管道运行英文翻译.docx

管道运行英文翻译.docx

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管道运行英文翻译

3Third-partyDamage

Index

Third-partyDamageIndex

A.MinimumDepthofCover0-20pts20%

B.ActivityLevel0-20pts20%

C.AbovegroundFacilities0-10pts10%

D.LineLocating0-15pts15%

E.PublicEducationPrograms0-15pts15%

F.Right-of-wayCondition0-5pts5%

G.PatrolFrequency0-15pts15%

0-100pts100%

Thistablelistssomepossiblevariablesandweightingsthatcouldbeusedtoassessthepotentialforthird-partydamagestoatypicaltransmissionpipeline（seeFigures3.1and3.2）.

Background

Pipelineoperatorsusuallytakestepstoreducethepossibilityofdamagetotheirfacilitiesbyothers.Theextenttowhichmitigatingstepsarenecessarydependsonhowreadilythesystemcanbedamagedandbowoftenthechancefordamageoccurs.

Third-partydamage,asthetermisusedhere,referstoanyaccidentaldamagedonetothepipeasaresultofactivitiesofpersonnelnotassociatedwiththepipeline.Thisfailuremodeisalsosometimescalledoutsideforceorexternalforce,butthosedescriptionswouldpresumablyincludedamagingearthmovements.Weusethird-partydamageasthedescriptorheretofocustheanalysesspecificallyondamagecausedbypeoplenotassociatedwiththepipeline.PotentialearthmovementdamageisaddressedinthedesignindexdiscussionofChapter5.Intentionaldamagesarecoveredinthesabotagemodule（Chapter9）.Accidentaldamagesdonebypipelinepersonnelandcontractorsarecoveredintheincorrectoperationsindexchapter（Chapter6）.

U.S.DepartmentofTransportation（DOT）pipelineaccidentstatisticsindicatethatthird-partyintrusionsareoftentheleadingcauseofpipelinefailure.Some20to40percentofallpipelinefailuresinmosttimeperiodsareattributedtothird-partydamages.Inspiteofthesestatistics,thepotentialforthird-partydamageisoftenoneoftheleastconsideredaspectsofpipelinehazardassessment.

Thegoodsafetyrecordofpipelineshasbeenattributedinparttotheirinitialinstallationinsparselypopulatedareasandtheirburial2.5to3feetdeep.However,encroachmentsofpopulationandlanddevelopmentactivitiesareroutinelythreateningmanypipelinestoday.

Intheperiodfrom1983through1987,eightdeaths,25injuries,andmorethan$14millioninpropertydamageoccurredinthehazardousliquidpipelineindustryduesolelytoexcavationdamagebyothers.Thesetypesofpipelinefailuresrepresent259accidentsoutofatotalof969accidentsfromallcauses.Thismeansthat26.7%ofallhazardousliquidpipelineaccidentswerecausedbyexcavationdamage[87].

Inthegaspipelineindustry,asimilarstoryemerges:

430incidentsfromexcavationdamagewerereportedinthe1984-1987period.Theseaccidentsresultedin26deaths,148injuries,andmorethan$18millioninpropertydamage.Excavationdamageisthoughttoberesponsiblefor10.5%ofincidentsreportedfordistributionsystems,22.7%ofincidentsreportedfortransmission/gatheringpipelines,and14.6%ofallincidentsingaspipelines[87].Europeangaspipelineexperience,basedonalmost1.2millionmile-yearsofoperationsinnineWesternEuropeancountries,showsthatthird-partyinterferencerepresentsapproximately50%ofallpipelinefailures[44].

Figure3.1Basicriskassessmentmodel.

Figure3.2Assessingthird-partydamagepotential:

sampleofdatausedtoscorethethird-partydamageindex.

Exposure

Toquantifytheriskexposurefromexcavationdamage,anestimateofthetotalnumberofexcavationsthatpresentachancefordamagecanbemade.Reference[64]discussestheGasResearchInstitute’s（GRI’s）1995studythatmakesanefforttodetermineriskexposureforthegasindustry.Thestudysurveyed65localdistributioncompaniesand35transmissioncompaniesregardinglinehits.Theaccuracyoftheanalysiswaslimitedbytheresponse-lessthanhalf（41%）ofthecompaniesresponded,andseveralmajorgas-producingstateswerepoorlyrepresented（onlyonerespondentfromTexasandonefromOklahoma）.TheGRIestimatewasdeterminedbyextrapolationandmaybesubjecttoalargedegreeoferrorbecausethedatasamplewasnotrepresentative.

Basedonsurveyresponses,however,GFUcalculatedanapproximatemagnitudeofexposure.Forthosecompaniesthatresponded,atotalof25,123hitstogaslineswererecordedin1993;fromthat,theGRIestimatedtotalU.S.pipelinehitsin1993tobe104,128.Forarateofexposure,thisnumbercanbecomparedtopipelinemiles:

For1993,usingareported1,778,600milesofgastransmission,main,andservicelines,thecalculatedexposureratewas58hitsper1000linemiles.Transmissionlineshadasubstantiallylowerexperience;arateof5.5hitsper1000miles,withdistributionlinessuffering71hitsper1000miles[64].Allratesarebasedonlimiteddata.

Becausetheriskofexcavationdamageisassociatedwithdiggingactivityratherthansystemsize,“hitsperdigs”isausefulmeasureofriskexposure.ForthesameyearthatGRIconducteditssurvey,one-callsystemscollectivelyreceivedmorethananestimated20millioncallsfromexcavators.（Thesecallsgenerated300millionwork-sitenotificationsforparticipatingmemberstomarkmanydifferenttypesofundergroundsystems.）UsingGRI’sestimateofhits,theriskexposureratefor1993was5hitsper1000notificationstodig[64].

Riskvariables

ManymitigationmeasuresareinplaceinmostWesterncountriestoreducethethreatofthird-partydamagestopipelines.Nonetheless,recentexperienceinmostcountriesshowsthatthisremainsamajorthreat,despiteoftenmandatorysystemssuchasone-callsystems.Reasonsforcontinuedthird-partydamage,especiallyinurbanareas,include

●Smallercontractorsignorantofpermitornotificationprocess

●Noincentiveforexcavatorstoavoiddamagingthelineswhenrepaircost（todamagingparty）issmallerthanavoidancecost.

●Inaccuratemaps/records

●Impreciselocationsbyoperator.

Manyofthesesituationsareevaluatedasvariablesinthesuggestedriskassessmentmodel.

Thepipelinedesigneran4perhapstoanevengreaterextent,theoperatorcanaffecttheprobabilityofdamagefromthird-partyactivities.Asanelementofthetotalriskpicture,theprobabilityofaccidentalthird-partydamagetoafacilitydependson.

●Theeasewithwhichthefacilitycanbereachedbyathirdparty

●Thefrequencyandtypeofthird-partyactivitiesnearby.

Possibleoffendersinclude

●Excavatingequipment

●Projectiles

●Vehiculartraffic

●Trains

●Farmingequipment

●Seismiccharges

●Fenceposts

●Telephoneposts

●Wildlife（cattle,elephants,birds,etc.）

●Anchors

●Dredges.

Factorsthataffectthesusceptibilityofthefacilityinclude

●Depthofcover

●Natureofcover（earth,rock,concrete,paving,etc.）

●Man-madebarriers（fences,barricades,levees,ditches.etc.）

●Naturalbarriers（trees,rivers,ditches,rocks,etc.）

●Presenceofpipelinemarkers

●Conditionofrightofway（ROW）

●Frequencyandthoroughnessofpatrolling

●Responsetimetoreportedthreats.

Theactivitylevelisoftenjudgedbyitemssuchas:

●Populationdensity

●Constructionactivitiesnearby

●Proximityandvolumeofrailorvehiculartraffic

●Offshoreanchoringareas

●Volumeofone-callsystemreports

●Numberofotherburiedutilitiesinthearea.

Seriousdamagetoapipelineisnotlimitedtoactualpuncturesoftheline.Amerescratchonacoatedsteelpipelinedamagesthecorrosion-resistantcoating.Suchdamagecanleadtoacceleratedcorrosionandultimatelyacorrosionfailureperhapsyearsinthefuture.Ifthescratchisdeepenoughtohaveremovedenoughmetal,astressconcentrationarea（seeChapter5）couldbeformed,whichagain,perhapsyearslater,mayleadtoafailurefromfatigue,eitheraloneorincombinationwithsomeformofcorrosion-acceleratedcracking.

Thisisonereasonwhypubliceducationplayssuchanimportantroleindamageprevention.Tothecasualobserver,aminordentorscratchinasteelpipelinemayappearinsignificant-certainlynotworthyofmention.Apipelineoperatorknowsthepotentialimpactofanydisturbancetotheline.Communicatingthistothegeneralpublicincreasespipelinesafety.

Severalvariablesarethoughttoplayacriticalroleinthethreatofthird-partydamages.Measuringthesevariablescanthereforeprovideanassessmentoftheoverallthreat.Notethatintheapproachdescribedhere,thisindexmeasuresthepotentialforthird-partydamage-notthepotentialforpipelinefailurefromthird-partydamages.Thisisasubtlebutimportantdistinction.Iftheevaluatorwishestomeasurethelatterinasingleassessment,additionalvariablessuchaspipestrength,operatingstresslevel,andcharacteristicsofthepotentialthird-partyintrusions（suchasequipmenttypeandstrength）wouldneedtobeaddedtotheassessment.

Assessingthird-partydamagepotential

A.Minimumdepthofcover（weighting:

20%）

Theminimumdepthofcoveristheamountofearth,orequivalentcover,overthepipelinethatservestoprotectthepipefromthird-partyactivities.

Ascheduleorsimpleformulacanbedevelopedtoassignpointvaluesbasedondepthofcover.Inthisformula,increasingpointsindicateasafercondition;thisconventionisusedthroughoutthisbook.Asampleformulafordepthofcoverisasfollows:

Amountofcoverininches-3=pointvalueuptoamaximumof20points

Forinstance,

42in.ofcover=42+3points=14points

24in.ofcover=24+3points=8points

Pointsshouldbeassessedbasedontheshallowestlocationwithinthesectionbeingevaluated.Theevaluatorshouldfeelconfidentthatthedepthofcoverdataarecurrentandaccurate;otherwise,thepointassessmentsshouldreflecttheuncerta