Table Of ContentMANUFACTURING
CONSTRUCTION
OPERATION
COATING AND CP
DEFECT INTERACTION
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MACAW.S PIPELINE DEFECTS
ACKNOWLEDGEMENTS
~DITiJHlr.. UABO Neither the publishersor the authors,
editorsand contributorsandtheir
We aregratefultoallthecolleaguesand Editor:
employingorganisations, nor any persons
friends in the pipeline industry that have Dr Colin Argent
actingon behalf of them a) makesany
contributed materialandconstructive warranty,express or implied,with respect
commentsduring the preparation of this Technical Editors:
to theuseof anyinformation,apparatus,
book. In particular we wish to thank the Dr Kevin Prosser (Metallurgy &Welding)
method or processdescribed inthis
following organisationsandindividuals: David Norman (Coatings)
publicationorthat suchusemaynot
infringe privately owned rights or b)
MACAWEngineering Ltd Associate Editors:
assumeanyliabilitieswith respecttothe
GE PIIPipelineSolutions Peter Morgan
use of,or for damagesresulting from the
KD Efird Roger Weatherhead
use of any information,apparatus, method
J O'Shea orprocessdisclosed inthispublication,and
Lithgow Associates the useofanysuchmaterials,processesor
David Norman Corrosion Control "'00LI5JlER - methodsissolelyat theriskof the user.
TWI-TheWelding Institute
Macaw's Pipeline Defects
Data containedwithinthispublicationis
ISBN 0-9544295-0-8
protected by copyright.All rightsreserved.
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'i) MACAWS' PIPWNE DEFECTS
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MACAW'S PIPELINE DEFECTS
INTRODUCTION
Theaimofthisbookisto illustratethe with in the section on construction along Each section in thisbookhasbeen
rangeofdefectsthat maybeencountered with poor construction practicessuch as compiled and edited by experienced
in high pressure steel pipelines and lackof cover, electricalshorts, poorpipe engineerswith manyyearspractical
pipelinecoatings.Itgivesadviceon the support etc. experiencein pipelineengineering,
probable cause and significance of the metallurgy, welding, coatings and
defectsand commentson appropriate The section dealing with operational corrosion.Webelievethisvolume will
remedialactions.Thisbookisnot intended defectsencompassesinternal corrosion, provide a useful pictorial reference for
asacomplete"Do ItYourself Manual"for externalcorrosion,erosion,fatigue,third engineersworking inthepipelineindustry.
thediagnosisand analysisof defectsand party damage,denting and buckling. We would welcome constructive
useofthismanualwillnot maketheuser comment,suggestionsor contributions
an"Instant Expert':Manyofthedefects Faults intheexternal corrosion control that wouldenhancethepracticalvalueof
require analysisand diagnosisbya systemaredealtwith inseparate sections. future editions.
qualified expert using specialist analytical Coating defectsareshown forthecommon
techniques. typesofmillapplied pipecoating andfield All photographs and information
appliedgirth weld coatings.Common contained in this document are intended
The defects included in this book problemswith cathodic protection for guidance only.No comment or
encompass allaspectsof high pressure schemesare also illustrated. suggestionshould beadoptedasan
steel pipeline manufacture,construction authoritative action without seeking
and operation. Thefinal section of the bookshows additional guidance from the relevant
examplesof the inter-action between fault codes,procedures orspecialistadvisors.No
The section on manufacture includes conditionsto create anew integrity riskto responsibilitycanbetakenfor any
defectsinsteelplate, seamless pipeand thepipeline;for exampleshieldingof the problemswhichmayariseas aresultofthe
seam weldsproduced byelectrical cathodicprotectionby adisbonded use of any information contained within
resistancewelding (ERW)and submerged coating to createtheconditionsforstress this document.
arcwelding (SAW).Girth weldsaredealt corrosion cracking.
IV ,~; MACAW'S PIPELINE DEFECTS
MACAW 'S PfP EU NE DEF ECTS
CONTENTS
MANUFACTURI NG DEFEGS OPERATtONAl. DEFEOS COATING AND CP DEFECTS
Tnefirst sectiondealswithdefectsthat The third section of the book deals with Thefourthsectiondealswith defects in
occur during steelrnakinq, rolling of the defects that initiateandgrowafterthe the external pipe coating and the
platefor pipemanufactureandthe pipeline has been commissioned. These cathodic protection system. These faults
manufacturing process itself. In principle, defects may initiate from a pre-existinq create theconditionsinwhichexternal
all critical defectsof this kind should be fault within the pipe or they may initiate corrosion can develop.
eliminated in the proof test carried out in fromanareaofthepipe surfacethat is
the pipe mill. freeof anymanufacturing or DEFECT INTERACTION
constructionfaults. The final section provides examplesof
how defects interact to generate new or
Thesecond section considers defects Operational faults represent the largest modified risks to pipeline integrity.
that maybe introduced into the pipeline problem for the pipeline operator who
during the construction process. Critical must assesswhichdefectsarelikelyto
defectsofthiskind should bedetected in develop,the rate at which they will
the post construction hydrostatic develop and the consequences for
pressure test. pipeline safety.
Alloftheseissuesaredealt withinthe
operational riskassessmentforthe
pipeline and the findings of this risk
assessment will decide the frequency
and type of periodic proof tests or
inspections designed to prevent
operational failures.
,j
MACAW'SPIPELINE DEFECTS
MANUFACTURING DEFECTS
INTRODUCTION
This sectiondealswith defectsgenerated Boththe milltests andthepost salt and moisture,including pre-heating,
intheplate,thepipeortheseam weldsup construction pressuretestaredesignedto waterwashing and chemicaltreatment.
tothetimewhenthe pipe passesthefinal locatedefects withasignificant'through
milltestandisdeclared'fit forpurpose' and wall'cornponent.Thesetestsare not Surface defectssuch as laps,sliversand
isshippedto theclient. optimised to locate defects running blisters alsocreate 'holidays:or defectsin
paralleltothepipewall,such ascentreline thin film coatings.
Major manufacturing faults will be segregationsor laps.Defectsrunning
detected bytheNDTinspectioninthe parallel to the pipe wall may assume Manufacturing defects are not normally
pipe mill,during thecold expansion ofthe greater significanceforstructural integrity considered to posea major risk to pipeline
pipe(thisisapplied to most U-and-D inspecificoperating conditions,for integrity if they have been subject to a mill
formed,straight seam, submerged arc examplewherethe pipelineissubject to test andapostconstruction hydrostatic
welded (SAW) pipe and some spirally bending loads induced from ground pressure test. Reassessment of
welded pipe)orbyhydrostatictesting of movement or where sour service corrosion manufacturing defectsmay be required
the individual pipes. mechanisms areactive. wherethereisevidenceforgrowth in
service,forexampleby corrosion orfatigue.
Ifthepipewasnot subject to ahigh-level Minor surface irregularities, such as small
milltestthenthecriticaldefectsshould be lapsorrolled inscale,pose noimmediate Manufacturingdefects aredealtwithin
detected in the post construction proof threat to pipelineintegrity but can initiate four sections.
test. pitting corrosion.Muchpipeisshipped by
sea,asdeckcargo,orcoatedat coastal
Wherethereisnorecord ofeithertypeof coating plants.Ineither case thesesmall
testasignificanceofdefect assessment irregularitiescanaccumulatesalt and
may be required for mill defects identified moisturebelow thepipesurface.Special
from intelligent pit inspections or non cleaning isrequiredtoremovealltracesof
destructive testing examination.
2 r, MACAW'S PIPELINE DEFEers
MANUFACTURING DEFECTS
INTRODUCTION
Section One describesdefects in rolled Section Three dealswith ERW,Electric Section Fourdealswithstraightseam
plate including structural featuresthat ResistanceWelded,pipe.Early ERWseam DSAW (double submerged arc welded)
become apparent during standard tests. weldswerecreatedby passinganelectric pipeand concentrateson seam weld
Platedefectsmay becarried forward into currentthroughthearea oftheweld defects.Thesedefectsmayalsobe found
straight seam,ERW and spirally welded fromcontactson eithersideofthefusion inspirallyweldedDSAW pipe.Inboth
pipe. line.Controlof weld quality wasa thesetypesof pipetheedgesofthe plate
particular problem with this type of arecrimped beforethe plate isformed
welding.Modern ERW pipe is produced into the pipeshape.Thiscrimping action
SectionTwodealswith seamlesspipe using the HFI, High Frequency Induction, givesmore precise'fit-up'fortheseam
that isformedfromasteelbillet.Thebillet techniqueand thisgenerally produces welding process. The crimp geometry will
ispiercedandthen progressivelyformed seamweldsof consistent quality.Most of be removed in cold expanded pipe but
into apipe.Seamlesspipeshowsvariable thefeaturesshowninthissection relate this area may be subject to higher strain
wallthickness along itslengthduetothis to weld quality but featureslisted under during hydrostatic pressure testing.
pipeforming process.Manyofthe platedefectsmay alsobepresent. Features listedunderplatedefectsmay
defects found in seamless pipe originate alsobe presentin both straight seam and
as defectsintheingotfromwhichthe spirally welded pipe.
pipe wasformed.
{) MACAW'SPI?EI.INEDEFECTS
MANUFACTURING: PLATE DEFECTS
BLISTERS
Avoid, close to the pipesurface,enclosed
byathin filamentof steel.
Entrapment ofgasreleasedduringthe
solidification ofthesteel.
Not structurally significant
Maycause problems with holidaysin thin
filmcoatings.Superficialblisters maybe
removed by grinding before application
of the coating.
Possibleinitiation sitefor pitting
corrosion iftheblisteriscontaminated
with soluble saltsduring storageor
transport.
'; MACAW'S PIPELIN E DEFECTS
MANUFACTU RING: PLATE DEFECTS
CENTRE LINE SEGREGATIONS
Concentrationsof non-metallic matenal
in the mid-wall position Including carbon
and manganese rich bands.
During solidification non-metallic
materialmaybecomeconcentrated at
thecentreoftheingot whichisthelast
areato solidify.
Centreline segregationsaregenerally not
structurally significantforpressure
retention.
Theymay provideaninitiation pointfor
crackinginsourserviceand may
contribute to weld defects.
e» MACAW'S PIPtLINEDEFECTS
