pushing

Oil and Gas Exploitation

and Production to

Farther and Deeper

Reservois in Difficult and

Hostile Environments

Technological Challenges in Pipeline and

Riser Design, Installation, Operation,

Inspection and Repair


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The Brazilian Pre-Salt Reservoir


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Key Characteristics

More than 2500 m Water Depth.

2000 m Thickness Salt Layer.

Gas Pipeline Larger than 18 in2500 m

Long Distance to Shore (300 km)

High CO2Content (8 ~ 20%)


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The Mysterious Design Factor....

High Design Stresses Do Not Cause Failure.

Damage Does!

The 0.72 Design Facto r isa Histo r ical Facto r SetMore than 50 Years Ago !

There is No Ration aland Convinc ing BasisAgains t Inc reasing It.


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Fracture is Always a Concern ....

Failure of Brazilian Pressure Vessel (2000)

(Fracture Initiated at Weld Defect)


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Conventional Defect Assessments

FFS or ECA Analys is Requ ired

Fundamental Procedure is Based on the GoodWorkmanship Phi losophy To Ensu re That thePipel ine/Riser is Free of Fabricat ion Defects

However, Larger and Often Severe Defects Wil lInvar iably Occur Du ring the Pipeline and RiserServ ice Life.


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Two-Parameter Assessment Line Describing

the Interacion of Two Failure Modes:

Bri t t le Fracture and Plast ic Col lapse

Failure Assessment Diagram Approach


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BS 7910 Level 2A


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Key Assumption is that the FAD Curve

Does Not Depend on Specimen

Geometry and Strain Hardening:

High Constra int Cond i t ionsLow to Moderate Duc t i le Material

FAD Approach

More Impo rtant, FAD Procedu re is aStress-Based Approach !


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Current Scenario

New Methods Should be Developed

There is Growing Concern Supported by

Strong Field Evidences that Conventional FFS

Procedures are not Necessarily Applicable to

Newer Materials and Complex Conditions:X100 Grade Steel, Ultra Deep Waters, Heavy

Thickness Pipes, Sour Environment, etc.


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Constraint Effects on Toughness


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Flawed Pipes vs . SE(B) Specimens

Cravero and Ruggieri (2007)


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Flawed Pipes vs. SE(T) Specimens



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V5

V6

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

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V5

V6

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

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-0.8

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SE(T)-P a/W=0,520 Pipe a/t=0,5

b

yb

y

b

x

b

x

Crack-Tip Plastic Zones



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Constraint Modified FAD Approach

]1[0 rQmatQmat LKK

]1[)( rQrr LLfK

ToughnessCorrect ion


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Constraint Mod if ied FAD


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Strain-Based Analys is Def ines a Lim it State

Cond i t ion in Which Structu ral Behavior isControl led b y Imposed Displacements

Strain-Based Analysis

The Col lapse Analys is Bui l t Into FAD Procedu resRel ies on Determ inig Net Sect ion Yielding in theCrack Ligament

For Higher Grade Steels or Overmatched Gir thWelds the App l ied Strain Can Be Much Higher

than the Yield Strain


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When the Material is in the Plast ic Range, SmallChanges in Stress Cause Large Changes in Strain


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Pos t-Yield Behavio r Does Affect the TolerableDefect Size in a Struc tural Component


After Yielding , the Evo lvin g Near-Tip Stressesand Crack Driving Forces (J, CTOD) Strong lyDepend on the Plast ic Straining Capaci ty

Pipe Steels w ith Lower YT-Ratios (X60) May A llowLarger Defects than Higher YT-Ratios (X100)


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Fracture Assessment Using API 579 L2

0

0.2

0.4

0.6

0.8

1

1.2

0 0.2 0.4 0.6 0.8 1 1.2

rK

rL

API Level 2

Limit Load

Correction

%25.0

f


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On-Going Research

Developm ent of Test Procedures forConstraint-Designed SE(T) Specim ens

FFS Procedures and B iaxial Loading Effects

on Reeled Risers

Structu ral Integr i ty As sessments o f LinedPipes fo r Reeling

Fat igue and Toughness Behavior of Gir thWelds o f Lined Pipes under H2Envi ronment


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Pipeline and Riser Installation

Riser Ins tal lat ion by Reeling


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FFS Procedures for Reeled Risers


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Pipe Reeling Behavior

(From SINTEF Materials Labor atory)


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Pipe Reeling Behavior

(From SINTEF Materials Labor atory)


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Full Compendium ofh1Factors Generated by

Chiodo & Ruggieri in Polynomial Form

for Easy Manipulation and Codification

Proportionality Between J(CTOD) andApplied Loading is Very Good for High and

Moderate Hardening (All Crack Config.) and

Low Hardening (Shallow Cracks)

Robust Procedure for Mos t Appl ications


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Application to Pipe Reeling

Est imation o f J Based Upon App l ied Strain(e.g ., DNV-OS-F101)

API Grade 5L X60


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J vs. Global Response


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Est imat ion of Maximum Crack

Driv ing Forces in Pipe Reel ing


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Lined Pipes

L ined p ipes cons is t o f a C-Mn p ipe wh ich has a layer o f CRA in con tac t w ith the product ion f lu id and hence, its co rros ive en viro nmen t. The lay er o f Co rro sio n Res is tan t A llo y (CRA ) is applied th ro ug h a mechan ic al b on d b etw een th e CRA and th e C-Mn p ip e.


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Key Issues

Wrink le Formation


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Key Issues

Fatigue and Fractu re Behavior o f Girth WeldsIncluding Hydrogen Assisted Cracking


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Summary

Exploitation and Production of Oil and Gas in

Ultradeep and Hostile Environment Represent New

and Difficult Challenges which Impact Directly the

Safety and Integrity Levels of Pipelines and Risers

Application of Current FFS Procedures to Newer

Materials and Complex/Severe Conditions Can Not

be Made by Simple Ad-HocExtension ofConventional Engineering Methodologies

Inn ovat ive and Yet More Ration al and ReliableApproaches Mus t Be Developed!


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Thank you!

Ruggieri Pipeline Integrity

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