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80 工 Konis/Jietロ1./5日ifety5cience53(2013)73-81
Fig.14.(a)Photographsofthemock-upboatafterthereproducibilitytest，(b)nodamagetofueltankintheportsidecompartment，(c)nodamagetothelifevestsinthe starboardcompartment，and(d)thelidintheworkdeckcompartmentthatwasblownbytheexplosion.
theexplosion10msafterignition.Incontrast，thelidofthestar- boardstoragecompartment，onwhichthewatertankwasplaced， remainedinplace.Thisalmostduplicatedtheactualacidentwith theexceptionofthefolowingphenomenon.Thelidoftheportside compartmentwasmovedbytheexplosioninthereproducibility test，butitwasnotblownawayintheactualacident.Thisdiscrep- ancyislikelytobeatributabletotheacumulationofgasolineva- porintheportsidecompartment.Intheactualacident，asthe operatoropenedthelidoftheportsidecompartmentforrefueling onthedayoftheacident，alowingthegasolinevaportodisperse. Butinthereproducibilitytest，sincepeoplewerenotalowedtoap- proachthemock-upboatforsafetyreasons，gasolinevaporcould notdisperse，asthelidoftheportsidecompa口mentremained c1osed， al lowing the ac cumulation of flammable vapo.r Photo- graphsofthemock-upboatafterthereproducibilitytestareshown inFig.14.Inthestarboardcompartment，nodamagetothelife vestsorthebaterywasobserved.Thisisalmostthesameoutcome as in the actual explosion. Therefore， the mock-up experiment reproducedtheactualacidentquitewel.l
5.Conclusions
(1)Thegasolinevaporwasleakedfromrustyweldsinthelower partofthefueltankandacorosionholeabout2m mindiameter inthesideofthefueltank.andanairventhole2m mindiameter inthetopoftherefuelingcap.
(2)Theleakedgasolinevaporizedreadilyandthevapordifused from the fuel-tank compartment to the bat tery compartment throughtheholesintentionalyboredbytheboatowner.Inthe bat tery compartment and the first work deck compartment， a flammable mixture was maintained from the 1.7th day to the 175thdayafterplacementofthefiledandleakingfueltank.
(3)Inthisacident，theexplosionpropagatesbetweenlinked compartments，a phenomenon caled “presure piling" ocurs， characterized by an increase in the initial pres sure and atmo- sphericdensityinthesecondcompartment.Theflammablevapor wasignitedbysparkingatthebaterywhenthestartingswitch oftheoutboardmotorwaspresedbytheoperato.rA flame
nuc1eus was created initial ly， fol lowed by a laminar premixed flame.Theflameinthestarboardwarehousepropagatedtothe workdeckcompartmentthroughholesinthebulkhead.Inthe work deck compartment， a turbulence premixed-flame was establishedandanexplosionaccompaniedbyarapidpresure buildupocured.Asthepresurebuildupintheworkdeckwas largerthanthatinthestarboardcompartment，theworkdeck wasbrokenandtwopasengersontheworkdeckwerethrown to the air by the explosion，while the operator，sit ting on the starboardstoragecompartment，wasnotinjuredduetothelow presureincreasethere.
Aclrnowledgements
TheauthorsthankthestafofOitaNationalColegeofTechnol- ogy，S.Naka，].Tsuyoshi，K.Hayashi，Y.Sadakata，H.SatoandM. Yoshikawa for their as sistance in performing the experimental work.AlsoweacknowledgeProfesorKenjiSatoofTohoUniversity forvaluablediscusionsongasexplosions.
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