九乡新闻网郑嘉颖佘诗曼的电视剧:General Cargo Ships and Safety
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General Cargo Ships and Safety
Bulkcargoes
The carriage of grain
General Cargoes
The carriage of timber on deck
Containerization
Cargo stowage and securing
The prevention of infestation
The Code of Safe Practice for Solid Bulk Cargoes
General precautions
Bulk cargoes having an angle of repose less thanor equal to 35 degrees
Bulk cargoes having an angle of repose greater than35 degrees
Safety of personnel
Cargoes which may liquefy
Sampling and test procedures for cargoes whichmay liquefy
Appendices to the Code
Materials possessing chemical hazards
Bulk cargoes which are neither liable to liquefynor possess chemical hazards
Duringthe last hundred years shipping, like other forms of transport has undergonegreat changes. Until the end of the last century most goods at sea were carriedin packaged form. Grain, for example, was carried in sacks and cotton inbales. Very few liquids were carried at all, but those that were - includingoil - were usually carried in barrels. Cargoes in fact were carried in muchthe same way as they always had been.
Today everything haschanged. Oil is the major commodity carried at sea in bulk; so are grain,coal and other minerals. Containerization is now common and the general cargoship has in many trades been replaced by specialized vessels such as containerships, ro-ro ships and car carriers among others.
Bulkcargoes
Virtually all liquidstransported by sea - such as crude oil and finished petroleum products - arecarried in bulk, and tankers now form by far the greatest percentage of theworld fleet of merchant ships. The second biggest group consists of solidbulk cargo carriers. The goods carried in this way include coal, grains,ores, concentrates, fertilizers and animal feeds. From the shippers' pointof view bulk carriage has numerous advantages. A bulk cargo can be loadedand unloaded far more quickly than one that is unitized, thereby leading togreat savings in time and money. However, there are a number of dangers inthe carriage of bulk cargoes which include the following:
1. Improper weightdistribution resulting in structural damage. This can be caused by puttingtoo much weight on the inner bottom of the ship or by wrongly distributingthe cargo between holds, leading to excessive stresses on the ship's structure.
2. Improper stabilityand cargo shift. Another result of improper loading can be excessivestability. This leads to the normal rolls of the ship becoming shorter butmuch more violent. Apart from being extremely uncomfortable for those onboard, this can in turn lead to damage to the ship's structure.
Stability of the shipcan also be affected by the cargo shifting during the course of the voyage. This can occur because the cargo is inadequately trimmed (levelled-off) orimproperly distributed. In some cases cargoes can liquify as a result ofvibration and the motion of the ship and then slide or flow to one side ofthe cargo hold. This usually happens when the cargo consists of finely-grainedmaterial, such as fine coal and ore concentrates, which are damp when loaded. However it occurs, a shift of cargo can lead to the ship listing and ultimatelycapsizing.
3. Spontaneous heating. Some cargoes carried in bulk have a tendency to heat spontaneously duringthe course of a voyage. The result can be a fire or explosion.
4. Chemical hazards. These hazards include the emission of toxic or explosive gases, oxygen depletion,spontaneous combustion or severe corrosion.
Measures to counterthese problems have been adopted at both a national and international level.
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In addition to thosesafety matters, the cargo officer must take into account commercial considerationsand separate tainting from taintable cargoes or sweating cargoes from thosethat may be damaged by moisture and that heavy items are not placed on frailpackages or packaged liquids on bagged cargoes. For some cargoes ventilationmust be encouraged or sometimes it must be restricted but the different climatologicalconditions in which a ship is expected to operate must always be taken intoaccount. In all cases, the drainage of liquids to the hold bilges or wellsshould be facilitated.
The securing of breakbulkcargoes is most conveniently done by planning stows to occupy the spaces fromside to side, incorporating, where appropriate, built-in anchors of dunnageor using locked stows. Heavy items are individually lashed and for some cargoes,known to have given rise to difficulties in the past, IMO has published a Codeof Safe Practice for Cargo Stowage and Securing (resolution A.714(17)). Forthe securing of freight containers a wide variety of standardized fittings areavailable. On open-top container ships, the need to secure cargoes is greatlydiminished as all containers are placed within cells. The securing of containerson general cargo ships can cause problems unless special fittings have beenprovided.
Barge carrying shipshave specialized arrangements to secure the barges and if problems arise,they stem from the cargoes within the barges. Ro-ro ships have fittings tosecure lorries, although these are not always used.
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TheCode of Safe Practice for Ships Carrying Timber Deck Cargoes gives furtherinformation and guidance on this subject. It was adopted by IMO in 1973 andamended in 1978 and 1990. Like the BC Code and contrary to the InternationalGrain Code, it is not a mandatory instrument but is intended to serve as guidanceto Governments who can implement it if they desire, either in whole or inpart. The Code is intended to apply to ships of 24 metres (79 feet) in lengthand over. Timber deck cargoes are defined as cargoes of timber, includinglogs, and sawn timber whether loose or packaged, which are carried on an uncoveredpart of a freeboard or superstructure deck.
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In many countries thetraditional cargo berths, located in the centre of urban areas, have losttrade because they do not provide the space needed for container operationsas berthing facilities in many cases have moved downriver, to where thereis more land available and the water is deep enough to accommodate containerships that have steadily increased in size. Usually ports have been developedwith a close eye on land transport as well, for one of the major advantagesof containers is that they enable an integrated transport system involvingroad, rail and sea elements to be established, the link being the port andthe common feature the container itself.
Morerecently another innovation has affected the shipment of cargoes, especiallyon short-sea routes: the trailer on board ship. The special-purpose roll/on-roll/offship offers many of the advantages of the container ship, including speedand security. A container on a trailer can be driven straight onto a shipin one port and off again when it reaches its destination. There is no cargohandling involved and consequently no extra costs or loss of time. Both developmentsoffer economic benefits and both raise problems.
In view of the rapidincrease in the use of freight containers for the consignment of goods bysea and the development of specialized container ships, in 1967 IMO undertookto study the safety of containerization in marine transport. The containeritself emerged as the most important aspect to be considered.
In the 1970s IMO and theInternational Labour Organisation began work on guidelines for training in thepacking of cargo in freight containers. These were published in 1978 as a shortguide which emphasized the effect upon the contents of the containers of seaitself. The movement of the ship in adverse weather can result in pitching,rolling and other movements greater than anything found ashore. The guidelineswere revised in 1984.
Experience had by thenshown that probably the greatest problem associated with ro-ro ship safetyconcerned cargo stowage. A survey carried out by the Norwegian classificationsociety, det Norske Veritas, showed that 43% of ro-ro losses couldbe attributed to faults in this area. The danger is even greater in the caseof ro-ro ships than on pure containerships, because containers are generallycarried on trailers: a loading error can result in the container and the trailerboth falling over or becoming dangerously unbalanced. In 1983 IMO thereforeadopted a resolution on elements to be taken into account when consideringsafe stowage and securing of cargo units and vehicles in ships and two yearslater, it adopted another resolution on securing arrangements for the transportof road vehicles on ro-ro ships. It contained guidelines intended to applyto commercial vehicles, including semi-trailers and road trains, with a totalmass (including cargoes) of up to 40 tons, and articulated road trains ofnot more than 45 tons but does not apply to buses.
Theresolution stipulates that given adequately designed ships and properly equippedroad vehicles, lashing of sufficient strength will be capable of withstandingthe forces imposed on them during the voyage. The side guards often requiredfor vehicles can obstruct proper securing and the guidelines take this difficultyinto account. They cover securing points both on the deck of the ship andon the vehicle, as well as lashings and stowage.
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providing advice toensure that the ship is equipped with proper cargo securing means;
providing generaladvice concerning the proper stowage and securing of cargoes to minimizethe risks to the ship and personnel;
providing specificadvice on those cargoes which are known to create difficulties and hazardswith regard to their stowage and securing;
advising on actionswhich may be taken in heavy sea conditions; and
advising on actionswhich may be taken to remedy the effects of cargo shifting.
The Code is basedon a number of general principles:
All cargoes shouldbe stowed and secured in such a way that the ship and persons on board arenot put at risk.
The safe stowage andsecuring of cargoes depend on proper planning, execution and supervision.
Personnel commissionedto tasks of cargo stowage and securing should be properly qualified andexperienced.
Personnel planningand supervising the stowage and securing of cargo should have a sound practicalknowledge of the application and content of the Cargo Securing Manual, ifprovided.
In all cases, improperstowage and securing of cargo will be potentially hazardous to the securingof other cargoes and to the ship itself.
Decisions taken formeasures of stowage and securing cargo should be based on the most severeweather conditions which may be expected by experience for the intendedvoyage.
Ship-handling decisionstaken by the master, especially in bad weather conditions, should take intoaccount the type and stowage position of the cargo and the securing arrangements.
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In 1971 IMO adoptedrecommendations on the safe use of pesticides in ships. It has been revisedseveral times since then. It gives guidance on the prevention of infestation,the use of insecticides, pesticides and fumigants.
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The Code has been updatedat regular intervals since then and is kept under continuous review by theSub-Committee on Containers and Cargoes. The practices contained in the Codeare intended as recommendations to Governments, ship operators and shipmasters. Its aim is to bring to the attention of those concerned an internationally-acceptedmethod of dealing with the hazards to safety which may be encountered whencarrying cargo in bulk. The Code does not deal with the transport of grain,which is covered by the International Code for the Safe Carriage of Grain(International Grain Code).
The Code of Safe Practicefor Solid Bulk Cargoes deals with three basic types of cargo: those whichmay liquefy; materials which possess chemical hazards; and materials whichfall into neither of these categories but many nevertheless pose some dangers,as stated above.
The Code highlightsthe dangers associated with the shipment of certain types of bulk cargoes;gives guidance on various procedures which should be adopted; lists typicalproducts which are shipped in bulk; gives advice on their properties and howthey should be handled; and describes various test procedures which shouldbe employed to determine the characteristic cargo properties.
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Loaded conditions varyaccording to the density of the cargo carried. General cargo ships are normallyconstructed so that one ton of cargo occupies about 1.39-1.67 cubic metresof space when loaded to full bale cubic and deadweight capacity. The ratioof volume of cargo to its mass is known as the stowage factor. When the highdensity bulk cargoes with a stowage factor of about 0.56 cubic metres perton or lower are carried, it is particularly important to pay attention tothe distribution of weight in order to avoid excessive stresses on the structureof the ship. Since hull arrangements vary, it is not possible to establishoverall rules applicable to all types of ships.
Itis essential that the master be provided with loading information sufficientlycomprehensive to enable him to load the ship without overstressing the structure. This applies to localized stresses on the structure as well as on the bendingstresses. The master must also be able to calculate the stability of hisship for the anticipated worst conditions during the voyage.The initial transverse stabilityof a ship is usually expressed as the metacentric height or GM. A large distancebetween the centre of gravity of ship and cargo (G) and the metacentre[1] (M) means that the ship has adequatestability. As G approaches M, i.e. when the centre of gravity of ship and cargorises, ships, when forced from a position of equilibrium, recover this positionsluggishly.
Generally speaking,high density cargoes should be loaded in the lower hold spaces rather thanthe 'tween decks[2]. Particular care should be taken when a ship has a high GM. In order to prevent cargoes from shifting the considerations dealt with belowunder the heading Bulk cargoes having an angle of repose greater than 35 degrees[3]should also be taken into account.
The Code gives variousprecautions to be followed when information on the physical properties ofthe cargo is not available.
The Code lists othergeneral precautions such as the need to protect machinery and the interiorof the ship from dust and to ensure that bilges and service lines are in goodorder and not damaged during loading.
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Cargoes with a low angleof repose are particularly liable to dry-surface movement aboard ship. Toovercome this problem, the Code states that such cargoes should be trimmedreasonably level and spaces in which they are loaded should be filled as fullyas is practicable, without resulting in excessive weight on the supportingstructure.
Special provisions shouldbe made for stowing dry cargoes which flow very freely, in a similar mannerto grain.
Securing arrangements,such as shifting boards or bins, should be used whenever the amount, locationor properties of the cargo could cause excessive heeling through cargo shift,taking into account the density of the cargo.
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The Code states thathigh density cargoes should be loaded entirely in the lower holds of the shipunless this results in the ship being too "stiff"[4]or in the cargo weight on the bottom structure being excessive. It shouldbe trimmed sufficiently level to cover evenly all of the tank top, to reducethe pile peak height and equalize weight distribution. In some circumstancesthe pile peak may be allowed to extend through the 'tween-deck hatchway butthe Code says that the importance of trimming as a means of reducing the possibilityof a shift of cargo can never be over-stressed. This is particularly truefor smaller ships of less than 100 metres in length.
Trimming also helpsto cut oxidation by reducing the surface area exposed to the atmosphere. It also helps to eliminate the "funnel" effect which in certaincargoes, such as direct reduced iron (DRI) and concentrates, can cause spontaneouscombustion. This occurs when voids in the cargo enable hot gases to moveupwards, at the same time sucking in fresh air. This effect is obviouslynot desirable, since it escalates the process of spontaneous combustion.
The Code goes on tolist various considerations which should be taken into account when cargois loaded in the 'tween-decks to reduce "stiffness".
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Health hazards can arisebecause of dust, and some cargoes can create dust or emit flammable gaseswhich create a danger of explosion.
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One purpose of thissection of the Code is to draw attention to the latent risk of cargo shiftand describe precautions which should be taken. Concentrates and similarfinely-particulate materials may appear to be in a relatively dry granularstate when loaded and yet may contain sufficient moisture to become fluidunder the stimulus of compaction and vibration. In the resulting semi-fluidstate, the cargo may flow to one side when the ship rolls but not completelyreturn when the ship rolls the other way. As in the case of cargoes liableto shift, this can result in the ship reaching a dangerous heel or eventuallycapsizing.
The stability of theship is also likely to be affected by "free surfaces"[5]of liquids in the cargo spaces. General cargo ships should only carry bulkcargoes which have a moisture content below the transportable moisture limit(TML), which is 95% of the flow moisture point (FMP) unless they are fittedwith special arrangements to restrain the cargo.
Cargo ships in whichinternal structural boundaries are sufficient to limit cargo shift may alsocarry cargoes whose moisture content exceeds the transportable moisture limit. All ships which carry cargoes of this type should carry evidence of approvalof the flag State. The Code stipulates the data which should be includedin submission for approval.
To prevent possibleincreases in the liquid content of concentrates, cargoes containing liquids(other than canned goods or the like) should not be stowed in the same compartmentas cargoes which may liquify. Precautions should be taken to prevent waterentering holds; this is even more important where contact with seawater couldlead to serious corrosion problems for hull or machinery. In this connectionmasters should be aware of the possible danger of using water to cool combustiblematerials such as coal at sea, as this may well bring the moisture contentto a flow state or create other hazards. Water, if used, is most effectivelyapplied in the form of spray or mist.
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The Code gives detailsof the various sampling procedures and tests which should be used before transportingconcentrates and similar materials. These include the selection of samplesfor laboratory tests to determine the transportable moisture content of concentrates;and the selection of samples to determine the flow moisture point and themoisture content at the time of loading. Procedures concerning the issuingof certificates by Administrations are also given including a recommendedtest procedure to be used by laboratories.
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materialslisted also appear in the International Maritime Dangerous Goods (IMDG) Codewhen carried in packaged form, but others become hazardous only when they arecarried in bulk - for example, because they might reduce the oxygen contentof a cargo space or are prone to self-heating. Examples are woodchips, coaland DRI.
The various types listedinclude: flammable solids; flammable solids or substances liable to spontaneouscombustion; flammable solids or substances which, in contact with water, emitflammable gases; oxidizing substances; poisonous substances; radio-activesubstances; or corrosives.
Such materials should becarefully segregated from other dangerous goods carried in packaged or unitizedform. The Code describes how this should be done.
Eachentry includes either the United Nations number[6] and IMO class[7] or the MHB (materials hazardous in bulk) classification and aBC number; the relevant MFAG (Medical First Aid Guide) table number[8]; approximate angle of repose andstowage factor; Emergency Schedule number; separation and stowage requirements;and properties, observations and special requirements.
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Bulkcargoes which are neither liable to liquefy nor possess chemical hazards
These cargoes do not normallyhave special hazards and are covered in Appendix C. The list ranges from aluminato zircon sand as well as many of the more commonly-carried bulk cargoes suchas clay, cement, iron ore, pig iron, sand and sugar. The list includes theangle of repose of each material, its approximate stowage factor, and the propertiesand special requirements connected with each one.
IMO Resolution A.713(17)
Despite the effortsof IMO and its Member Governments, the number of bulk carriers sinking duringthe late 1980s and early 1990s, sometimes without trace, began to cause seriousalarm. As a result, resolution (A.713(17)) which contains interim measuresdesigned to improve the safety of ships carrying solid bulk cargoes, was dulyadopted.
Owners are encouragedto fit vessels with equipment to monitor the stresses on the ship's structureduring the voyage and during cargo operations. They are also encouraged toinstall equipment required by the Global Maritime Distress and Safety System(GMDSS), which enters into force on 1 February 1992.
The impact of this resolutionwas immediately beneficial. The number of bulk carrier losses dropped fromaround one a month to just two within the next year. It is significant thatthe resolution did not introduce any new measures but simply stressed theimportance of implementing existing standards.
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[1] For ships with a small list the metacentre may beconsidered to be the point on a line drawn vertically through the ship whichis intersected by a line drawn vertically from the centre of buoyancy whenthe ship is rolling. If this point is below the centre of gravity the shipwill roll over. The term GM means the vertical distance from the metacentre(M) to the centre of gravity (G).
[2]A 'tween-decker is a ship with more than one deck, thus providing spacebetween the two adjacent decks.
[3] Thesesections of the Code are currently under revision, the aim being to developnew criteria for shifting of cargoes.
[4] i.e. having a large metacentricheight.
[5] Whena cargo space contains a liquid, the metacentric height of the ship is reducedby an amount depending mainly on the width of the free surface of the liquid. The effect is independent of the amount of liquid in the cargo space.
[6] TheUN Committee of Experts on the Transport of Dangerous Goods numbers eachdangerous substance, with the exception of MHB.
[7] Substancesincluded in the IMDG Code are arranged in different classes according totheir properties (e.g. explosives, flammable liquids, corrosives, etc.).
[8] TheMedical First Aid Guide is intended for use in conjunction with the IMDGCode. Poisons are divided into groups and given individual numbers.
Bulkcargoes
The carriage of grain
General Cargoes
The carriage of timber on deck
Containerization
Cargo stowage and securing
The prevention of infestation
The Code of Safe Practice for Solid Bulk Cargoes
General precautions
Bulk cargoes having an angle of repose less thanor equal to 35 degrees
Bulk cargoes having an angle of repose greater than35 degrees
Safety of personnel
Cargoes which may liquefy
Sampling and test procedures for cargoes whichmay liquefy
Appendices to the Code
Materials possessing chemical hazards
Bulk cargoes which are neither liable to liquefynor possess chemical hazards
Duringthe last hundred years shipping, like other forms of transport has undergonegreat changes. Until the end of the last century most goods at sea were carriedin packaged form. Grain, for example, was carried in sacks and cotton inbales. Very few liquids were carried at all, but those that were - includingoil - were usually carried in barrels. Cargoes in fact were carried in muchthe same way as they always had been.Today everything haschanged. Oil is the major commodity carried at sea in bulk; so are grain,coal and other minerals. Containerization is now common and the general cargoship has in many trades been replaced by specialized vessels such as containerships, ro-ro ships and car carriers among others.
Bulkcargoes
Virtually all liquidstransported by sea - such as crude oil and finished petroleum products - arecarried in bulk, and tankers now form by far the greatest percentage of theworld fleet of merchant ships. The second biggest group consists of solidbulk cargo carriers. The goods carried in this way include coal, grains,ores, concentrates, fertilizers and animal feeds. From the shippers' pointof view bulk carriage has numerous advantages. A bulk cargo can be loadedand unloaded far more quickly than one that is unitized, thereby leading togreat savings in time and money. However, there are a number of dangers inthe carriage of bulk cargoes which include the following:1. Improper weightdistribution resulting in structural damage. This can be caused by puttingtoo much weight on the inner bottom of the ship or by wrongly distributingthe cargo between holds, leading to excessive stresses on the ship's structure.
2. Improper stabilityand cargo shift. Another result of improper loading can be excessivestability. This leads to the normal rolls of the ship becoming shorter butmuch more violent. Apart from being extremely uncomfortable for those onboard, this can in turn lead to damage to the ship's structure.
Stability of the shipcan also be affected by the cargo shifting during the course of the voyage. This can occur because the cargo is inadequately trimmed (levelled-off) orimproperly distributed. In some cases cargoes can liquify as a result ofvibration and the motion of the ship and then slide or flow to one side ofthe cargo hold. This usually happens when the cargo consists of finely-grainedmaterial, such as fine coal and ore concentrates, which are damp when loaded. However it occurs, a shift of cargo can lead to the ship listing and ultimatelycapsizing.
3. Spontaneous heating. Some cargoes carried in bulk have a tendency to heat spontaneously duringthe course of a voyage. The result can be a fire or explosion.
4. Chemical hazards. These hazards include the emission of toxic or explosive gases, oxygen depletion,spontaneous combustion or severe corrosion.
Measures to counterthese problems have been adopted at both a national and international level.
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Thecarriage of grain
Grain has been transportedby sea for many thousands of years - it was an important feature of commercein the Mediterranean in ancient times - and nowadays, is generally carried inbulk. However, grain has one great hazard when carried at sea in bulk; it tendsto shift within the cargo space of the ship. Because of this danger and thegreat amount of grain transported by sea, special rules governing its carriagein bulk have appeared in various international instruments including the InternationalConvention on the Safety of Life at Sea.Backto top
GeneralCargoes
General cargoes, even ifnot classed as dangerous, can pose dangers to ships or those on board, if certainprecautions are not observed. If the cargo is to be discharged in generallythe same condition as when loaded, further common sense considerations apply. In order to plan stowage, the responsible officer should have information onthe nature, mass and stowage factor of the individual cargo. Where large itemsof cargoes are concerned, information on the dimensions of the cargo is required. Such information will then be used to distribute the cargo in such a way asto ensure adequate stability and workable trim at all stages of the voyage andto have the cargo gear rigged so as to ensure that heavy items can be liftedwithout the possibility of a stow collapsing and endangering the ship; of itemsof machinery or steel shafts falling and penetrating the ship's shell-plating;or of shifting deck-cargoes causing fractured deck piping and ventilation trunks.In addition to thosesafety matters, the cargo officer must take into account commercial considerationsand separate tainting from taintable cargoes or sweating cargoes from thosethat may be damaged by moisture and that heavy items are not placed on frailpackages or packaged liquids on bagged cargoes. For some cargoes ventilationmust be encouraged or sometimes it must be restricted but the different climatologicalconditions in which a ship is expected to operate must always be taken intoaccount. In all cases, the drainage of liquids to the hold bilges or wellsshould be facilitated.
The securing of breakbulkcargoes is most conveniently done by planning stows to occupy the spaces fromside to side, incorporating, where appropriate, built-in anchors of dunnageor using locked stows. Heavy items are individually lashed and for some cargoes,known to have given rise to difficulties in the past, IMO has published a Codeof Safe Practice for Cargo Stowage and Securing (resolution A.714(17)). Forthe securing of freight containers a wide variety of standardized fittings areavailable. On open-top container ships, the need to secure cargoes is greatlydiminished as all containers are placed within cells. The securing of containerson general cargo ships can cause problems unless special fittings have beenprovided.
Barge carrying shipshave specialized arrangements to secure the barges and if problems arise,they stem from the cargoes within the barges. Ro-ro ships have fittings tosecure lorries, although these are not always used.
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Thecarriage of timber on deck
Timber is often carried onthe decks of ships and sometimes cause the combined centre of gravity of shipand cargo to rise, which adversely affects stability, a situation made worsewhen the deck cargo absorbs rain and seawater during the voyage, especiallywhen freezing occurs and ice accumulates on deck. However, there is usuallyan increase in buoyancy and the timber also gives the ship greater protectionagainst the rough sea conditions. Thus, ships which carry timber deck cargoesmay be granted reduction of the freeboard applicable under the 1966 InternationalConvention on Load Lines except in the North Atlantic zone in winter where icingcan be a problem.TheCode of Safe Practice for Ships Carrying Timber Deck Cargoes gives furtherinformation and guidance on this subject. It was adopted by IMO in 1973 andamended in 1978 and 1990. Like the BC Code and contrary to the InternationalGrain Code, it is not a mandatory instrument but is intended to serve as guidanceto Governments who can implement it if they desire, either in whole or inpart. The Code is intended to apply to ships of 24 metres (79 feet) in lengthand over. Timber deck cargoes are defined as cargoes of timber, includinglogs, and sawn timber whether loose or packaged, which are carried on an uncoveredpart of a freeboard or superstructure deck.Backto top
Containerization
Since first introduced inthe 1950s, containers have revolutionized the carriage of general cargoes whichpresented great advantages both in ease and speed of handling, cargo security,and together with other factors have transformed both ships and ports.In many countries thetraditional cargo berths, located in the centre of urban areas, have losttrade because they do not provide the space needed for container operationsas berthing facilities in many cases have moved downriver, to where thereis more land available and the water is deep enough to accommodate containerships that have steadily increased in size. Usually ports have been developedwith a close eye on land transport as well, for one of the major advantagesof containers is that they enable an integrated transport system involvingroad, rail and sea elements to be established, the link being the port andthe common feature the container itself.
Morerecently another innovation has affected the shipment of cargoes, especiallyon short-sea routes: the trailer on board ship. The special-purpose roll/on-roll/offship offers many of the advantages of the container ship, including speedand security. A container on a trailer can be driven straight onto a shipin one port and off again when it reaches its destination. There is no cargohandling involved and consequently no extra costs or loss of time. Both developmentsoffer economic benefits and both raise problems.In view of the rapidincrease in the use of freight containers for the consignment of goods bysea and the development of specialized container ships, in 1967 IMO undertookto study the safety of containerization in marine transport. The containeritself emerged as the most important aspect to be considered.
In the 1970s IMO and theInternational Labour Organisation began work on guidelines for training in thepacking of cargo in freight containers. These were published in 1978 as a shortguide which emphasized the effect upon the contents of the containers of seaitself. The movement of the ship in adverse weather can result in pitching,rolling and other movements greater than anything found ashore. The guidelineswere revised in 1984.
Experience had by thenshown that probably the greatest problem associated with ro-ro ship safetyconcerned cargo stowage. A survey carried out by the Norwegian classificationsociety, det Norske Veritas, showed that 43% of ro-ro losses couldbe attributed to faults in this area. The danger is even greater in the caseof ro-ro ships than on pure containerships, because containers are generallycarried on trailers: a loading error can result in the container and the trailerboth falling over or becoming dangerously unbalanced. In 1983 IMO thereforeadopted a resolution on elements to be taken into account when consideringsafe stowage and securing of cargo units and vehicles in ships and two yearslater, it adopted another resolution on securing arrangements for the transportof road vehicles on ro-ro ships. It contained guidelines intended to applyto commercial vehicles, including semi-trailers and road trains, with a totalmass (including cargoes) of up to 40 tons, and articulated road trains ofnot more than 45 tons but does not apply to buses.
Theresolution stipulates that given adequately designed ships and properly equippedroad vehicles, lashing of sufficient strength will be capable of withstandingthe forces imposed on them during the voyage. The side guards often requiredfor vehicles can obstruct proper securing and the guidelines take this difficultyinto account. They cover securing points both on the deck of the ship andon the vehicle, as well as lashings and stowage.Backto top
Cargostowage and securing
In 1991 the IMO Assemblyadopted the Code of Safe Practice for Cargo Stowage and Securing. Its purposeis to provide an international standard to promote the safe stowage and securingof cargoes by:
providing advice toensure that the ship is equipped with proper cargo securing means;
providing generaladvice concerning the proper stowage and securing of cargoes to minimizethe risks to the ship and personnel;
providing specificadvice on those cargoes which are known to create difficulties and hazardswith regard to their stowage and securing;
advising on actionswhich may be taken in heavy sea conditions; and
advising on actionswhich may be taken to remedy the effects of cargo shifting.
The Code is basedon a number of general principles:
All cargoes shouldbe stowed and secured in such a way that the ship and persons on board arenot put at risk.
The safe stowage andsecuring of cargoes depend on proper planning, execution and supervision.
Personnel commissionedto tasks of cargo stowage and securing should be properly qualified andexperienced.
Personnel planningand supervising the stowage and securing of cargo should have a sound practicalknowledge of the application and content of the Cargo Securing Manual, ifprovided.
In all cases, improperstowage and securing of cargo will be potentially hazardous to the securingof other cargoes and to the ship itself.
Decisions taken formeasures of stowage and securing cargo should be based on the most severeweather conditions which may be expected by experience for the intendedvoyage.
Ship-handling decisionstaken by the master, especially in bad weather conditions, should take intoaccount the type and stowage position of the cargo and the securing arrangements.
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Theprevention of infestation
Infestation by insects androdents is a threat which all ships face. It can have serious consequencesfor a variety of reasons. Pests can damage equipment and spread disease andinfection, contaminate food in galleys and stores and cause damage to cargoes. Although pesticides can be used to eliminate or control infestation, very fewpesticides are suitable against all types of pests and if improperly used canthemselves present dangers.In 1971 IMO adoptedrecommendations on the safe use of pesticides in ships. It has been revisedseveral times since then. It gives guidance on the prevention of infestation,the use of insecticides, pesticides and fumigants.
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TheCode of Safe Practice for Solid Bulk Cargoes
The dangers associated withthe carriage of cargo in bulk have been known for a long time and the 1960 InternationalConference on the Safety of Life at Sea recommended that IMO draw up an internationalcode of safe practice dealing with this subject. Work began immediately andin 1965 the first Code of Safe Practice for Solid Bulk Cargoes was adopted.The Code has been updatedat regular intervals since then and is kept under continuous review by theSub-Committee on Containers and Cargoes. The practices contained in the Codeare intended as recommendations to Governments, ship operators and shipmasters. Its aim is to bring to the attention of those concerned an internationally-acceptedmethod of dealing with the hazards to safety which may be encountered whencarrying cargo in bulk. The Code does not deal with the transport of grain,which is covered by the International Code for the Safe Carriage of Grain(International Grain Code).
The Code of Safe Practicefor Solid Bulk Cargoes deals with three basic types of cargo: those whichmay liquefy; materials which possess chemical hazards; and materials whichfall into neither of these categories but many nevertheless pose some dangers,as stated above.
The Code highlightsthe dangers associated with the shipment of certain types of bulk cargoes;gives guidance on various procedures which should be adopted; lists typicalproducts which are shipped in bulk; gives advice on their properties and howthey should be handled; and describes various test procedures which shouldbe employed to determine the characteristic cargo properties.
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Generalprecautions
It is of fundamental importancethat bulk cargoes be properly distributed throughout the ship so that the structureis not overstressed and the ship has an adequate standard of stability.Loaded conditions varyaccording to the density of the cargo carried. General cargo ships are normallyconstructed so that one ton of cargo occupies about 1.39-1.67 cubic metresof space when loaded to full bale cubic and deadweight capacity. The ratioof volume of cargo to its mass is known as the stowage factor. When the highdensity bulk cargoes with a stowage factor of about 0.56 cubic metres perton or lower are carried, it is particularly important to pay attention tothe distribution of weight in order to avoid excessive stresses on the structureof the ship. Since hull arrangements vary, it is not possible to establishoverall rules applicable to all types of ships.
Itis essential that the master be provided with loading information sufficientlycomprehensive to enable him to load the ship without overstressing the structure. This applies to localized stresses on the structure as well as on the bendingstresses. The master must also be able to calculate the stability of hisship for the anticipated worst conditions during the voyage.The initial transverse stabilityof a ship is usually expressed as the metacentric height or GM. A large distancebetween the centre of gravity of ship and cargo (G) and the metacentre[1] (M) means that the ship has adequatestability. As G approaches M, i.e. when the centre of gravity of ship and cargorises, ships, when forced from a position of equilibrium, recover this positionsluggishly.Generally speaking,high density cargoes should be loaded in the lower hold spaces rather thanthe 'tween decks[2]. Particular care should be taken when a ship has a high GM. In order to prevent cargoes from shifting the considerations dealt with belowunder the heading Bulk cargoes having an angle of repose greater than 35 degrees[3]should also be taken into account.
The Code gives variousprecautions to be followed when information on the physical properties ofthe cargo is not available.
The Code lists othergeneral precautions such as the need to protect machinery and the interiorof the ship from dust and to ensure that bilges and service lines are in goodorder and not damaged during loading.
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Bulkcargoes having an angle of repose less than or equal to 35 degrees
When a bulk cargo is emptiedon to a flat surface, such as the hold of a ship, it forms a cone whose angleof repose varies according to the type of cargo. This angle is the one formedbetween the horizontal plane and the cone slope.Cargoes with a low angleof repose are particularly liable to dry-surface movement aboard ship. Toovercome this problem, the Code states that such cargoes should be trimmedreasonably level and spaces in which they are loaded should be filled as fullyas is practicable, without resulting in excessive weight on the supportingstructure.
Special provisions shouldbe made for stowing dry cargoes which flow very freely, in a similar mannerto grain.
Securing arrangements,such as shifting boards or bins, should be used whenever the amount, locationor properties of the cargo could cause excessive heeling through cargo shift,taking into account the density of the cargo.
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Bulkcargoes having an angle of repose greater than 35 degrees
Generally speaking, high-densitycargoes, such as most iron ores, have a high angle of repose, i.e. above 35degrees.The Code states thathigh density cargoes should be loaded entirely in the lower holds of the shipunless this results in the ship being too "stiff"[4]or in the cargo weight on the bottom structure being excessive. It shouldbe trimmed sufficiently level to cover evenly all of the tank top, to reducethe pile peak height and equalize weight distribution. In some circumstancesthe pile peak may be allowed to extend through the 'tween-deck hatchway butthe Code says that the importance of trimming as a means of reducing the possibilityof a shift of cargo can never be over-stressed. This is particularly truefor smaller ships of less than 100 metres in length.
Trimming also helpsto cut oxidation by reducing the surface area exposed to the atmosphere. It also helps to eliminate the "funnel" effect which in certaincargoes, such as direct reduced iron (DRI) and concentrates, can cause spontaneouscombustion. This occurs when voids in the cargo enable hot gases to moveupwards, at the same time sucking in fresh air. This effect is obviouslynot desirable, since it escalates the process of spontaneous combustion.
The Code goes on tolist various considerations which should be taken into account when cargois loaded in the 'tween-decks to reduce "stiffness".
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Safetyof personnel
After listing various regulationsadopted by the International Labour Organisation, which should be taken intoaccount during cargo handling operations, the Code gives details of other dangerswhich may exist. Some cargoes, for example, are liable to oxidation which mayresult in the reduction of the oxygen supply, the emission of toxic fumes andself-heating. Others may emit toxic fumes without oxidation or when wet. Theshipper should inform the master of chemical hazards which may exist and theCode gives details of precautions which should be taken.Health hazards can arisebecause of dust, and some cargoes can create dust or emit flammable gaseswhich create a danger of explosion.
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Cargoeswhich may liquefy
These include concentrates(materials obtained from a natural ore by a process of purification, by physicalor chemical separation and removal or unwanted constituents), some coals andother materials with similar properties.One purpose of thissection of the Code is to draw attention to the latent risk of cargo shiftand describe precautions which should be taken. Concentrates and similarfinely-particulate materials may appear to be in a relatively dry granularstate when loaded and yet may contain sufficient moisture to become fluidunder the stimulus of compaction and vibration. In the resulting semi-fluidstate, the cargo may flow to one side when the ship rolls but not completelyreturn when the ship rolls the other way. As in the case of cargoes liableto shift, this can result in the ship reaching a dangerous heel or eventuallycapsizing.
The stability of theship is also likely to be affected by "free surfaces"[5]of liquids in the cargo spaces. General cargo ships should only carry bulkcargoes which have a moisture content below the transportable moisture limit(TML), which is 95% of the flow moisture point (FMP) unless they are fittedwith special arrangements to restrain the cargo.
Cargo ships in whichinternal structural boundaries are sufficient to limit cargo shift may alsocarry cargoes whose moisture content exceeds the transportable moisture limit. All ships which carry cargoes of this type should carry evidence of approvalof the flag State. The Code stipulates the data which should be includedin submission for approval.
To prevent possibleincreases in the liquid content of concentrates, cargoes containing liquids(other than canned goods or the like) should not be stowed in the same compartmentas cargoes which may liquify. Precautions should be taken to prevent waterentering holds; this is even more important where contact with seawater couldlead to serious corrosion problems for hull or machinery. In this connectionmasters should be aware of the possible danger of using water to cool combustiblematerials such as coal at sea, as this may well bring the moisture contentto a flow state or create other hazards. Water, if used, is most effectivelyapplied in the form of spray or mist.
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Samplingand test procedures for cargoes which may liquefy
The Code strongly recommendsthat, prior to loading cargoes of this type, masters should obtain a certificatestating the flow moisture point, the transportable moisture limit of the cargotogether with its actual moisture content.The Code gives detailsof the various sampling procedures and tests which should be used before transportingconcentrates and similar materials. These include the selection of samplesfor laboratory tests to determine the transportable moisture content of concentrates;and the selection of samples to determine the flow moisture point and themoisture content at the time of loading. Procedures concerning the issuingof certificates by Administrations are also given including a recommendedtest procedure to be used by laboratories.
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Appendicesto the Code
A list of cargoes which mayliquefy is contained in appendix A to the Code. The stowage factor is generallylow (from 0.33 to 0.57 cubic metres per ton) and it is emphasized that the listof materials is not exhaustive. It includes concentrates derived from copper,iron, lead, manganese, nickel, and zinc ores, various pyrites, fine-particulatecoal, coal slurry and various other substances.Backto top
Materialspossessing chemical hazards
Appendix B gives an extensivelist of materials of this type ranging from aluminium dross to zinc ashes. Some of the classifiedmaterialslisted also appear in the International Maritime Dangerous Goods (IMDG) Codewhen carried in packaged form, but others become hazardous only when they arecarried in bulk - for example, because they might reduce the oxygen contentof a cargo space or are prone to self-heating. Examples are woodchips, coaland DRI.The various types listedinclude: flammable solids; flammable solids or substances liable to spontaneouscombustion; flammable solids or substances which, in contact with water, emitflammable gases; oxidizing substances; poisonous substances; radio-activesubstances; or corrosives.
Such materials should becarefully segregated from other dangerous goods carried in packaged or unitizedform. The Code describes how this should be done.
Eachentry includes either the United Nations number[6] and IMO class[7] or the MHB (materials hazardous in bulk) classification and aBC number; the relevant MFAG (Medical First Aid Guide) table number[8]; approximate angle of repose andstowage factor; Emergency Schedule number; separation and stowage requirements;and properties, observations and special requirements.Back to top
Bulkcargoes which are neither liable to liquefy nor possess chemical hazards
These cargoes do not normallyhave special hazards and are covered in Appendix C. The list ranges from aluminato zircon sand as well as many of the more commonly-carried bulk cargoes suchas clay, cement, iron ore, pig iron, sand and sugar. The list includes theangle of repose of each material, its approximate stowage factor, and the propertiesand special requirements connected with each one.IMO Resolution A.713(17)
Despite the effortsof IMO and its Member Governments, the number of bulk carriers sinking duringthe late 1980s and early 1990s, sometimes without trace, began to cause seriousalarm. As a result, resolution (A.713(17)) which contains interim measuresdesigned to improve the safety of ships carrying solid bulk cargoes, was dulyadopted.
Owners are encouragedto fit vessels with equipment to monitor the stresses on the ship's structureduring the voyage and during cargo operations. They are also encouraged toinstall equipment required by the Global Maritime Distress and Safety System(GMDSS), which enters into force on 1 February 1992.
The impact of this resolutionwas immediately beneficial. The number of bulk carrier losses dropped fromaround one a month to just two within the next year. It is significant thatthe resolution did not introduce any new measures but simply stressed theimportance of implementing existing standards.
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[1] For ships with a small list the metacentre may beconsidered to be the point on a line drawn vertically through the ship whichis intersected by a line drawn vertically from the centre of buoyancy whenthe ship is rolling. If this point is below the centre of gravity the shipwill roll over. The term GM means the vertical distance from the metacentre(M) to the centre of gravity (G).
[2]A 'tween-decker is a ship with more than one deck, thus providing spacebetween the two adjacent decks.
[3] Thesesections of the Code are currently under revision, the aim being to developnew criteria for shifting of cargoes.
[4] i.e. having a large metacentricheight.
[5] Whena cargo space contains a liquid, the metacentric height of the ship is reducedby an amount depending mainly on the width of the free surface of the liquid. The effect is independent of the amount of liquid in the cargo space.
[6] TheUN Committee of Experts on the Transport of Dangerous Goods numbers eachdangerous substance, with the exception of MHB.
[7] Substancesincluded in the IMDG Code are arranged in different classes according totheir properties (e.g. explosives, flammable liquids, corrosives, etc.).
[8] TheMedical First Aid Guide is intended for use in conjunction with the IMDGCode. Poisons are divided into groups and given individual numbers.
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