ventilation and cargo sweat p&i circular

8/8/2019 Ventilation and Cargo Sweat P&I Circular

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r -. , i :, , I .; 1;.,,'Non-hygrotcofic iodurJ '' "'Non-hygoscopicroductshave Do watercontent. Howevel, celtain cormodities (egsteel)ay be damagedf stowed a moistenvircrunent,and othersmay be hamed ifpackagedusing a hygoscopicmaterial(egwood,paper),

lnlluencig factorsSaturation

Typsof SwtCargo sweat Apaf fbm periods f fog or rain. ambientair is rarely saturated.Moreover, t willnever be -tdtally dry' Within these twoextiemei the amou of wate retainedbythe ai ill vry accordihg o tle pevilingconditions.. , , i . i " 'Relatiie humidity

Reltive umidity s lhe actualarnount lwatervapor n the aif codpafedwith thesatuationamountof watervapour n theairat thesae temperte ndpressure hefiglre is usully xpresseds a percentage.with saturatedair having a relativehumiditvdf 100%: l : , 'Al maindeck evel,abiet seaa over heopenoceanswill normallyhavea reiativehumidityn excess f 80%.DewpointefiPetutureWhen ran'isolatedvolume of ai cools'relative humidity inceases as thefalls. Once he tempetature asdescededo the level at ihich saturationoccus, watel begins to condense Thisteripeiat is knovn as he"dewpoint"Dewpoint eperatemaybe measurcoya variety of methods Shipsgenerallyuse a2

ANOGIVENMOISTUE

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Lradjroralet alrd dry bulb arrangemen-consisng of two idendcal mercurylhermomerers,ne of which has a dampwick covedng he bulb. Theseare nomallyhousedn aprotectivemarinesqee.The dewpoint temperatrre Inay then bedetermined y usinga 'DewpoinrTable'(see Anex D. This figure is importatwhen considering cargo venlilaonequirements.Wetand dry bulb thermometersWhen sing haditional wet ad dry bulbthemometers, the accuacy of the de!'point temperaturewill depend oD thecondition of the equipmeIt.The uslincoveringhe wet bulb shouldbeclean, hewater in the reservoir should be distilledand hebulb tselfshould ewet.In oder to ensue that the readil8s arecoect, the device should always bepositioned learof anyexhaust ents, thedughtsand all soucesof heat.DewpointmeasurementTheoetically,all decisions egardingcargoventilalionshouldbe basedon dewpoin.lemperat{res.omparinghe dewPointoflhe ambientair wjrh dewpontof the airinsidehehold.Given that most ships me customarilyequipped with wet and dry bulbrhermoretersocated loseto te bridgedetemining the dewpoint tempe.atureofthe ambientai is r-sually traighdorwad.However, ascettaining the dewpointlemperturensidea cargo space6 moreproblertic.Oneof the simplestmethodssto use a "whirling psychrometer", wingingthe insfument inside the hold until the wetbulb temperaturehas stoppedfalling adrerains steady,All readings should be taken well awaylrom anyair inlets.ensuringhatonly holdai is tested. Enclosed space entryprocedureshould lways eobserved.

If access o the holds is impossibleorundesirable, and provided there is nosignificant ai flow, wet and dy btlbthermometercmay beplaced n the runkingof anexhaust entilator r similarpipeworkleadingrom becompartment.llowinBhedevice o bedrawn out ad read rornabovedeck.VetrtilationOnce the above ifomatiotr has beenobtaied, herules arcsimple;DewpointRuIe!'ENTILATE if the dewpoint of the alrinside hehold s higherha te dewpointof the ai outside he hold.DO NOT \ENTILATE if the dewpoint ofthe ak inside the hold is lower than thedewpointof the a outside he holdmree DegreeRuleI ,rnayinstalces it is impacticabletomeasue hold de$?oit temperaturesaccately,o atallI suchcases entilationequirements ybe estjmatedby comparhg the averagecargo ternperatureal thz time of loadinSwi the outsideair temperaoreseveraltimes a day. ventilation may t-hen btcarriedouto thefollowing basis;VENTILATE ifrhe dry bulb tempeatue flheoulside ir sat least oCcoolerhan heaveragecago temperate al the time ofloadig.DO NOT VENTILATE if the dry bulbtempeature f the outsideair less han3"Ccoolef han he average ago emperaleat the ime of loadirg, o. warmer.In orde! to apply the ThreeDegreeRule, itwill be necessaryo theship's staff to takea nunber of cargo tempelaturereadingsdudrg loadirg.


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FurtherobsenationsDuing peiods of heary wether' stepsshould be taken to prevent ain'iand spayfiom entering the cargo spaces.This maymea suspending ventilation'.untilconditions mpove. f so,the cicumstancesshould e ogged.It is importantto apFeciate hat ventilationshouldalso trecariedout dring e ightif the readings ndicate that ventilation isappropriate.Ambient temperatues reuiually owerar nighr.erefore le risk ofship's sweat developing is mie likelyduring the hoursof darless.i . ,In additio to, ventilating the holdsaccordig to the above egimes' it isimportat that regula inspectionsof eachcompament ae carried out wheepossib)e. his neednot involveeotry ntothecargospacelself - for exarpleshipssweat rnay be seen forming on theundeside of anhole coves. In suchinstances,ndespecially t night, hecargoshould be ventilated inespective of theDewpoint or Three Degee Rules,weathepermittiDg.What to expectln broad terms it is often Possible toesdmare ventilation requireents inadvance by considering the cli'ticchangesikely o beecouDtereduring hevoyage.The following examplesndicatewhat my be expectedon passage, ut donot obviate he need or detailedmonitotingand ecording:Hygroscopccargo cold to wa clmatelf a stablecold cagois ca$ied to a wamclirate, ventilation will always be'unnecessaty,ndeed, n someciculllstancesventilationmay eadto cargodainage.Hygroscopiccargo ' wan to collclimatevigoros surface ventilation of the cagospaceswill almostcenainlyberequieddue

tor e, kelihood of ship's sweatdeveloping.No:tr-hrgroscopic arSo ' coa tu waftnclimate ,Ventilation is never equired. Cagoswealis lible to occur if warm rioist ai comesinto contactwith cold cargo.Thereforeholdsshould sually emi sealedo allowthecrgoaDdntemalair to warmgaduallydurirg thevoyage.Non-hygroscopiccarSo ' wam to covclittate 'Vetilarion is largely inelevantDevelopmeotf significant hip'ssweat sveryunlikely.Combined arSoesProblems ayarise fhygroscopic ndnoo-hygroscopiccargoeswith different inherenttempetes ae loaded into the samecornpaftnent. Their vendlarionrequireets rday differ, resulting indamageo oneor otherof theproductsnspiteof omal routines eig ollowed Asfa as possible, hygroscopicand non-hygroscopicargoes houldnot be sto\r/edtogether.StorageGiven the sensitive nature of manYhygoscopicproductsand thepossibilityofsweat,'efforts houldbe made o ensurehatsch cargoes o not come nto contactwithhold steelwork This is palicularlyimportart in the caseof baggeda8icultualpr;dce interded for humanconsumptionsuchasnce,beansand lo.For baggedcargo. rows of dunnage rbamboo poles should be laid in tledirection f thebilges c aid drainage. olmore han20 centimeues Paf A secondlayershould eplaced nrcp at ightanglesto the first beforecoveingthe whole aeawith matting.


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If the cargo space s not fully fitted withcargo battens,bamboo poles or duageshould be positioedcrosswiseagaist thekmes o keep the bags away fro thesidesof the ship. Ideally, they shouldalsobe lashedtogetherat the i[tesections toprevent tlem from becomingdisorbecuring oading. s anexm but notessentialprecaution, atsmy beplaced gajnstlsarranqement,n the samecoltext' the topsurfa;e of e slow Iay be coveredwiththick kaft paper.ExDet oDinion is oow that biologicallystatebalged hygroscopiccagbsdo notrequire ventilation channels, unlessspicificallydemandedy lhe IMDC Coder"g so.e tpes of seedcake, ishEeal)Nevelheless,or celarncorunoditiesmychaferes still require ventilationchanelsto bebuilt into thestow.If so, hechadeersshould be asked for witteI hstructio8reeardig he numberard positiooof suchch'anekland theseshould be foowedaccordigly.A check list addressingthe cariage ofhygroscopic argo s featud in Arex IIBunker taDksHgroscopic roductsmaybe darnagedyloclised ources f heat. cidentshaveoccuedwhere parts of parcels of gainhave bee scorched or have becomediscolouedwhen lying agai$t hot bunkertanks.As far aspossible, he bunkesusedduring the voyage should be dawn fomtanks situated well away from holdscontainig hygroscopic ploducts. Ifimpracicable,bunker anksadjoiniDgcagospaces should be heated oly whenrquired,ensuring hat thetempere doesnot rise abovenormaloperationalevels,RecordsVertiltionrecordsare crucial ln theeventof moistuedamage, videnceshowing hatthe vessel veotilated coredy may beinstrumental n defendiDgany ensuing iclaims. .,

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If the DewpbiDtRule has been followed'wet ad dY bulb temPeralures ancdewpoints should be logged once pelwatch, bearing i mind that lhese maychaDgecotrsiderablyover a short PeriodFor tbe sa$e reason,he sea emperatureshould also be noted. This iformationshouldbe recorde-dor eachhold rogetherwith tie timesof commencing,easing rresurDg entilaton, d the reasonsordoingso.If e Thee Degree Rule has beenfollowed,a recordshouldbe kept of lheambient ai temperanue and e seatemperaheonce per watch together theavemqeemDemtle f thecagoat the tmeof loadig.Onceagain.venlla$o deullsshouldbe documentedor eachhold.Aex m contans a specimen orm whichmay be used to captue all relevavetilatio details.


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ANMXIIHygroscopicCargo- Checklist

On passage

Ensue oldsareclean and ree omodourE..iF bi'in".l.rn. Itrq req_999!r_q!!f$!!4i " tabi le""""-"trm t^l*s nd iShevel lrmiwhereitledcovers ithburlap nd ecuren-lrrh soundhg nd h.rmometeripes i lh Larerheckholds or siensof infestation e(s,seals)aewor\4gjgggqqEnsure entilalion i (eg ans, rDnkthathatch overs ndholdaccessoors reTestsmoke etection ndgnEnsue allast uction over resar-e ecurebalIast oldsonlRecorddetaiisof measuesn thedeckanwith stevedoresEnsure nlysound rgos oadedMeasure nd ecord aro\,r'irh bnomallyxcessryg94p9I3!EV N

Cover ank ;irh double umage r bambgg

F-rerenrr. ol cargo andlingooks y srevedoresrsnrebagsarenot oadgdn the

Followenclosed uesf necessayo eterholdsnii-ri... *lt.tw"ntilalion wascornmencedlopped r resumed onRecord oundingsf holdbilsesat east ailRecod etailsfs deteriorationreobservedNotify club io to rival if cargodeteiorationoccuIsI Rej@tbags hichare om,slained apor n olhewiseuspectonditiont r.y *t yt . t."- of re bil8es,not dore tlr 20 ctu apan lv secod averat ight agls lo e i6t' r., **i"i+g"o *'g*r, *ti lationchnb dav berequiredbv tneIMDG code' (essone tt?es of s*d cle' fishflal)a oemoior nut ootv If follwing thcThr4 De8eeRule' tecodextmal air tempchE andsea empeBrurconcePeiwatch


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ventilation and cargo sweat p&i circular

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