2020.01.29 NTSB關(guān)于麥哲倫管輸公司2016年10月17日氨氣泄露事故調(diào)查報(bào)告 PAB2001

NationalTransportationSafetyBoard

PipelineAccidentBrief

MagellanPipelineAnhydrousAmmonia

SAFETYBOARD

Release

NearTekamah,Nebraska

October17,2016

TheAccident

OnOctober17,2016,shortlyafter9:00p.m.localtime,an8-inch-diameterunderground

transmissionpipelinerupturedandreleased2,587barrels(108,654gallons)ofliquidanhydrous

ammoniaonprivatepropertyadjacenttomilepost(MP)263.32onCountyRoadPinBurt

County,nearTekamah,Nebraska.'ThepipelinewasownedandoperatedbyMagellan

MidstreamPartners,LP,(Magellan).Uponreleaseandexposuretotheatmosphere,theammonia

vaporizedandproducedatoxicplume.(Seefigure1.)Alocalresidentwhohadlefthishometo

investigatetheaccidentscenediedofrespiratoryfailureduetoexposuretotheammoniavapor;

additionally,twopeoplesustainedminorinjuries.Atotalof29households,involving49people,

wereevacuated.U.S.Highway75,amainroadwayinthearea,wasclosedforseveraldays.2

TheammoniapipelinewasoperatedandmonitoredfromacontrolcenterlocatedinTulsa,

Oklahoma.Lowpressurealertswerereceivedinthecontrolcenterat9:03p.m.,andarupture

alarmfirstoccurredat9:14p.m.At9:21p.m.,controlcenterpersonnelreceivedathird-partyreport

ofstrongammoniaodorandavaporcloudlocated8.5milesnorthofTekamah,Nebraska.

'Tekamah,Nebraska,islocatedabout8milesdirectlysouthoftheaccidentsite,andDecatur,Nebraska,isabout

6.5milesdirectlynorth.

2Formoredetailedinformationaboutthisaccidentinvestigation,seethethepublicdocketat

/investigations/dms.htmlandsearchforaccidentnumberDCA17FP001.

64660

NTSB/PAB-20/01

AnhydrousAmmoniaRelease

51

Anhydrous

Decatur

ammonia

leak

77

75

32

BURT

Co.

Tekamah

N

NEBRASKA

CountyRoadP

Figure1.Aerialphotographofactiveanhydrousammoniareleasewithmapinsertshowing

releaselocation.(Source:Magellan.)

ActivitiesatTimeofAccident

DuringtheearlyeveningofOctober17,2016,nooperationalissueswerereportedbythe

on-dutycontrolleratshiftchange,andoperationalrecordsdidnotindicateanyoperating

irregularities.About9:00p.m.,thecontrollerwaspumpingammonianorthonthepipelinesystem

foracustomerdelivery.At9:03:45p.m.,theammoniapipelinepressuredropped42psionthe

suctionsideoftheHermanpump,whichwaslocatedsouthoftheBurtCountylineandnearwhere

thereleaseoccurred.Then,at9:03:49p.m.,a68-psipressuredecreaseoccurredonthedischarge

sideoftheHermanpump.Theseeventstriggeredanalertinthecontrolcenterandledtoan

automaticshutdownoftheHermanpump.

At9:11:38p.m.,theon-dutycontrollercontactedtheleakdetectionanalyst(LDA)after

receivingadditionalalertsandnoticesfromthecontrolsystem.Theon-dutycontrollertold

NationalTransportationSafetyBoard(NTSB)investigatorsthathedidnotinitiallythinkhehada

rupture.Rather,hestatedthathecontactedtheLDAtoseekanopiniononwhythesystemappeared

tobelosingpressure.Thecontrollerwantedtodetermineifthealertswerecausedbyanirregularity

intheMagellansoftware.

At9:14:40p.m.,theon-dutycontrollerreceivedanalarmindicatingthatarupturehad

occurred.TheSCADAcontrollerimmediatelybegantoshutdowntheammoniapipeline.At

2

AnhydrousAmmoniaRelease

9:17:15p.m.,anotherleakalertwasreceivedafterthecontrollerhadinitiatedapipelinesystem

shutdown.

PostReleaseActions

Followingthe9:14:40p.m.alert,Magellan'son-dutycontrollerbeganisolatingthepipeline

rupturebyshuttingdownpumpsandclosingvalves.Thesequenceofvalvesclosedtostopthe

dischargeofammoniaisshowninfigure2.

MagellanWESTLEG8\"Ammonia

PipelineValveActionsontheNightof

theAccident

N

DecaturSouthRemotely

OperatedValve(ROV)

atMP269.66

MissouriRiver

ClosedbySCADA

Decatur

controllerat

9:15:13pm

IsolationValveMP263

Closedat02:03am

DecaturNorthRemotely

(October18)by

OperatedValve(ROV)at

NebraskaStatePatrol

MP272.05

HazMatTeam

ClosedbySCADAcontroller

at9:16:16pm

2MileRadius

EvacuationZone

Tekamah

Locationof

Ammonia

PipelineBreach

MP263.32

IsolationValve

Herman

MP252.79Closed

at11:21:34pm

IsolationValve

MP241Closed

at10:44:31pm

RemotelyOperated

Valve(ROV)atMP246.9

ClosedbySCADA

controllerat9:15:11pm

NottoScale

Figure2.Magellanammoniapipelineshowingvalveslocatedatmilepostssurroundingthe

releasesite.

EmergencyResponse

At9:26:23p.m.,Magellan'son-dutycontrollerissuedaCodeRed,whichinitiated

emergencyresponseactionsbyMagellanstaff,andestablishedaphonebridgeat9:35:10p.m.for

3

AnhydrousAmmoniaRelease

communicationsamongresponders.3AMagellanoperationscontrolreliefcontrollernotifiedthe

BurtCountySheriff'sofficeat9:35:50p.m.andadvisedthat500barrelsofammoniahadbeen

releasedandtoavoidgasclouds.

ThecommunityemergencyresponseinvolvedtheTekamahFireandRescueAssociation

(TFRA)andtheBurtCountySheriff'sDepartment.About10:33p.m.,theTFRAfirechiefassumed

theroleofincidentcommanderanddevelopedatacticalresponseplan,whichinvolvedisolating

anareaonCountyRoadPbetweenCountyRoad32andU.S.Route75.Theyplannedtoevacuate

anyonefoundinthatarea.TheTFRAdispatchedfireandrescueresourcestothescene.The

sheriff's911/dispatchcentermadephonecallstoresidentswithinaninitial1/2-mileevacuation

zonedownwindoftherelease.

AMagellanemployeewasdesignatedtoprovidetechnicalsupporttoemergency

responders.TheMagellanemployeerecommendeda2-mileevacuationdistanceandtookoverthe

incidentcommand.TheTFRAfirechiefrequestedmutualaidfromtheDecaturRuralVolunteer

FireDepartment.Personnelfrombothagenciesconductedtheevacuationbydoor-to-door

canvasingofresidences.Afterward,theNebraskaHazardousIncidentTeam(hazardousmaterials

releaseresponseunitoftheNebraskaStatePatrol)arrivedtoassistwiththeemergencyresponse.

PipelineOperation

Magellanisaninterstatepipelineoperatorthatprimarilytransports,stores,anddistributes

crudeoilandrefinedpetroleumproducts.In2016,Magellanhadmorethan1,700employeesin23

states,withabout9,700milesofoilandpetroleumrefinedproductpipelinesand56storage

terminals,throughout15states,extendingfromtheGulfCoastthroughoutthemiddleoftheUnited

StatestoMinnesota.Amongtheseassets,Magellanoperatedan1,100-milecommoncarrier

ammoniapipeline4

Magellan'sammoniapipelinesystemhasthreebranchesthatoriginateinBorger,Texas,

Verdigris,Oklahoma,andEnid,Oklahoma,andterminateinMankato,Minnesota.Liquid

ammoniaisinjectedintothepipelinefromthird-partyproductionfacilitiesandistransportedto

agriculturalcentersinlowa,Kansas,Minnesota,Nebraska,Oklahoma,andSouthDakota.The

ammoniaisusedtoproducenitrogencompoundssuchasurea,ammoniumnitrate,ammonium

phosphate,andammoniumsulfate.

Magellan'sammoniapipelinewasinstalledin1968.Thepipelinehasanoutsidediameter

of8.625inchesand,intheareaoftherelease,wasburied48inchesbelowgrade.Thepipewall

3TheCodeRedprocedureprovidesaplay-by-playsetofactionsforMagellanstaff,on-sceneMagellanparties,

andsubcontractsupportstaff.TheCodeRedprocedureincludestherolesandresponsibilitiesofeachparticipantfrom

theonsetofareleasetothepointthereleasehasbeenneutralized.CodeRedEventProcedure9.02-ADM-011covers

astandardizedmethodforeventresponse,focusingonasafeandpromptresponsesforthepublicandemployees,

environmentalprotection,minimizationofreleasevolume,containmentofreleasevolume,andcontainmentin

primaryvessel(pipeline,tank,etc.)TheprocedureaddressesSCADA-indicatedpipelinerupturesandnotifications

reportingpipelinefire,explosion,orvaporcloudthatleadstosuspicionorconfirmationofapipelineruptureorhigh-

raterelease.

4Commoncarrierpipelinesprovidetransportationservicesforanypersonorcompany,andthecarriersare

responsibleforthelossofgoodsduringtransportasauthorizedbyaregulatorybodysuchastheFederalEnergy

RegulatoryCommissionorbystateagencies.Privatecarrierpipelinesarenotauthorizedtoprovideservicestothe

public.

4

AnhydrousAmmoniaRelease

thicknesswas0.156inch.Themaximumoperatingpressure(MOP)atthereleaselocationwas

1,198psig.5ThepipelinewasmanufacturedbyLoneStarSteelinaccordancewithAmerican

PetroleumInstitute(API)Specification5LusingGradeX46steelandalowfrequencyelectric

resistancelongitudinalseamweldingprocess.Thepipelinehadanimpressedcurrentcathodic

protectionsystemaswelasafield-appliedpolyethylenetapewraptomitigateexternalcorrosion.

ThereleaseoccurredonasegmentoftheammoniapipelineknownastheWestLeg.

MagellanrecordsindicatedthattheWestLeginBurtCountyhashadmultipleleaksandrepairs

sinceitwasinstalled.InApril1984,168gallonsofammoniawerereleasedduetoadefectivepipe.

Between1988and1990,fiveminorammonialeaksoccurredthatrequiredpipelinerepairs.From

May1993toOctober1994,therewerethreepinholeleaksthatreleased221gallonsofammonia.

InspectionofDamagedPipeline

OnOctober20,2016,therupturedsectionofammoniapipelinewasunearthed.Thepipe

hadfractureonitsunderside(6o'clockposition)andexhibiteddownwardbendingproximaltothe

fracturelocation.(Seefigure3.)Thefracturefollowedthespiralseampatternofthefield-applied

polyethylenetapewrap(Seefigure4.)Thefractureranroughly45°fromthelongitudinalaxisof

thepipeinaspiralpath.Thefracturehadsawtooth-likefeatures,withnumerousshortcracks

mergingintothemainfracture.Thetotallengthofthefracturewas117/8inches,andthewidest

openingofthefracturewas0.19inch.Abouta60-inchsectionofthepipelinecontainingthe

fracturewasremovedandwasshippedtotheNTSBMaterialsLaboratoryinWashington,DCfor

furtherexamination.

Portionsoftheprotectivepolyethylenetapecoatingadjacenttothefractureweredisplaced

fromthepipebutrecoveredduringtheinvestigation.Whenloosepiecesoftapewerepositioned

onthepipesurface,thefracturealignedwiththeedgesofsuccessivewindingsofthetape,where

thetapeoverlapped.Also,therewereareasonthepipesegmentwherethetapewraphadvisibly

shifted.Oneareaofthetapehaditsedgesfoldedover,exposingthepipesurface.Brown-colored

corrosionwasvisibleontheexposedpipesurface.Tentingofthetapewrapwasobserved

longitudinallyalongthe6o'clockpositionofthepipe,roughlyinlinewiththefracture.6

Numerousthumbnail-shapedcracksconsistentwithfatiguecrackswerevisibleonthe

fracturesurfaces.Thepatternswereorientedsuchthatthethumbnail-shapedcracksemanatedfrom

theoutsidediameterofthepipe.Thepresenceofnumerousthumbnail-shapedcrackswas

consistentwithmultipleinitiationfatiguecracking.Thedeepestthumbnail-shapedfatiguecrack

extendedthroughapproximately75percentofthepipewallthickness.Theareasbetweenthe

thumbnailsandadjacenttotheinsidediameterofthepipeexhibitedmicrovoidcoalescence

consistentwithoverstressfracture.Overall,thefracturefeatureswereconsistentwithcorrosion

fatigue.

5Maximumoperatingpressure(MOP),asdefinedinTitle49CodeofFederalRegulations(CFR)$195.406,is

themaximumpressurepermittedfornormallineorvesseloperation;MOPisrelatedtopipestrengthandtheability

ofapipetowithstandinternalpressure.MOPratingsarebasedonthreefactors:designpressure,hydrostatictest

pressure,orflangerating.Internaldesignpressureforapipelineisdeterminedaccordingtoanestablishedformula.

6Tentingisaformofdisbondmentofapipelinecoating.Disbondmentreferstothelossofthebond(adhesion)

betweenapipelineanditsprotectivecoating,whichhasbeenknowntoallowmoisturetobecometrappedbetween

thesurfaceofthepipeandthetapewrap,creatinganenvironmentthatmaybecorrosive.

5

AnhydrousAmmoniaRelease

PREF

+041.90197/-096.24939°1418ft08:03:55

MAIL

POSITIONALTITUDE-TIME

MAP

LOG

Approximate

failurelocation

-05

HORIZON

ELEVATION

45

-03.3

42.6

Ammonia

ANGLE

Flow

ANGLE

40

00

AZIMUTH-BEARING

272N88W4836milsTRUE

ZERO

A-B

CAL

240

300

LENS

1.0X

os

Figure3.Photographoffailedsectionofammoniapipeline.

INCH

Figure4.Photographofammoniapipelinecrackshowingalignmentwithseaminprotectivetape

andsawtoothcrackfeatures.

Theresidualcurvatureofthepipesectionafterremovalfromthepipelineindictedthatthe

stressfromthebendingloadshadexceededtheyieldstressofthesteel.Thetensilestressfrom

bendingwouldhavebeenthegreatestonthebottomofthepipe,attheexternalsurface,inthearea

wherecrackinginitiated.ThehoopstressfromtheMOPattherupturelocationisabout70percent

ofthespecifiedyieldstressofthesteel.

6

AnhydrousAmmoniaRelease

Samplesweretakenfromthepipelinetotestthechemicalcompositionandmaterial

properties(yieldstress,tensilestrength,andelongationatfailure)ofthesteel.Thetestresultswere

consistentwiththeAPI5LX46specification.

MagellanrecordsindicatethattheWestLeghadbeenin-lineinspectedperiodicallyfrom

2004to2015usingNACEInternationalstandardpractices.'Thelastin-lineinspection(ILI)run

throughthesectionofpipewheretheruptureoccurredwasinSeptember2015,usingmagnetic

fluxleakage(MFL)measurementsandsmartpiggingtoolsfordetectionofwall-losscorrosionand

otherindicationsofpipelineintegrityissues.8TheMFLassessmentusedcontractor-supplied

specificationsfordefectsizingformetalloss,pitting,axialgrooving,circumferentialgrooving,

andcircumferentialslottinginthepipebodyandgirthweldheat-effectedzones.\"Technicians

reviewedthe2015ILIdataanddidnotfindanyanomaliesorindicationsofpipelinefailuresat

thattime.

Magellanrecordsindicatethathydrostatictestingoftheammoniapipelineoccurredfrom

September2008toJanuary2012.Thehydrostatictestswerenotrequiredbyfederalregulations,

butMagellanneverthelessperformedtheconventional8-hourtestmethodologyrecommendedby

thePipelineandHazardousMaterialsSafetyAdministration(PHMSA)aswellasspiketests.1o

Thehydrostatictestsrevealedfiveleaks,twoofwhichwereattributedtostresscorrosioncracking.

Magellanrepairedtheseleakspriortotheaccident.

PostaccidentActions

OnOctober21,2016,PHMSAissuedCorrectiveActionOrder(CPFNo.3-2016-5009H),

whichrequiredMagellantoshutdowna49-milesectionoftheanhydrousammoniapipeline

extendingfromValley,Nebraska,(MP223.61)totheMissouriRiver(MP272.05).Afterrepairs

weremade,MagellanwasorderedbyPHMSAtooperatethepipelineata20percentreduction

fromtheactualoperatingpressurepriortotheOctober17,2016,accident.

MagellantrainsitspipelineoperatorsannuallyusingSCADAsimulationsrepresenting

variousoperatingconditions.Followingtheaccident,Magellanrecognizedthatthesimulation

trainingdidnotfullypreparetheircontrollerstoquicklyrecognizeandhandleanammoniarelease.

MagellandevelopednewsimulatortrainingusingtheSCADAlogsfromtheaccidenttotrain

operatorstorecognizepipebreachconditions;thisnewtrainingisrequiredfortheannual

certificationofSCADAcontrollers.

Followingtheaccident,MagellantoldtheNTSBthattheyhadre-examinedthe2015MFL

ILIdataforcharacteristicsobtainedfromtherupturedpipeline.Magellantechnicianswereableto

defineanewsignaturefromtheILIdatatoforecastthepipelinefailure.Magellanthenusedthe

newILIsignaturetoscreenthepipelinefromValley,Nebraska,toDecatur,Nebraska,wherethey

7In-LineInspection(ILI)isaninspectionofapipelinefromtheinteriorofthepipeusinganin-lineinspection

tool.Itisalsocalledintelligentorsmartpigging.(NACEInternationalPracticeSP0102-2010In-LineInspectionof

Pipelines).

*MagneticFluxLeakage(MFL)testingisanondestructiveprocedurefordetectionofcorrosionandpittingin

steelstructures.MFLisusedforintegrityassessmentofpipelinesandstoragetanks.

9TDWMagpieSystems,Inc.MFLSizingAccuracySpecification.Rev.BofDecember2,2005.

1ASpikeHydrostaticTestusesatest-pressure-to-operating-pressureratiothatsignificantlyexceedstheminimum

valueof1.25requiredbyfederalregulation49CFR195,SubpartEandthedurationconsiderablyshorter(1/2to1

hour)thanaminimumtimeof8hoursrequiredbythisfederalregulation.

7

AnhydrousAmmoniaRelease

foundadditionalindicationsofpendingfailures.Magellancompleteddirectassessmentsand

repairsfortheselocations.

InJanuary2019,Magellanannouncedthattheywoulddecommissionthe1,100-mile

TexastoupperMidwestammoniapipelinesystemlaterintheyear.Theyinitiatedtheshutdown

andproductdisplacementoftheanhydrousammoniapipelinesys