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DeformationMeasurementsinIndustrialFacilitiesUsingLaserScanners–ExampleofColumn321‐C‐001inRijekaOilRefinery,UrinjLukaBabić,AlminĐapo,BoškoPribičević,UniversityofZagreb,FacultyofGeodesy,Kaciceva26,Zagreb,Croatia,lbabic@geof.hrAbstract. Laser scanning has been used for a number of years as a method ofsurveying in extremely complex projects demanding high level of precision anddetailcoverage.Themostprominentsectorutilizingthesetypesofsurveysistheenergy production and distribution. The emphasis is laid upon various facilitiesranging from oil platforms and refineries, measurement and control stations ofpetrolandgaslines,waterandelectricitydistributionfacilitiesallthewaydowntodistribution networks of such energy systems. Historically speaking, surveyorswereinitiallyintroducedtolaserscanningsystemsthroughthosedesignedforthedata acquisition of the terrain form and modelling employing Airborne LaserscanningSystems ALS .However,duetotechnologicalrevolution,bothITandlasersystems,theapplicationshaveproliferatedtoamyriadofotherareas.Theabilityofthesesystemstoprovideglobalinsteadofsparseanddiscretecoverageofobjectsofinterest, to collect 3D information directly in poor or even completely darkconditions,andmanyotherbenefitscontributedtosignificantproliferationoflasersystems.This paper will describe an application of laser scanning for the purposes ofindustrialsurveyontheexampleofanatmosphericcolumn321‐C‐001ofthesection321‐topping3 foratmosphericdistillation in theOilrefineryRijeka.Thisspecificprojecthadataskofconductingdeformationanalysisofacolumnenvelopeforthepurposeoftherecoveryprojectdesign.Duetothesurveyconditions,therequestedprecisionlevels,aswellasdensityofdatathatneededtobepresentedintheresults,laserscanningwasemployedastheonlymethodthatmetalltherequirements.Keywords:deformations,industrialfacilities,laserscanning,recoveryprojects

1. IntroductionINA‐Industrijanafte,d.d. INA,d.d. isamedium‐sizedEuropeanoilcompany.

INAGrouphasaleadingroleintheCroatianoilbusinessandastrongpositionintheregionintheoilandgasexplorationandproduction,oilprocessing,andoilproductsdistributionactivities.

One of the company’s facilities is Rijeka oil refinery, Urinj located at thenorthernpartoftheAdriaticSea,occupying3.5squarekilometresofcoastalareaof

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KostrenaandBakar,12kilometrestothesouthofRijeka.ItistheshortestandmostconvenientconnectionwithCentralEuropeandwiththeMediterranean.InRijeka,INA has a road, railway, marine and pipeline infrastructure for the supply andshipmentofgoods,crudeoilandpetroleumderivates.

The business activities of INA’s refineries are in accordance with therequirementsoftheinternationalstandardsoftheQualityManagementSystemISO9001:2000,EnvironmentalManagementSystemsISO14001:1996andHealthandSafety Management System OHSAS 18001:1999 that have been certified by theawardedcertificates.Quality controlof INA’sproducts is carriedoutbyapplyingmodern testing methods in the refinery’s laboratories in accordance with theAuthorizationbasedonthestandardHRNENISO/IEC17025:2000thatwasgrantedbytheCroatianStateBureauofStandardsandMetrology.

TheproductionprogramofINA’srefineriesincludes:LiquefiedPetroleumGas,virginnaphtha,motorgasoline,kerosene,aviationturbinefuel,dieselfuels,fueloil,bunkersandliquidsulphur.ThequalityofproductsisregulatedbyINA’s,CroatianandEuropeanstandards,andtheproductionaccordingtobuyers’specialrequests,stipulatedincontracts,isalsoanoption URL1 .

Tomeetalltheabovementionedoperationandsafetystandardsandtoachievecorresponding product quality levels, regular maintenance and revitalizationprojectsarenecessary.Forthatreason,inspectionsandsurveyshavetobecarriedout to ascertain which elements, objects or even entire sections are in need ofrevitalization.

Figure1Column321‐C‐001inOilRefineryRijekaThus,whentheinspectionfindingsindicatedthatthecolumn321‐C‐001might

beinneedofrevitalization Figure1 ,asurveywasrequestedtoestablishtheextentof observed deformations and produce a sound and comprehensive basis for arevitalization project. Since the deformations of the column’s envelope are notuniform and equally distributed, a detailed survey was necessary. Such level ofdetailisdifficultifnotimpossibletoachieveusingtraditionalmethods,aswillbeclarified lateron.Ontheotherhand,theabilityofa laserscanning instrumenttocollect high‐resolution data over an object or a surface is an advantage over

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traditional surveying techniques such as total station or GPS , especially formonitoringofdeformedsurfaces.Globalcoverageisacquiredratherthanasparsenetworkofdiscretepoints.Thepointscloudsmaybequicklymodeledintoregulargridded or triangulated surfaces permitting local deformation trends to beidentified,which otherwisemay have beenmissed by the traditional techniquesGordonetal.2001 .2. Fieldworkanddataacquisition

Thesurveyofthecolumn’senvelopesectionwasdonefromtheinsideofthecolumn.Thesectionsurveyedhasa5,6minternalradiusandis9,86mhigh,butonlythe top 8,5‐meter segment is the envelope,while the bottom segment serves asseparationfromlowerpartsofthecolumn.Oneoftheprimaryreasonsforthisisamuchlowernumberofscanpositonsrequired,andthereductionoferrorsinscanregistration thatwould result fromgoingall aroundanda fewstoriesupon thescaffolding which doesn’t provide firm footing which would result in causingadditional errors. The chosen method of scanning provided higher efficiency,precision and overall reliability of the survey. But this decision also createschallengesinthesurveyprocess.Thefirstonewasintheformofaccessibility,wherethesurveyorwithalltheequipmenthadtoenterthrougharelativelysmallhatchonthesideof thecolumn Figure2 .Thesecondchallengewasrelatedto thesafetyregulationsandproceduresthathadtobefollowedtoensurethathumanlifewouldnotbeindanger.Itmadethesurveyprocesslastlonger,butstillnotnearlyaslongasitwouldlastwhenperformedfromtheoutside.

Figure2Accesshachtotheinsideofthecolumn’ssectionThethirdchallengewasrelatedtotheaccuracytobeobtainedinthesurveying

ofan8,5‐meter‐highenvelopesectionmadeonlyabout1‐1,5metersawayfromtheenvelope itself. This was due to a sizable segment hanging from the middle,obstructingtheviewofthetopoftheenvelopefromadistance.Thiswasalso,thereason why multiple scan positions were necessary to have the whole objectcapturedwithas littleshadows areaswithnodata aspossible.However, thesemultiple stations provided enough overlap and scans from “the side” of the topsegment thanks to its cylindrical shape allowing for a smaller laser beam

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inclination angle in order to provide adequate accuracy assessment and datareconciliation.

The surveys were conducted in two sessions in the period of one year, inJanuaryandagaininDecember.Thus,theanalysisofdeformationprogresscouldbemade, i.e.whetherornottherehasbeenanyfurtherdeterioration.Thisrequiredhavingbothdatasetsinthesamecoordinatesystem.Thatisaneasytaskforlaserscanningdatabecausethedatamatchingcanbedoneusingcloudtocloudmatching,which doesn’t require any pre‐established reference system but relies oncorresponding feature identification.Withenoughoverlap this is amethodoftenusedwhenconductingmanydifferenttypesoflaserscanningsurveys.Nevertheless,thespheretargetswereusedforcloudregistrationinthisproject,bothforfasterdataprocessing,andbecauseallthestationsregisteredexactlythesamespheres,with high resolution and at small distance, providing thus high accuracy ofsubsequentregistrationprocess.

Figure3Panoramicviewsfromscanner January2015top,December2015bottom This brings us to the last challenge. During the first survey the scanning

conditions insidethecolumnwereoptimal.Thecolumnwasdry,noobstructionsotherthanthestructuralelementswereintheway Figure3top .But,beforeandduring the second survey, there were higher levels of fire danger indicatorsrecorded,andtherewasanexplosionwhenthegassesfromthewastedrainsnearthecolumncaughtfire,whichiswhythesurveyhadtobepostponedandthecolumndoused in water for prevention. The scanning conditions were therefore ratherpoor,aseverythingwaswetormoist,andthewaterwasdrippingheavilyfromthehangingcentralsegment.Thescaffoldinghadtobeplacedinthesectiontoprovidefootingforthescannerawayfromthedripping.Becauseoftherestrictednumberofpossiblescanpositions,thescannerwasplacedevenclosertotheenvelopethatwas

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notasstableandasfreeofvibrationasduringthefirstsession,andduetomoisture,thereweregenerallypoorerconditionsprovided Figure3bottom .Eventhoughtheinvestorswerewarnedoftheseconditions,theyinsistedontheperformanceofthesurvey.Theresultingpointcloudwas,accordingly,notaspreciseasthefirst,andcontainedalotofnoise.3. Theresults

The data in the form of point clouds obtained from two surveys werepositionedinthesamereferencecoordinatesystemaftertheregistrationofeachindividualdatasetusingthefirstsetofdataobtainedfromthesurveyinJanuaryasareference,andthenmatchingtheDecemberpointcloudsettoit.Consideringthefact that there were enough distinguishable features for registration to besuccessful,thetwopointcloudswerealignedwithatwocentimetreaccuracy.Thislevelwassufficient,butalsothebesttobeexpectedconsideringtheconditionsinwhich the second survey was performed, and the fact that the atmosphericconditionsalsoinfluencedthebehaviouroftheenvelope.Itiswellknownthatmetalcontractsincolderweather,andviceversa.

Figure4ComparisonoftwosetsofdatafromdiferentsurveysesionsAfter they were properly positioned and oriented, the relevant data were

comparedinordertodetermineanymajordiscrepanciesbetweenthem Figure4 .Therelevantdatamentionedrefertotheenvelopportionofthepointclouds,since

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theotherdatarepresenttheelementsofnointerestfortherehabilitationproject.Thiswasaninitialanalysismadeforthepurposeofsubmittingfastreportsaboutthe results to the investors, so theywould knowwhat preparations tomake forfurtheroperations.

The final report comprised the detailed Inspection map representations,horizontalandverticalcrosssections.Inspectionmapisarepresentationmadebycomparing thepoint cloud to an idealizedmodel, in this casea vertical cylinder.Figure5 showsthetwoinspectionmapsmade,whereitisclearlyvisiblethatthefirstdatasetismuchsmootherbecauseofthebetterqualityofthedataobtained,but when compared to the second one, similar or even same deviations can beobserved,allowingthusforaneasyvisualinspectionoftheenvelope.

Figure5Inspectionmapsforthepointclouds Januaryleft,Decemberright Forthepurposeofobtainingtheresultsthataremorepreciseandagreeable

fromtheengineeringpointofview,thecrosssectionsweremadeinthehorizontalandverticalplane.Thehorizontalsectionsweremadeevery25cmwitha1°divisionintervalofdeviationvalues Figure6 ,whileverticalsectionswereeach10°witha1cmdivision Figure7 .

Such fine divisionwould have been impossible to achieve using traditionalsurveymethods.However,therearetworeasonssupportingsuchfinedepictionofresults. The first is obviously done for thepurpose of identifyingdeviations anddeviationtrends.Theotheris,however,duebothtogreatadvantagesandtheflawof the laser scanners. As mentioned earlier, the laser scanners provide globalcoverage of the object, which provides many benefits, but it also means thatirrelevantdataarecapturedthatcanevenbemisleadinginthiscase.Manytimes,notallsuperfluousdatacanberemovedfromthepointcloudrequiringadditional

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informationaboutwhethersomethingisinthiscasequalifiedasadeformationorastructural element adjacent to the envelope. In caseof total station survey, suchelementscanbeavoided,sincethesurveyorhimself/herselfchoosesthepointontheenvelopetobesurveyed.Still, theresultsofaclassicsurveywouldhardlybesufficientforsuchadetailedanalysisofdeformationsandtrendscomparedtothoseobtainedbymeansoflaserscanning.

Figure6Horizontalcrossectionsoftheenvelope

Figure7Verticalcrossectionsoftheenvelope

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4. ConclusionOutofmanyaspectsofapplyingthelaserscanning,themostprominentand

effectiveoneisbeyonddoubtitsapplicationindeformationanalysis.Laserscanninghasprovided thepossibility forsurveyors to conducta comprehensivesurveyofobjectsneededfortheanalysisofdeformation,allowingthusathoroughinspectionand ascertaining of all causes of deformations. In comparison to conventionalsurveyingtechniquesandmethods,thismethodpresentsasignificantprogressforallprofessionsincludedinthisfield.Apartfrommakingtheanalysisprocessmoreefficient,accurateandcomprehensive,italsomakesitmorecosteffective,becauseallrelevantanalyticalprocedurescanbedonefromthesamedataset,i.e.thepointcloud Babićetal.2014 .

The proliferation of laser scanners, has not been so significant in Croatiabecauseofitsinitialcostandcomplexityofoperation.AnotheremergingfactorinthisrespectisthecurrentUAVinfatuationandexpansion.UAV’sdoprovideanothergreat addition to surveyor’s resources but cannot replace traditional surveyingmethods,orcompetewithlaserscanningwhendealingwiththeprojectssuchastheone described here, ormany others aswell. The authors hope it is going to berecognizedbymoresurveyorsinCroatia,whichwillresultinchangingthecurrentsituationcharacterizedbythefactthattherearemorefirmsnotinvolvedingeodeticactivitiesthatuselaserscanningwithoutknowingorunderstandingsurveying,orwhatshouldbedonetoobtainhighqualityandtruevalue.

Thebestexampleofwhythisshouldbesohasbeenshowninthispaperwheretheinvestorswere,ultimately,providedwithaverydetailedanalysisoftheobject,alltheirdemandsandexpectationswerenotonlymetbutevenexceeded,andtheyexpressed satisfaction with great value for money. All subsequent questions,inquiriesandchallengeswere,also,easytoresolveasallthedatawassodetailedandeasytouseforsettlinganyconcerns.Boththesurveyorandinvestorwere,thus,protected from possible misinterpretations and a sound basis for furthercooperationwasestablished.ReferencesGordon,S.;Lichti,D.;Stewart,M. 2001 .Applicationofahigh‐resolution,ground‐

basedlaserscannerfordeformationmeasurements,The10thFIGInternationalSymposium on Deformation Measurements, Orange, California, pp. 23‐32,2001.

Babić, L.; Pribičević, B.; Đapo, A. 2014 . Application of 3D Laser Scanning forDeformationMeasurementon IndustrialObjects,TheXXVFIG InternationalCongress,KualaLumpur,Malaysia,2014.

URL1:INA‐Industrijanafte,d.d. INA,d.d. ,http://www.ina.hr, 10.03.2016