10-05 offsore magazine intertek dimensional control for offshore titan project (1)

7/21/2019 10-05 Offsore Magazine Intertek Dimensional Control for Offshore Titan Project (1)

1/8

UsingdimensionalcontroltomitigateriskforATPTitan

installation

Published:May1,2010

TomGreaves,SparPointGroup

RobertShivers,ATPOil&GasCorp.

JoseVasquez,RoyCottrell,Bennett&AssociatesLLC

IanMackie,KeithMedley,IntertekHiCad

Theclientisasmallindependentthatjustmadea$600millionbetonanew

deepwaterfloatingplatformtodevelopaGulfofMexicofieldthemajorsconsidered

toosmalltodevelopthemselves.Getitrightandtheclientdoublesproductionnext

year.Getitwrongwell,donotgothere.Mitigatinginstallationriskwith

dimensionalcontrolmakesalotofsensewhenthestakesaresohigh.Hereishow

BluewaterIndustriesdiditforATPOilandGasCorp.(ATP)ontheTitanMinDOC

projectearlierthisyear.

Themomentoftruthforalloffshoreinstallations:Willthetopsidestohull

integrationbe

performed

successfully,

on

the

first

attempt

and

without

interferences?BluewaterIndustriesdeployeddimensionalcontrolservicesfrom

IntertekHiCadatrelevantstagesoffabricationtolimitthepotentialforinstallation

problems,andcostandscheduleimpactsforATP'sMinimumDeepOffshore

(MinDOC3)floatingplatformproject.Installationandintegrationofthetopsides

moduleswascompletedoffshoreinJanuarywithoutincident;nodimensionalfitting

orclashproblemswereencountered.

TheATPTitanproject,adeepwaterdrytreeplatform,isthefirstofitstypetobe

usedintheGoM.ThepatentedMinDOChull,designedbyBennett&Associates

(BASS),consists

of

three

circular

columns

connected

by

triangular

pontoons

and

a

toptensionedriser(TTR)framethatsupportstherisersthroughthecenterofthe

hull.Ontopofthehullsetsatwomodule,"Tshaped"facilitydesignedbyMustang

Engineering.Thestructuremeasuresapproximately726ft(221m)fromthebaseto

thetopofitsderrickandhasadesigncapacityof25Mbbl/dofoiland100MMcf/d

ofgas.TheTitanMinDOChasbeendeployedintheMiragefield(MississippiCanyon

block941),aspartoftheTelemarkHub,andwillbeinitiallyproducingpartofthe

Telemark(AtwaterValleyblock63)andMorgus(MississippiCanyonblock942)fields

viasubseatiebacksinwaterdepthsofapproximately4,000ft(1,219m).Thestakes

arehighdevelopmentoftheTelemarkHubisexpectedtodoubleATP'sproduction

thisyear.
http://www.offshore-mag.com/


2/8

TitanhullfloatinghorizontallyingravingdockatGulfMarine

Fabricatorspriortosailaway.

Atfirstglance,Titan'sthreecolumnstructureresemblesasemisubmersible,but

motionwise,itsdeepdraftandlowcenterofgravitygiveitpitch,roll,andheave

motionsmoreinlinewithspardesigns.ThisisparticularlyimportantforpostKatrina

designconditions.Thenaturaloscillationperiodsfortheplatformfallwelloutside

thewaveperiodstypicallyexperiencedintheGoM.Furthermore,theMinDOCwas

designedto

be

moved

to

new

locations

over

its

expected

service

life.

The

Titancan

operateindepthsrangingfrom2,000ft(610m)to7,500ft(2,286m)with

comparablepayloadandenvironmentconditions.Moreover,theunitcanbetowed

toanewlocationwiththetopsidesinplace.Assuch,theTitanallowsATPto

considerfieldsthatwouldotherwisebecommerciallymarginalwithconventional

completions.

The18,000ton(16,329metricton),485ft(148m)longhullwasconstructed

horizontallybyGulfMarineFabricatorsatthecompany'spurposebuiltgravingdock

inIngleside,Texas.Duringconstruction,twoofthethree52ft(16m)diameter

uppercolumns

were

supported

by

saddles

located

directly

on

the

concrete

floor

of

thegravingdock,whilethethirdcolumnwasassembledmorethan100ft(30m)up

intheair.Afterhullfabricationwascompleted,the40ft(12m)deepgravingdock

wasfloodedandTitanwasfloatedandtowedtoitsdeepwaterinstallationsite

whereitwasupendedtoitsoperationalpositionbycontrolled,freefloodingofits

lowerhull.


3/8

ProcessmodulebeingloadedoutatGulfIsland

Fabrication.Photo

by

Jeff

Rushing.

Thetopsidesconsistofa3,600ton(3,266metricton)processmoduleanda2,500

ton(2,268metricton)utilitymodulethatwerefabricatedatGulfIslandFabricators

inHouma,Louisiana.Inplanview,thetopsidesstructureisTshapedwiththe

processmodulespanning150ft(46m)acrosstheportandstarboardcolumns.The

utilitymodulespansfromtheforwardcolumntotheprocessmodule,wherethetwo

areconnectedviaastructuralinterface.Weightconstraintsmadeitimpracticalto

fabricatethetopsidesasoneunit;theliftwouldhaveinducedunacceptable

deflectionsorrequiredanimpossiblylargespreaderbarortwocranebargestolift.

UtilitymoduleatGulfIslandFabricationpriortoloadout.

PhotobyJeffRushing.


4/8

IntertekHiCaddelivereddimensionalcontrolforpreinstallationstructuralinterface

compatibilityandidentificationofpotentialinterferencesbetweenthemodulesand

hull.

BluewatercontractedIntertekHiCadinApril2009toprovidedimensionalcontrol

(DC)services

for

the

Titan.In

addition

to

general

construction

support

for

key

components,IntertekHiCad'sscopeincludeddetailedandhighaccuracyasbuilt

dimensionaldatathatassuredcompatibilitybetweenthetopsidestohulland

moduletomodulestructuralinterfaces.Thiscompatibilityanalysisincludedclash

checkingoftheinterfaceenvelopestoidentifypossiblehardclashesandclose

proximitycomponentsthatcouldcauseproblemsduringmoduleinstallation.Asthe

projectprogressed,BluewaterelectedtoexpandIntertekHiCad'sscopetoinclude

assistancewiththeinstallationofthefour80ton(73metricton)risertensioners

andpreinstallationverificationofthetopsidestohullinterconnectpipingspools

basedonasbuiltmodulelocationsrelativetothehull.

Discoveringclashesandinterferencesduringinstallationisaprojectteam's

schedule andbudgetbustingnightmare.Withdayratesforoffshoreinstallation

operationsoftenexceeding$1millionperday,thereiseveryincentivetoshorten

thedurationrequiredforinstallation.Dimensionalcontrolislowcost,highvalue

insurancetosignificantlyreducethatduration.Althougharrangementscanvary,

dimensionalcontrolcontractstypicallyamounttolessthan0.2%oftotalinstalled

cost."ThecostofIntertekHiCad'sserviceswasinsignificantincomparisontothe

negativescheduleandcostimpactsthatcouldhavebeenencounteredduring

fabrication,installation,oroperations.Theirattentiontodetailandcommitmentto

maintainingour

project

schedule

have

solidified

their

involvement

in

future

projects

ofthismagnitude,"saysGeorgeFriedel,VPofOperationsforBluewaterIndustries.

Ofcourse,safetyalwayscomesfirst.Whenliftingsignificantloads,whetheratseaor

onland,thepriorityistosafelyandefficientlylandtheload.Leavingaloadthat

weighsthousandsoftonshangingonthecrane,foranylengthoftime,while

resolvinginstallationissuesintroducesseriousadditionalrisks,includingthe

potentialforacatastrophicaccident.

Inthecaseofoffshoreinstallations,successininstallingmodules(whosetendencyis

to

flex

in

the

lift

condition)

from

a

barge

onto

a

floating

hull

structure

demands

understandingthepotentialdimensionalissuesthatcanbeencounteredduringthe

approach,engagement,andtouchdownofthemodulestothehull.

"Withmatingtolerancesaslittleas0.5in.orlessonmajorstructuralcomponents

fabricatedinseparatelocationsindifferentstates,youneedtheprecisionand

accuracyofDCtomakesureitallfitstogether.Inmostinstances,youonlygetone

shottoinstallmodulesthesizeoftheTitan's,"saysJeffRushingwithBluewater

Industries."Physicalinfluencesinanoffshoreenvironmentmakeitimpracticalto

haveasecondchance."


5/8

InstallationoftheprocessmodulebyJ.RayMcDermott'sDB50.Photo

byJamieArmstrong.

Thismakesreversingtheprocedure(i.e.,liftingthemodulesbackuptofieldcorrect

forstructuralcompatibilityandinterferenceissues)animpractical,andsometimes

impossible,option.

Dimensionalcontrolworkflow

IntertekHiCadoperationsmanager,KyleMcNeil,ledtheteamthatconductedthe

dimensionalcontrolwork.SteponewastomeetwithBluewaterprojectpersonnel

tounderstandthedesigntolerances,deflection,andmovementissuesspecifictothe

Titaninstallationactivities.McNeilisnostrangertooffshoreworkhe'sbeenwith

IntertekHiCadforthreeyearsandspent26yearswithKBRandMcDermottbefore

that.McNeilviewsdimensionalcontrolasaninvestment:"It'sdowntotheclientand

the

investment

in

managing

potential

risk."

UnderMcNeil'ssupervision,IntertekHiCadsurveypersonnelvisitedthehulland

topsidesfabricationfacilitiesatappropriatetimestoexecutethesurveyworkusinga

proprietarysurveyingprocessesandsupportingsoftware.Theaccuracyanddetailof

thesurveyworkwascriticaltoassessthestructuralinterfacecompatibilityandto

detectandvisualizepossibleclashesthatcouldariseduringinstallation.Aseachpart

oftheasbuiltsurveyworkwascompleted,IntertekHiCadprogressivelycalculated

andfittedthepiecestogethertoobtaina"bestfit"amongallstructures.

Constructionsupport

Atonestageofconstruction,theforwardcolumnoftheTitanwassupported

elasticallybystrandjacksandtrusses100plusft(30m)intheairafterassemblyand

justpriortotheinstallationoftheTTRframewhichwouldtieallthreeoftheupper

columnsoftheTitantogether.BASScalculatedtheamountofdeflectionexpectedas

thestrandjackswerereleasedandthestructurewaspositionedinalocationthat

wouldminimizelockedinstressesonthehull.Aspartofthiscriticalconstruction

activity,IntertekHiCadwasaskedtomonitorthepositionoftheTTRframerelative

tothetargetpositionsprovidedbyBASStoanaccuracyof1/16in.(1.586mm)

duringtheweldout.EndResult?Thestresseswereminimizedaspredicted.

Topsidestohullstructuralinterface


6/8

Toproperlymatewiththemodulelegs,stabbingguidesonthehullweredesignedto

allowadjustmentinthex,y,andzdirectionbeforeweldingthemtothehull.This

adjustmentallowancehadtoaccountforfivefactors:1)theasbuiltgeometryofthe

modulelegs,2)theasbuiltgeometryofthemoduletomodulestructuralinterface,

3)theasbuiltgeometryofthehull,4)theweldingtoleranceofthehull,and5)the

geometrychange

anticipated

as

the

hull

moved

from

the

horizontal,

laterally

supportedconditiontotheuprightandfreefloatingconditionoffshore.IntertekHi

Cadsurveyedtheasbuiltlocationsofboththemodulelegsandmoduletomodule

structuralinterfacestodeterminethe"bestfit"ofthemodulesrelativetothehull.

Withthisinformation,BASSwasabletopinpointtheoptimumlocationsforthe

stabbingguidesonthehullwhichsignificantlyreducedinstallationrisksoffshore.

Oncefittedandinplace,IntertekHiCad'sscopecontinuedwithmonitoringthe

stabbingguidesduringweldoutrelativetotargetpositionsthatwereestablished.

WithIntertekHiCad'sexperienceandtwiceadayreadings,theseoptimum

locationswere

accomplished

despite

the

movement

of

the

target

positions

due

to

expansionandcontractionofthehullduringthesummerheat.

OffshoreDCverification

IntertekHiCadcarriedonwiththeDCservicesbymeasuringpossibledeflections

thatmayhaveresultedfromtransportationandupendingofthehullonceitwas

floatedtotheuprightservicepositionandfullyballasted.Thesurveyreadingsthen

werecalculatedandmodeledinAutoCADtodeterminethepositionofthestructural

interfaces,primarilythestabbingguides.ResultsfromIntertekHiCad'swork

confirmedthat

the

forward

leg

column

had

deflected

out

board

by

close

to

the

predictedoffsetandallelevationsheldtoplanewithin3/16in.(4.75mm).

Loweringoftheprocessmoduleontothehullstabbing

guides.PhotobyIsidroRodriguez.


7/8

Oncethehullandtopsidesweremated,thenextstepwastoconnectthepiping

systemsandinstallthespecificallydesignedrisertensionersystem.WithIntertekHi

Cad'sforesighttopresurveythepositionsofthepipingtieinpointsonboththe

topsidesandhullpriortoinstallation,itwasstraightforwardtocarryouttheminimal

surveyworknecessarytocalculatethegeometryoftheclosingspools,which

includedlengths,

flange

angles,

and

bolt

pattern

orientation,

where

applicable.

The

requireddimensionalinformationforselectedspoolswascompletedandissuedto

pipingpersonnelforfabricationcompletionthegoal:firsttimefit.

Theutilitymodulebeinginstalledatnight.PhotobyColes

Hairston.

Confinedwithinthewellbaystructureoftheutilitymodule,therisertensioners

hungsuspendedinmidairforthetransportationoffshore.Surveyworkhadbegun

manymonthsearlierinpreparationoftheinstallation.IntertekHiCADhadplaced

targetsinstrategicpositionsonthetensionersthatwouldallowtheproper

alignmenttobeachievedasthetensionerswereloweredtotheirfinalresting

positionontheTTRframe.Thisalignmentwascritical,asthetensionerswereonly

abletobeloweredintopositionpriortobeingputintoservice.Considerationofthe

utilitymodulewellbaypositionswasincludedintheIntertekHiCADbestfit

calculationsforlocatingthemoduletothehull.Onceagain,goodsurveypreparation

allowedforefficientandaccuratepositioningofthetensionersduringtheoffshore

installation.

DCtechnology

TotalstationsurveyinstrumentsandaccessoriessupportedbyDIMES(IntertekHi

Cad's3Dcalculationsoftware)andAutoCADsoftwarewereusedasthemaintools

fortheprojectsurveywork.TheDIMESsoftwareiscompatiblewithAutoCAD.

IntertekHiCadsurveyorsareexperiencedwith3DCADmodelingtechniques,

allowingtheassurveyeddatatobemanipulatedinAutoCADforthepurposeof

modelingrelevant

information

and

possible

overlay

against

the

design

model

for

interrogation.Inthisinstance,threeseparatemodelswerepreparedforthetopof


8/8

thehullandtheundersidesoftheprocessandutilitymodules.Basedonthe

calculations,themodulesweremovedintopositiononthehullmodel,thereby

allowinginterrogationofthefullinterfaceenvelope.Workingoffshorewithatotal

stationinstrumentoftenrequiresflexibilityandknowledgeoftheacceptable

parameterstobeabletosetuptheinstrumentindifficultsituationsandmaintain

highaccuracy

in

order

to

achieve

the

required

tolerances.

Howisdimensionalcontroldifferentthaninspection?

Here'swhereexperiencewithdesign,fabrication,andinstallationpaysoff.A

dimensionalcontrolexpertengagedthroughoutfabricationcannotonlyidentify

potentialfabricationdimensionalproblemsandtoleranceaccumulationsbutcan

alsoadviseonpracticalsolutionstocorrectfortheaccumulations.Dimensional

controlinsightintofabricationprocesses,experienceandunderstandingof

installationproceduresaswellasknowledgeaboutthecapabilitiesofindividual

contractorslets

DC

experts

inform

project

teams

about

how

to

make

mid

course

correctionsandadjustmentstoavoidpotentialseriousexpensiveproblemsfrom

occurringatthecriticalstages.McNeilsays"ittakesaclientwithanopenmindto

getfullvaluefortheinvestmentbecauseitisnotbusinessasusual."

Otherlessonslearned

Constructionofsomeoffshorestructuresrequiresthecoordinationofmultiple

fabricationcontractors,eachresponsibleforproducingcomponentstoaspecified

tolerance.Thechallengefortheprojectteamistomanagetheaccumulationofthe

variationsbetween

the

nominal

design

dimensions

and

the

as

fabricated

dimensions.Tighteningthespecificationshascostandscheduleimplicationsandin

mostcasesbecomesimpractical.Duetocostandscheduleconcernsaprojectteam

canbepushedtotakeriskonoutoftolerancedimensions.Dimensionalcontrol

appliedaccuratelyandwithconstructionexperienceandknowledgecanprovidethe

assurancethatcomponentswillfittogetherwhenitreallycounts,thefirsttime.

ends

IntertekMediaenquiries:http://www.intertek.com/news/mediacontacts/

IntertekSalesEnquiries: NorthandSouthAmerica:+17134754022

EAME:+390295383833/AsiaPacific:+81352450648

AboutIntertek(www.intertek.com)

Intertekisaleadingproviderofqualityandsafetysolutionsservingawiderangeof

industriesaroundtheworld.Fromauditingandinspection,totesting,qualityassuranceand

certification,Intertekpeoplearededicatedtoaddingvaluetocustomers'productsand

processes,supportingtheirsuccessintheglobalmarketplace.Intertekhastheexpertise,

resourcesandglobalreachtosupportitscustomersthroughitsnetworkofmorethan1,000

laboratoriesandofficesandover25,000peopleinmorethan100countriesaroundthe

world.
http://www.intertek.com/http://www.intertek.com/

10-05 offsore magazine intertek dimensional control for offshore titan project (1)

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