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2 Shipdimensions,form,size,or category

ChapterOutline

Oiltankers13

Bulkcarriers13

Containerships15

IMOoiltankercategories15

Panamacanallimits15

Suezcanallimits16

Someusefulwebsites16

Thehullformofashipmaybedeﬁnedbyanumberofdimensionsandtermsthatare oftenreferredtoduringandafterbuildingthevessel.Anexplanationoftheprincipal termsisgivenbelow:

AfterPerpendicular(AP):Aperpendiculardrawntothewaterlineatthepointwherethe aftersideoftherudderpostmeetsthesummerloadline.Wherenorudderpostisﬁtteditis takenasthecenterlineoftherudderstock.

ForwardPerpendicular(FP):Aperpendiculardrawntothewaterlineatthepointwherethe fore-sideofthestemmeetsthesummerloadline.

LengthBetweenPerpendiculars(LBP):Thelengthbetweentheforwardandaftperpendicularsmeasuredalongthesummerloadline.

Amidships:Apointmidwaybetweentheafterandforwardperpendiculars.

LengthOverall(LOA):Lengthofvesseltakenoverallextremities.

Lloyd’sLength:UsedforobtainingscantlingsifthevesselisclassedwithLloyd’sRegister. Itisthesameaslengthbetweenperpendicularsexceptthatitmustnotbelessthan96%and neednotbemorethan97%oftheextremelengthonthesummerloadline.Iftheshiphasan unusualstemorsternarrangementthelengthisgivenspecialconsideration.

RegisterLength:Thelengthofshipmeasuredfromthefore-sideoftheheadofthestemto theaftsideoftheheadofthesternpostor,inthecaseofashipnothavingasternpost,tothe fore-sideoftherudderstock.Iftheshipdoesnothaveasternpostorarudderstock,theafter terminalistakentotheaftermostpartofthetransomorsternoftheship.Thislengthisthe officiallengthintheregisterofshipsmaintainedbytheflagstateandappearsonofficial documentsrelatingtoownershipandothermattersconcerningthebusinessoftheship. Anotherimportantlengthmeasurementiswhatmightbereferredtoasthe IMOLength. This lengthisfoundinvariousinternationalconventionssuchastheLoadLine,Tonnage, SOLASandMARPOLconventions,anddeterminestheapplicationofrequirementsof thoseconventionstoaship.Itisdefinedas96%ofthetotallengthonawaterlineat85%of

theleastmoldeddepthmeasuredfromthetopofkeel,orthelengthfromthefore-sideof stemtotheaxisofrudderstockonthatwaterline,ifthatisgreater.Inshipsdesignedwith arakeofkeelthewaterlineonwhichthislengthismeasuredistakenparalleltothedesign waterline.

Moldeddimensionsareoftenreferredto;thesearetakentotheinsideofplatingon ametalship.

BaseLine:Ahorizontallinedrawnatthetopofthekeelplate.Allverticalmolded dimensionsaremeasuredrelativetothisline.

MoldedBeam:Measuredatthemidshipsection,thisisthemaximummoldedbreadthofthe ship.

MoldedDraft:Measuredfromthebaselinetothesummerloadlineatthemidshipsection. MoldedDepth:Measuredfromthebaselinetotheheeloftheupperdeckbeamattheship’s sideamidships.

ExtremeBeam:Themaximumbeamtakenoverallextremities.

ExtremeDraft:Takenfromthelowestpointofkeeltothesummerloadline.Draftmarks representextremedrafts.

ExtremeDepth:Depthofvesselatship’ssidefromupperdecktolowestpointofkeel.

HalfBreadth:Sinceaship’shullissymmetricalaboutthelongitudinalcentreline,often onlythehalfbeamorhalfbreadthatanysectionisgiven.

Freeboard:Theverticaldistancemeasuredattheship’ssidebetweenthesummerloadline (orservicedraft)andthefreeboarddeck.Thefreeboarddeckisnormallytheuppermost completedeckexposedtoweatherandseathathaspermanentmeansofclosingallopenings,andbelowwhichallopeningsintheship’ssidehavewatertightclosings.

Sheer:Ariseintheheightofthedeck(curvatureorinastraightline)inthelongitudinal direction.Measuredastheheightofdeckatsideatanypointabovetheheightofdeckatside amidships.

Camber(orRoundofBeam):Curvatureofdecksinthetransversedirection.Measuredasthe heightofdeckatcenterabovetheheightofdeckatside.Straightlinecamberisusedon manylargeshipstosimplifyconstruction.

RiseofFloor(orDeadrise):Theriseofthebottomshellplatinglineabovethebaseline. Thisriseismeasuredatthelineofmoldedbeam.Largecargoshipsoftenhavenoriseof ﬂoor.

HalfSidingofKeel:Thehorizontalﬂatportionofthebottomshellmeasuredtoportor starboardoftheship’slongitudinalcenterline.Thisisausefuldimensiontoknowwhendrydocking.

Tumblehome:Theinwardcurvatureofthesideshellabovethesummerloadline.Thisis unusualonmodernships.

Flare:Theoutwardcurvatureofthesideshellabovethewaterline.Itpromotesdrynessand isthereforeassociatedwiththeforeendofship.

StemRake:Inclinationofthestemlinefromthevertical.

KeelRake:Inclinationofthekeellinefromthehorizontal.Trawlersandtugsoftenhave keelsrakedafttogivegreaterdepthaftwherethepropellerdiameterisproportionately largerinthistypeofvessel.Smallcraftoccasionallyhaveforwardrakeofkeeltobring propellersabovethelineofkeel.

TweenDeckHeight:Verticaldistancebetweenadjacentdecksmeasuredfromthetopsof deckbeamsatship’sside.

ParallelMiddleBody:Thelengthoverwhichthemidshipsectionremainsconstantinarea andshape.

Entrance:Theimmersedbodyofthevesselforwardoftheparallelmiddlebody.

Run:Theimmersedbodyofthevesselaftoftheparallelmiddlebody.

Tonnage:Thisisoftenreferredtowhenthesizeofthevesselisdiscussed,andthegross tonnageisquotedfromLloyd’sRegister.Tonnageisameasureoftheenclosedinternal volumeofthevessel(originallycomputedas100cubicfeetperton).Thisisdealtwithin detailinChapter30.

Deadweight:ThisisdeﬁnedinChapter1.Itshouldbenotedthatfortankersdeadweightis oftenquotedin‘longtons’ratherthan‘metrictons(tonnes)’;however,MARPOLregulationsforoiltankersareinmetrictons.

Theprincipaldimensionsoftheshipareillustratedin Figure2.1

TEUandFEU:Indicatethecargo-carryingcapacityofcontainerships.TEU(twenty-foot equivalentunit)indicatesthenumberofstandardshippingcontainersthatmaybecarriedon someshippingroutes;containershipsmaycarrystandardcontainersthatare40feetin length.FEUisforty-footequivalentunit.

Anindicationofthesizebycapacityofoiltankers,bulkcarriers,andcontainerships isoftengivenbythefollowingtypes:

Oiltankers

l ULCC(Ultra-LargeCrudeCarrier)isatankerusuallybetween300,000and550,000tonnes deadweight.

l VLCC(VeryLargeCrudeCarrier)isatankerusuallybetween200,000tonnesand300,000 tonnesdeadweight.

l SuezmaxindicatesthelargestoiltankerthatcantransitthecurrentSuezCanalfullyladen, beingabout150,000tonnesdeadweight.

l Aframaxthestandarddesignationofsmallercrudeoiltankers,beingthelargesttankersize intheAFRAFreightRateAssessmentScaleLargeOneCategory.AFRAstandsfor ‘AmericanFreightRateAssociation’.Variouslyreportedasbeing80,000to115,000tones deadweight.

l Panamaxisthemaximumsizeofoiltanker,withbeamrestrictionof32.2metersandlength restrictionof275meters,thatcantransitthePanamaCanalpriortocompletionofthe plannednewlocks.Typicalsizeisabout55,000–70,000tonnesdeadweight.

l Handysize/Handymaxaretypicalproducttankersofabout35,000–45,000tonnes deadweight.

Bulkcarriers

l CapesizeshipsthataretoolargetotransitthecurrentPanamaCanalandthereforevoyage aroundCapeHorn.Allbulkcarriersabove80,000tonnesdeadweightfallintothiscategory. Mostareupto170,000tonnesdeadweightbutasmallnumberarelargerforspeciﬁctrade routes,thebiggestbeing365,000tonnesdeadweight.

l Panamax—Asforoiltankers.

l Handymaxshipsarebetweenaround35,000and60,000tonnesdeadweight.

l Shipsbetween10,000and35,000tonnesdeadweighthaveformedthemajorityoftheﬂeet formanyyearsandaredesignated‘Handysize’.Inrecentyearsthesizeoftheseshipshas beenincreasingandtheterm‘Handymax’hasbeenappliedtodesignatethelargerbulk carriers.

Sheer

Amidships

Length between perpendiculars (LBP)

Length on waterline (LWL) Length overall (LOA)

Aft perpendicular Ford perpendicular

Camber

Tumblehome

Figure2.1Principalshipdimensions.

Containerships

l Ultra-largecontainerships.Shipswithacapacityofover14,000TEU.Fewhavebeenbuilt todate.Theseshipsaretoolargeforanycanals.

l Post-PanamaxshipsaretoolargetotransitthecurrentPanamaCanalandundertaketransoceanvoyages.Theirsizeistypically5500–8000TEUthoughlargershipswithover10,000 TEUcapacityhavebeenbuilt.

l NewPanamaxships(includingmostPost-Panamaxships)wouldbeabletotransitthe expandedPanamaCanal.Theymaycarryuptoaround12,000TEU.

l PanamaxshipsthatcantransitthecurrentPanamaCanalcarrybetween3000and5000 TEU.

l Feedershipsaresmallervesselsthatdonotundertakeoceanicvoyagesbutaregenerally engagedinshippingcontainers.ThesmallestofthesemayonlycarryseveralhundredTEU. ThereisnospeciﬁcsubclassbelowPanamaxsize.

IMOoiltankercategories

l Category1(commonlyknownasPre-MARPOLtankers)includesoiltankersof20,000 tonnesdeadweightandabovecarryingcrudeoil,fueloil,heavydieseloil,orlubricatingoil ascargo,andof30,000tonnesdeadweightandabovecarryingotheroils,whichdonot complywiththerequirementsforprotectivelylocatedsegregatedballasttanks.Theseships havebeenphasedoutunderIMOregulations.

l Category2(commonlyknownasMARPOLtankers)includesoiltankersof20,000tonnes deadweightandabovecarryingcrudeoil,fueloil,orlubricatingoilascargo,andof 30,000tonnesdeadweightandabovecarryingotheroils,whichdocomplywiththe protectivelylocatedsegregatedballasttankrequirements.Theseshipsareduetobe phasedout.

l Category3includesoiltankersof5000tonnesdeadweightandabovebutlessthanthe tonnesdeadweightspeciﬁedforCategories1and2.Alsoduetobephasedout.

Note: FortankerscarryingHGO(heavygasoil)thelowerlimitsforCategories2and 3fallto600tonnesdeadweight.

Panamacanallimits

Thesearesetbylocksizes.Currentlocksare‘Panamax’.Newlockswillbelargerfor ‘NewPanamax’ships(see Table2.1).

Table2.1 PanamaCanallimits

Suezcanallimits

Therearenolocksandshipsizeislimitedbythecanaldimensions.Thereis amaximumbreadthlimitof75meters.Withnolockstheshiplengthisalsounrestricted.Themaximumdraftis20meters.

TheSaintLawrenceSeawaylinkstheNorthAmericanGreatLakestothe Atlantic.Thelimitsforshipsbasedonthelocksarelength226m,breadth24m,and draft7.92m.

Someusefulwebsites

www.pancanal.com/eng/general FordetailsofPanamaCanal. http://www.suezcanal.gov.eg http://www.greatlakes-seaway.com

3 Developmentofshiptypes

ChapterOutline

Drycargoships17

Containerships21

Barge-carryingships21

Ro-roships21

Hullform23

Cargohandlingequipment23

Bulkcarriers23

Carcarriers26

Oiltankers26

Passengerships30 Furtherreading33

Abreakdownintobroadworkinggroupsofthevarioustypesthattheshipbuilderor shipdesignermightbeconcernedwithareshownin Figure3.1.Thiscoversawide rangeandreﬂectstheadaptabilityoftheshipbuildingindustry.Itisobviouslynot possibletocovertheconstructionofallthosetypesinasinglevolume.Thedevelopmentofthevesselswithwhichthetextisprimarilyconcerned,namelydrycargo ships(includingcontainershipsanddrybulkcarriers),tankers(oil,liquidgasand chemical)andpassengerships,follows.

Drycargoships

Ifthedevelopmentofthedrycargoshipfromthetimeofintroductionofsteampropulsionisconsidered,thepatternofchangeissimilartothatshownin Figure3.2.The ﬁrststeamshipsfollowedinmostrespectsthedesignofthesailingship,havingaﬂush deckwiththemachineryopeningsprotectedonlybylowcoamingsandglassskylights. Atquiteanearlystageitwasdecidedtoprotectthemachineryopeningswithan enclosedbridgestructure.Erectionsformingaforecastleandpoopwerealsointroduced attheforwardandafterrespectivelyforprotection.Thisresultedinwhatispopularly knownasthe‘threeislandtype’.Anumberofdesignsatthattimealsocombinedbridge andpoop,andafewcombinedbridgeandforecastle,sothatasinglewellwasformed. Anotherformoferectionintroducedwastheraisedquarterdeck.Raisedquarter deckswereoftenassociatedwithsmallerdeadweightcarryingvessels,e.g.colliers.

High speed craft

Off shore oil vessels

Fishing vessels

Multi-hulls Including wave piercers

Small waterplane area, twin-hull (SWATH)

Surface effect (SES) and Hovercraft ship

Hydrofoil

Wing in ground effect craft (WIG)

Supply ship

Pipe layers

Crane barges

Semi-submersible drill rigs

Trawlers purse seiners

Factory

Harbor/ocean work craft Dry cargo ships Liquid cargo ships Passenger ships

SubmersiblesWarships

Dredgers

Salvage/ buoy vessels

Tenders

Pilot craft

Drill ships

Accommodation barges

Production platforms

Floating storage unit (FSU)

Floating production and storage unit (FPSO)

Figure3.1Shiptypes.

Bulk carriers

Cargo liners

Container vessels

Barge carriers

Liquefied gas carriers

Chemical carriers Liners Cruise ships

Emigrant and pilgrim ships (STPs)’

Cross-channel ferries

Coastal ferries Harbor ferries

Ro-ro ships

Refrigerated cargo ships

Timber carriers

Livestock carriers

Car carriers

Withthemachineryspaceaft,whichisproportionatelylargeinasmallvessel,thereis atendencyforthevesseltotrimbythebowwhenfullyloaded.Byﬁttingaraised quarterdeckinwayoftheafterholdsthistendencywaseliminated.Araisedquarter deckdoesnothavethefullheightofatweendeck,abovetheupperdeck.

Furtherdeparturesfromthe‘threeislandtype’werebroughtaboutbythecarriage ofcargoandcattleondeck,andthedesignsincludedalightcoveringbuiltoverthe

Figure3.2Developmentofcargoship.

wellsfortheprotectionofthesecargoes.Thisresultedintheawningorspardecktype ofship,thetemporaryenclosedspacesbeingexemptfromtonnagemeasurement sincetheywerenotpermanentlyclosedspaces.Theseawningorspardeckstructures eventuallybecameanintegralpartoftheshipstructurebutretainedalighterstructure thantheupperdeckstructureofothertwo-deckships,laterreferredtoas‘full scantling’vessels.The‘shelterdecktype’,asthisformofvesselbecameknown,apart fromhavingalighterupperstructurewastohavethefreeboardmeasuredfromthe seconddeck,andthetweendeckspacewasexemptfromtonnagemeasurement.This exemptionwasobtainedbytheprovisionofopeningsintheshelterdeckandtween deckbulkheadscomplyingwithcertainstatutoryregulations.

Atalaterdate,whatwereknownasopen/closedshelterdeckshipsweredeveloped.Thesewerefullscantlingshipshavingtheprescribedopeningssothatthetween deckwasexemptfromtonnagemeasurementwhenthevesselwasoperatingataload draftwherethefreeboardwasmeasuredfromtheseconddeck.Itwaspossibletoclose permanentlythesetemporaryopeningsandreassignthefreeboard,itthenbeing measuredfromtheupperdecksothatthevesselmightloadtoadeeperdraft,andthe tweendeckwasnolongerexemptfromtonnagemeasurement.

Openshelterdeckvesselswerepopularwithshipownersforalongperiod. However,duringthattimemuchconsiderationwasgiventotheirsafetyandthe undesirableformoftemporaryopeningsinthemainhullstructure.Eliminatingthese openingswithoutsubstantiallyalteringthetonnagevalueswastheobjectofmuch discussionanddeliberation.Finally,TonnageRegulationsintroducedin1966 providedfortheassignmentofatonnagemark,atastipulateddistancebelowthe seconddeck.Avesselhavinga‘modifiedtonnage’hadtonnagemeasuredtothe seconddeckonly,i.e.thetweendeckwasexempt,butthetonnagemarkwasnottobe submerged.Whereavesselwasassigned‘alternativetonnages’(theequivalentof previousopen/closedshelterdeckship),tonnagewastakenasthattotheseconddeck whenthetonnagemarkwasnotsubmerged.Whenthetonnagemarkwassubmerged, tonnagewastakenasthattotheupperdeck,thefreeboardbeingaminimummeasured fromtheupperdeck.Thetonnagemarkconcepteffectivelydispensedwiththe undesirabletonnageopenings.Furtherchangestotonnagerequirementsin1969ledto theuniversalsystemoftonnagemeasurementwithouttheneedfortonnagemarks, althougholdershipsdidretaintheiroriginaltonnagesupuntil1994(seeChapter30). Originallythemachinerypositionwasamidshipswithpaddlewheelpropulsion. Also,withcoalbeingburntasthepropulsivefuel,bunkerswerethenfavorablyplaced amidshipsfortrimpurposes.Withtheuseofoilfuelthisproblemwasmoreorless overcome,andwithscrewpropulsiontherearedefiniteadvantagesinhavingthe machineryaft.Takingthemachineryrightaftcanproduceanexcessivetrimbythe sterninthelightconditionandthevesselisthenprovidedwithdeeptanksforward. Thismayleadtoalargebendingmomentintheballastcondition,andacompromise isoftenreachedbyplacingthemachinerythree-quartersaft.Thatis,therearesay threeorfourholdsforwardandoneaftofthemachineryspace.Ineitherarrangement theamidshipsportionwithitsbetterstowageshapeisreservedforcargo,andshaft spaceslosttocargoarereduced.Theall-aftcargoshipillustratingthefinalevolution ofthedrycargoshipin Figure3.2 couldrepresentthesophisticatedcargolinersofthe

mid1960s.Bythemid1970smanyofthecargolinertradeshadbeentakenoverby thecontainershipandmuchoftheshorthaultradeundertakenbytheconventional drycargoshiphadpassedtothe‘roll-onroll-off’(ro-ro)typeofvessel.

Containerships

Afeatureofthecontainershipisthestowageoftherectangularcontainerunitswithin thefullerrectangularportionofthehullandtheirarrangementintiersabovethemain decklevel.Inordertofacilitateremovalandplacingofthecontainerunitsofinternationallyagreedstandard(ISO)dimensionsholdandhatchwidthsarecommon.The narrowdeckwidthoutboardofthehatchopeningformsthecrownofadoubleshell spacecontainingwingballasttanksandpassageways(seeFigure17.9).Later containershipdesignsfeaturehatchlessvesselsthatprovideafasterturnaroundin port.Thesemayhavehatchcoversontheforwardholdsonly,ornoneatall,andare providedwithsubstantialstrippingpumpsforremovingrainandgreenwaterfromthe holds.Inrecentyearsthesizeofcontainershipsmakingoceanicvoyageshas substantiallyincreased.ThelargestshipsarethoseoperatedbyMaersk,whichcan carryareported13,500TEU.Theseareunusualandmostlargeshipsarebetween withoneclassiﬁcationsocietyreportingmorethan60vesselsofatleast8000TEU classed(see Figure3.3b).

Barge-carryingships

Anotherdevelopmentinthecargolinertradewastheintroductionofthebargecarryingvessel.Anearlyversionofthistypeofshiphadaparticularadvantagein maintainingascheduledservicebetweentheportsatmouthsoflargeriversystems suchasbetweentheMississippiriverintheUSAandtheRhineinEurope.Standard unitcargobarges(sometimesreferredtoasLASH—lighteraboardship—barges)are carriedonboardshipandplacedoverboardorliftedonboardatterminalportsbylarge deck-mountedgantriesorelevatorplatformsinassociationwithtravelingrails.Other designsmakeprovisionforﬂoatingthebargesinandoutofthecarryingship,which canbeballastedtoaccommodatethem.Thisdevelopmentappearsnottohavebeenas successfulaswasinitiallyenvisagedinthelate1970s,andwhilstthemeritsofthis typeofcraftarestilloftenreferredto,thetypeisnowrarelyseen.

Ro-roships

Theseshipsarecharacterizedbythesternandinsomecasestheboworsidedoors givingaccesstoavehicledeckabovethewaterlinebutbelowtheupperdeck(see Figure3.3a).Accesswithintheshipmaybeprovidedintheformoframpsorlifts leadingfromthisvehicledecktoupperdecksorholdbelow.Ro-roshipsmaybeﬁtted withvariouspatentrampsforloadingthroughtheshelldoorswhennottradingto regularportswherelinkspanandothershore-sidefacilitiesthataredesignedtosuit areavailable.Cargoiscarriedinvehiclesandtrailersorinunitizedformloadedby fork-liftandothertrucks.Inordertopermitthedrive-throughvehicledeck

arestrictionisplacedontheheightofthemachineryspaceandthero-roshipwas amongtheﬁrsttopopularizethegearedmedium-speeddieselenginewithalesser heightthanitsslow-speedcounterpart.Thedramaticlossofthero-ropassengerships HeraldofFreeEnterprise in1987and Estonia in1994sawmuchattentiondirectedat thedamagestabilityofthistypeofpassengershipwhenwaterenteredtheopen unsubdivideddeckspace.Thishasresultedininternationalregulationrequiring, amongstotherthings,strengtheningandsurveillanceofbowdoors,surveillanceof internalwatertightdoorsusedatsea,enhanceddamagestabilitycriteria(SOLAS90) andadditionalsimpliﬁedstabilityinformationforthemaster.The Estonia lossledto furtherstringentdamagestabilityrequirementsadoptedonaregionalbasisby northernEuropeancountries(StockholmAgreement1997).Amidshipsectionof aro-ropassenger/vehicle/trainferrycomplyingwiththerequirementsofthelatter agreementisshowninFigure17.10.

Hullform

Betweenthe1940sand1970therewasasteadyincreaseinthespeedofthedrycargo shipandthiswasreflectedinthehullformofthevessels.Amuchfinerhullis apparentinmodernvessels,particularlyinthoseshipsengagedinthelongercargo linertrades.Bulbousbowformsandopenwatersternsareusedtoadvantageand considerableflaremaybeseeninthebowsofcontainershipstoreducewetnesson deckwherecontainersarestowed.Insomeearlycontainershipsitisthoughtthatthis wasprobablyoverdone,leadingtoanundesirabletendencyforthemainhulltowhip duringperiodswhenthebowspitchedintoheadseas.Largercontainershipsmayhave thehousethree-quartersaftwiththefullbeammaintainedrighttothesterntogivethe largestpossiblecontainercapacity.

Cargohandlingequipment

Cargohandlingequipment,whichremainedrelativelyunchangedforalongperiod,has receivedconsiderableattentionsincethe1960s.Thiswasprimarilybroughtaboutbyan awarenessofthelossofrevenuecausedbythelongperiodsoftimethevesselmayspend inportdischargingandloadingcargoes.Conventionalcargoshipsarenowﬁttedwith steelfoldingand/orrollingsteelhatchcoversofonepatenttypeoranotherorliftable slabcoversofsteel,whichreducemaintenanceaswellasspeedcargohandling.Various newliftingdevices,derrickforms,andwincheshavebeendesignedandintroducedwith marineshipbornecranesnowalmostcompletelyreplacingriggedderrickinstallations onmodernships.Theseprovidefurtherincreasedratesofloadinganddischarge.

Bulkcarriers

Awiderangeofbulkcommoditiesarecarriedinbulkcarriers,includingcoal,grain, ore,cement,alumina,bauxite,andmineralsandplusshipmentsofproductssuchas packagedsteelandtimber.

ThelargebulkcarrieroriginatedasanorecarrierontheGreatLakesatthe beginningofthetwentiethcentury.FortheperiodoftheSecondWorldWardedicated bulkcarrierswereonlybuiltspasmodicallyforoceantrading,sincealargeamountof thesecargoescouldbecarriedbygeneralcargotrampswiththeadvantageoftheir beingabletotakereturncargoes.

Aseriesofturret-decksteamerswerebuiltforore-carryingpurposesbetween1904 and1910;asectionthroughsuchavesselisillustratedin Figure3.4a.Since1945 asubstantialnumberofocean-goingorecarriershavebeenbuiltofuniformdesign. Thisformoforecarrierwithadoublebottomandsideballasttanksﬁrstappearedin 1917,onlyatthattimethesidetanksdidnotextendtothefullholddepth(see Figure3.4b).Toovercomethedisadvantagethattheorecarrierwasonlyusefully employedononelegofthevoyage,theoil/orecarrieralsoevolvedatthattime.The lattershiptypecarriedoilinthewingtanks,asshownin Figure3.4c,andhad apassagewayforcrewprotectioninordertoobtainthedeeperdraftpermittedtankers.

Thecommongeneralbulkcarrierthatpredominatedinthelatterhalfofthe twentiethcenturytooktheformshownin Figure3.4dwithdoublebottom,hopper sides,anddeckwingtanks.Theselattertankshavebeenusedforthecarriageoflight graincargoesaswellaswaterballast.Speciﬁcvariationsofthistypehavebeenbuilt; Figure3.4eshowsa‘universalbulkcarrier’patentedbytheMcGregorInternational Organizationthatofferedaveryﬂexiblerangeofcargostowagesolutions.Another type,shownin Figure3.4f,hadalternateholdsofshortlength.Onsinglevoyagesthe vesselcouldcarryhigh-densitycargoesonlyintheshortholdstogiveanacceptable cargodistribution.Suchstowageisnotuncommonongeneralbulkcarrierswith uniformholdlengthswherealternateholdloadingorblockholdloadingmaybe utilizedtostowhigh-densitycargoes.Withsuchloadingarrangementshighshear forcesoccurattheendsoftheholds,requiringadditionalstrengtheningoftheside shellinwayofthebulkheads.

Ageneralarrangementofatypicalbulkcarriershowsacleardeckwithmachinery aft.Largehatcheswithsteelcoversaredesignedtofacilitaterapidloadingand dischargeofthecargo.Sincethebulkcarriermakesmanyvoyagesinballast,alarge ballastcapacityisprovidedtogiveadequateimmersionofthepropeller.Thesizeof thistypeofshiphasalsosteadilyincreasedandthelargestbulkcarriershavereached 365,000tonnesdeadweight.

Shipsofthegeneralbulkcarrierformexperiencedarelativelyhighcasualtyrate duringthelate1980sandearly1990s(between1980and2000some170bulkcarriers weretotallylost),givingrisetoconcernastotheirdesignandconstruction. Throughoutthelate1990sbulkcarriersafetyreceivedconsiderableattentioninthe workofIMO,theclassificationsocietiesandelsewhere.Basedonexperienceof failuresoflesserconsequence,itwasconcludedthatthecasualtiesoccurredthrough localstructuralfailureleadingtolossofwatertightintegrityofthesideshell,followed byprogressivefloodingthroughdamagedbulkheads.Thefloodingresultedeitherin excessivehullbendingstressesorexcessivetrim,andlossoftheship.Muchofthis workconcentratedonthestructuralhulldetails,stressesexperiencedastheresultof loadinganddischargingcargoes(pastexperienceshowedthatshipswereoftenloaded inpatternsnotapprovedintheship’sloadingmanual),damagetostructureand

(a)TURRETTYPE ORE CARRIER 1910

(d) GENERAL BULK CARRIER

ORE CARRIER

CARRIER

Figure3.4Bulkcarriers.

protectivecoatingsarisingfromdischargingcargoes,poormaintenance,andsubsequentinadequateinspectionoftheshipstructure.Theinitialoutcomeofthiswork wastheintroductionofanewChapterXIIofSOLAScoveringdamagestability requirements,structuralstrengthrequirements,andenhancedsurveyproceduresfor bulkcarriers.Atits79thsessioninDecember2004,theMaritimeSafetyCommittee ofIMOadoptedanewtextofChapterXIIofSOLASthatincludedrestrictionson sailingwithanyholdemptyandrequirementsfordouble-skinconstructionasan optionalalternativetosingleside-skinconstruction.Theoptionofdoubleside-skin constructionappliesonlytonewbulkcarriersof150metersormoreinlength, carryingsolidbulkcargoeshavingadensityof1000kg/m3 andabove.These amendmentsenteredintoforceon1July2006.ThemidshipsectionofaHandysize bulkcarrierwithdouble-skinconstructionisshowninFigure17.8.

Carcarriers

TheincreasingvolumeofcarandtruckproductionintheEast(Japan,Korea,and China)andalargecustomerbaseintheWesthasseentheintroductionandrapid increaseinthenumberofshipsspeciﬁcallydesignedandbuilttofacilitatethe deliveryofthesevehiclesglobally.

Probablytheugliestshipsafloat,carcarriersarestrictlyfunctional,havingavery highboxlikeformabovethewaterlinetoaccommodateasmanyvehiclesaspossible on,insomecases,asmanyasadozendecks.Whilstmostdeckspacingistosuitcars, sometweendeckheightsmaybegreaterandthedeckstrengthenedtopermitloading ofhigherandheaviervehicles.Withinsuchgreaterdeckspacingliftablecardecks maybefittedforflexibilityofstowage.Thespacingoffixedcardeckscanvaryfrom 1.85to2.3meterstoaccomm odatevaryingshapesandheightsofcars.Transfer arrangementsforvehiclesfromthemaindeckarebymeansofhoistableramps, whichcanbeliftedandloweredwhilstbearingthevehicles.Loadinganddischargingvehiclesontoandofftheshipisviaalargequarterrampatthesternand asideshellorsternramp.Thecrewaccommodationandforwardwheelhouse, providinganadequateviewforward,sitatoptheuppermostcontinuousweather deck.Propulsionmachineryissituatedaftwithbowthruster(s)forwardtoaid mooring/maneuvering.

Theshipshownin Figure3.5 hasanoveralllengthof148meters,abeamof 25meters,andaspeedof19knotsona7.2-meterdraft.Itcancarrysome2140units. Aunitisanoverallstowageareaof8.5squaremeterspercarandrepresentsavehicle 4.125metersinlengthand1.55meterswideplusanall-roundstowagemargin.

Oiltankers

Until1990theformofvesselsspeciﬁcallydesignedforthecarriageofoilcargoeshad notundergoneagreatdealofchangesince1880,whenthevesselillustratedin

Deck No. 4

Figure3.5Carcarrier.

Figure3.6awasconstructed,theexpansiontrunkanddoublebottomwithinthecargo spacehavingbeeneliminatedmuchearlier.Thegreatestchangesinthatperiodwere thegrowthinshipsizeandnatureofthestructure(see Figure3.6b).

Thegrowthinsizeofocean-goingvesselsfrom1880totheendoftheSecond WorldWarwasgradual,theaveragedeadweightrisingfrom1500tonnestoabout 12,000tonnes.Sincethentheaveragedeadweightincreasedrapidlytoabout20,000 tonnesin1953andabout30,000tonnesin1959.Todaythereareaﬂoattankers rangingfrom100,000to500,000tonnesdeadweight.Itshouldbemadeclearthatthe largersizeofvesselisthecrudeoilcarrier,andfueloilcarrierstendtoremainwithin thesmallerdeadweights.

Servicespeedsofoiltankershaveshownanincreasesincethelate1940s,going from12to17knots.Theservicespeedisrelatedtotheoptimumeconomicoperation ofthetanker.Also,theoptimumsizeofthetankerisverymuchrelatedtocurrent marketeconomics.Thetankerﬂeetgrowthincreasedenormouslytomeetthe expandingdemandforoiluntil1973/1974,whentheOPECpriceincreasesslowed thatexpansionandledtoaslumpinthetankermarket.Itisunlikelythatsuch asigniﬁcantriseintankersizeandriseinspeedwillbeexperiencedintheforeseeable future.

Structurally,oneofthegreatestdevelopmentshasbeenintheuseofwelding,oil tankersbeingamongsttheﬁrstvesselstoutilizetheapplicationofwelding.Little Length

Figure3.6Oiltankers.

difﬁcultyisexperiencedinmakingandmaintainingoiltightjoints:thesamecannotbe saidofriveting.Weldinghasalsoallowedcheaperfabricationmethodstobeadopted. Longitudinalframingwasadoptedatanearlydateforthelargershipsandrevisionof theconstructionrulesinthelate1960sallowedthelengthoftankspacestobe increased,withasubsequentreductioninsteelweight,makingiteasiertopump dischargecargoes.

Asfarasthegeneralarrangementisconcerned,thereappearsalwaystohavebeen atrendtowardsplacingthemachineryaft.Movingalltheaccommodationandbridge aftwasalaterfeatureandisdesirablefromtheﬁreprotectionpointofview.Location oftheaccommodationinoneareaismoreeconomicfromabuildingpointofview, sinceallservicesareonlytobeprovidedatasinglelocation.

TherequirementsoftheInternationalConventionforthePreventionofPollution fromShips1973(seeChapter29)andparticularlyitsProtocolof1978havegreatly inﬂuencedthearrangementofthecargospacesofoiltankers.Amajorfeatureofthe MARPOLConventionanditsProtocolhasbeentheprovisioninlargertankersof cleanwaterballastcapacity.Whilstprimarilyintendedtoreducethepollutionrisk, theﬁttingofsegregatedwaterballasttanksinthemidshipregionaidsthereductionof thestillwaterbendingmomentwhenthetankerisfullyloaded.Italsoreduces corrosionproblemsassociatedwithtankspaces,whicharesubjecttoalternateoiland seawaterballastcargoes.

InMarch1989thetanker ExxonValdez,whichcompliedfullywiththethencurrent MARPOLrequirements,ranagroundanddischarged11milliongallonsofcrudeoil intothepristinewatersofPrinceWilliamSoundinAlaska.Thesubsequentpublic outcryledtotheUnitedStatesCongresspassingtheOilPollutionAct1990(OPA90). ThisunilateralactionbytheUnitedStatesgovernmentmadeitarequirementthat existingsingle-hulloiltankersoperatinginUnitedStateswatersweretobephased outbyanearlydate,afterwhichalloiltankersweretohaveadoublehull(see Figures 3.6and22.2).

InNovember1990theUSAsuggestedthattheMARPOLConventionshouldbe amendedtomakedoublehullscompulsoryfornewtankers.Anumberofother IMOmemberstatessuggestedthatalternativedesignsofferingequivalentprotectionagainstaccidentaloilspillsshouldbeaccepted.Inparticular,Japanproposed analternative,themid-decktanker.Thisdesignhassideballasttanksproviding protectionagainstcollisionbutnodoublebottom.Thecargotankspace(see Figure3.6)hadastructuraldeckrunningitsfulllengthatabout0.25–0.5thedepth fromthebottom,whichensuresthatshouldthebottomberupturedtheupward pressureexertedbytheseawouldpreventmostoftheoilfromescapinginto thesea.

In1992IMOadoptedamendmentstoMARPOLthatrequiredtankersof5000 tonnesdeadweightandabovecontractedforafterJuly1993,orwhichcommenced constructionafterJanuary1994,tobeofdouble-hulledormid-deckconstruction,or ofotherdesignofferingequivalentprotectionagainstoilpollution.Existingtankers withsinglehullswithoutsegregatedballasttankswithprotectivelocationweretobe phasedoutbyJune2007.Thosewithsegregatedballasttankswithprotectivelocation weretobephasedoutbyJuly2021.

StudiesbyIMOandtheUSNationalAcademyofSciencesconﬁrmedtheeffectivenessofthedoublehullinpreventingoilspillscausedbygroundingandcollision wheretheinnerhullisnotbreached.Themid-decktankerwasshowntohavemore favorableoutﬂowperformanceinextremeaccidentswheretheinnerhullisbreached. TheUnitedStatesauthoritiesconsideredgroundingthemostprevalenttypeof accidentintheirwatersandbelievedonlythedouble-hulltypepreventedspillsfrom tankergroundingsinallbutthemostsevereincidents.Thus,whilstMARPOL providedfortheacceptanceofalternativetankerdesigns,theUnitedStateslegislation didnot,andnoalternativedesignswerebuilt.

Astheresultofthebreak-upofthetanker Erika andsubsequentpollutionofthe Frenchcoastlinein1999,IMOmembersdecidedtoacceleratethephase-outofsinglehulltankers.Asaresult,inApril2001astrictertimetableforthephasingoutof single-hulltankersenteredintoforceinSeptember2003.InDecember2003adecisiontofurtheracceleratethephase-outdatesofsingle-hulltankerswasagreed,PreMARPOLtankersbeingphasedoutin2005andMARPOLtankersandsmalltankers in2010(seeChapter2fordeﬁnitions).

Oiltankersnowgenerallyhaveasinglepumpspaceaft,adjacenttothemachinery, andspeciﬁedsloptanksintowhichtankwashingsandoilyresiduesarepumped.Tank cleaningmaybeaccomplishedbywater-drivenrotatingmachinesonthesmaller tankersbutfornewcrudeoiltankersof20,000tonnesdeadweightandabovethetank cleaningsystemusescrudeoilwashing.

Passengerships

Earlypassengershipsdidnothavethetiersofsuperstructureassociatedwith modernvessels,andtheyalsohadanarrowerbeaminrelationtotheirlength.The reasonfortheabsenceofsuperstructuredeckswastheMerchantShippingAct 1894,whichlimitedthenumberofpassengerscarriedontheupperdeck.An amendmenttothisActin1906removedthisrestrictionandvesselswerethenbuilt withseveraltiersofsuperstructures.Thisproducedproblemsofstrengthand stability,stabilitybeingimprovedbyanincreaseinbeam.Thetransmission ofstressestothesuperstructurefromthemainhullgirdercreatedmuchdifference ofopinionastothemeansofovercomingtheproblem.Bothlightstructuresof adiscontinuousnature,i.e.ﬁttedwithexpansionjoints,andsuperstructureswithheavierscantlingsabletocontributetothestrengthofthemainhullgirder wereintroduced.Presentpractice,wherethelengthofthesuperstructureis appreciableandhasitssidesattheshipside,doesnotrequiretheﬁttingof expansionjoints.

Theintroductionofaluminumalloysuperstructuresprovidedincreasedpassenger accommodationonthesamedraft,and/oraloweringofthelightweightcenterof gravitywithimprovedstability.Thiswasbroughtaboutbythelighterweightofthe aluminumalloystructure.Subsequentexperience,however,hasshownthatfor passengerliners,thatarerequiredtomaintainaservicespeedinaseaway,the maintenancecostsofaluminumalloysuperstructurescanbehigher.

Afeatureofthegeneralarrangementisthereductioninsizeofthemachinery spaceinthistime.Itiseasytoseethereasonforthisifthe Aquitania,builtin1914and havingdirectdriveturbineswith21double-endedscotchboilers,iscomparedwith the QueenElizabeth2.Thelatterasoriginallybuilthadgeareddriveturbineswith threewatertubeboilers.Manymodernpassengershipshavehadtheirmachinery placedaft;thisgivesoverthebestpartofthevesselamidshipsentirelytopassenger accommodation.Againstthisadvantage,however,allowancemustbemadeforan increasedbendingmomentifasuitabletrimistobeobtained.Themorerecent provisionofelectricpoddedpropulsorsasﬁttedonthe QueenMary2 has,withthe removalofshaftlines,permittedoptimizationoftheinternalarrangementsofthe passengerlinerandcruiseship.

Passengeraccommodationstandardshaveincreasedsubstantially,thevolumeof spaceallottedperpassengerrisingsteadily.Tweendeckclearancesaregreaterand publicroomsextendthroughtwoormoredecks,whilstenclosedpromenadeand atriumspacesarenowcommoninthesevessels.Theprovisionofair-conditioning andstabilizingdeviceshasalsoaddedtopassengercomfort.Particularattentionhas beenpaidtoﬁresafetyinthemodernpassengership,structuralmaterialsoflowﬁre riskbeingutilizedinassociationwithautomaticextinguishinganddetection systems.

Therehasbeenademiseofthelargerpassengerlinerandlargerpassengerships arenoweithercruiseships,short-haulferries,orspecialtradepassenger(STP)ships, thelatterbeingunberthedimmigrantorpilgrimpassengershipsoperatinginthe MiddleEasttoSouthEastAsianregion.

Whilstthesafetyofpassengershipsingeneralhasbeengoodinrecentyears,the growthinthesizeandnumberofcruiseshipshasledIMOtoinitiateareviewof passengershipsafety.Inparticular,itislookingatplacinggreateremphasisonthe preventionofacasualtyfromoccurringintheﬁrstplace.Thatis,futurepassenger shipsshouldbedesignedforimprovedsurvivabilitysothatintheeventofacasualty passengersandcrewcanstaysafelyonboardastheshipproceedstoport.

Thedevelopmentofhigh-speedpassengerferriesoflightweightconstructionand oftenofradicalhullformand/ornondisplacementmodesofoperationhasbeen notablesincetheearly1980s.Initiallyrelativelysmall,thesecraftmaynowbemore than100metersinlengthandcarryupwardsof500personsplus100cars/30trucksor more.Thelightweightconstructionisusuallyofaluminumalloybutsomehavebeen constructedoflighterhigher-tensilesteels,andﬁber-reinforcedplasticsmaybeused inthesuperstructureandaccommodationareas.Withspeedsofupto50knots,many craftareoftwin-hullformandincludeconventionalcatamarans,wavepiercerswith twinhullsandafairedbuoyantbridgingstructureforward,andsmallwaterplane twin-hulled(SWATH)ships.Thelatterhaveahighproportionoftheirtwin-hull buoyancybelowthewaterline(see Figure3.7).Otherhigh-speedcraftinclude hydrofoilsandvarioussurfaceeffectships(SESs)includinghovercraft,which maintainacushionofair,fullyorpartially,betweenthehullandthewatertoreduce drag.Theincreasinguseofthesevesselsledin1994tothepromulgationbyIMOof speciﬁcinternationalregulationsconcerningtheirdesign,safety,andoperation.An updatedversionofthisCodeofSafetywasadoptedinDecember2000. Figure3.7

TPECNOC HTAWS

NARAMATAC LLUH-ITLUM

Figure3.7Varioustypesofhigh-speedcraft.

illustratesthevarioustypesofhigh-speedcraft.AlsoseeFigure17.11,whichshows themidshipsectionofahigh-speedwave-piercingcatamaran.

4 Classiﬁcationsocieties

ChapterOutline

Rulesandregulations38

Lloyd’sregister38

Lloyd’sregisterclassiﬁcationsymbols39

Classiﬁcationofshipsoperatinginice40

Structuraldesignprograms40

Periodicalsurveys41

Annualsurveys41

Intermediatesurveys41

Dockingsurveys41

In-watersurveys42

Specialsurveys42

Hullplannedmaintenancescheme43

Damagerepairs43

Furtherreading43

Someusefulwebsites43

Acargoshipperandtheunderwriterreque stedtoinsureamaritimeriskrequire someassurancethatanyparticularvesselisstructurallyfittoundertakeaproposed voyage.Toenabletheshipperandunderwritertodistinguishthegoodriskfromthe bad,asystemofclassificationhasbeenformulatedoveraperiodofmorethan200 years.Duringthisperiodreliableorgani zationshavebeencreatedfortheinitial andcontinuinginspectionofshipssothatclassificationmaybeassessedand maintained.

RecentamendmenttotherequirementsoftheInternationalConventionforthe SafetyofLifeatSea(SOLAS—seeChapter29)haverequiredshipstowhichthat conventionappliestobedesigned,constructed,andmaintainedincompliancewith thestructural,mechanical,andelectricalrequirementsofaclassificationsocietythat isrecognizedbytheflagadministrationorwithapplicablenationalstandardsofthat administrationthatprovideanequivalentlevelofsafety.Ingeneral,flagadministrationsrecognizespecificclassificationsocietiesforthispurposeratherthanmaintainingsuchnationalstandards.

Whilsttherearereportedtobemorethan50shipclassiﬁcationorganizations worldwide,the13majorclassiﬁcationsocietiesthatclaimtoclassover90%ofall commercialtonnageinvolvedininternationaltradeworldwidearemembersofthe ShipConstruction.DOI: 10.1016/B978-0-08-097239-8.00004-0 Copyright 2012ElsevierLtd.Allrightsreserved.

InternationalAssociationofClassiﬁcationSocieties(IACS).Thesemembersofthe IACSare:

AmericanBureauofShipping(ABS) USA

BureauVeritas(BV) France

ChinaClassiﬁcationSociety(CCS) China

CroatianRegisterofShipping Croatia

DetNorskeVeritas(DNV) Norway

GermanischerLloyd(GL) Germany

IndianRegisterofShipping India

KoreanRegister(KR) Korea

Lloyd’sRegister(LR) GreatBritain

NipponKaijiKyokai(ClassNK) Japan

PolishRegisterofShipping Poland

RegistroItalianoNavale(RINA) Italy

RussianMaritimeRegisterofShipping(RS) Russia

Rulesandregulations

Theclassificationsocietieseachpublishrulesandregulationsthatareprincipally concernedwiththestrengthandstructuralintegrityoftheship,theprovisionof adequateequipment,andthereliabilityofthemachinery.Shipsmaybebuiltinany countrytoaparticularclassificationsociety’srulesandtheyarenotrestrictedto classificationbytherelevantsocietyofthecountrywheretheyarebuiltorowned.

Inrecentyears,undertheauspicesoftheIACS,membersocietieshavebeen engagedinthedevelopmentofcommonstructuralrulesforships.Theﬁrsttwoof thesecommonstructuralrules,forbulkcarriersof90metersormoreinlengthandfor oiltankersof150metersormoreinlengthcameintoforceon1April2006.These commonruleswillbeincorporatedintoeachmembersociety’srulebook.In November2008theIACSlaunchedtheIACSCSRTrackingDatabase(www.iacscsrtrack.org.uk)toprovideuserseasyandquickaccesstofullrevisionhistoryof CSRrulesonaparagraphbyparagraphbasis.

TheseandothercommonrulestobedevelopedbyIACmembersanticipatethe natureoffuturestandardstobemadeundertheInternationalMaritimeOrganization’s proposedGoal-BasedNewShipConstructionStandards(seeChapter29).

Lloyd’sregister

OnlytherequirementsofLloyd’sRegister,whichistheoldestoftheclassiﬁcation societies,aredealtwithindetailinthischapter.TherequirementsofotherclassiﬁcationsocietiesthataremembersoftheIACSarenotgreatlydifferent.

Foundedin1760andreconstitutedin1834,Lloyd’sRegisterwasamalgamated withtheBritishCorporation,theonlyotherBritishclassiﬁcationsocietyinexistence

atthattime,in1949.ShipsbuiltinaccordancewithLloyd’sRegisterrulesor equivalentstandardsareassignedaclassintheRegisterBook,andcontinuetobe classedsolongastheyaremaintainedinaccordancewiththerules.

Lloyd’sregisterclassiﬁcationsymbols

AllshipsclassedbyLloyd’sRegisterareassignedoneormorecharactersymbols. Themajorityofshipsareassignedthecharacters100A1or 100A1.

Thecharacterfigure100isassignedtoallshipsconsideredsuitableforsea-going service.ThecharacterletterAisassignedtoallshipsthatarebuiltinaccordance withoracceptedintoclassascomplyingwiththesociety’srulesandregulations. Thecharacterfigure1isassignedtoshipscarryingonboardanchorand/ormooring equipmentcomplyingwiththesociety’srulesandregulations.Shipsthatthesociety agreeneednotbefittedwithanchorandmooringequipmentmaybeassignedthe characterletterNinlieuofthecharacterfigure1.TheMaltesecrossmarkis assignedtonewshipsconstructedunderthesociety’sspecialsurvey,i.e.asurveyor hasbeeninattendanceduringtheconstructionperiodtoinspectthematerialsand workmanship.

Theremaybeappendedtothecharactersymbols,whenconsiderednecessaryby thesocietyorrequestedbytheowner,anumberofclassnotations.Theseclass notationsmayconsistofoneoracombinationofthefollowing:typenotation, cargonotation,specialdutiesnotation,specialfeaturesnotation,servicerestriction notation.Typenotationindicatesthattheshiphasbeenconstructedincompliance withparticularrulesapplyingtothattypeofship,e.g.100A1‘Bulkcarrier’.Cargo notationindicatestheshiphasbeendesignedtocarryoneormorespecificcargoes, e.g.‘Sulfuricacid’.Thisdoesnotprecludeitfromcarryingothercargoesforwhich itmightbesuitable.Specialdutiesnotationindicatesthattheshiphasbeen designedforspecialdutiesotherthanthoseimpliedbytypeorcargonotation, e.g.‘research’.Specialfeaturesnotationindicatestheshipincorporatesspecial featuresthatsignificantlyaffectthedesign,e.g.‘movabledecks’.Servicerestrictionnotationindicatestheshiphasbeenclassedontheunderstandingitisoperated onlyinaspecifiedareaand/orunderspecifiedconditions,e.g.‘GreatLakesand StLawrence’.

Theclassnotation LMCindicatesthatthemachineryhasbeenconstructed, installed,andtestedunderthesociety’sspecialsurveyandinaccordancewiththe society’srulesandregulations.Variousothernotationsrelatingtothemainand auxiliarymachinerymayalsobeassigned.

Vesselswitharefrigeratedcargoinstallationconstructed,installed,andtested underthesociety’sspecialsurveyandinaccordancewithitsrulesandregulations maybeassignedthenotation Lloyd’sRMC.Aclassedliqueﬁedgascarrieror tankerinwhichthecargoreliquefactionorcargorefrigerationequipmentisapproved, installed,andtestedinaccordancewiththesociety’srulesandregulationsmaybe assignedthenotation Lloyd’sRMC(LG).

Whereadditionalstrengtheningisﬁttedfornavigationiniceconditionsan appropriatenotationmaybeassigned.

Classiﬁcationofshipsoperatinginice

ClassificationsocietiessuchasLloyd’sRegisterandanumberofadministrations whosewatersexperienceicinghaveformanyyearshadregulationsdefiningand categorizingiceconditionsandspecifyingdesignandstandardrequirementsforships operatinginice.Lloyd’sRegisterhaveassignedspecialfeaturesnotationstomany existingshipsforoperationinfirst-yeariceandforoperationinmulti-yearice.Firstyearicenotationsareforadditionalstrengtheningwherewatersiceupinwinteronly andmulti-yeariceforserviceinArcticandAntarcticwaters.

TheincreasingmaritimetradingwithinArcticwatersinthepastdecadeandthe desiretoshipoil,gas,andothercommoditiesfromthereallyearroundappearsto haveresultedintheclasssocietiesadoptingtosomeextenttheicestrengthening requirementsofthe‘Finnish–SwedishIceClassRules1985’developedforvessels tradinginwinterandforwhichthekeelwaslaidafter1November1986.These requirementswereintendedprimarilyforvesselsoperatingintheNorthernBalticin winteraregivenforfourdifferenticeclasses:

l IceClass1AA

l IceClass1A

l IceClass1B

l IceClass1C.

Thehullscantlingrequirementsdeterminedundertheserulesarebasedoncertain assumptionsconcerningthenatureoftheiceloadtheship’sstructuremaybesubjectedto.Theseassumptionshavebeendeterminedfromfull-scaleobservationsmade intheNorthernBaltic.

ThisincreasedtradinginArcticwatershasalsocreatedparticularinterestinthe establishmentofuniversalrequirementsforshipsoperatinginice.

BoththeIMOandIACShavebeeninvolvedinthiswork,withtheIMOproducing guidelinesinDecember2002forshipsoperatinginArcticice-coveredwatersforwhich theyprescribeseven‘PolarClass’descriptions.TheserangefromPC1foryear-round operationinallArcticicecoveredwaterstoPC7forsummer/autumnoperationinthin ﬁrst-yearicethatmayincludeoldiceinclusions.Subsequently,theIACSsetup aworkinggrouptodevelopUniﬁedRequirementsforPolarShipsthatwouldcover:

a. Polarclassdescriptionsandapplications

b. StructuralrequirementsforPolarclassships

c. MachineryrequirementsforPolarclassships.

ItwasintendedthatwiththecompletionoftheseUniformRequirementsforPolar ShipsandtheiradoptionbytheIACSCouncil,theIACSmembersocietieswillhave oneyearinwhichtoimplementthesecommonstandardsforshipsoperatinginice.

Structuraldesignprograms

Inrecentyearstheprincipalclassiﬁcationsocietieshavedevelopedsoftwarepackages forusebyshipyardsthatincorporatedynamic-basedcriteriaforthescantlings,