Application

+ Construction of Offshore Wind Farms (OWFs) – Monopile Foundations Installation

monopile gripper Arms (mgA) Fixing the position of the monopiles during lowering to the seabed for stability and safety

The Gripper Arms provide the horizontal restraint required to resist environmental forces acting on the large foundation piles during installation, providing a necessary support for efficient installation and to reduce safety hazards.

• Providethehorizontalrestraintrequiredtomaintainaccuracyandseepuppileinstallation

• Armsrequireminimaldeckspace.Theyaremechanicallystowed“latched”atmaindecklevel.

• Inherentlysafewithfailsafehydraulicsandredundancy

• Singleconsoleondecklocatedonthedeckforefficiency

benefits relevAnt codes, stAndArds & legislAtion

TheMonopileGripperArmsystemcomplieswiththerequirementsof:

• DNV-OS-C101-DesignofSteelStructures,General,LRFDMethod,April2011

Alloperationsshallbeengineeredinaccordancewiththemostrecentversionsof,orsimilarto:

• DesignaccordingtotheregulationsstatedintheEuropeanMachineryDirectiveRegulationsandderivedstandards(e.g.ENISO14122)

• NobleDentonGuidelines0030–GuidelinesfortheMarineTransportations

• DNVRulesforPlanningandExecutionofMarineOperations(DNV-OS-J101)

• DNV-GLGuidelines(DNVGL-ST-N001)

• ApplicableDanishLaw

• InternationalMaritimeOrganizationStandards&Guidelines

• SOLAS&MARPOL

Houlderhasoneunitavailableforhire.

hire options

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design pArAmeters

Themaindesignparametersarepresentedbelow:

MainDesignParameters

Monopilemaxdiameter 7.5m

operAting conditions

Themainoperatingconditionsarelistedbelow:

MainOperatingConditions

Significantwaveheight 2m

Maxcurrent 3knots

Conditionsvarywithpilediameter.Smallerpilesmay

havehigherlimits.

system specificAtion

Inrecognitionofthesystemrequirementsandinresponsetogeneralrequirements,themaindesignspecificationsarelistedbelow:

• Tobefittedonthedeckofanominatedconstructionvesselinalocationwithsufficientspacetomaximisethecapacityofthemaincrane

• Shallprovidelateralstabilityandrestraintomonopiles

• Maximumpermissibleloadduringtheinstallationofpilesisapproximately150tsideload

• ShallbedesignedtowithstandallforcesimposedduringthepositioningofmonopilestakingintoaccountallnecessaryDAFfactorsandthepotentialloadsimposedbypileoscillationsduringinstallation

• Thesystemshallprovideadequatelateraladjustabilitytoensurethepileisinstalledwithinaverticaltoleranceof+/-0.25º

• Toleranceforpositioningradiallyinplanfromconsentedlocationtobe+/-1.5m

• Tobedesignedsuchthatitissafeasisreasonablypracticableanddoesnotpresentasignificantrisktohealthorenvironment

• CanbeintegratedwithHoulderUpendingFrame

• GripperArmallowshammersleevetopassduringpilingbyopeningofjaws

• Equipmenttoincludesafeandeasyaccessstructuresparticularlyonthearms

• Maintenancefriendly

technicAl detAils

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system components

Thefollowinglistgivesanindicationofthemainitemsandcomponentsthatmakeupthegrippersystem.

SystemComponents

Jawassembly(x2)

Innerarmassembly(x2)

Outerarmassembly(x2)

Hingeassembly(x2)

Outercylinder(x2)

Innercylinder(x2)

Liftingcylinder(x2)

Liftinglinkassembly(x2)

Liftingframeassembly(x2)

Deckframeassembly(x2)

Grillage

HydraulicPowerUnit(HPU)

hpU

Theequipmentispoweredbyatwin110kwHydraulicpowerthatiselectricallydriven,openframeanddeckmounted.TheHPUissuppliedwitha2000ltrstainlesssteeltank.TheoptimalpositionfortheHPUisbetweenthetwodeckframesasshowninFigure3howeveritwillrequirerepositioningforthisspecificprojectduetothelocationoftheUpendingHinge.Theequipmentrequiresthefollowingpowersupplywhichisexpectedtobederivedfromvesselpoweranddistributionsystem:

• 415/440v3ph

• 50/60HZ

• 200A

operAting procedUre & fUnction

Thefollowingoperationsaretypicallyundertakenduringmonopileinstallation:

• Thewindfarmconstructionvessel(loadedwithpiles)ispositionedoverreferencetargetatpre-definedorientation.(Orientationcandependoncableroutes,currentandweatherdataetc.)Vesselisjackedtoworkingheight

• Thegripperarmsareloweredtothehorizontalposition,onearmatatime.Botharmswillbeattheirmaximumopeningwithbothoutercylindersfullyretracted

• Thegripperarmsareextendedattheirmid-strokepositionandarekeptopened

• Thepileisupendedfromhorizontaltoverticalusinginstallationvesselcraneanddecktools

• Cranemovesthepiletothepre-calculatedcraneradius(actualcentreofgripperradius).Thisradiusvariesaccordingtopilediameter

• Craneslewsuntilcentreofpilemeetsthecentrelineofgripperarms

• Thepileisloweredthroughtheopenpilegripper.Pileiskeptoutofthewater

• Thepileorientationisverifiedandpilemayberotatedasrequired

• Thepilegripperarmsareclosedaroundthepiletorestrainandguideitlaterally.Asmallgapismaintainedbetweenthegripperjawsandthepile

• Thepileisloweredthroughtheopenpilegripperuntiltheself-weightpenetratestheseabed

• Pileinclinationisverified(byhumanintervention)andadjustedbythegripperarmsifnecessarytobringthepiletothe‘truevertical’position

• Themaincraneisunlatchedfromthepile(viapileupendingandliftingtool)

• Themaincraneinstallsthedrivinghammerontothepiletop

• Pileinclinationisfrequentlyverified(byhumanintervention)beforeandbetweenthehammeringoperations(hammerblows).Theinclinationofthepileisadjustedbythegripperarmsifnecessarytomaintainitsverticalposition

• Thepileisdriventothepredetermineddepthwherethepilecanholditselfverticallywithouttheassistanceofthegripper.Thegripperarmsarethenfullyopenedtoallowclearanceforthepilehammer

• Thepileisdriventothetargetdepth

• Thegripperisretractedandraisedpriortothe“TransitionPiece”installation

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trAining

Trainingcanbeprovidedtopersonnelnominatedbytheclient.Trainingshallcompriseofon-site,handsonsupervisoroperatorandmaintainertraining.Thiswillbespecifictotheequipmentsuppliedunderthisagreementandinstructionintheproceduresandroutinescontainedintheequipment’soperationsandmaintenancemanual.Theclientshallonlynominatepersonnelthatitconsiderstobecompetentandexperiencedgenerallywithintheirrespectiveroles,inoffshoreliftingandinstallationworks.

offshore sUpport

Houldercanmakeavailableoneoffshoretechnicianfamiliarwiththesystemoperationandtroubleshootingtosailwiththenominatedinstallationvesselonthefirstcycle.AlternativelyHouldercanprovideoffshoreoperationsforthefulloffshoreperiodtooperatethegripper.

mAintenAnce

HouldercancarryoutmaintenanceworkontheitemsofequipmentinaccordancetotheO&Mmanual.Clientmaycarryoutsuchworkusingpersonneltrainedtodoso.

vAriAtions

hoUlder mgA-01

HoulderprovidedthefirstMonopileGripperArmsystemtoMPIOffshorein2013whichisinstalledupontheirwindturbineinstallationvesseltheMPIDiscovery.TheequipmenthasaidedinstallationworksforvariouswindfarmprojectsincludingtheLondonArray,HumberGateway,AmrumbankWest&Rampionoffshorewindfarms.Thesystemiscurrentlyconfiguredtohandlepileswithamaximumdiameterof6.5m

hoUlder mgA-02

HoulderrecentlysuppliedasystemtoRampionOffshoreWindLtd(asubsidiarycompanyofE.ONClimate&Renewables)aspartofahireagreement.

ThesystemhasaidedthemonopileinstallationworksoftheRampionOffshoreWindfarmandwasdemobilisedfromSwireBlueOcean’sPacificOrcaduringNovember2016.

Theequipmentdiffersfromtheoriginaldesignduetotheincorporationofamodulargrillagewhichenablesthesystemtobeconnectedtothevesseldeckwithnoattachmenttothetransom.Thisallowstheequipmenttobemobilisedanddemobilisedfromvesseltovessel.

7.5m JAw

Theexistinggripper’sjawconfigurationcanbemodifiedtosuitamaximumpilediameterof7.5m.

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HOulder lIMITed22 Witney WayBoldon Business ParkTyne & WearNE35 9PEUKT: +44 (0)191 536 2777

enquiries@houlderltd.comwww.houlderltd.com

contAct Us

Houlder is an independent, innovative offshore engineering company. We build on 30 years’ offshore expertise and work closely with clients to design solutions for their technical challenges. We provide complete EPCI services with special equipment, consultancy, project management and engineering solutions for the offshore wind and wider energy sector.