Kongsberg EM 712 User manual

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July2015©KongsbergMaritimeAS
KongsbergEM712
Multibeamechosounder
Installationmanual

KongsbergMaritimeAS
www.kongsberg.com
Copyright
©CopyrightKongsbergMaritimeAS
TheinformationcontainedinthisdocumentremainsthesolepropertyofKongsbergMaritimeAS.Nopart
ofthisdocumentmaybecopiedorreproducedinanyformorbyanymeans,andtheinformationcontained
withinitisnottobecommunicatedtoathirdparty,withoutthepriorwrittenconsentofKongsberg
MaritimeAS.Thedocument,oranypartofit,maynotbetranslatedtoanyotherlanguagewithoutthe
writtenapprovalfromKongsbergMaritimeAS.
Disclaimer
KongsbergMaritimeASendeavourstoensurethatallinformationinthisdocumentiscorrectandfairly
stated,butdoesnotacceptliabilityforanyerrorsoromissions.
Warning
Theequipmenttowhichthismanualappliesmustonlybeusedforthepurposeforwhichitwasdesigned.
Improperuseormaintenancemaycausedamagetotheequipmentand/orinjurytopersonnel.Allusers
mustbefamiliarwiththecontentsoftheappropriatemanualsbeforeattemptingtoinstall,operate,
maintainorinanyotherwayworkontheequipment.
KongsbergMaritimeASdisclaimsanyresponsibilityfordamageorinjurycausedbyimproperinstallation,
useormaintenanceoftheequipment.
Supportinformation
Ifyourequiremaintenanceorrepair,contactyourlocaldealer.Youcanalsocontactususingthefollowing
address:[email protected].Ifyouneedinformationaboutourotherproducts,
visithttp://www.km.kongsberg.com.

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Tableofcontents
ABOUTTHISMANUAL..............................................................5
KONGSBERGEM712................................................................7
Systemdiagram0.5x0.5degreessystem.........................................................................7
Systemunits.....................................................................................................................10
Transducerdescription...........................................................................................10
TXUnitdescription................................................................................................11
RXUnitdescription................................................................................................11
EM712ProcessingUnitdescription......................................................................12
HydrographicWorkStationdescription.................................................................12
PREPARATIONS.....................................................................14
NecessarytoolsandequipmentforEM712installation.................................................14
Requirementsforshipyardworkerskills.........................................................................15
Sonarroomrequirements.................................................................................................16
Environment...........................................................................................................16
Watertightintegrity.................................................................................................16
Sizeandaccess.......................................................................................................17
Insulation,heatingandventilation.........................................................................17
Electricalinstallations,cablesandcommunication................................................18
Bilgepumpanddecking.........................................................................................18
Wheretoinstallthetransducer........................................................................................19
Introduction............................................................................................................19
Mountthetransducerdeep.....................................................................................19
Avoidprotrudingobjects........................................................................................20
Stayfarawayfromthepropellers..........................................................................20
Chooseapositionfarawayfromthebowthruster(s)............................................20
Summaryandgeneralrecommendations...............................................................21
Acousticnoise..................................................................................................................22
Contributingfactors................................................................................................22
Selfnoise................................................................................................................23
Ambientnoise.........................................................................................................26
Electricalnoise.......................................................................................................26
Somemeanstoreduceacousticnoise....................................................................26
Vesselcoordinatesystem.................................................................................................28
INSTALLINGTHETRANSDUCER.............................................31
Transducerinstallation.....................................................................................................31
INSTALLINGTHEEM712HARDWAREUNITS.........................32
InstallingtheTXUnit......................................................................................................32
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InstallingtheRXUnit......................................................................................................34
CABLELAYOUTANDINTERCONNECTIONS.............................36
Readthisrst...................................................................................................................37
Cableplans.......................................................................................................................38
Cableplan,ProcessingUnit...................................................................................39
Cableplan,TransmitterUnit..................................................................................40
Cableplan,ReceiverUnit,0.5degree....................................................................42
Topsidecableplan..................................................................................................45
ListofEM712cables......................................................................................................45
Cabledrawingsandspecications...................................................................................50
RS–232seriallineusingthree3wiresandRJ45connector..................................51
RS-422seriallineusingvewiresandRJ45connector........................................52
1PPS(Onepulsepersecond)usingacoaxcable...................................................54
Remotecontrol.......................................................................................................56
RemoteControlusingK-Rem................................................................................57
Dummyplugfornotusingremotecontrol.............................................................58
ExternalSynchronization.......................................................................................58
DRAWINGFILE......................................................................62
EM712TransmitterUnitoutlinedimensions..................................................................63
EM712ReceiverUnitoutlinedimensions......................................................................64
ProcessingUnitdimensions.............................................................................................65
HydrographicWorkStationoutlinedimensions..............................................................66
RemoteControlUnit(K-REM)outlinedimensions........................................................68
TECHNICALSPECIFICATIONS................................................70
Weightsandoutlinedimensions......................................................................................70
Powerrequirements.........................................................................................................72
Environmentalrequirements............................................................................................73
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Aboutthismanual
ObservethisgeneralinformationabouttheEM712Installationmanual;itspurpose
andtargetaudience.
Purpose
Thepurposeofthismanualistoprovidetheinformationandbasicdrawingsrequiredfor
thephysicalinstallationoftheEM712.
FormoredetailedinformationaboutthepracticaluseoftheEM712,refertothe
Operatormanualand/ortheReferencemanual.
Targetaudience
Themanualisintendedfortechnicalpersonnel;suchasskilledshipyardworkers,
electricians,qualiedengineersandnavalarchitects.Itisassumedthatyouunderstand
thegeneralprinciplesofmaritimeelectronicequipment.Y oumustalsobefamiliarwith
computerhardware,interfacetechnologyandinstallationofelectronicandmechanical
products.
Weassumethatyouarefamiliarwiththebasicacousticprinciplesofsoundinwater,
andthatyouhavesomeexperiencewithmultibeamand/orsinglebeamechosoundersin
hydrographicapplications.
Installationinstructions
Youmustfollowtheinstructionsinthismanualtoensureoptimalperformance.Asa
guide,installationproceduresarepresentedintheordertheymustbedone.
Theequipmentdescribedinthismanualincludesthecompletesystemwithrelevant
cabinets.Unitsprovidedlocallybythecustomer,installationshipyardorlocal
representativearenotdescribed.
Themanualalsodenestheequipmentresponsibility,andprovidesapplicable
instructionsforunpackingandstorageofunits.
Aboutthismanual

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Note
Youmustfollowtheinstructionsgiveninthismanual.Ifnotitmayaffectthewarranty.
KongsbergMaritimeASwillacceptnoresponsibilityforanydamageorinjurytothe
system,vesselorpersonnelcausedbyequipmentthathasbeenincorrectlyinstalledor
maintained,orbydrawings,instructionsorproceduresthathavenotbeenprepared
byus.
Installationdrawings
Thecustomer,ortheshipyardcontractedtodotheinstallation,mustproviderelevant
detailedvesselspecicmechanicaldrawings.
Note
Ifrequired,alldrawingsprovidedbytheshipyardforthephysicalinstallationof
theEM712mustbeapprovedbythevessel’ snationalregistryandcorresponding
maritimeauthorityand/orclassicationsociety.Suchapprovalmustbeobtainedbefore
theinstallationcanbegin.Theshipownerandshipyarddoingtheinstallationare
responsibleforobtainingandpayingforsuchapproval.
KongsbergMaritimeASmay,onspecialorder,provideassistancetothesedrawings.
Applicablegenericoutlinedimensionandproductionsdrawingsareprovidedinthe
Drawinglechapter.
On-lineinformation
ForinformationabouttheEM712andotherproductsfromKongsbergMaritime,visit
ourwebsiteon
•http://www.km.kongsberg.com
Registeredtrademarks
Observetheregisteredtrademarksthatapply.
Windows®,WindowsXP®,andWindows®7areeitherregisteredtrademarks,or
trademarksofMicrosoftCorporationintheUnitedStatesand/orothercountries.
EM®isaregisteredtrademarkofKongsbergMaritimeASinNorwayandothercountries.
KongsbergEM712

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KongsbergEM712
Topics
Systemdiagram0.5x0.5degreessystem,page7
Systemunits,page10
Systemdiagram0.5x0.5degreessystem
ThesystemdiagramidentiesthemaincomponentsofabasicEM712system,aswell
asthekeyconnectionsbetweentheunits.Interfacecapabilitiesandpowercablesare
notshown.
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(CD020106_100_002)
F
G G H H
TX TX RX RX
F
AHydrographicWorkStation(HWS)
BInterfaces:
•Soundspeedsensor
•Tide
•Centerdepthoutput
CProcessingUnit(PU)
DProcessingUnitinterfaces:
•Positioningsystems
•Attitude(roll,pitchandheave)
•Velocity
•Heading
•Clock
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ProcessingUnitspecialinterfaces:
•Triggerinput/output
•Clocksynchronization(1PPS)
ETXUnit
FRXUnit
GTransmittransducer
HReceivetransducer
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Systemunits
EM712comprisesamodularsetofelectronicunits.
Topics
Transducerdescription,page10
TXUnitdescription,page11
RXUnitdescription,page11
EM712ProcessingUnitdescription,page12
HydrographicWorkStationdescription,page12
Transducerdescription
Atransducerisadevicethatconvertsoneformofenergytoanother.Inanechosounder
systemthetransducerconvertselectricenergytosound.TheEM712usesseparate
transducerarraysfortransmittingandreceivingsoundpulses.Bothtransducerarrayscan
haveseveralmoduleswhichareassembledinmountingframes.
Thetwotransducerarraysarenormallymounted
as“T”or“L”congurationsunderthevessel’shull
(MillsCrossconguration).Thetransmittransducer
arrayshouldbealignedparalleltothevessel’skeel.
Thereceivertransducerarrayshouldbealigned90º
onthekeel.Bothtransducersshouldbehorizontal
onaplaneonthekeel.
TheEM712canusetwosizesoftransmit(TX)andreceive(RX)modules:
•1degreetransmittransducer:TX1
•2degreestransmittransducer:TX2
•1degreereceivetransducer:RX1
•2degreesreceivetransducer:RX2
ThenumberofindividualTXandRXmodulesinthetwoarraysdependsonthechosen
EM712conguration.Thestandardtypesidentiedbythe“transmissionxreception”
beamwidthare:
•0.5x0.5degreessystem:2TX1modulesand2RX1modules
•0.5x1degreesystem:2TX1modulesand1RX1module
•1x1degreesystem:1TX1moduleand1RX1module
•1x2degreessystem:1TX1moduleand1RX2module
•2x2degreessystem:1TX2moduleand1RX2module
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Note
Theredprotectivecoatingisanvitalpartofthetransducer.Itisveryimportantthat
neitherthiscoatingnortheinternalpartsofthetransduceraredamagedduringthe
handling,installationorcleaning.Anyholesand/orscratchesinthetransducersurface
willallowwatertopenetratethetransducer.Ifaleakoccurs,thetransducermustbe
replaced.
Atransducermustalwaysbehandledasadelicateitem.Wrongfulactionsmaydamage
thetransducerbeyondrepair.
Observetheserules:
•Donotactivatethetransducerwhenitisoutofthewater.
•Donotliftthetransducerbythecable.
•Donotsteponthetransducercable.
•Donothandlethetransducerroughly,avoidimpacts.
•Donotexposethetransducertodirectsunlightorexcessiveheat.
•Donotusehighpressurewater,sandblasting,metaltoolsorstrongsolventstoclean
thetransducerface.
TXUnitdescription
TheEM712TX(transmit)Unithasalltransmitelectronics.
TheEM712TXUnitisawall-mountedsteelcabinet
withintegratedshockandvibrationabsorbers.It
holdsthecircuitboardsfortransmission.Itisnormally
locatedina'sonarroom'closetothetransducer
arrays.AnEthernetcableconnectstheTXUnittothe
ProcessingUnit.
RXUnitdescription
TheEM712RX(receive)Unithasallreceiveelectronics.
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TheEM712RXUnitisawall-mountedsteelcabinet
withintegratedshockandvibrationabsorbers.Itholds
thecircuitboardsforreception.Itisnormallylocated
ina'sonarroom'closetothetransducerarrays.An
EthernetcableconnectstheTXUnittotheProcessing
Unit.
EM712ProcessingUnitdescription
TheEM712ProcessingUnitisprovidedtoprocessthesignalstoandfromthe
TransmitterandReceiverUnits.
TheEM712ProcessingUnitisanindustrial
computerusingbothCOTS(commercialoff-the-shelf)
componentsandcustommadecomponents.Theunitis
designedandtestedforruggeduse.TheProcessingUnitisthecentralcontrollingdevice
intheEMmultibeamsystem.ItadministersthetransmittalofpingsviatheTXunit(s)
andreceptionofdatafromtheRXunit(s).
The48VoutputfromtheProcessingUnitcanbeusedforremotecontrolofthe
TransmitterandReceiverUnits.
HydrographicWorkStationdescription
TheHydrographicWorkStationisamaritimecomputer.Itcontainstheoperational
software,andofferstheuserinterfacethatallowsyoutocontroltheEM712system.
Adedicatedmaritimecomputerisprovidedwith
theKongsbergEM712system.Itissetupwithall
necessarysoftware.
ThecomputerisbasedontheMicrosoft®Windows®
7operatingsystem.
TheHydrographicWorkStationisnormallymounted
onthebridgeorinascienticlaboratory.
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Inthispublication,thecomputerisreferredtoastheHydrographicWorkStation.
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Preparations
Topics
NecessarytoolsandequipmentforEM712installation,page14
Requirementsforshipyardworkerskills,page15
Sonarroomrequirements,page16
Wheretoinstallthetransducer,page19
Acousticnoise,page22
Vesselcoordinatesystem,page28
NecessarytoolsandequipmentforEM712
installation
TheinstallationoftheEM712musttakeplaceindrydock,andtheworkmustbedone
byaqualiedshipyard.
InordertodotheEM712installation,allnecessarytoolsandequipmentformechanical
hullwork,cabinetinstallationandelectricalwiringmustbeavailable.Itisnotpractical
toprovideadetailedlistofallnecessarytoolsandequipment.However,youmustmake
surethatthefollowingspecializedtoolsareavailable.
•Allnecessarytoolsandconsumablesrequiredforwelding
•Allnecessarytoolsandconsumablesrequiredforphysicalinstallationofunits,
cabinetsandracks
•Allnecessarytoolsandconsumablesrequiredforelectricalinstallations
•Acranecapableofliftingthesystemcabinets
•Acranecapableofliftingtheentirehullunit
Note
Wheneverspecicconsumablesorspecialtoolsortestinstrumentsarerequired,these
areidentiedintherelevantprocedure(s).
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Requirementsforshipyardworkerskills
TheinstallationoftheEM712isademandingtask.Itisveryimportantthattheshipyard
workersinvolvedintheinstallationtasksarecompetent.
Asaminimum,thefollowingcertiedcraftsmenmustbeavailable:
•navalarchitects
•welders
•electricians
•projectmanager
Note
Thequalityoftheweldingiscriticaltothesafetyofthevessel.Weldingmustonlybe
donebyacertiedwelder.
Thenalinstallationworkmustbeapprovedbythevessel’ snationalregistry,the
correspondingmaritimeauthorityand/orclassicationsociety.Theshipownerand
shipyarddoingtheinstallationareresponsibleforobtainingandpayingforsuch
approval.
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Sonarroomrequirements
ObserveminimumrequirementstoobtainsuitableworkingconditionsforEM712
installation,useandmaintenance.
Topics
Environment,page16
Watertightintegrity,page16
Sizeandaccess,page17
Insulation,heatingandventilation,page17
Electricalinstallations,cablesandcommunication,page18
Bilgepumpanddecking,page18
Environment
TheEM712cabinetsmustbeinstalledinadryanddust-freeenvironment.Thecabinets
arenotfullyprotectedagainsthumidity,dustorwater.
ObservetheenvironmentalspecicationsrelatedtotheEM712cabinets.
Watertightintegrity
Thesize,locationanddesignofthesonarroommustfullallrequirementstothe
vessel’swatertightintegrity.
Intheeventofamajorleakinthesonarroom,itmustbepossibletocloseallwatertight
hatchesand/ordoorstothesonarroomtomaintainthevesselstabilityandsafety.
Thephysicalsizeofthesonarroommustbelimited,sothatintheeventofamajor
leak,theoodingofthesonarroomwillnotinduceinstability,orcausethevesselto
capsizeorsink.
Ensurethatallwatertightdecksandbulkheadsareinspectedperiodicallytoverifythat
therearenounprotectedopeningsorimproperpenetrationsthatwillallowprogressive
oodingfromthesonarroom,andthatthewatertightdoorsandhatchesareinplaceand
inworkingorder.
Ensurebilgehighlevelalarmsarearrangedtoprovidetheearliestwarningsofabnormal
accumulation.Thehighlevelbilgealarmsmustbesetaslowaspossibletothedeck
orbilgewellandpositionedalongthecentreareaofthecompartmentorinalocation
atwhichtheuidswillgravitatetorst.
Allcablesleadinginandoutofthesonarroommustberuninsteelconduits.Thesesteel
conduitsmustreachupandabovethefreeboarddeck.
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Sizeandaccess
Awelldesignedsonarroomwithawellttedsizeandeasyaccessreducestheriskof
corrosion,andsimpliesmaintenance.Thisincreasessystemreliability.
Note
Thephysicalsizeofthesonarroommustbelimited,sothatintheeventofamajorleak,
theoodingoftheroomwillnotinduceinstability,orcausethevesseltocapsizeorsink.
Thesonarroommustbedimensionedtohousealltherelevantcabinetsthatcomprise
theEM712system.
1Theroommustnotbeusedforanyotherheavymachinery.
2Theroommustnotbeunnecessarilyobstructedbygirders,pipesetc,whichmay
causeinstallationproblemsorimpedemaintenance.
3Theroommustbeaccessibleunderallconditionsatseaorataberth.
4Alldoorsorhatchesmustbedesignedsothatthetoolsandequipmentcanbe
removedwithoutbeingdisassembled.
5Allcablesleadinginandoutoftheroommustberuninsteelconduits.Thesesteel
conduitsmustreachupandabovethefreeboarddeck.
Insulation,heatingandventilation
Thebulkheadsinthesonarroommustbeinsulatedandprovidedwithaninteriorwall
tothedeck.Theroommustbeequippedwithheater,anditmustbeconnectedtothe
vessel'sventilationsystem.
Insulation
Theinsulationinthesonarroomshouldbetheminimumequivalentof50mmof
rock-wool.
Inaddition,pipingpassingthroughthespacepronetocondensationmustbeproperly
insulated.
Heater
Thisheaterinthesonarroommustdimensionedtomaintaintheequipmentwithinits
environmentaltolerances(atleast1000W).Itmustbeinstalledclosetothedeck.
Heatingisaneffectivemethodforreducinghumidity.
Ventilation
Thesonarroommustbeconnectedtothevessel'sventilationsystem.Ifthisisnot
possible,two3”ventsmustbeprovidedfromthesonarroomtothemaindeck.
Intheroom,theairinletmustwheneverpossiblebelocatedclosetothedeckandthe
outletashighaspossible.Afunnelshapeddrip-collectormustbemountedbelowthe
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ventpipestodivertmoisturetothebilge.Onthemaindeck,thebestventilationis
providedwhentheoutletpipeisatleastfourmetershigherthantheinletpipe.Tokeep
outseawater,rainandspray,theventilationpipesshouldbettedwithgoosenecks
oraequivalentdesign.
Note
Ifthevesselislikelytooperateintropicalconditions,asuitableairconditioningsystem
mustbeinstalled.Thissystemmustbeabletoprovideanambienttemperaturenot
exceedingthemaximumoperatingtemperaturesofthecabinetsinstalledintheroom.
Electricalinstallations,cablesandcommunication
Theelectricalinstallationsinthesonarroommustmeetminimumrequirementsto
providesuitablelightsandsupplypower.
1Ifthecablesbetweenthesonarroomequipmentandothersystemunitslocatedin
differentcompartmentsonthevesselpassthroughhatchesorareaswherethey
maybedamaged,theymustberunthroughconduits(minimum2”conduitis
recommended).
2Thesonarroommustbeequippedwithatelephone,anintercomsystem,orany
othermeansoforalcommunicationbetweenthesonarroomandthebridgeand/or
controlroom(s).
3Thesonarroommustbeequippedwithsuitablelightingtosimplifytheinstallation
andtoaidfuturemaintenance.
4Eachsystemunitinthesonarroomshouldbeprovidedwithaseparatecircuit
breakeronthemainssupply.
5Propervesselgroundmustbeprovided.
6Aminimumnumberofadditionalelectricaloutletsmustbeprovidedforother
equipment.
7Makesurethatallsystemcablesareproperlysecure,butalsoinstalledwithsome
slack.Thisisessentialtowithstandvibrations,andtofacilitatemaintenance.
Bilgepumpanddecking
Ifthesonarroomislocatedbelowthewaterline,itmustbeconnectedtothevessel's
bilgepumpsystem.
Ifthisisnotpossible,aseparatebilgepumpforthesonarroommustbeinstalled.
Oncetheinstallationhasbeencompleted,thesonarroommustbesuitablydecked
withoutrestrictingaccesstotheequipmentandthecables.
KongsbergEM712

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Wheretoinstallthetransducer
Topics
Introduction,page19
Mountthetransducerdeep,page19
Avoidprotrudingobjects,page20
Stayfarawayfromthepropellers,page20
Chooseapositionfarawayfromthebowthruster(s),page20
Summaryandgeneralrecommendations,page21
Introduction
Asingleanswertothequestion“wheretoinstallthetransducer”cannotbegiven.
Thephysicallocationofthetransducerdependsonthevessel'sdesignandconstruction,
howthehullisshaped,andhowthewaterrunsalongthehull.Therearehowevera
numberofimportantguidelines,andsomeoftheseareevenconicting.
Note
Theinformationheremustbeconsideredasgeneraladvice.EachEM712installation
mustbehandledseparatelydependingonthehulldesign.
Mountthetransducerdeep
InordertoachievethebestpossibleEM712performance,mountthetransduceras
deepaspossibleunderthevessel’shull.
Considerthesituationswhenthevesselisunloaded,andwhenitispitchinginheavyseas.
Thereareseveralreasonsforthis.
1Theupperwaterlayersoftheseacontainamyriadofsmallairbubblescreated
bythebreakingwaves.
Inheavyseastheupper5to10metresmaybelledwithair,andthehighest
concentrationswillbenearthesurface.Airbubblesabsorbandreectthesound
energy,andtheymayinworstcasesblockthesoundtransmissionaltogether.
2Anotherreasontogodeepiscavitation.
Cavitationistheformationofsmallbubblesinthewaterclosetothetransducerface
duetotheresultinglocalpressurebecomingnegativeduringpartsoftheacoustic
pressurecycles.Thecavitationthresholdincreaseswiththehydrostaticpressure.
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3Thetransducermustneverbeliftedfreeofthewatersurface.
Transmittingintoopenairmaydamagetheitbeyondrepair.Mountingthe
transduceratadeeppositiononthehullwillinmostcasespreventthis.
4Ifthetransducerisliftedupfromthewaterduringheavyseas,itmaybedamaged
whenthehullstrikesbackattheseasurface.
Thisisespeciallyimportantforlowfrequencytransducerswithlargefaces.
Avoidprotrudingobjects
Objectsprotrudingfromthehullwillgenerateturbulenceandownoise.Thiswill
reducetheEM712performance.
Suchobjectsmaybezincanodes,sonartransducersoreventhevessel'skeel.Holes
andpipeoutletsarealsoimportantnoisesources,aswellasroughsurfacescausedby
badwelding.Alltheseprotrudingobjectsmayactasresonantcavitiesamplifyingthe
ownoiseatcertainfrequencies.
Donotplaceatransducerinthevicinityofsuchobjects,andespeciallynotclosebehind
them.Forthesamereason,itisveryimportantthatthehullareaaroundthetransducer
faceisassmoothandlevelaspossible.
Eventracesofsealingcompound,sharpedges,protrudingboltsorboltholeswithout
llingcompoundwillcreatenoise.
Stayfarawayfromthepropellers
Thepropulsionpropellersisthedominantnoisesourceonmostvessels.Thenoiseis
transmittedthroughtheseawater,andmayoftenreducetheperformanceofyourEM
712system.
Forthisreason,thetransducermustbeplacedfarawayfromthepropellers,whichmeans
ontheforepartofthehull.Positionsoutsidethedirectlineofsightfromthepropellers
arefavourable.
Onsmallvesselswithshortdistancesitisadvisedtomountthetransduceronthatsideof
thekeelwherethepropellerbladesmoveupwards,becausethepropellercavitationis
strongestontheotherside.Thecavitationstartsmosteasilywhenthewaterowsin
thesamedirectionasthepropellerblade,andthatistosomedegreethecaseatthatside
ofthekeelwherethepropellerbladesmovedownwards.
Chooseapositionfarawayfromthebowthruster(s)
Bowthrusterpropellersareextremelynoisy.
Wheninoperation,thenoiseandcavitationbubblescreatedbythethrustermaymake
yourEM712systemuseless,almostnomatterwherethetransducerisinstalled.
KongsbergEM712