2009.07.31 材料试验结果 关于 2009年4月 燃气管道泄露事件 Materials Lab 15 - Factual Report 09-046-Master

NATIONALTRANSPORTATIONSAFETYBOARD

OfficeofResearchandEngineering

MaterialsLaboratoryDivision

Washington,D.C.20594

July31,2009

SAFETYBOARD

MATERIALSLABORATORYFACTUALREPORT

ReportNo.09-046

A.ACCIDENT

Place

:Tampa,Florida.

Date

:May9,2009.

Vehicle

1995SeaRaySundancer.

NTSBNo.

DCA09SM015.

Investigator

:LarryD.Bowling.

B.COMPONENTSEXAMINED

Gasolinecondenserassembly.

C.DOCUMENTSREVIEWED

1.WesterbekeCorporationdrawing38051.Condenser,gasoline,sub-assembly.

2.WesterbekeCorporationdrawing38127.Coil,gasolinecondenser.

3.WesterbekeCorporationdrawing38201.Gasolinecondenser,finalassembly.

D.DETAILSOFTHEEXAMINATION

Thegasoline-condenserassemblyreceivedforexaminationandleaktestingis

illustratedandidentifiedinFigure1withcoolingwaterhosesstillattached.Thecondenser

assemblyhadreportedlybeenremovedfromthefuellinethatsuppliedfueltothegasoline

enginethatpoweredthevessel'selectricalgenerator.Thegeneratorwasreportedly

manufacturedbyWesterbekeCorporation(Taunton,MA)andratedat4.5kilowatts.

Areviewofdrawings38051and38127(documents1and2respectivelyinsection

C)revealedthatthecondenserassemblyconsistsofacoppertube,1-inchdiameterx6

incheslong,withasoftcoppertube,0.31-inchdiameterandapproximately18incheslong,

coiledarounditapproximately8times.Ononeendofthecoppercoilafemalethreaded

connectorissilversolderedinplaceandontheotherendaflarenutisinstalledandthe

coppertubingisflared.Areviewofdrawing38201(document3insectionC)revealedthat

theconnectorwasattachedtothefuelsupplylineandtheflaredendwasattachedtothe

fuelpump.Thecoilwascoveredwithalengthofwaterhosethatwassplitlongitudinally,

placedonthecoilsandwrappedwithanadhesivealuminumfoiltape.Thefoiltapeandthe

hoseweretoberetainedonthecoilbytwohoseclamps.Thehose,thefoiltapeandone

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remaininghoseclamparealsoidentifiedinFigure1.Itwasnotedthatthecondenser

assemblyandoneofthecoolingwaterhoseshadbeenpaintedredatonetime.

Inordertoexaminethecondenser,thecoolingwaterhosesidentifiedinFigure1

wereremovedtorevealbothendsofthecoolingwatertube.Thehoseclamponthe

condenserwasremovedandthealuminumfoilwascutalongthelongitudinalaxisofthe

waterhose.Thewaterhose,withthefoilstilladheredtoit,wasremovedtorevealthecoils

ofthecondensercoil.Theexposedcoolingwatertubeandcondensercoilareillustrated

andidentifiedinFigure2withthefuelsupplyconnectorandtheflarenut(withtheflare)

identified.Toprovideasealbetweenthecoolingwatertubeandthewaterhoses,theends

ofthetubewerecircumferentiallydeformedafterthecoilwasinstalledtoproducethe\"bib\"

identifiedinFigure2.Examinationofthecondensercoilandthecoolingwatertube

revealedthegreencorrosionproductindicatedbytheyellowarrowsinFigure2and

commonlyknownasverdigris'.

Thecondensercoilwasremovedfromthecoolingwatertubebycuttingthetube

adjacenttooneofthebibsandslidingthecoiloff.Thecoilwasmicroscopicallyexamined

andthenreexaminedaftercleaninginadetergentsolution.Inbothconditions,the

examinationrevealednosignificantlossofmaterialorholesinthetube.Theendofthecoil

adjacenttothefuelsupplyconnectorisillustrated,asremoved,intheleftimageinFigure3

withgreenarrowsindicatingtheverdigrisandaredarrowindicatingaslighttwisttothe

tubing,afeatureconsistentwiththeconnectorbeingallowedtorotateslightlywhen

connectedtothefuelsupply.Theendofthecoiladjacenttothefuelsupplyconnectoris

illustratedintherightimageinFigure3aftercleaning,withwhitearrowsindicatingthe

patinathatwasbelowtheverdigrisandyellowarrowsindicatingremainingverdigris.The

endofthecoiladjacenttotheflarenutisillustrated,asremoved,intheleftimageinFigure

4withyellowarrowsindicatingtheverdigris.Theendofthecoil,aftercleaning,is

illustratedintherightimageinFigure4withwhitearrowsindicatingthepatinathatwas

belowtheverdigrisandyellowarrowsindicatingremainingverdigris.

Examinationoftheflaredendofthecondensercoilrevealedthattheflaredseatwas

undamaged,uniformlycolored,anddisplayedarelativelysmoothsurfacewith

circumferentialmarks,featuresconsistentwithitprovidingasealedconnectionwhenitwas

installedinthefuelpump.Anendviewoftheflaredendisillustratedintheleftimagein

Figure5withwhitearrowsindicatingtheflaredseat.Thebluearrowsindicatemechanical

damagethatwaslocatedoutsideoftheflaredseat.

ExaminationofthefuelsupplyconnectoridentifiedinFigure2revealedpatchesof

redpaintontheoutersurfaceandagreydeposit,consistentwithathreadsealant,onthe

firsttwointernalthreads.Thethreadswereintactwithnoindicationofanydeformation

indicativeofbeingcross-threaded.Anendviewofthefuelsupplyconnectorisillustratedin

'Verdigrisisthecommonnameforthegreencoatingformedwhencopper,brassorbronzeisweatheredand

exposedtoairorseawateroveraperiodoftime.Initially,theexposurediscolorsanddarkensthesurfaceandis

oftenreferredtoas\"patina\".

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therightimageinFigure5withredarrowsindicatingthegreydepositandwhitearrows

indicatingredpaintobservedonthedeposit.

Althoughthevisualexaminationrevealednoholesinthecondensercoilaleaktest

wasperformed.Bothendsofthecoilweresealedandpressurizedairwasintroduced

throughoneoftheseals.Thepressurizedcoilwasthenimmersedinwaterandtherewere

noescapingbubblesofairtoindicatealeak.

Astheflaredendofthecoilassemblydisplayedfeaturesconsistentwithagoodseal

andthefuelsupplyconnectordisplayedtheuseofasealant,thematingfuelsupply

connector(withaportionofhose)wasrequested.Thefuelsupplyhosesuppliedis

illustratedinFigure6withtheelbowthatwasreportedlyscrewedintothefuelsupply

connectoridentified.TheinsetinFigure6isacloserviewoftheelbowthreadthatwas

originallyengagedinthefuelsupplyconnector.Intheinset,theredarrowindicatessome

ofthegreythreadsealantandredpaint.Theyellowarrowindicatestheterminationofthe

sealant/paint,suggestingthatthreethreadswereengagedinthefuelsupplyconnector.

Thefuelsupplyhoseelbowwasthenscrewedintothematingthreadinthefuelsupply

connectoruntilthesealant/paintterminationcontactedthefuelsupplyconnector.The

condensercoilandfuelsupplyhosewerethensealedasbeforeandimmersedinwater

untiltheelbowwascovered.Theassemblywaspressurizedandtherewerenoescaping

bubblesofairtoindicatealeak.

DerekNash

MechanicalEngineer