cargo hold

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    A Cargo hold is an enclosed structure in a ship whose main purpose is to store cargoes in the ship. A ballast tank is acompartment within a boat or ship that holds water. A vessel may have a single ballast tank near its center or multiple ballasttanks typically on either side. A large vessel typically will have several ballast tanks including double bottom tanks, wing tanksas well as forepeak and aft peak tanks. Adding ballast to a vessel lowers its center of gravity, and increases the draft of the

    vessel. Increase draft may be required for proper propeller immersion. A ballast tank can be filled or emptied in order to adjustthe amount of ballast force. Ships designed for carrying large amounts of cargo must take on ballast water for proper stabilitywhen travelling with light loads and discharge water when heavily laden with cargo. Small sailboats designed to be light weightfor being pulled behind automobiles on trailers are often designed with ballast tanks that can be emptied when the boatis removed from the water. In submarines ballast tanks are used to allow the vessel to submerge, water

    being taken in to alter the vessel's buoyancy and allow the submarine to dive. When the submarine surfaces, water is

    blown out from the tanks using compressed air, and the vessel becomes positively buoyant again, allowing it to rise to thesurface. A submarine may have several types of ballast tank: the main ballast tanks, which are the main tanks

    used for diving and surfacing, and trimming tanks, which aroused to adjust the submarine's attitude (its 'trim') both on thesurface and when underwater. A hatch or hatchway is the opening at a wall or floor particularly on the shipsdeck at the top of

    a cargo hold. The mechanical devices which allow hatches to be opened and closed are called hatch covers. In general, hatchcovers are between 45% and 60% of the ship's breadth, or beam, and57% to 67% of the length of the holds. To efficiently load

    and unload cargo, hatches must be large, but large hatches present structural problems. Hull stress is concentrated around theedges of the hatches, and these areas must be reinforced. Often, hatch areas are reinforced by locally increasing thescantlings or by adding structural members called stiffeners. Both of these options have the undesired effect

    of adding weight to the ship.

    General Guidance: Preparation for Survey

    1. Tanks and spaces are to be safe for access, i.e. gas freed, ventilated and illuminated.

    2. In preparation for survey, thickness measurements and to allow for a thorough examination, all spaces are to be cleaned

    including removal from surfaces of all loose accumulated corrosion scale. Spaces are to be sufficiently clean and free

    from water, scale, dirt, oil residues etc. to reveal corrosion, deformation, fractures, damages or otherstructural deterioration. However, those areas of structure whose renewal has already been decided by the owner needonly be cleaned and de-scaled to the extent necessary to determine the limits of renewed areas.

    3. Sufficient illumination is to be provided to reveal corrosion, deformation, fractures, damages or otherstructural deterioration.

    4. Means are to be provided to enable the Surveyor to examine the structure in a safe and practical way.

    5. For surveys, including close-up survey where applicable, in cargo spaces and ballast tanks, one or more of the followingmeans of access, is to be provided:

    a) Permanent staging and passages through structures.b) Temporary staging and passages through structures.c) Lifts and movable platforms.d) Boats or rafts.

    e) Other equivalent means.

    6. Survey at sea or anchorage may be undertaken when the Surveyor is fully satisfied with the necessaryassistance from the personnel onboard and provided the following conditions and limitations are met:

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    a) Surveys of tanks by means of boats or rafts is at the sole discretion of the attending Surveyor, who is to take into account thesafety arrangements provided, including weather forecasting and ship response in reasonable sea conditions. Appropriate life

    jackets are to be available for all participants. The boats or rafts are to have satisfactory residual buoyancy and stability even ifone chamber is ruptured. A safety checklist is also to be provided. An oxygen-meter, breathing apparatus, lifeline and whistlesare to be at hand during the survey. For oil tankers and chemical tankers an explosimeter is also to be provided.

    b) A communication system is to be arranged between the survey party in the tank and the responsible officer on deck. Thissystem must include the personnel in charge of ballast pump handling if boats or rafts are to be used.

    c) Surveys of tanks by means of boats or rafts will only be permitted for the under deck areas of tanks when the coating of theunder deck structure is in GOOD condition and there is no evidence of wastage. The only exception to this, at the discretion ofthe Surveyor, is where the depth of under deck web plating is 1,5 m or less. Alternatively, rafting may be used if a permanent

    means of accesses provided in each bay to allow safe entry and exit. This means of access is to be direct from deck via a verticalladder and a small platform fitted approximately 2 m below deck. Where these conditions are not met, then the

    under deck area will require to be staged for survey.

    7. On ships of 20,000 tones deadweight and above, and where the notation ESP is assigned starting with Special Survey III, allspecial and Intermediate hull surveys are to be carried out by at least two exclusive surveyors attending on board to jointly

    perform the Survey. On single side skin bulk carriers of 100,000 tones deadweight and above the Intermediate Survey between10 and 15years of age is also to be carried out by at least two exclusive Surveyors attending onboard to jointly perform theSurvey. Though each attending Surveyor is not required to perform all aspects of the required survey, the attending Surveyors

    are required to consult with each other and to do joint examinations to the extent necessary for them to agree onactions required to complete the survey (i.e. with respect to Overall surveys, Close-up surveys, renewals, repairs,and conditions of class).

    Corrosion in Cargo Spaces and Ballast Tanks

    Corrosion of cargo tank structure is a fact of life when operating oil tankers in the harsh environment encountered at sea. Theinternal structure of the cargo tanks, often un-coated, is exposed to potentially corrosive gases, sea water, and crude oil and oil

    products. The effect of this corrosion over a period of years is to reduce the material thickness and hence

    the strength of the structure .Corrosion in the cargo tanks of oil tankers can generally be classified as general corrosion,local corrosion, pitting corrosion or weld metal corrosion.

    a. General Corrosion This type of corrosion generally appears in tanks that are un-coated as a crumbly scale that is evident

    over large areas and which, when it is dislodged, exposes fresh steel to the corrosion cycle. Generalcorrosion is allowed for in the design and construction of the oil tanker and an average value of in-service wastage is generallyaccepted as being around 0.1mm/year or less. Classification Society corrosion allowances would typically offer a useful life for

    structural members of around 20-25years.

    b. Local Corrosion highly stressed structural components tend to "work" during alternate compression and tension cycles whenthe ship is in-service. Surface rust or scale on these components becomes dislodged during this flexing process, exposing bare

    steel to further insidious corrosive attack. To further exacerbate the situation, as the material thickness diminishes,

    the stress on the component is incrementally raised and the corrosion continues at an acceleratedrate. Localized corrosion, in grooving form, occurs at structural intersections where water collects or flows. Grooving

    corrosion can also occur on the vertical structural members at the water flow path or on the flush sidesofbulkheads in way of flexing of platings.

    c. Pitting Corrosion Pitting corrosion is a localized corrosion that is more commonly found in the bottom plating of tanksand horizontal surfaces or structural detail where water tends to accumulate. Bare steel plates in cargo tanks

    are often coated with black rust and a residual waxy oil coating from previous cargoes which tends to protect the metal surfacefrom heavy corrosion. Localized breakdown of these natural tank coatings, particularly in way of cargo bell mouths, or

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    cleaning medium impingement areas, can quickly cause very severe pitting where seawater collects and electrolytic and/ormicrobial induced corrosion can occur. Severe pitting corrosion creates a tendency for the pits to merge to form long grooves or

    wide scabby patches with an appearance resembling that of general corrosion. Extreme pitting corrosion in addition to causingloss of structural strength necessitating extensive and costly steel renewals can, if not adequately repaired, lead to hull

    penetration and a serious pollution incident.

    d. Weld Metal Corrosion

    To reduce the risk of machinery failures at this critical time, OCIMF recommends that if

    significant maintenance or repair is carried out on the main propulsion machinery and / or the steering

    gearsystem and / or any auxiliary machinery / systems essential to the propulsion and safety of the

    ship,then on conclusion of the repair period the operation of the complete machinery system should

    beverified under controlled conditions by a test run which includes at least 1 hour at full power. OCIMF

    further recommends that should the vessel be required to be deactivated for a period exceeding 2 weeks

    then upon reactivation the operation of the complete machinery system should be verified under

    controlled conditions by a test run which includes at least 1 hour at full power.

    INFORMATION EXCHANGE DURING CARGO LOADING AND UNLOADING OPERATIONS

    INFORMATION GIVEN BY THE SHIP TO THE TERMINAL

    In order to plan the proper disposition and availability of the cargo so as to meet the ships loading plan,

    the loading terminal should be given the following information..

    1.The ships estimated time of arrival (ETA) off the port as early as possible. This advice should be

    updated as appropriate..

    2.At the time of initial ETA advice, the ship should also provide details of the following:.

    2.1. Name, call sign, IMO Number of the ship, its flag State and port of registry;.

    2.2. a loading plan stating the quantity of cargo required, stowage by hatches, loading order and the

    quantity to be loaded in each pour, provided the ship has sufficient information to be able topreparesuch a

    plan;

    2.3. Arrival and proposed departure draughts;

    2.4. Time required for de-ballasting;

    2.5. the ships length overall, beam, and length of the cargo area from the forward coaming of theforward-

    most hatch to the after coming of the aft-most hatch into which cargo is to be loaded orfrom which cargo

    is to be removed;

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    2.6. Distance from the water line to the first hatch to be loaded or unloaded and the distance fromthe ships

    side to the hatch opening;

    2.7. The location of the ships accommodation ladder;.

    2.8. Air draught;.

    2.9. Details and capacities of ships cargo handling gear;

    2.10. Number and type of mooring lines; and

    2.11. any other item related to the ship requested by the terminal..3Similar information in respect of ETA,

    unloading plan and details of the ship are required by unloading terminals.

    3. Ships arriving at loading or unloading terminals in a part loaded condition should also advise:

    1. berthing displacement and draughts;

    2. previous loading or unloading port;

    3. nature and stowage of cargo already on board and, when dangerous goods in bulk are on board,the

    name of the material, IMO Class and UN Number or BC Number.

    4. Distribution of cargo on board, indicating that to be unloaded and that to remain on board.

    4.Combination carriers (OBO or O/O) should advise of the following additional information:

    1. nature of the preceding three cargoes;

    2. date and place at which the last oil cargo was discharged;

    3. advice as to content of slop tanks and whether fully inerted and sealed; and

    4. date, place and name of authority that issued the last gas free certificate which includes pipe lines and

    pumps

    5.As soon as possible the ship should confirm that all holds into which cargo is to be loaded are clean,

    and free from previous cargo residues which in combination with the cargo to be loaded could create a

    hazard.

    6. Information on the loading or unloading plan and on intended arrival and departure draughts should be

    progressively updated, and passed to the terminal as circumstances change.

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    7. On receipt of the ships initial notification of its ETA, the terminal should give the ship the following

    information as soon as possible:.1the name of the berth at which loading or unloading will take place and

    the estimated times for berthing and completion of loading or unloading;

    INFORMATION BY THE TERMINAL TO THE SHIP

    1. On receipt of the ship s initial notification of its ETA, the terminal should give the ship thefollowing

    information as soon as possible:

    1. the name of the berth at which loading or unloading will take place and the estimated times forberthing

    and completion of loading or unloading;

    2. characteristics of the loading or unloading equipment, including the terminal s nominal loading

    orunloading rate and the number of loading or unloading heads to be used;

    3. features of the berth or jetty the master may need to be aware of, including the position of fixedand

    mobile obstructions, fenders, bollards and mooring arrangements;

    4. minimum depth of water alongside the berth and in approach or departure channels;

    5. water density at the berth;

    6. the maximum distance between the water line and the top of cargo hatch covers or coamings,whichever

    is relevant to the loading operation, and the maximum air draft;

    7. Arrangements for gangways and access;

    8. Which side of the ship is to be alongside the berth;

    9. maximum allowable speed of approach to the jetty and availability of tugs, their type and bollard pull;

    10. The loading sequence for different parcels of cargo, and any other restrictions if it is not possible to

    take the cargo in any order or any hold to suit the ship;

    11. any properties of the cargo to be loaded which may present a hazard when placed in contact with

    cargo or residues on board;

    12. advance information on the proposed cargo handling operations or changes to existing plans forcargo

    handling;

    13. if the terminals loading or unloading equipment is fixed, or has any limits to its movement;

    14. mooring lines required;

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    15. Warning of unusual mooring arrangements;

    16. any restrictions on de-ballasting;

    17. maximum sailing draught permitted by the port authority; and

    18. any other items related to the terminal requested by the master.

    2. Information on estimated times for berthing and departure and on minimum water depth at theberth

    should be progressively updated and passed to the master on receipt of successive ETAadvices.

    3.The terminal representative should be satisfied that the ship has been advised as early as possibleof the

    information contained in the cargo declaration as required by chapter VI of SOLAS 1974, asamended.