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Bluewater Turret BuoyTechnical Description
“ The Bluewater turret buoy eliminates the disadvantages of the turntable buoy. The buoy body with deckhouse rotates around a central turret fixed to the seabed. The deckhouse protects the main bearing and all mechanical and electrical equipment and offers a safe place to work during operations and maintance. From experience with this buoy design, Bluewater is confident in offering an extended guarantee on the main bearing for the design life time of the turret buoy system.”
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Contents
1 Introduction 2
1.1 BluewaterCompany 2
1.2 GeneralapplicationofSPMsystems 2
1.3 Summaryoftheadvantagesofthe
TurretBuoy 3
2 Developmentoverviewofthe
differentSPMbuoytypes 4
2.1 HistoryoftheSPMloadingbuoys 4
2.2 Thirtyyearsofexperiencewithboth
TurntableandTurretBuoys 7
2.3 Overviewofhighlightsofthe
BluewaterTurretBuoy 8
3 Technicaldescriptionofthe
TurretBuoy 13
3.1 General 13
3.2 Buoybody 13
3.3 Skirtandprotection 13
3.4 Flat,unobstructeddeck 13
3.5 Turretandspider 14
3.6 TheMainBearing 14
3.7 TheProductSwivel 15
3.8 Protectiondeckhouse 16
3.9 BoatLanding 17
3.10 FloatingHoseInstallationPlatform&
ProtectionFrames 17
3.11 MooringLug 17
3.12 ChainHawse-pipesandturret
lockingsystem 18
3.13 ChainStoppers 18
3.14 AncillaryEquipment 19
4 AuxiliaryEquipment 21
4.1 General 21
4.2 BuoyMooringArrangement 21
4.3 TankerMooringArrangement 22
4.4 FloatingHoses 22
4.5 TheSubmarineHoseString(s) 23
5 EnvironmentalProtection 24
5.1 General 24
5.2 Stabilitybuoy 24
5.3 Enclosedsystem 24
5.4 Doublesealsproductswivel 24
5.5 Flexiblejoints 24
5.6 Leakdetection&recuperationsystem 25
5.7 RemotePLEMvalveoperatingsystem 25
5.8 Remoteoperation&monitoring 25
5.9 Surgereliefsystem 25
5.10 Break-awaycouplings 26
5.11 Doublecarcasshoses 26
6 RequirementstostartanSPMproject 27
6.1 Introduction 27
6.2 Informationrequired 27
6.3 Contractingstrategy 28
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1 Introduction
1.1 BluewaterCompany
AtBluewater,wedesignandsupplyinnovativeCALMbuoysandotherMooringandTransferSystems.
Bluewaterhassuppliedmorethanseventy(70)oftheseSPMandCBM/MBMsystemsworldwide,suchas:
• SinglePointMooring(SPM)SystemsincludingCatenaryAnchorLegMooring(CALM)Buoys,TurretBuoysand
Turntablebuoys
•ConventionalBuoyMoorings(CBM)
•Disconnectable,ExternalandInternalTurretMooringSystemscompletewiththeirfluidSwivelAssemblies
•TowerMooringSystems
1.2 GeneralapplicationofSPMsystems
SPMsystemsaretypicallyusedforloadingoroffloadingtankers,offshorenearthecoast.TheSPMsystemis
normallyapointofexportorimportforarefinery,tankfarm,powerplantorotheronshoreinstallations,forthe
transferofcrudeoranyliquidorgasproduct
SPMsystemscanalsobeusedfortheexportofcrudeoilatanoffshoreoilproductionlocation.
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1.3 SummaryoftheAdvantagesoftheTurretBuoy
Bluewater has designed and supplied various Turntable and Turret type SPM buoy systems worldwide.
BothCALMbuoytypesarelargesuccessesinthemarketandbothhaveimpressivetrackrecords.
TheTurretBuoyisthethirdgenerationofSPMbuoydesign.ThedifferencebetweentheTurretBuoyandearlier
generationSPMbuoys,theconventionalTurntablebuoyandtheBogeyWheelbuoy,isinthegeometryofthebuoy.
Whereaswiththeearliergenerationsthevulnerablepartsareoutsideandexposedtoseawater,theTurretBuoy
offersthepossibilitytokeepallcriticalequipmentprotectedinsidethedeckhouse.
BasedonBluewater’sexperiencewithbothCALMbuoytypes,andbasedontheexperienceofourClients,the
mostprominentadvantagesoftheTurretBuoyconceptare:
• Safetyduetoflat,notobstructeddeck,norotatingormovingpartsontheoutside,easyaccesstothebuoyfrom
aworkboatandthepresenceofaprotecteddeckhouse,
• Operationalreliabilityduetotheeffectiveprotectionandventilationofthemainbearing,overboardpipingand
allequipment.
AnSPMbuoyisnormallyacriticalequipmentsinceanotherlargecapital investmentlikearefinery,tankers
farm,productionfacilitiesorelectricalplantdependsonthebuoy.Therefore,theavailabilityoftheSPMbuoy
isimportantfortheoverallinvestment.TurretBuoyshaveaproventrackrecordof20-25yearsofuninterrupted
servicetothemainasset(refinery,etc),withouttheneedforperiodicremovalorchange-outandtheassociated
downtimeoftheentirefacility.
• Lowermaintenancecostsduetoeasierandaccessiblemaintenanceandthepossibilityofkeepingthebuoyin
thewaterforlongperiodswithoutoverhaul(mainbearingandallequipmentiswellprotectedinsidethedeck-
house).Onlypreventivemaintenanceisneeded;noreplacementofheavypartsoffshore,incontrastwith,for
example,thewheel-and-railbuoydesign.
Duetoeffectiveprotectionofthemainbearingandotherequipmentinsidetheweatherproofdeckhouseand
othertechnicaldesignbenefits,sofarnoneoftheTurretBuoysworldwidehasseentheneedforperiodicover-
haulduringitslifetime.
• TurretBuoyshavethelargestresistanceagainsttankercollisions.Thefactsshowthat,despitethatmanyTurret
Buoyshavesufferedseverecollisionswithworkboatsortankers;noTurretBuoyhasbeentakenoutofservice
duetothesecollisions.However,inthecaseofturntablebuoys,manyhavebeentakenoutofserviceaftercol-
lisions.
ThebenefitsoftheTurretBuoyresultinthelowestTotalCostofOwnershipforthisSPMbuoycomparedtoothers.
ThetrackrecordoftheTurretBuoyhasproventhattheTurretBuoy,whichisdesignedtostayinthewaterduringits
lifetime,isfarmoreeconomicaltotheend-userthananyotherSPMbuoytype(non-Turrettype)whichneedsperiodic
removal.
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2 DevelopmentoverviewofthedifferentSPMbuoytypes
2.1 HistoryoftheSPMloadingbuoys
CBMorMBMsystems
Thedevelopmentofloadingbuoysstartedinabout1920,whenthegrowthintankersizesdemandedtheexten-
sionofharbourfacilitiesintodeeperwater.UptotheinstallationofthefirstgenerationofSinglePointMooring
(SPM)systems,tankersweremooredwithinapatternoffourtoeightmooringpoints,consistingofrigidbuoys
mooredtotheseabedbyachainandanchor.ThisConventionalBuoyMooring(CBM)orMulti-BuoyMooring
(MBM)systemdoesnotenabletankerstoweathervaneandhasthereforeoperationallimitations.
SPMsystems
The1stgeneration(wheelandrail),2nd(turntable)and3rd(turret)generationbuoysystemsarecollectively
called“SinglePointMooring”(SPM)systems.Duetothecharacteristiccatenarycurveoftheanchorchainsfixing
theSPMbuoysystemstotheseabed,themooringsystemswiththesebuoysystemsarealsocalled“Catenary
AnchorLegMooring”(CALM)systems.
FirstgenerationCALMbuoy:WheelandRailbuoy
ThefirstbuoyswecanindicateastheforerunnerofthecurrentbuoytypeswerebuiltandinstalledinSwedenin
1959fortheSwedishNavy.Thesefirstgenerationbuoyswere
oftheWheelandRail(orBogeyWheel)type.Ithasabuoy
bodywithacentralmoonpoolandarotatingbogeyplatform
on wheels, allowing the tanker to weathervane around the
buoy.Thefluidtransferrunsthroughaswivel.Thisbuoyhas
onlyonebearing,theswivelbearing.Thebogeywheeltable
issupportedbywheelsrunningonrails.
WheelandRailbuoy
5
Thewheelandrailbuoyhasseveraldisadvantages,thereforesecondgenerationCALMbuoywasquicklydevel-
opedwithactiveinvolvementofoilmajorShell.Inco-operationwithanengineeringcompanyintheNetherlands
abuoysystemwasdevelopedwhichischaracterisedbyacylindricalbuoybody,mooredtotheseabedbyfourto
eightanchorchainsandarotatingplatformstructureontop,theturntable.Thetankermooringhawserandthe
flexiblefloatingloadinghosesareconnectedtotherotatingplatform,enablingthetankertoweathervanearound
thebuoy.Thisbuoytype,schematicallydepictedinthefigurebelow,iscalledthe“TurntableBuoy”.
SecondgenerationCALMbuoy:Turntablebuoy
TheTurntablebuoy,thesecondgenerationCALMbuoy,hasbeenaworldwidesuccessandmanyofthesebuoys
wheresolduntil1980.However,theexperiencehasshownthattheturntablebuoyneedsperiodicoff-location
overhaul(dry-docking),whichinitselfisofaclient’sdisadvantage.
• ThereisaDirectcostinvolvedfromoffshoredismantling,transport,dry-docking,yardrepairsandre-installation
offshore.
• Indirectcost:non-availabilityoftheTurretBuoyduringtheoverhaulperiod,typicallyaperiodoftwomonthsor
longer,duringwhichtheterminalcannotservicetheconnectedasset(e.g.refineryorproductionfacility)and
whichmaythereforebeforcedtostopitsoperations,causingdowntime.
• Often thisdowntime issolvedbypurchasingasparebuoy.Thismeansadoublepurchaseexpenditure, in-
creasedmaintenance,storageandconservationcostsasanadditionalbuoyneedstobestoredandmaintained.
• Riskisinvolvedinthemarineremovalandreconnectoperations,transportandrepairworksanduncertaintyis
introducedforthereturndateandhenceavailabilitytotheassetitservices,e.g.refineryorplant.
Furthermore,inbetweentheperiodicoverhauls,themaintenanceinthewaterrequiresaconsiderableeffort.The
deckisobstructedbytheturntableandwalkingonthe
buoymeansclimbingupanddowntovariouslevels.
Duetotherotatingturntablethereisnosafetyhand
railingaroundtheperimeterofthebuoy,noprotecting
deckhousetocoverthevulnerableequipmentsuchas
themainbearinganditisdifficulttomooramainte-
nanceoroperationalworkboattothebuoy.
Turntablebuoy
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ThirdgenerationCALMbuoy:TurretBuoy
Bluewaterdevelopedanew,improvedbuoyconceptinordertoovercomethedisadvantagesoftheTurntable
andCALMbuoys.Inthisdesign,thebuoybodyitselfcanfreelyrotatearoundaturretstructure.Theturretis
mooredtotheseabedbytheanchorchains.Thebuoyoffersanenormousimprovementintermsofsafety,ease
ofmaintenance,protectionanddurability.TheexperienceworldwidehasshownthattheTurretBuoycanremain
inoperationatitsoriginallocationforaperiodofatleast25years,withoutperiodicoff-locationoverhauland
withoutreplacementofheavyparts(suchaswheelsorrailsofthebogeywheelbuoy).Thenewtypeofbuoyis
calledthe‘TurretBuoy’.
Since1980theTurretBuoyhasbeenverysuccessfulinthemarketandisthepreferredchoiceofmanymarine
terminaloperators.After thedevelopmentof theTurretBuoy, theconceptof turretmooringhasbecomethe
leadingtechnologyforthepermanentmooringoftankersasFloatingProduction,StorageandOffloading(FPSO)
andFSOunits.
TheschematicsbelowillustratethedifferenceincrosssectionoftheTurntableandTurretBuoy:
TurntableBuoy TurretBuoy
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TurretBuoy
2.2 ThirtyyearsofexperiencewithbothTurntableandTurretBuoys
Overthepast30years,BluewaterhasdesignedandsuppliedmanyTurntable(2ndgeneration)andTurret(3rd
generation)SPMbuoysystems.
SinceBluewateristheonlyfabricatorofbothTurretandTurntabletypesofbuys,wehavebeenabletocompare
theoperationalperformanceofbothbuoytypes.
However,afteralmost30yearsfabricatingbothsystemsandreceivingoperationalfeedbackfromourclientsand
fromotherusersofbuoys,ithasshownabigdifferenceintheclientsatisfactionofeachtypeofbuoy.
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2.3 TechnicalhighlightsoftheBluewaterTurretBuoy
TheBluewaterTurretBuoyconcepteliminatesthedrawbacksofearliergenerationbuoydesignsandprofitsfrom
severaldistinctadvantagesinherenttotherotatingbuoybody.
ThemostprominentadvantagesoftheTurretBuoyarehighlightedbelow:
1. Safety:TheTurretBuoyhasaflatdeck,notobstructedbyaturntableoranyothermovingpartsandiseasily
accessibleviaaproperboatlandingdesignedtomooraworkboatalongsidethebuoy.
2. Safety:TheTurretBuoyhasalargeboatlandingtowhichaworkboatcanbesafelymoored,givingoperating
personnelsafeaccesstothebuoy.Downtimeduetoinaccessibilityisthereforelessthanwithothertypes
ofbuoys.
3. Durability:TheTurretBuoyisprovidedwithadeckhouse.Themostimportantcomponentforthemechani-
calfunctioningofthebuoy,themainbearing,ispositionedinsidethedeckhouseandisthereforeoptimally
protectedagainstallforcesfromtheenvironment.
Personnelonthedeckofaturntablebuoyneartotherotat-
ingarmoftheturntablewhichcanmove.Thepersonnelis
notprotectedbyahandrailing.
PersonnelondeckofaTurretBuoy.
Safety:nomovingparts;safetyhandrailaroundthe
perimeterofthebuoy.Alsovisibleisthelargeboatlanding
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4. Durabilityandmaintenancefriendly:Extrafeatures,suchasadditionalelectronic(control)equipment,winch,
instrumentsandvalvesarealsofittedinsidetheprotectedareaofthedeckhouse.
5. Durability:Thehawserload,aswellasloadsgeneratedbytanker-buoycontact(tankerkissing)orbywork
boat,isdirectlytransferredintothebuoybody.Duetothelargemassofthebuoybody(incl.deckhouseand
allequipment)andtheaddedmassofthewateraroundthebuoybody,loadsandvibrationsfromthehawser
areabsorbed,resultinginonlyalimitedtransferoftheseloadstothemainbearing.Asaresult,theopera-
tionallifetimeofthemainbearingisbetterensured.
TurretBuoy:externalloadsonthebuoybodyareabsorbedbymassand
wateraddedmass,resultinginonlyalimitedtransferoftheseloadsto
themainbearing.
Turntablebuoy:externalloadsontheturntable
willpass100%throughthemainbearing
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6. Durability:Theloadsgeneratedbytanker-buoycontact(tankerkissing)andbymooringaworkboatagainst
theboatlanding,areabsorbedbythemassofthebuoybodyandsurroundingwaterasdescribedabove,
thusprotectingthemainbearingfromexcessiveshockloads.
7. Maintenancefriendly:Theflatand“clean”deckstructurecombinedwiththeenclosureofallequipmentin
thedeckhousereducessignificantlythemaintenanceandrepaircoststhroughoutthelifetimeofthebuoy
system.
8. Safetyandmaintenancefriendly:Operating, inspectionandmaintenancecrewscanboardthebuoyand
workundersafecircumstances,protectedfromsunorrainandallowsworkeveninrelativelyroughseasas
mostoftheworkisdoneinsidethedeckhouse.Downtimeduetorestrictioninmaintenanceandrepairis
thereforelowerthanwithothertypesofbuoys.
9. Durability:Bylockingthedoorsofthedeckhouse,unauthorisedaccesstotheequipmentcanbeprevented.
10. Durability:Theoverboardpipingisatthelowerpart,closetothewaterline,directlysupportedbythebuoy
structure.Anadequatefendersystemprotectsthepipingfromtankercollisions.
Overboardpipingdirectlyconnectedto
buoyhull–strongsupport
11. Durability:WithanyCALMbuoy,atslackweather,thefloatinghosestringmaywraparoundthebuoy
body.TheadvantageoftheTurretBuoydesign–wheretherotatingbuoybodycanbeseenasareel-is
thatthehosesautomaticallyunwrapwhentheweatherpicksup,orwhenthehoseispulledoutbya
smallservicecraft.
Overboardpipingwellprotectedbyfenderbelowandabove
theflanges.
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12. Durability:Asthechainstoppersarenotfittedattheouterperimeterofthebuoybody,butinthespider
underneathandwellwithinthecontoursofthebuoybody,theyarenotpronetodamagebytankercontact.
TurntableBuoy TurretBuoy
13. Durability:Thankstotheinwardpositionofthechainstoppers,theclearancebetweenthetankerbowand
theanchorchaincatenaryislarger,thuseliminatingtheriskofatankerhittingthechainstoppersandreduc-
ingtheriskoftankersdamagingtheanchorchain.
14. Durability:ThecentreofgravityoftheTurretBuoyisrelativelylow,providingahigherstabilityduringinstal-
lation,operationandmaintenanceofthebuoy.Italsoreduceswearontheupperchainlinks.
15. Flexibility:TheshapeoftheTurretBuoyisnotrestrictedtoacylindricalshapeonly.Thesquareshapeis
structurallyidealtofithingesforawishboneMooringarm,permanentlyorsemi-permanentlymooringofa
tanker:
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16. Flexibility:Extrafeatureslikeasurgereliefsystem,encompassingreliefvalves,tanksandpumps,canbe
fittedinthedeckhouseandinthebuoybody.
17. Safety:HAZOPstudiesontheTurntableandTurretBuoyconcepthaverevealedthattheTurretBuoyissafer
forpersonnelandenvironment.InparticulartheprobabilityforspillageincaseofTurretBuoyisconsiderably
lessthanincaseofTurntablebuoy.
Asaresultoftheadvantagesdescribedabove,boththeoperationandmaintenancecostsofaTurretBuoyare
substantiallowerthanwithaTurntableBuoy.Mostimportantfortheuseristhemorereliable,higheravailability
oftheTurretBuoysystem,reducingcostondemurrageandondelaysinthetransferofcargo.
TomostoftheforegoingaspectscanbeseeninthepicturesofrecentBluewaterTurretBuoyprojectswhichare
enclosedinthisreport.
Thesurgereliefvalvesareprotected inside
thedeckhousetogetherwiththeswiveland
as shown in thispicture, togetherwith the
flexiblejointsandthemainbearing.
FullintegrationofaSurgeReliefSystemispossibleintheTurretBuoy,
withallpartsprotectedinsidethedeckhouseandbuoybody.
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3 TechnicaldescriptionoftheTurretBuoy
3.1 General
TheTurretBuoyconsistsoftwostructuralmaincomponents,theturretstructure(thepartthatisfixedtothesea-
bed)andthebuoybody(rotatingpart).Theturretstructureislocatedinthecentreofbuoybody.Theturretand
buoybodyareconnectedatdecklevelbymeansofarollerbearing.Theconnectionbetweenthepipingsections
intheturretandinthebuoybodyismadebymeansofafluidswivelalsooutfittedwitharollerbearing.Thetanker
ismooredtothebuoybodyviaahawserandcanfreelyweathervaneinresponsetochangingweatherconditions,
therebyrotatingthebuoybodyaroundtheturret.
ThemaincomponentsoftheTurretBuoysystemwillbehighlightedinthefollowingsubsections.
3.2 Buoybody
ThebuoybodyforaTurretBuoycanbearectangularorcircularconstruction.Thebuoybodyisdividedinwater-
tightcompartments,eachofthemaccessibleviaamanholeinthedeck.Thecompartmentsaredesignedtomeet
theexistingClassrequirementsrelatedtothedamagedstabilitysituation.Themanholesgivingaccesstothebuoy
compartmentsareflushwiththedecksurface.
3.3 Skirtandprotection
Alongtheperipheryofthebuoybody,justabovebottomlevel,askirtisfittedtoprotectthebuoybodyagainst
directcontactwithships.Thefreeside(s)ofthebuoybodyareprotectedagainstcontactswithverysmallcrafts
andfloatingobjectsbymeansoffenders(half–pipes),weldeddiagonallytothehullplating.
3.4 Flat,unobstructeddeck
Thedeckofthebuoybodyisflat,unobstructedandwithahandrailingallalongitsperiphery.
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3.5 Turretandspider
Theturretassemblyconsistsofaturretshaftandachaintableorspider.Theturretshaftisalargediameterconi-
calsection.Atthetopsidethemainbearingisfitted,atthebottomsidetheturretisclosedbyadiaphragmplate.
Theinsideoftheturretisthereforeadrycompartment,whichisdirectlyaccessiblefromthedeckhouse.Inside
theturret,valvesbetweensubmarinehosesandswivelaswellasgeostatic(control)equipmentcanbemounted.
Thespiderorchaintableisaboxgirderframing,whichsupportsthechainstoppersthroughwhichtheanchor
chainsareattachedtomoorthebuoyatlocation.
3.6 TheMainBearing
Thebuoybodyandtheturretshaftareinterconnectedbymeansofalargediameterbearinglocatedatdeck
level.ThismainbearingisthelargestofthetwobearingsinaTurretBuoy;theotherbearingispartoftheprod-
uctswivel.Themainbearingisathree-racerollerbearingandismountedonreinforced,machinedfoundation
flanges,fixedbyhightensionmountingbolts.Thebearingisthemostcriticalmechanicalcomponentofthebuoy.
Maximumattentionisthereforegiventothecorrectmachiningofthebearingsupportsandthefittingofthe
bearing.Thebearingispositionedinthedryenvironmentofthedeckhouseandinternalsealsprovideadditional
protectionofthebearingagainstingressofwateranddust.
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Lubricationofthemainbearingcanbedonethroughthegreasingpointsprovidedinthebearingrings.Grease
samplingpointstomonitortheconditionofthebearingarelocatedatthebearinguppersurface.Ifrequired,the
lubricationcanalsotakeplacefromoneortwomanifoldswithgreasepipestothegreasingpoints.Asanextra
feature,afullyautomatedgreasingsystemcanbeordered.
3.7 TheProductSwivel
While themainbearingprovides themechanical connection in theTurretBuoy, the swivel provides thefluid
transferbetweenthefixedandtherotatingpartsoftheTurretBuoy.Theswivelallowsunlimitedrotationofthe
buoywithoutmixingthedifferentproductchannels.Itisequippedwithitsownbearingandseveralproductseals.
Beingoneofthemostcriticalcomponentsofthebuoysystem,Bluewaterdesignsandbuildstheswivelsitself.
Bluewaterhasextensiveexperienceinthedesignandfabricationofdifferenttypesofproductswivels,suchas
singleandmulti-productswivels,andhigh-pressureswivelsforspecialapplications.
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Easyaccessenablesregularinspectionsontheproductswiveltodetectleakageoroilseepageattheflangecon-
nections.Theswivelbearingisgenerallymanuallygreasedatperiodicintervalsviathegreasepoints/nippleson
thefixedflangebetweenthebearingbolts.Theswivelhasadualsealconstruction.Anyleakageofthefirst,inner
sealcanbemonitoredbyleakdetectioninthespacebetweentheinnerandouterseal.Intheunlikelyeventthat
leakagethroughtheinnerandoutersealoccurs,thespillagewillbecontainedintheturretcompartment,pre-
ventingpollutionoftheenvironment.Asanextrafeature,anautomaticleakdetectionsystemcanbeprovided.
3.8 Protectiondeckhouse
OneofthemainadvantagesoftheTurretBuoy:awatertightdeckhouseisfittedoverthecentralareaoftheTurret
Buoy.Itprotectstheturret,mainbearing,productswivel,electricalequipment,winchandallotherequipment
againstallenvironmentalforcessuchassun,rain,windandseawater.Atthesametime,itallowsventilationof
themainbearingtoavoidaccumulationofcondensedwater.Shieldedlouverpanelslocatedclosetothedeck-
houserooflevelensurepermanentventilationoftheinterior.
Thedeckhouseisdesignedtowithstandallloadsduetowindandovercomingwaves.Thedeckhousehastwo
doorsinoppositewalls.Oneofthedoorsneartotheboatlandingisextrawideandhasaliftingbeamextending
fromtheinsidetotheoutsideofthedeckhousetoenablethetransferofequipmenttoandfromthecentralarea
insidethedeckhouse.Intheceilingofthedeckhousearailbeamisfittedoverwhichalittletrolleyhoist(which
ispartofthestandarddelivery)canberuntoperformsmallliftingoperationsinthedeckhouse.Thisgreatly
facilitatesrepairormaintenanceworkstotheequipmentinthedeckhouse.
Ontheroofofthedeckhouseadeckhasbeencreated,whichisprovidedwithhandrailing.Thedeckisgenerally
largeenoughtofitthebatteryboxes,solarpanels,navigationlightsandantennas.Thedeckisaccessibleviaa
fixedorremovableladderwithsafetycage.
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3.9 BoatLanding
AnotherstrongpointoftheTurretBuoy:alongtheentiresideofthebuoybody,agenerouslysizedboatlanding
isfittedtoprovidesafeaccesstothedeckofthebuoy.Theboatlandingisconstructedfromtubularsteelmem-
bersandcompriseshorizontalfenderpipesintegratedatdeckandskirtlevelandverticalmemberswithrubber
fenderstopreventship-to-steelcontacts.Theboatlandingisoutfittedwithaladderinarecess,forsafeaccess
fromsmallerboats,withbollardsforberthingsmallcraftsandwithaliftingdevicetofacilitatethetransportof
equipmentontothebuoy.
3.10 FloatingHoseInstallationPlatform&ProtectionFrames
Atthelocationoftheoverboardpiping,aworkplatformisprovidedtofacilitatethedisconnectionandre-connec-
tionofthefloatinghose(s).Theplatformisconstructedfromtubularsteelsectionsandgalvanisedsteelgrating.
Atmaindecklevelasolidprotectionframeoftubularsteelisprovidedtogivefurtherprotectiontotheoverboard
piping.
3.11 MooringLug
Onthedeckofthebuoybodyamooringlughasbeenfittedforconnectingthemooringhawser.Frompractical
experience, thefloatinghosestring(s)andthehawserattachmentpointonthebuoybodyshouldapparently
bekeptapart,buttheanglebetweenthemshouldbelessthan90degrees.OnthesquareTurretBuoytype
thisisachievedbyplacingthemooringlugatacornerofthebuoybodyonthesidewheretheoverboardpiping
isfitted.
Overthemooringluglocation,aprotectionframefromtubularmembersisfittedtoprovideprotectionincaseof
failureofthehawserundertension.
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Themooringlugcanbefittedwithanelectronichawserload-measuringdevice.Themonitoringequipmentfor
thisdeviceispositionedinthedeckhouse.Dependingontherequirements,warningsforoverloadingthehawser
canbesignalledthroughthenavigationlamps,thefoghornor,viaatelemetrysystemtoamobileorfixedshore
station.
3.12 ChainHawse-pipesandturretlockingsystem
Dependingonthenumberandconfigurationofthemooringlegs,twoorthreehawse-pipesarefittedinthebuoy
bodyanddeckhousewalltofacilitatefastinstallationofthemooringlegs.Severalanchorlegscanbepulledin
ateachposition,
Theturretcanbeeasilylockedintotherequiredpositionsbymeansofastraightforwardlockingpininthedeck-
house.Thislockingpincanalsobeusedtofixtheturrettothebuoybodyforgeneraltransport,installationand
maintenancepurposes.
3.13 ChainStoppers
Thechainstoppersareabletofreelyoscillateverticallyandtoalignwiththechainangle,preventingwearon
thefirstchainlinksbelowthechainstopper.Thelockingofthechainsinthechainstoppersisachievedbytwo
automaticlatches,whichallowthechaintobepulledinuntiltherequiredpositionorchainangleandthenlock
thechainsinthestopperautomatically.
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3.14AncillaryEquipment
Winch
Awinchisinstalledonthebuoydeck,insidethedeckhouse.Thisallowsthewinchtobeeasymaintainedand
alwaysavailabletofunction.Thewinchisprotectedinsidethedeckhouseandthereisnoneed,aswithprevious
generationbuoytypes,toremovethewinchfromthebuoy.Thecompressedairorhydraulicsnecessarytorunthe
winchhastobeprovidedfromaworkboat.Thewinchcanbeusedforthere-tensioningoftheanchorchains,to
pullinandconnectthesubmarineandfloatinghosestringsandtoperformliftoperationsforanybuoycompo-
nent,suchasswivel,valves,flexiblejoint(s)etc.Forenablingthesedifferentliftoperationsandtoguidethewinch
wiretotheworklocation,sheavesarepresentatvariouslocationsinandontopofthebuoydeckhouse.
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Navigation Aids
Anobstructionlight,foghorn,andradarreflectorareprovidedandmountedonthebuoyasanavigationaidfor
shippingandtoreduceanyhazardtohappen.Theelectronicequipmentrunsonthepowerpacksinstalledina
largebatterybox.Thepositionofthebatteryboxisoutsidethedeckhouseinorderthepreventvapourbuild-up
inthedeckhouse.Thebatteriesarere-chargedbysolarpanelswhicharepositionedonthedeckhouseroof.
Safety Equipment
Thestandardsafetyequipmentdeliveredonboardofthebuoyencompassestwoportablefireextinguishers,
eachstoredinawatertightredcabinet,andtwolife-buoysfittedwithselfilluminatinglightsandbuoyantlifelines.
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4 AuxiliaryEquipment
4.1 General
ThemaincomponentofacompleteSPMterminalsystemistheSPMbuoyitself.Inaddition,anumberofauxiliary
equipmentcomponentsareanintegralpartofsuchaSPMsystem.Thesecomponentsaredescribedinthefol-
lowingsubsections.
4.2 BuoyMooringArrangement
TheTurretBuoyissecurelyanchoredtotheseabedbymeansofasetofmooringlines(legs)whicharefixedto
theseabedwithanchorpoints.Generally,anaveragebuoysystemisfixedtotheseabedwithsixmooringlegs.
Sometimesthisnumberisincreasedtoeightorninelegs.Dependingontheprojectsituation,thesixmooring
legsareequallyspacedorclusteredinthreeseriesoftwoorthreelegs,120degreesspaced.(typicalmooring
patterns…;TurretBuoycanaccommodateany)
Themooringlinesareinmostcasesheavychainswithlinkdiametersizesrangingfromthreetosixinches.The
lengthofthelegsvarieswiththewaterdepth,thetankersizeandtheloadconditions.Lengthsof200to600
metersarecommon.
Eachmooringlegwillbeconnectedtoananchorpoint.ThesecanbeHighHoldingPower(HHP)marineanchors,
drivenordrilledpiles(opentubularsections),suctionpilesandgravityboxesorframes(boxesfilledwithgravity
material),respectivelyframeswithgravitymaterialontop.Thefinalselectionoftheanchorpointconceptwill
dependonthesoilconditionsandtheavailabilityofrequiredinstallationequipment.
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4.3 TankerMooringArrangement
Inprincipletwotankermooringsituationscanbeidentified:thetemporarymooringofatankerforthedurationof
aloadingoperation(generally24hours)andthe(semi-)permanentmooringofatankerfordurationinexcessof
weekslikeinaFloatingStorageandOffloading(FSO)system.Forthe(semi-)permanentsituation,severalbuoy-
to-tankermooringconstructionsexist,likewishbone,yokeandrigidarmconnectionstructures.Whereasthese
structuresareveryprojectspecific,thefocusofthisdocumentisonthetypicalloadingoroffloadingsituations,
wherebythetankerismooredforabout24hours
Thetankermooringarrangementisahawserarrangement,encompassingapolyestermooringlinewithchain
sectionsonbothsidestopreventwearandtearattheconnectionpoints.Thepolyestersectionofthemooring
linehascertainelasticitycapacities,whichdampenstheloadsandtankermovementsintheoverallmooring
system.Forthedesign,fabricationanduseofthesehawsersystemsextensivecodesandstandardsexist.(OCIMF
publication“StandardsforEquipmentEmployedintheMooringofShipsatSinglePointMoorings”).
4.4 FloatingHoses
Theconnectionofthetankerwiththebuoypipingismadebytheuseofoneormorefloatinghosestrings.The
numberandsizeofthestringsdependsonthemaximumsizeofthetankerstobemooredandloadedviathe
buoysystemandtherelatedpumpingcapacity.Alsoforthedesign,constructionanduseoffloatinghosesexten-
sivecodesandstandardsexist.(OCIMFpublication“BuoyMooringForumHoseStandards”)
Thefloatinghosesfromthebuoytothetankerwillbeelectricallycontinuousuptothelastthreehosesatthe
tankerend.Thehoseshaveaminimumreservebuoyancyof20%.
AidsfortheInstallationandMaintenance
Adequateequipmentisprovidedonthebuoytosimplifytheinstallationandmaintenanceofthefloatinghose
string(s).
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4.5 TheSubmarineHoseString(s)
Thesubmarinehosesystemwillbedesigned,manufacturedandtestedaccordingtotherequirementsofthelatest
OCIMFpublication“BuoyMooringForumHoseStandards”.
Thesubmarinehosestring(s)connectsthePLEMtothebuoy’spipingandwillbedesignedwithsufficientlength
toadapttotheexcursionsandheavemotionsofthebuoy.
AidsfortheInstallationandMaintenance
Ahosepull-inhawserpiperunsfromthemainbuoydeckleveldownthroughtheturret.Theliftlinefromthe
winchisrunthroughthispipe,pullingthesubmarinehosestring(s)untilitismeetsitsconnectionpointwiththe
buoypiping.
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5 EnvironmentalProtection
5.1 General
TheTurretBuoysystemhasbeendesignedtooperatetothehigheststandardsofsafetyandtominimizethe
riskforpersonnelinjuriesand/ordamagetotheenvironment.Allaspectswithanimpactonsafetyinoperating
thebuoysystemhavebeenanalyzedandmeasurementsaretakenwherepossibletoenhancethesafety.This
alsocomprehendsthetrainingofoperationpersonnelandtheprovisionofadequateoperationdocumentsin
achievingthesafetygoals.Thesubsectionsbelowhighlightthemainaspectswheresafetyhasbeenofparticular
importance.
5.2 Stabilitybuoy
Comparedtootherbuoydesigns,theTurretBuoyhasarelativelowcentreofgravityandasubsequenthigh
stability.Thisenhancesthemotionbehaviourofthebuoy,makingitasaferplacetoworkon.
Thebuoybodyisdividedintosixoreightwatertightcompartments.Thedesignofthesecompartmentsissuch
that,incasethebuoyisinvolvedinanaccidentandtwoadjoiningcompartmentsarepenetratedandflooded,the
buoyhassufficientresidualbuoyancyandstabilitylefttoremainafloatanddonotcapsize.
5.3 Enclosedsystem
TheTurretBuoyisdesignedasanenclosedsystem,i.e.allmechanicalcomponentsintheproductlinesinthe
buoysystemaresituatedinaconfinedspace.Thisspaceisthedeckhouseandtheturretspace.Asdescribed
before,theturretisclosedatthebottomsideandisthereforeadryspace.Also,thefloorinthedeckhouseis
watertightandwiththehighthresholdsofthedoors,nofluidscanstreaminoroutofthedeckhouse.
Incaseoftheunlikelyeventthataleakageoccursinanyofthemechanicalcomponentsintheproductline(prod-
uctswivel,valves,andflexiblejoints),thespillagefromthisleakingwillbecontainedinthedeckhouseand/or
theturretspace.Thechancesthatsuchaleakageoccurswithoutbeingnoticedisunlikely,asthebuoyisalways
mannedduringloadingoperationsandbecausecertainpipingcomponentsliketheproductswivelhaveanactive
leakdetectionsystem.
5.4 Doublesealsproductswivel
Theproductswivelisoneofthemostcriticalcomponentsinabuoysystem.Tohavefullcontroloverthequality
ofthiscomponent,Bluewaterdesignsandbuildstheproductswivelsforitsownbuoyandturretsystemprojects.
Theseswivelsareprovidedwitharollerbearing,adualmainsealingconstructionanda leakagemonitoring
system.Incasetheprimary,innersealstartsleaking,theleakagecanbenotedbythemonitoringsystem,butno
spillagecanoccurasthesecondarysealwillcontainthefluidwithintheswivel.
5.5 Flexiblejoints
Inthepipingsystem,betweenthefluidswivelandthefixedpipeworkonboardthebuoy,highqualityflexible
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jointsarefitted.Theseflexiblejointspreventanysecondaryforcestobeintroducedtotheswivelandtothepip-
ingsystemwhichmayresultfromsmallmisalignmentsbetweenthebuoyandtheturretpartofthebuoysystem
duringrotation.Thesesecondaryforcesmayintroduceunexpectedfatiguetothepipingsystem,whichonitsturn
mayresultintocracksandleakage.
5.6 Leakdetection&recuperationsystem
AllBluewaterswivelsarestandardprovidedwithamechanicalleakdetectionsystem.Asanoptionalextra,the
systemcanbeextendedwithanelectronicmonitoringsystem,whichcaneitherbeconnectedtotheonboardnavi-
gationlightandfoghorn,orcanbeconnectedviaatelemetrysystemtoa(mobile)monitoringstationonboard
thetankeroronashorebase.Inadditionthesystemcanbeextendedbyarecuperationsystem,whichcollects
theleakedfluidandre-injectsitautomaticallyintothemainpipingsystem.
5.7 RemotePLEMvalveoperatingsystem
ThePLEMhasbeenoutfittedwithvalveswiththepurposeofisolatingthepipeline(s)andortheriser(s)fromthe
restofthefacility.Thisincaseareplacementorrepairofanyofthecomponentsisrequired.Ifthevalvesareused
forthispurposeonly,theoperationofthePLEMvalvesbymeansofdiverassistanceisthemostcommon,widely
acceptedprocedure.
Itwillenhancethesafetyofthebuoysystemsubstantiallyif,duringtheperiodsbetweenloadingoperations,the
valvesareclosedandthefluidpathisdividedintoseveralcompartments.Thiscanbecombinedwithprovisions
forflushingthelineinwholeorpartlytoreplacetheproductwithwater.Inparticularthisisworthwhiletobe
consideredfortherisers,buoypipingandfloatinghoses.
InordertomaketheregularopeningandclosingofPLEMvalvespracticallyfeasible,thesevalveshavetobe
operatedremotely,i.e.fromthebuoyorviaatelemetrysystemfromtheshorebase.Toachievethis,anelectri-
cal/hydraulicumbilicalcanbeinstalledbetweenthePLEMandthebuoy(totheturretpart).Intheturretspacea
nitrogen/hydraulicpowerpackandoperatingconsoleisinstalled.Duetothegeo-staticpositionoftheturret,no
electrical/mechanicalswivelsarerequiredintheumbilicalline.
5.8 Remoteoperation&monitoring
Ifdesired,thevalveoperationscanbecommandedand/ormonitoredattheshorebaseviaatelemetrysystem.
5.9 Surgereliefsystem
Surgeisthephenomenonofhigh-pressureshockwavesinapipingsystemduetosuddendrasticchangesinthe
flow.Thiscanforinstancebecausedbythesuddenclosureofavalveortheactivationofabreak-awaycoupling.
Thesesuddenhighpressuresmaycausedamagetothebuoypipingsystemsand/ortothehosearrangements,
whichmaybefollowedbyaspillage.
Fromexperienceitisknownthatthesurgephenomenonoccursinpractice.Topreventthepossiblesubsequent
damage,asurgereliefsystemcanbeinstalledasafullyintegratedsafetysystem.Forthis,surgereliefvalves
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areinstalledintheuppersectionofthemainpipingsystem.Thesevalvesopenautomaticallywhenacertain
predeterminedpressurelevelisexceededandasmallvolumeoftheproductflowsdirectlyintotanksfittedinto
oneofthebuoybodycompartments.
Aftersuchasurgeoccurrence,thetankcanbeemptiedbyre-injectingthefluidsbackintothemainpipingby
meansofanelectricalorair-drivenpump.
5.10 Break-awaycouplings
Duringtheloadingoperations,thetankerismooredtothebuoysystembymeansofahawserandtheloading
takesplaceviathefloatinghosesbetweenthetankerandthebuoy.Incasethehawserfailsandthetankerdrifts
away,thereisalargeriskthatthefloatinghosescannotbedisconnectedandclosedproperlybeforethelines
arestretched.
Topreventthebreakingofthehose(s)andacertainspillageoftheproductintothesea,automatic,mechanical
break-awaycouplingscanbeinstalledineachofthefloatinghosestrings.Thesecouplingswillfunctionwhena
pre-settensionforceinthecouplingisexceeded.Thecouplingwillsplitandtheopenendsofthecouplingwill
closeoffveryfast,limitingthespillagetoanabsoluteminimum.
5.11 Doublecarcasshoses
Duringtheoperationofthebuoysystem,thefloatinghosesaresubjecttowearandtear.Thiswearandtear
canbeontheinsidefromerosionofparticlesintheproductfluidsandontheoutsidefromUVlight,seawater
andfrommechanicaldamage.Thedoublecarcasshoseshaveadoubleskin,whichlaylooseovereachother.
Whetherthedamageiscomingfromtheinsideortheoutside,onceoneoftheskinsispenetratedandleaking,
thehosescanstillbeusedforcompletionoftheongoingloadingoperation.Thispreventsdemurragecostsof
thetankerincasehosereplacementcannotbepostponed.
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6 RequirementstostartanSPMproject
6.1 Introduction
Theneedforamarineterminalisalwayssubsequenttodecisionsonmuchlargerprojectsliketheerectionofa
refinery,powerplantorstoragefacility.Oncetheneedforamarineterminalhasbeendefinedandthetypeof
terminalisdetermined,consultantsarecontractedtopreparearecommendation.Itisofteninthisphasethat
Bluewateriscontactedbyeitheraconsultantorbytheclientdirectlyforinformationandadviceregardingthe
applicationofanSPMsystem.Bluewaterhasalwaystakenanactiveapproachininformingclientsonthepossibili-
tiesofSPMsystems,whichmostlyconcernsSPMbuoysystems.Mostimportantinthisprocessistoexplainthe
functioningofanSPMbuoysystemandtoprovideinformationonwhatistechnicallypossibleandwhatshould
beincludedinthefunctionalspecificationforsuchanSPMbuoysystem.
6.2 Informationrequired
Inordertobeofassistanceintheselectionprocessandtocometoasatisfactory,costefficient(pre-)designfor
anewSPMbuoysystem,twokindsofinformationarerequired:
- Environmentalinformation
- Functionalinformation
TheClienthastomakeavailableencompassonthefollowingenvironmentalinformation:
- Geographicalinformation(whereistheproject)
- Meteorologicalinformation(weatherconditions)
- Nauticalinformation(waveconditions,current,temperature)
- Bathometricinformation(seabedcondition)
- Soilsurveyreport.
IfcertaininformationisnotavailablewiththeClient,Bluewatercanassistinobtainingthisinformationfromexpert
companies.
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ThefunctionalinformationprovidedbytheClientshouldinclude:
- Siteinformation: - Detailedsitemap
- Lay-outoftheprojectfacilities
- Productdata: - Productstobeimportedorexported
- Compositionofproduct(s)
- Temperature
- Viscosity
- Gravity
- Tankerdata: - Size(orrangeofsizes)
- Frequencyloadingoperations
- Max.operatingconditions: - Significantwaveheight
- Waveperiodrange
- Current
- Wind
- Tidalrange
- Waterdepth
- Pipingrequirements: - Flowrate
- Piggingrequirements
- Designpressure
- Subseapipelinediameter(s)
DependentontheexperienceofClientwithsimilarterminaloperations,Bluewateradvisestomutuallydevelop
thefunctionalrequirementspriortothestartofanybudgetorpricingexercise.Bluewaterhasavastexperience
withdesigningandbuildingSPMsystemsallovertheworld.Thisexperiencemightpreventthedefinitionof
insufficientorexuberantrequirements,whatmayresultinanunsatisfactoryperformanceoftheSPMfacilityor
intoohighprojectcosts.
6.3Contractingstrategy
The marine part of an SPM buoy terminal includes two main components: the SPM buoy system and the
pipeline(s)connectingthissystemwiththefacilitiesonshore.Forthedesign,constructionandinstallationof
theSPMandthepipeline,twoexpertcontractorsareinvolved,beingtheSPMdesigner/supplier,likeBluewater
andthepipelinedesigner,supplierandinstallationcontractor.Thissecondpartyisgenerallyalsoinvolvedinthe
installationoftheSPMsystem.
TheClienthastheoptionstoeithersubcontracteachportionofthemarineterminaldirectlytoaspecialized
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companyortosubcontractthecompletemarinepartoftheterminaltooneEPCIcontractor.Inthefirstcase,Client
hastomanagethetwocontracts,theinterfacebetweenthetwocontractsandtheinterfacewiththeconnection
totheonshoreplant.Inthesecondcase,Clienthastomanageonlyonecontractandoneinterface(atthecon-
nectiontotheshoreplant).
BluewaterofferstoexecutethecompletemarinepartoftheterminalasanEPICcontractor.Dependentonthe
situationandtheextentofeachofthescopeparts,Bluewaterofferstoexecutetheprojectasamaincontractor
orasaconsortiumwithapipelinecontractor.
PhotoReportofaBluewaterTurretBuoy
InthissectionaphotoreportisenclosedshowingavarietyofbuoyprojectsBluewaterhasexecutedintherecent
years.ThephotosprovideafurtherimpressionoftheTurretBuoydesignandtheadvantagesofthisdesignas
highlightedinthisbooklet.
Ocensa,Colombia,TLU-2,TurretBuoywithworkboatmooredtoboatlanding
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ApacheStagField,Australia,TurretBuoyduringinstallation
Apache,StagField,Australia,FSOmooredtoTurretBuoy
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Ocenca,Colombia,TLU-2Terminal,InteriordeckhousewithBluewaterswivel
Figure1LargeandEasyAccessBoatlanding
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Ocensa,Colombia,TLU-2Terminal;PipingforSurgeReliefSysteminsidedeckhouse
Woodside,LegendreFieldAustralia;
Overboardpipingsolidconnectedtobuoyandwellprotected
The Netherlands
Bluewater Energy Services B.V.
Marsstraat 33
2132 HR Hoofddorp
The Netherlands
Tel +31 (0)23 568 2800
Fax +31 (0)23 565 2053
United Kingdom
Bluewater Services (U.K.) Ltd.
Bluewater House, Badentoy Crescent Portlethen
Aberdeen AB12 4YD
United Kingdom
Tel +44 (0)1224 403 300
Fax +44 (0)1224 403 340
Angola
Bluewater International B.V. “Sucursal”
Trav. Do Teatro de Providencia
No. 9, 3 Andar-Apto 1, Coqueiros
Ingombotas, Zona 4
Luanda, Angola
Tel/Fax +244 (0)222 330 573
www.bluewater.com January 2011