Non-destructive-Testing-Robots-(NDTBOTs)-for-In-Se

JournalofMechanicsEngineeringandAutomation8(2018)103-109doi:10.17265/2159-5275/2018.03.001Non-destructiveTestingRobots(NDTBOTs)forIn-ServiceStorageTankInspectionRichardAnvo1,TariqP.Sattar1,Tat-HeanGan2andIvanPinson1.LondonSouthBankInnovationCentre(LSBIC),TWILtd,GrantaPark,GreatAbington,CambridgeCB216AL,UnitedKingdom22.IntegrityManagementGroup,TWILtd,GrantaPark,GreatAbington,CambridgeCB216AL,UnitedKingdomAbstract:Petrochemicalstoragetanksaregenerallyinspectedwhenthetankisofflinemostlytoassesstheextentofundersidecorrosiononthetankfloor.Emptying,cleaningandopeningatankforinspectiontakemanymonthsandareveryexpensive.Inspectioncostscanbereducedsignificantlybyinsertingrobotsthroughmanholesonthetankrooftoperformnon-destructivetesting(NDT).Thechallengeistodeveloprobotsthatcanoperatesafelyinexplosiveandhazardousenvironmentsandmeasurethethicknessoffloorplatesusingultrasoundsensors.Thispaperreportsonthedevelopmentofasmallandinexpensiveprototyperobot(NDTBOT)whichisdesignedtobeintrinsicallysafeforzonezerooperation.Therobot“hops”acrossthefloortomakemeasurements,withoutanyexternalmovingparts.Thepaperdescribesthedesign,experimentaltestingoftheNDTBOTandpresentsresultsofsteelplatethicknessmeasurementsmadeunderwater.Keywords:Storagetankinspection,NDTBOT,in-serviceinspection.1.IntroductionStoragetanksconstructedofcarbonsteeldegradeduetointeractionwiththestoredmaterials,suchascrudeoil,oilproducts,petroleumchemicalandrawpetrochemical.Mosttanksareconstructedofplatesweldedtogethertoformthestructure.Overtimecorrosion,andinsomecircumstances,crackscanformthatleadtoleakageofthecontents,resultingineconomiccostsandsevereenvironmentalpollution[1].Toavoiddamagetotheenvironment,inspection,evaluation,andrepairactivitiesareperformedperiodicallyaccordingtoAmericanPetroleumInstitutesafetyregulations(API)653[2]andEngineeringEquipmentandMaterialsUsersAssociation(EEMUA)Publication159[3].Mostofthetankweldsandsurfaces,suchasthewallsanddome,whicharesubjectedtothesechemicalsthatareaccessiblefromtheoutside.Currentmanualinspectionmethodsmeanthetankisout-of-serviceforCorrespondingauthor:RichardAnvo,PhDcandidate,researchfield:non-destructiverobotforstoragetankinspection.severalweeks,dependentonthesizeofthetank.Non-destructivetesting(NDT)inspectionrequirestransportationofthechemicalproducttoalternativestorage,andcleaningofthetanksbeforeahumaninspectorcangainaccesstoperformtheinspection.Thesefactorspresentseveraldisadvantagessuchasimplicationcost,periodtocarryoutinspectionand,ultimately,lossofrevenueduetodowntime.High-riskexposureofworkerstochemicalsduringthecleaningoperationandinspectiontaskisanotherlimitationtohumaninvolvementinthesetasks.Clearly,onlyexternalcorrosionandweldscanbeinspectedfromoutside[4],whereascorrosionofthetankfloorcanbeinspectedonlyfromtheinside.2.OverviewofStorageTankRoboticsInspectionsSeveralin-servicestoragetankfloorinspectiontechniqueshavebeenimplementedbytankownersandoperatorstoassesscorrosionandpitting.Abovegroundstoragetank(AST)bottominspectionsareusuallyacombinationofanumberofNDTtechniques;visual,ultra-sonictesting,magneticDDAVIDPUBLISHINGNon-destructiveTestingRobots(NDTBOTs)forIn-ServiceStorageTankInspection104particletestingandacousticemission.Recently,Mohammadetal.[5]presentedapaperonawall-climbingmobilerobotwithapermanentmagneticadhesionmechanismthatcanbeusedfortankinspection.Theroboticsystemconsistedofamobileplatform,athree-wheeledlocomotionunitandanadhesionmechanismthatcanmoveonaverticalwall.Andres[6]proposedasimilarrobotdesignwithateleoperatedwall-climbingrobotforoiltankinspection.Heproposedasystemconsistingofwheellocomotion,whichusespermanentmagnetsastheadhesionmechanism,andacordlessteleoperatedmobileplatformthatcanmoveonthevertical(ferromagnetic)wall.AnumbilicalfreemobileNDTclimbingrobotforindustrialapplicationswasproposedbySattaretal.[7].Thiscarriesasinglewheelprobeoperatingbetween1MHzand10MHztoinspectdefects,thicknessandcorrosion.Thiswall-climbingrobotiscapableofinspectingoiltanks,petrochemicaltanks,bridges,andrailwaysinfrastructure.Kalraetal.[8]proposedawall-climbingrobotfornon-destructiveinspectionofabovegroundtanksfloors,whichconsistsofanautonomousmobileplatformthatcanmoveontheverticalwallsofthetanks,carryingtheprobesfortestingfaultsorinternalcracksinthetankwalls.Anotherrobotforinternalin-serviceinspectionofpetrochemicalstoragetankfloorswaspresentedbySattaretal.[9],awall-climbingrobottoinspecttheinternalwallsandfloorsofoilandpetrochemicalstoragetanks.AsurfaceswitchingmobilerobotwithbuoyancycontrolusedinRobTankwassuccessfullytestedinthewatertank.Inanotherdevelopment,Solexenvironmentalsystems,inconjunctionwiththeTexasNaturalConservationCommission,developedanddemonstratedtheoperationofMaverick[10],aremote-controlrobotsystemforinspectingin-service,abovegroundpetroleumandpetrochemicalstoragetanks.Maverickperformsfloorinspectionsfrominsidethetankwhilesubmergedinrefinedproductsincludinggasoline,dieselandfueloil,usingamulti-channelultrasonicsensor,on-boardvideosystemandasonar-basedtrackingsystem.Similarly,arobotsystemforab