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Tandem Loading Guidelines Volume 2 The Use of Towing Assistance for F(P)SO and Shuttle Tanker Operations

TandamLoadingGuidelinesVolume2TheUseofTowingAssistanceforF(P)SOandShuttleTankerOperations

RevisionD IssueDate21stJune2018 Page2of23

TandemLoadingGuidelines

Volume2

TheUseofTowingAssistanceforF(P)SOandShuttleTankerOperations

Rev Date Description By Check ApprovedD 21/06/18 ReviewandUpdate BE KF KFC 17/03/02 IndustryCommentsIncorporated KJ FP-B MTB 01/10/01 RedraftedbyUKOOAcommittee BJ MT A 28/02/01 Draftforclientreview JH JRL



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Contents

ABBREVIATIONS...........................................................................................................................................................................6 1. INTRODUCTION...................................................................................................................................................................8 2. GENERALREQUIREMENTSFORTOWINGASSISTVESSELS................................................................................8 2.1. Functionalrequirements.....................................................................................................................................8 2.2. Propulsion.................................................................................................................................................................8 2.3. BollardPull...............................................................................................................................................................8 2.4. TowingRigging........................................................................................................................................................8 2.5. TowingWinch..........................................................................................................................................................9 2.6. TowlineControl.......................................................................................................................................................9 2.7. Deck...........................................................................................................................................................................10 2.8. IntegralDeckEquipment...................................................................................................................................10 2.9. AncillaryTowingEquipment............................................................................................................................10 2.10. CommunicationEquipment..............................................................................................................................10

3. TAVOPERATIONS.............................................................................................................................................................11 3.1. Overview..................................................................................................................................................................11 3.2. CrewCompetency.................................................................................................................................................11

4. ASSURANCEANDVERIFICATION................................................................................................................................11 4.1. VesselSelection.....................................................................................................................................................11 4.2. FunctionalAssurance..........................................................................................................................................11

5. SHUTTLETANKEREMERGENCYTOWING...............................................................................................................12 5.1. AssessmentofTankerAssistRequirements...............................................................................................12 5.2. ShuttleTankerType............................................................................................................................................12 5.3. ProximityofotherInstallationsandFieldSpecificSubseaInfrastructure.......................................12 5.4. FieldLocation.........................................................................................................................................................13 5.5. RisktoTAV&Crew..............................................................................................................................................13 5.6. MetoceanConditions...........................................................................................................................................13 5.7. EmergencyResponseandRescueVessel(ERRV)provision..................................................................14 5.8. ShuttleTankerApproach...................................................................................................................................14 5.9. Loading.....................................................................................................................................................................15 5.10. EmergencyOperations.......................................................................................................................................16 5.11. Disconnection&Departure...............................................................................................................................16 5.12. Procedures,TrialsandWeatherLimitations..............................................................................................16

6. SHUTTLETANKEROPERATIONALASSISTANCE...................................................................................................17



7. F(P)SOPLANNEDOPERATIONALHEADINGCONTROL......................................................................................17 7.1. General.....................................................................................................................................................................17 7.2. Operatingprocedure...........................................................................................................................................17 7.2.1. GeneralOperatingProcedureRequirements........................................................................................17 7.2.2. OperationSpecificCriteria...........................................................................................................................18

8. F(P)SOEMERGENCYSTATIONKEEPINGASSISTANCE........................................................................................18 8.1. General.....................................................................................................................................................................18 8.2. EmergencyTowingFacilities............................................................................................................................18 8.3. StationKeepingEmergencyResponseProcedures...................................................................................19 8.4. StationKeepingEmergencyResponseAssistance-MobilisationProcedure..................................19 8.5. StationKeepingEmergencyResponseAssistance–OperationsProcedure....................................20

9. F(P)SOCONTINGENCYSTATIONKEEPINGASSISTANCE...................................................................................23 10. REFERENCES...............................................................................................................................................................23



ABBREVIATIONS

The following abbreviations have been used in the body of the text

AHTS Anchor Handling Tug Supply Vessel

ALARP As Low As Reasonably Practicable Risk CMID Common Marine Inspection Document CSV Construction Support Vessel

DP Dynamic Positioning DSV Dive Support Vessel

ERRV Emergency Response & Rescue Vessel F(P)SO Floating (Production), Storage and Off take Vessel GOG/GOB line Mechanical device or wire /shackle combination fitted on centre

line to prevent awathartships movement of the tow line.

GOMO Guidelines for Offshore Marine Operations Hs Significant Wave Height

IMCA International Marine Contractors Association IMO International Maritime Organisation

MBL Minimum Breaking Load MODU Mobile Offshore Drilling Unit

NM Nautical Mile OCIMF Oil Companies International Marine Forum

OVID Offshore Vessel Inspection Database OPL Oilfield Publications Ltd.

ST Shuttle Tanker STCW 2010 International Convention on Standards of Training, Certification

and Watch keeping for Seafarers TAV Towing Assist Vessel (applied in this document to any vessel

which has a towing assist function, and which may be in addition to other roles).



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1. INTRODUCTIONThepurposeoftheseguidelinesistoenhancethesafetyandefficiencyofoperationsinvolvingtheuseofvesselsfortowingoperationsatF(P)SOfacilities,includingshuttletankeroperations.

Relevantinformation&guidanceisprovidedforusebydutyholders,relatingtotheuseofsupportvesselsforthefollowingoperations:

• ShuttleTankerEmergencyTowing• ShuttleTankerOperationalAssistance• F(P)SOOperationalHeadingControl• F(P)SOEmergencyStationKeepingAssistance• F(P)SOContingencyStationKeepingAssistance

Nothingintheseguidelines,ortheexerciseofauthorityofthepersonnel incomplyingwiththem,shalloverride the responsibilities ofOIMs andMasters from their obligation to ensure safe and injury-freeoperations.

2. GENERALREQUIREMENTSFORTOWINGASSISTVESSELS

2.1. Functionalrequirements

ThebasicfunctionalrequirementofaTowingAssistVessel(TAV)istheabilitytooperateincloseproximitytoanFP(S)OorShuttleTanker(ST),connectusingatowlineandapplyatowingforceinordertocontrolthepositionand/orheadingoftheFP(S)OorST.

ThereareseveraltypesofvesselwhichmaybesuitableforuseasaTAV,includingenhancedERRVs,AHTS,andMulti-purposetugs.

2.2. Propulsion

AstheTAVwillberequiredtoworkincloseproximitytotheF(P)SOandshuttletankersinvaryingweatherconditionsitmustbehighlymanoeuvrableandhavesufficientreservepropulsioncapabilitytominimisethepotentialforacollisionintheeventofanysystemfailure.

2.3. BollardPull

It isrecommendedthatDutyHoldersconductananalysisofthecontinuousBollardPullcapabilityofaproposedTAVtoensurethatitissufficientfortheintendedoperation.

ThebollardpullselectedshoulddependonthefunctiontheTAVisexpectedtoperform,andshouldbeverifiedbyacertifiedbollardpulltest.VesselswithexistingBollardPullcertificatesneednotbere-tested,providingnosubsequentmajormodificationshavebeenmade to thevesselormachinerywhichcouldaffectthetowingcapability.

2.4. TowingRigging

TheTAVtowingequipmentdesignshouldalloweasyconnectionofthetowlinewiththeminimumofhumaninterventiononthedeck.Connectionoftowingequipmentinadverseweathercanbeveryhazardousandthedesignshouldminimiserisktopersonnelondeck.

Theloadsontowingequipmentshouldbecapableofbeingmonitoredfromthebridge.

TheTAVshouldbeequippedwithagalvanised,lubricated,&certifiedtowwiremountedonthetowingwinch.



WhereaTAVisnotfittedwithaconstanttensionwinch,anylonstretchershouldbeusedoutboardofthetowlinetohelpabsorbshockloadingwhenworkinginaseaway.TheMBLofthestretchershouldbeatleast1.5xTowlineMBL. Ifthestretcherbreaksinoperationthenthecontingencywillbetore-connectthetowlinewithoutthestretcherandpayoutadequatetowlinebeforere-commencingthetow.

Thevesselshouldcarryafullycertifiedsparesetofshacklesandotherjewelleryrequiredtoconnecttothetankerrigging.JewelleryshouldhaveanMBLof110%oftheTowlineMBL.

2.5. TowingWinch

Aremotelyoperatedtowingwinchisanessentialrequirementforthesafetyofthecrewandforeffectiverecoveryoftowlinesinadverseweatherconditions.

Thetowwinchshouldcompriseasaminimumtwodrums,aworkingdrumandatowdrum.Thewinchshouldberemotelyoperatedfromanaftbridgecontrolconsole,preferablybysinglejoystickoperation.Thestatusofthetowwinch(hydraulicpressure,brakeposition,speed,towtension,lineoutetc.)shouldbedisplayedatthewinchoperationconsole.Localwinchcontrolsshouldbepositionedwheretheycanbeoperatedsafelygiventhattheymayhavetobeoperatedwhilstthewinchandtowwireareunderheavyload.

Thewinchshouldbedesignedwithanemergencyquickreleasemechanismhavingthecapabilitytoreleasethewinchbrakeandreducethetowlinetensionifrequiredtomaintaincontrolofthevessel,includinginthosecircumstanceswhichposeariskof‘girting’orcapsizing.Crewmembersmustfamiliarisethemselveswiththeseship-specificarrangements, includinglimitationsifany. Itmustbeborneinmindthattheseemergency quick release arrangements may not always release instantaneously due to variouscontributingfactorssuchasthedirectionofpull,theheelingangleetc.andhenceallowancemustbemadewhencontemplatingitsactivation.

2.6. TowlineControl

Atowlineundertensionwillexertaheelingmomentonthevesselifthelineisleadingoffinanydirectionotherthanoverthecentreofthestern.Aswithanyvesselwhichissubjecttoaheelingmoment,arightinglever is formed as the centre of buoyancymoves in the same direction as the heelingmoment. Themovementofthecentreofbuoyancyimpartsarightingmomenttoreturnthevesseltoanuprightcondition.However,itispossiblefortheheelingforceexertedbythetowlinetoexceedtherightinglever,resultinginthevessel‘girting’andpotentiallycapsizing.Girtingcanoccurveryrapidlyandincidentshaveoccurredwherecrewmembershavenotbeenabletoescapeintime.Itshouldnotbeassumedthatthewinchorwinchbrakewillrenderorthatthetowlinewillbreakbeforeapotentialgirtingsituationoccurs,aslessforcemayberequiredtocapsizethetug.

ATAVshouldbeequippedwithameansofcontrollingtheleadofthetowwire,usingtowingpins,atowingpod,oragog/gobwirewhichcanbemechanicallyoperatedfromaremotelocation(e.g.apoweredtuggerwinchorcapstan).

Information should be made available to the vessels crew and displayed on the bridge showing themaximumverticalandhorizontal forcesthatcanbeexertedonthevesselwhilstremainingwithinIMOstabilitycriteria.Thisinformationshouldbedisplayedinaneasytounderstandformatsothatoperatorscancheckagainsttheactualtowlinetensionandensurethattheydonotexceedthelimitingcriteria.

Itshouldbenotedthatwhenoperatingwithashortlengthoftowlinedeployed,thedifferenceinheightbetweentheF(P)SO/STandthedeckoftheTAVcancausethetowlinetoleadupatapooranglewhichmayresultindamagetothetowingwireandlesseffectivecontrol.



2.7. Deck

Thevesselaftdeckshouldbewoodensheathedexceptinanchorhandlingareasandwhereintegraldeckequipment is located. The deck should bewell illuminatedalong its length,andhavebarriersateachprovidingsafehavensforpersonnel.Asfaraspracticable,duringtowingoperationsthedeckshouldbeclearofobstructionswithalllooseequipmentsecurelystowed.

The vessel sternmust incorporate a roller, free from sharp edges, gouges or protrusionswhich coulddamagethetowwireorpreventitfromfreelateralmovement.

Whenengagedintowingoperations,allweather-tightdoors,hatches,manholes,portsandwindowsontheweatherdeckshouldbeclosedandsecuredtopreventdownfloodingintheeventofdeckedgeimmersion.Achecktoensurethatsucharrangementsareclosedshouldbeincludedinapre-towingchecklist.

ShouldasituationarisewheretensioninthetowlinecausestheTAVtoheeloverandthedeckedgetobeimmersed,thedelayindownfloodingaffordedbyhavingwatertightintegrityontheweatherdeckmaybevital in providing sufficient time for the quick releasemechanism to be activated, for the vessel to bemanoeuvredtolessenthetensioninthetowlineandforpersonneltoreachasafelocation.

Watertightandweather-tightdoors,hatches,vents,windows,ports,sidescuttles,allassociatedsealsandsecuringdevicesandtheautomaticclosingdevicesonventilatorsshouldbeincludedinthevessel’splannedmaintenancesystemandbeinspectedandtestedregularly.

2.8. IntegralDeckEquipment

The aft deck should be fitted with stoppers, comprising either ‘shark’s jaws’ or a ‘Karm fork’ typemechanismforsecuringthetowingwire,pennantsetc.

• Thestoppersshouldbeequippedwithsuitableinsertsforvariouswiresizes.• Theoperatingpanelforthepinsandforksshouldbeattheaftbridgeconsole.• Thepanelshouldhavestatuslights,withanaudiblewarningsoundingintheeventoflowhydraulic

oilpressure.

Thedeckshouldalsobeequippedwithremotelyoperatedcapped(orwinged)towingpinsclosetothestern,designedtopreventthetowlinepassingoverthequarter.

2.9. AncillaryTowingEquipment

TAVsusedforassistingwithhawserandhosetransfersshouldbeequippedwithsuitablegrapples,boathooks,wirestropsandshacklestoenablesaferetrievalanddeploymentoftheequipment.

Inaddition, thevessel shouldbeequippedwithaPneumaticLineThrowingApparatus (PLT).TheTAVshouldbepreparedbywayofidentifiedpositionswherethePLTcanbesafelyandeffectivelyfiredfrom,andinadditionanareashouldbedesignatedforreceiptofaPLTprojectile.ThecrewshouldbeadequatelytrainedintheuseofsafeandefficienthandlingofthePLT.

2.10. CommunicationEquipmentThevesselshouldbefittedwithatleasttwomethodsfordirectcommunicationwiththeF(P)SO/ST.

An adequate number of portableVHF/UHF sets should beavailable toallow the personnel on deck tocommunicatewiththebridge,andinadditionapublicaddresssystemwithloudspeakersondeckshouldbeavailableforuseintheeventofradiofailure.



3. TAVOPERATIONS

3.1. Overview

ThefollowingsectionprovidesgeneralguidanceontheutilisationofTAVs.Specificproceduresshouldbedevelopedforeachoperation.

WhereanERRVisusedtoperformTAVfunctionsthentheroles,responsibilitiesandprecedenceshouldensurethattheERRVprimerolesandresponsibilitiesarenotcompromised.

3.2. CrewCompetency

Thenumberofcrewandindividualcompetenciesmustbeadequateforall intendedaspectsoftheTAVoperation,includingbridgeoperations,shipmanoeuvringanddeckoperations.

Thefollowingspecificcompetencyrequirementsmustbefulfilled;

• CompliancewithIMOSTCW2010standardsofcrewcompetency.• Competencyinshiphandlingincloseproximityoperations.• Masterandotherkeypersonneltohavepreviousexperienceinsimilaroperations,ortowing/

anchorhandling.• Seniordeckofficerstobecapableoftakingcontrolofthevesselwhileincloseproximitysituations.

Whenusedforshuttletankeroperations,theTAVcrewmustbefamiliarwiththecontentandrequirementsofthefieldspecificJointOperationsManual.Industrystandardorowner/operatorstowingmanualsshouldbeavailable,providingguidanceontowvesselhandlinganddeckpractices.

4. ASSURANCEANDVERIFICATION

4.1. VesselSelection

DutyholdersshouldverifythatanyproposedTAVissuitablefortheintendedusebycarryingoutanOVIDorCMIDinspection,oralternativelybyreviewofanexistinginspectionreport.

In addition to an industry standard inspection, the suitability of the vessel for the intended operationshouldbecheckedbycomparingthecapabilitiesofthevesselagainstthespecificoperationalrequirements.

4.2. FunctionalAssurance

Wherepractical,itisrecommendedthatatrialconnectioniscarriedoutinthefollowingcircumstances;

• Foraplannedheadingcontroloperation,inadvanceofthecommencementoftheworkscopeforwhichtheheadingcontrolisrequired.AsanexampleitisconsideredprudenttoconnecttheTAVandcarryouta limitedperiod (e.g.one-hour)F(P)SOheadingcontrol,12 to24hoursprior toarrivalofaDSV/CSV.

• Whenavesselismobilisedforshuttletankeremergencytowingsupport,withouthavingrecentexperienceofthetypeofoperation.

TheintentionofatrialconnectionistoensurethatwhentheactualrequirementfortheTAVarises,therewillbeassurancethattheconnectionandcontroloftheF(P)SOortankerwillhappenasintended.



5. SHUTTLETANKEREMERGENCYTOWING

5.1. AssessmentofTankerAssistRequirements

CurrentUKSafetyCaseregulationsrequireallF(P)SOsoperatingwithintheUKCStohavearrangementsinplace for the rescueandrecoveryofpersonnel. This isnormallyprovidedbymeansofanEmergencyResponseandRescueVessel(ERRV),withsomeERRV’salsobeingcapableofperformingemergencyoroperationaltowingassistance.Itisrecommendedthatanassessmentoftheneedtoprovidein-fieldtowingassistcapabilityiscarriedoutaspartofthefielddevelopmentconcept.

The decision on whether and when to use towing assistance vessels (TAV) should be based on thedemonstration ofALARP life of field risks for the development asawhole. TheALARPdemonstrationshould take account of the fact that whilst the provision of a TAV may be beneficial, it involves theintroductionofanadditionalhazardwherebyasmallvesselisrequiredtomanoeuvreincloseproximitytooneormorelargervessels.

ThefollowingfactorsshouldbetakenintoconsiderationinassessingtheneedforusingaTAVinanoverallconceptriskassessmentofthefield.

• Shuttletankertype(NonDP,DPI,DPII)• Proximityofotherinstallations(nearbyplatformsorin-fieldMODU)• FieldSpecificfeatures(location,environmentalsensitivity,prevailingweather)• RisktoTAVcrew

TheAssessmentshouldbereviewedperiodicallythroughoutfieldlifetoaccountforanychangeswhichcouldaffecttheinitialdecision.

In the event that an ERRV is utilised for this additional role then Oil & Gas UK’s “ERRVManagementGuidelines”andTheGuidelinesforMarineOperations(GOMO)shouldbecompliedwith.

Wheretheremaybea limiteddurationrequirementfortankertowingassistance(e.g.whileaMODUistemporarilylocatednearbyanoperationalF(P)SO),useofanAHTSmaybethemosteffectivemeansofprovidingTAVcover.

5.2. ShuttleTankerType

DPIItankersarethepreferredindustryoptionintheUK.DPIIClassvesselshavealevelofredundancysuchthatnosinglefaultinanactivesystemwillcauselossofpropulsionandcontrolcapability.

DPIEnhancedtankershavealesserlevelofequipmentredundancyandhaveaninherentlygreaterriskofafailurewhichcouldcausealossofallpropulsion.

5.3. Proximity of other Installations and Field Specific SubseaInfrastructure

ThelevelofriskpresentedbyadriftingtankerinthevicinityofanF(P)SOaresignificantlyhigherwhenthereareoneormoreotherinstallationsnearby.

Thelargedisplacementofatankermeansthatanycollisionwithaninstallationislikelytoresultinamajoraccident. The decisionwhether to havea TAV available during shuttle tanker operations should takeaccount of the number, proximity and type of platforms in the surrounding area, together with theestimatedtimerequiredforconnectionandcontrolofadriftingtanker.



Table1TowingVesselConnectionTimeExample

OPERATION WINDBeaufort<F5

WINDBeaufort6-7

WINDBeaufort8-9

Makeconnection 10min 15min 20minTakecontrol 5min 5min 10minTowoutofsector 10min 10min 15minTOTAL 25min 30min 45min

Driftrateof120,000tonnevesselinincreasingwindspeedslightandloadedcondition

5.4. FieldLocation

Theleveloftankerassistanceprovidedshouldreflecttheproximityofthefieldtothenearestcoastlineandanyareasofparticularenvironmentalsensitivity.

5.5. RisktoTAV&Crew

TheriskstotheTAVandcrewshouldalwaysbetakenintoaccount.AcloseproximitycollisionhasthepotentialtobemuchmoreseriousfortheTAVanditscrewthanforeithertheF(P)SOortanker.

Thedeckcrewareatriskofpersonalinjuryparticularlyduringconnectionanddisconnectionoftowinggearinaseaway.Itisrecommendedthatdutyholders,tankeroperatorsandTAVoperatorsconsiderthebenefitsofusinglightweighthigh-strengthsynthetictowlineequipment.

5.6. MetoceanConditions

ApermanentTAVmayberequiredwhenanF(P)SOis locatedinanareawheretherearehigh surfacecurrents,widelyvariablewindconditions,orlongperiodsofadverseweather.InsomecircumstancetheuseofaTAVmayreduceoperationaldowntimebyassistingwithinitiallineconnectionfromeitheranF(P)SO,STLorSALtypesystem.

0

1

2

3

4

5

6

0 5 10 15 20 25 30 35 40 45 50 55 60

light

loaded

Wind speed in knots

Drift speed in knots

Tow connection times [ 25 mins ] 30 mins ] over 45 mins >



InareasofhighcurrentthereisatendencyforaloadedF(P)SOtobe‘currentrode’withtheheadingintothe prevailing current and a light tanker to be ‘wind rode’ heading into the wind, thus creatingmisalignmentreferredtoas‘fishtailing’.Inthiscircumstance,‘tauthawser’modemaybeutilisedbythetankertomaintainalignmentwiththeF(P)SO,andinadditionaTAVmaybeconnectedtothetankersterntoassist.

IngeneralifanF(P)SOislocatedinanareawheretherearehighsurfacecurrents,significanttidaleffect,widely variablewind conditions, or long periods of adverseweather, then the following should beconsidered;

• TheinherentadditionalreliabilityandcapabilityprovidedbyDPClassIItankers.• The requirement for increased levels of propulsion andmanoeuvrabilitycapacity for anyTAV

assignedtoprovideoperationaland/oremergencyassistance.

Foralllocations,theselectionofTAVintermsofsize,propulsioncapabilityandtheneedtooperatesterntoweather(withtheincreasedrisktodeckcrews)mayleadtoithavingsea-statelimitationswhicharelowerthanthestandardlimitsfortheofftakeoperationitisintendedtosupport.

5.7. EmergencyResponseandRescueVessel(ERRV)provision

AllUKsectorF(P)SOscurrentlyhaveanemergencyresponse&rescuevessel(ERRV).Theconceptriskassessment for newdevelopments should always consider themerits andhazards of having anERRVperformasecondaryroleasaTAV.AdualroleERRV/TAVcanincreaseoperationaluptimeandprovidecontingencysupportintheeventofanabnormalsituation,buttheadditionalroleshouldonlybecarriedoutwhenitdoesnotimpairthevessel’sabilitytoperformitsprimaryemergencyresponseandrescuefunctions.

TheEmergencyResponseandRescueVesselManagementGuidelines (Oil&GasUK)includesguidancerelatingtotheuseofanERRVforanadditionalrole

“Intheeventthattheemergencyresponseandrescuevesselisutilisedinanadditionalrolethenanassessmentshouldbemadeofanyadditionalrisksinvolved,inparticularanythatcouldaffectitsrescueandrecoveryrole.Theriskassessmentshouldbecarriedoutbyknowledgeable,experiencedandcapablepersonscloselyinvolvedwiththework.Allrisksshouldbeconsideredtogether,andmitigatingorremedialmeasuresshouldbeputinplacetoreducethetotalresidualrisktoanacceptablelevel.Wheretheassessmenthasusedthetermslow,mediumandhightheresidualriskshouldnotbehigh.Acopyofthedetailsoftheriskassessmentshouldbekeptonboardtheshipandshouldbemadeavailabletosurveyorsandotherinterestedpartiesattheirrequest.”

5.8. ShuttleTankerApproach

InadvanceofarrivalofaST,theTAVshouldpreparethetowingequipmentreadyforimmediateuseifrequired,andradiocontactshouldbeestablishedwhentheShuttletankerreachesthe10nmzone.TheTAVshouldbepositionedsuchthatitcanreadilyassistthetankerifrequested,whilemaintainingclearofthetankersapproachroute,andalwaysprovidingacleardeparturerouteforthetankerintheeventoftheapproachbeingaborted.

Similarly,theSTshouldensurethatitsemergencytowingsystemisreadyforimmediatedeployment.

When there are other installations nearby, there is a higher collision risk potential in the event of STpropulsionfailureandtheF(P)SOoperatormaydefineprohibitedandrestrictedareas.

Adiagramofatypicalarrangementisshown,incorporatingthefollowing;

• AProhibitedZoneofradius1000maroundanadjacentMODU,whichashuttletankerisforbiddenfromenteringduringapproachanddeparture.



• ARestrictedSectorbetweentheFPSOandadjacentinstallation,whichashuttletankermayonlyenterfollowingagreementwiththeF(P)SOandotheradjacentinstallation.Thisrestrictionappliesduringshuttletankerapproach,departureandalsowhilemooredtotheF(P)SO.

Theextentandnatureofanyprohibitedorrestrictedareaswilldependonarangeoffactorsincludingfieldlayout,proximityofanyadjacentinstallationsandlevelofshuttletankerredundancy,andwillbedefinedwithinthefieldspecificjointoperationsmanual.

5.9. Loading

STsdonotgenerallyneedon-goingassistancewhencargo transfer is takingplace,although itmaybedecidedtohaveaTAVconnectedtotheSTsternincertaincircumstances,e.g.;

• Wherethereisasignificanttidaleffect–inordertoprevent/controlfishtailing(largedifferencesbetweenF(P)SOandSTheading).

• Wherethereisanotherinstallationwithinrelativelycloseproximity(<4NM)–inordertoreducetheriskofcollisionintheeventofconcurrenthawserfailure/ESD2andSTlossofpropulsion.

ConsiderationmustbegiveniftheSTisoperatinginDPmodeandatowinghawserisconnectedasitgivesanunknownforceontheSTDPsystem.

DedicatedTAVsshouldremaininapositiondownenvironmentfrom,butreasonablyneartheSTsothattheycangiveassistanceifrequired. TheTAVshouldnotstayincloseproximitytoeithertheSTortheF(P)SOunlessrequestedtodoso.

IntheeventofpropulsionfailureonthetankerwhilstconnectedtotheF(P)SO,theTAVshouldconnecttothesternofthetankerifrequestedtodosobytheST.



5.10. EmergencyOperationsDealingwithemergencysituationsinadverseweatherrequireparticularcareand,theTAVMastershouldconsiderthesafetyofhiscrewduringsuchsituations,especiallywhenattemptingtopickupatowinheavyseaswhenthedeckistakingonwater.

IntheeventofSTpropulsionorcontrolsystemfailureandariskofcollision,theTAVmayberequestedtoconnecttothesternofthetanker.

IntheeventofalossofpositionoftheSTanddrifttowardstheF(P)SO,theTAVshouldprovideassistanceasrequestedbytheSTMaster,butshouldnotputitselfinapositionbetweentheFP(SO)andtheST.

5.11. Disconnection&DepartureTAVassistanceisnotgenerallyrequiredduringthedisconnectionanddepartureprocess,otherthaninthefollowingcircumstances;

• An operator may stipulate that if a ST is within a restricted sector, disconnection is onlypermissiblewithaTAVeitherinattendanceorconnected.

• TAVassistancemayberequiredatSTL/SAL locations for reconfiguring, stowingor installinglightingonfloatingmessengers.

5.12. Procedures,TrialsandWeatherLimitationsWhereaTAVisrequired,regulartrialstomaintaintheeffectivenessoftheemergencytowingarrangementsshouldbecarriedoutbetweentheTAVandSTs.Thefrequencyofthesetrialswillbebasedontheresultsachieved,butingeneralwillbeinaccordancewiththeOil&GasUKguidelines;

• DPClassIvessels:Emergencytowingshouldbeconductedminimumevery3months;• DPClassIIvessels:Emergencytowingshouldbeconductedminimumevery6months.• AvesselnewtothefieldshouldperformTowingTrialsaspertheprocedurepriortofirsthookup.

More frequent trials may be carried out to ensure all personnel are familiar with the system andprocedures,particularlyduringtheinitialcontractperiodofanextendedTAVdeployment,whensignificantchangesinpersonnelareinvolvedorwhenaspecificneedhasbeenidentified.

TheTAVshouldhaveacopyofthefieldspecificF(P)SO/ShuttleTankerjointoperatingproceduresonboard.TheseprocedureswillhighlightanynormaloperatingdutiesthattheTAVisexpectedtoperformpriortoorduringofftakeanddefineweatherlimitationsforspecifictankeroperationse.g.initialtankerconnectionandon-goingofftake.Theproceduresshouldalsodefinetherequirementsandlimitsforanyjointtowingtrialsorconnectionexercises.Asaguideline,emergencytowingtrialsshouldbeperformedwithsea-stateoflessthan3.5mHs.tominimiseneedlessrisktotheTAVcrew.Trialsinhighersea-statesshouldbelimitedtotheminimumrequiredtoprovethesystemcapability.

TheTAVshouldhavecopiesofrelevantindustryguidanceonrescuetowingandequipmentonboardorpreferably theowner/managersdetailed in-house guidanceextracted fromthesedocumentsandappliedtoSTtowing.Thisshouldcover

• Equipment,techniquesandtheneedtopayoutadequatetowlinebeforetakingload.• Likelyfreedriftingorientationofdisabledtankers.• Directionofwave,windandcurrentyawmomentsonstationarytankersversustankerheading,

e.g.1. Tankerheadwillfallawayfromtheweatherdirectiontoonesideorotherifhawserparts

followingblackoutinmoderatesea-state.2. Tankerisprobablyeasytokeepturninginthatdirectionuntilheadingbetween45degree

and135degreeheadingrelativetowindandwaves.3. Oncethetankerheadhasstartedtofallawayinaparticulardirectionitisprobablyvery

hardandwastedefforttryingtoreversethedirection.



4. Alltankersunderaftemergencytowwillturnmoreeasilyintotheweather,iftheTAVfirstbuildsupasternwayonthetankerandtheninitiatestheturn.

5. EvenifashuttletankerhasamainengineblackoutitmaystillbeabletorunbowandsternthrusterstohelptheTAVtoturnthehull.

• WinchtechniquestoenabletheTAVtoturnitselfupintotheweatherandthentakeloadonthetowwirewithoutexcessivesnatchloading.

6. SHUTTLETANKEROPERATIONALASSISTANCEAtsome fieldsaTAVcanbeused toassistwithexportoperationsbycarryingoutoneormoreof thefollowingfunctions;

• Deploymentandrecoveryofmooringsystemmessengerlines• Assistancewithmooringthetankeratthelocation.• Assistancewithtankerheadingcontrolinnormaloperations.• Other assistance, e.g. providing source of illuminationduring periods of darkness,monitoring

separationdistance,checkingtheconditionofhoseandhawser,etc.

AstheTAVisintendedtoassistwithexportoperationsandthusshouldbeabletofulfilthisrolewithoutpresentinganysignificanthazardstotheF(P)SO,shuttletanker,itselforpersonnelonanyofthesevessels.

Fortankersworkingintauthawsermodewithlimitedtransversethrust,theTAVmaybeusedtolayoutthefloatingmessengerlinesasternoftheF(P)SOandprovideassistanceifrequiredfortheSTtopickuptheselines.Inthiscasethepickupismadeatconsiderabledistanceoffthesternandnotattheloadingpoint.DuringtheapproachphasetheTAVshouldhaveacommunicationscheckwiththeSTandF(P)SO.TheriskofthemessengerfoulingtheTAV’sthrustersshouldberiskassessedandmitigatedagainst.

7. F(P)SOPLANNEDOPERATIONALHEADINGCONTROL

7.1. General

ThissectionprovidesguidanceforusewhenF(P)SOheadingcontrolmayberequiredforthefollowingtypesofoperations;

• DivingorsubseaconstructionworkwithinanF(P)SOswingcircle.• F(P)SOmooringinspectionorreplacement.• Liftingoperationsorconstructionactivitiesinvolvingtransferbetweenageostationaryturretand

rotatingF(P)SOhull.

7.2. Operatingprocedure

Operatingproceduresmustbedevelopedforeachdifferenttypeofoperation.Theformofproceduresmaycompriseeitherofthefollowing;

• A generic F(P)SO heading control procedure, supplemented for each operation by separatelydocumenteddetailsofthespecificoperationandlimitingfactors.

• Aseparateheadingproceduregeneratedforeachplannedoperation.

7.2.1. GeneralOperatingProcedureRequirementsEachprocedureshouldincludedetailsofthefollowing;

• Personnelresponsibilities.• Communicationfacilitiesandcontactdetails• Communicationprotocols;• Radiotoolboxtalks&agenda



• Routinereportingpoints• Deviationreportingcriteria• TAVspecificationrequirements(incl.vesselcontrol,propulsion,redundancy,fuelduration,towing

equipmentandcrewcompetency)• Definedoperatinglimits;

- Weatherlimitations- TAVpropulsionutilisation- Towingequipmentstrengthutilisation

• Descriptionof the terminationandanycomponentsontheoutboardendof theF(P)SO towingpennant.

• Preferredpositionofthesupportvesselduringtheinitialmessengerlineconnection• Messengerandtowlinetransferandconnectionprocedure• Locationof subseaequipment,whichmaybepotentiallydamagedbydroppedequipmentora

towlinecatenary.• Towlinerefreshingrequirements• Towlinedisconnectionprocedure• Emergencycallandstopprotocols• Emergencyresponsearrangements

7.2.2. OperationSpecificCriteriaWhenheadingcontrolisrequiredtoallowaccessfordivingorsubseaconstructionworkswithinorclosetotheF(P)SOswingcircle,theallowableF(P)SOheadingsectorsmustbejointlydefinedbytheF(P)SOoperatorandDSV/CSVoperator.

TheF(P)SOshouldholdanelectronicfilewithrelevantdetailsofallsubseainfrastructuresthatmaybeaffected by the catenary of the tow wire or any operations carried out by the support vessel. ThisinformationshouldbeavailableinasuitableformatthatcanbetransmittedelectronicallytotheTAV.

Operatingproceduresshouldbeclearandconcise.

8. F(P)SOEMERGENCYSTATIONKEEPINGASSISTANCE

8.1. General

F(P)SODutyHoldersmustevaluatetheriskandmakeappropriatecontingencyplansforforeseeableeventsincludingmooringsystemfailureand/orlossofheadingcontrol.

Intheeventofafailure,oneoftheinitialresponseactionsis likelytobedeploymentoftheinfieldTAVand/ormobilisationofanAHTSvesselforconnectiontotheF(P)SO.

Thissectionprovidesguidanceonthefollowingaspectsofemergencyresponse;

• ProvisionoffacilitiesonboardeachF(P)SOtopermitsafeandtimelyconnectionofaTAVintheeventofastationkeepingemergency.

• DevelopmentoffieldspecificproceduresrelatingtoTAVselection,mobilisation,connectionandoperation.

8.2. EmergencyTowingFacilities

FailureofanF(P)SOmooringsystemwillrequiretheuseofaTAVtoassistwithstationkeeping,withthevesselconnectedtothebowoftheF(P)SOusinganemergencytowingarrangement.

The arrangement should as far as practicable replicate the standard features of an IMO compliantemergencytowingsystem(asfittedonalltankers>50,000teDWT),havingthefollowingcharacteristics;

• Capableofdeploymentinanyweatherconditionsandwithoutexposingpersonneltoriskofinjury.



• Capableofdeploymentwithnorequirementforpowersupply(black-outcondition).• Comprisingtowingcomponentsandconnectionswithaminimumbreakingloadof200T• Incorporateatowingpennantofsufficientlengthtopermitthetowingvesseltomaintainasafe

clearancefromtheF(P)SOwhilethetowingconnectionisbeingmade.

SomeF(P)SOsmaybefittedwithEmergencyTowingSystemsatthestern, intendedonlytoassistwithheadingcontrolintheeventoffailureoftheF(P)SOheadingcontrolsystem.

TheFP(S)Otowlineconnectionandassemblymaycompriseeitherofthefollowingarrangements;

• Chafechainsecuredtoatowingbracket,passingthroughafairleadandconnectingtotheTAVtowline.

• Shuttletankerhawser(manyofftakehawser&reelsystemscomplywiththerequirementsofanemergencytowingarrangement).

ExamplesofF(P)SOemergencytowingarrangementsareshownattheend.

8.3. StationKeepingEmergencyResponseProcedures

Itisrecommendedthattwoseparateproceduresshouldbedevelopedinlinewiththefollowing;

• AprocedureforusebythoseresponsibleforsourcingandmobilisingtheTAV(s),equipmentandpersonnelrequiredtoassistwithstationkeeping.

• A procedure for use by those on board the F(P)SO and TAV(s) covering the connection andoperationoftheassistingTAV(s).

8.4. StationKeepingEmergencyResponseAssistance-MobilisationProcedure

ThedevelopmentofaMobilisationProcedureisintendedtoassistintheresponsetoanymajormooringorheading control failure. The purpose of the procedure is to ensure the fastest possible response forsourcing,selectingandmobilisingsuitableTAV(s)andanyshorebasedequipment.

The procedure should document pre-determined information relating to vessel selection criteria,equipmentandpersonnelrequirements,tominimisethedecisionmakingandsourcingofinformationatthetimeoftheincident.

AsuggestedcontentlistingfortheemergencyresponsemobilisationprocedureforaspecificF(P)SOisasfollows;

1. Personnelresponsibilities:FPSOOIM,TAVMaster,AHTSMaster.2. Contactdetails

• F(P)SO• Onshoreemergencyresponse• DutyHolderlogisticsandchartering• Personnelsuppliers(i.e.TowMasters,Surveyors)• Equipmentsuppliers(ifrequired)

3. Vesselselectioncriteria4. Guidanceonvesselchartering&mobilisation5. Equipmentrequirementsandstoragelocation(s)6. F(P)SOtowingconnectionfacilitiesandmethodology7. Provisionofstationkeeping/headingcontrolprocedures



8.5. StationKeepingEmergencyResponseAssistance –OperationsProcedure

TheprocedureprovidedforusebytheTAVMastershouldprovidetheessentialinformationrequiredbytheMasterforsafeconnectiontotheF(P)SOandsubsequentstationkeepingassistance.

Theprocedureshouldbeasconciseaspossible,whileincludingthefollowinginformation;

• Designatedcommunicationfacilitiesandcontactdetails.• AdiagrammaticsketchshowingthelocationandarrangementoftheF(P)SOemergencytowing

equipment.• Descriptionoftheemergencytowingarrangement.• Methodforinitialconnectionanddeploymentoftheemergencytowingarrangement.• Summaryoflimitingfactors(incl.subseaequipment).

AnexampleofanF(P)SOEmergencyTowingprocedureisshown(ref-xxxxx).

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9. F(P)SOCONTINGENCYSTATIONKEEPINGASSISTANCE

ContingencyF(P)SOstationkeepingassistancemayberequiredorimplementedinthefollowingscenarios;

• KnownweaknessorwearinanF(P)SOmooringsystem.

• Reducedornon-availabilityofF(P)SOthrusterscapacity(wherethrustersarerequiredforstation

keeping)

• FMEAprovingtrials,reducedpowergenerationcapacityorotheroperatingconditionwhichcould

introduceariskoflossofstationkeepingcapability.

• Fortrainingandfamiliarisationinthedeploymentofemergencytowingequipment

ThesesituationsandtherequiredresponsedifferfromtheemergencyconditionslistedinSection7,inthe

followingways;

• TheyallowforaplannedmobilisationandconnectionofaTAV.

• Theymayeitherutilisetheemergencytowingarrangementdescribedinsection6,ormaybebased

onaseparatetowingarrangement.

• ContingencyarrangementswouldnotnormallyinvolveconnectionofaTAVinadverseweather

conditionsandsomaybebasedontheuseofpoweredequipmentandpersonnelontheF(P)SO.

10. REFERENCES

• DetNorskeVeritas(DNV)‘RulesforPlanningandExecutionofMarineOperations’.

• Oil&GasUKEmergencyResponse&RescueVesselSurveyGuidelines

• Oil&GasUKEmergencyResponse&RescueVesselManagementGuidelines

• GuidelinesforOffshoreMarineOperations(GOMO)

• CommonMarineInspectionDocument(CMIDbyIMCA)

• OffshoreVesselInspectionDocument(OVIDbyOCIMF)

• GuidelinesfortheApprovabilityofTowingVessels(NobleDenton)

• RescueTowing–OilfieldSeamanship–Volume1(OPL)

• AnchorHandling–OilfieldSeamanship–Volume3(OPL)

• MSC.1/circ 1255 Annex Guidelines for owners/operators on preparing emergency towing

procedures.

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