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Monitoring general cargo ships Loaded Condition

Loaded Condition

The officer in charge should closely monitor the ship's condition during cargo operations to ensure that if a significant deviation from the agreed loading/unloading plan is detected all cargo and ballast operations must STOP.

The officer in charge should ensure that,

i) the cargo operation and intended ballast procedure are synchronised.

ii) draught surveys are conducted at appropriate steps of the loading plan to verify the ship's loading condition. The draught readings, usually taken at amidships and the fore and aft perpendiculars, should be in good agreement with values calculated in the loading plan.

iii) ballast tanks are sounded to verify their contents and rate of ballasting/deballasting.

iv) the cargo load is in agreement with the figures provided by the terminal.

v) the SWSF, SWBM and, where appropriate, hold cargo weight versus draught calculations are performed at intermediate stages of the cargo operation. These results should be logged, for recording purposes, against the appropriate position in the loading plan.

Following a deviation from the loading plan, the officer in charge should take all necessary corrective actions to:

i) Restore the ship to the original loading/unloading plan, if possible, or

ii) Replan the rest of the loading/unloading operation, ensuring that the stress and operational limits of the ship are not exceeded at any intermediate stages.

The modified loading/unloading plan should be agreed by both the officer responsible for the loading plan and the cargo terminal representative. Cargo operations should not resume until the officer in charge gives a clear indication to the terminal of his readiness to proceed with the cargo operation.

Loading limits

Exceeding the permissible limits specified in the ship's approved loading manual will lead to over-stressing of the ship's structure and may result in catastrophic failure of the hull structure. When deviating from the cargo load conditions contained in the ship's approved loading manual, it is necessary to ensure that both the global and local structural limits are not exceeded. It is important to be aware that over-stressing of local structural members can occur even when the hull girder still water shear forces (SWSF) and bending moments (SWBM) are within their permissible limits.

Exceeding the maximum permissible cargo load in any hold will lead to over-stressing of local structure. Over-stressing of the local structure will occur when:-

i) The weight of cargo loaded into a hold exceeds the maximum permissible value specified at full draught.

ii) The weight of cargo loaded into adjacent holds exceeds the maximum combined value at full or reduced draught.

Cargo ship unstable in a seaway

Fig:Cargo ship unstable in a seaway

Over-stressing of the local structure may also occur when the weight of cargo loaded into an individual hold has insufficient support of upward buoyancy force; this circumstance can occur when cargo is transported by the ship in a shallow draught condition (for example, partial load condition with some holds full and remaining holds empty).

Use of loading plan computer

Most Modern cargo ships are now equipped with loadicator systems or a loading computer with appropriate software. It is usually a conveniently sited visual display for the Master and the Loading Officers and is gainfully employed on Ro-Ro vessels, bulk carriers, tankers and other cargo ships.

The main aim of the loading computer being to ensure that the vessel always departs the berth with adequate stability for the voyage. If this situation can be achieved quickly, costly delays can be eliminated and safety criteria is complied with.

The system should ideally be interlinked with the shore side base to enable data transmissions on, unit weights/tonnages/or special stow arrangements.The Computer would permit the location and respective weights of cargo/units to be entered quickly and provide values of limiting ‘KG’ and ‘GM’ together with deadweights at respective draughts/displacements. It would also have the capability to provide a printed record of the state of loading and show a visual warning in the event of an undesirable stability condition or overload occurring. Distribution of the ship’s tank weights, stores and consumables affecting final calculations and total displacement would also be identifiable within the completed calculations.

The data required to complete the hull strength & stability calculations would need to be supplied by the shore side base with regard to cargo weights. Draught information would inevitably come from a ‘Draught Gauge System’ for the larger vessel and be digitally processed during the period of loading.

Ship’s personnel could expect to become familiar with manipulation of the changing variables very quickly alongside the fixed weight distribution throughout the ship .This would include amounts of bunkers,water and stores are consumed and stability datas may change for arrival conditions.

The loadicator programmes provide output in the form of:

i) Shear forces and bending moments effecting the vessel at its state of loading.

ii) Cargo, ballast and fuel tonnage distributions.

iii) A statement of Loaded ‘GM’, sailing draughts and deadweight.

Other useful articles :
  1. Assigning loadlines marks

  2. Loadlines are marks punched into and painted on the sides of general cargo ships.The assigning of the vessels loadline and the issue of the Certificate is the responsibility of the Marine Authority of the country. .
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  3. Cargo ships Loaded Condition

  4. closely monitor the ship's condition during cargo operations to ensure that if a significant deviation from the agreed loading/unloading plan is detected all cargo and ballast operations must STOP..
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  5. Packing a container recommended method

  6. Packing a container should always be done on level plane either on the ground,on a railcar, or on a trailer. In the case of a trailer, care should be taken to ensure the trailer cannot tip whilst being packed especially if a forklift truck is being used. If necessary the trailer should be propped. Brakes should be securely applied and wheels choked.
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  7. Packing principles relating to cargo in containers

  8. Where relevant, stowing should be carried out in a sequence which will permit rapid checking and storage operations during and after unloading. Should the consignment include cargo subject to customs pre-entry procedures, customs examination would be made easier and unloading avoided if the cargo were stowed at the end of the container by the door.
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  9. Container Securing guidance

  10. Containers have very little strength in any direction other than vertically through the corner posts thus it is necessary to provide substantial support to the containers when they are on the ship. Stowage of containers is with their longer dimension fore and aft since the ship motion transmitted to cargo is greater in rolling than pitching and it is therefore prudent to limit any possible cargo movement within the container to the shorter transverse dimension.
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  11. Trim and stability booklet for cargo ships

  12. Contain either curves of form or hydrostatic tables and stability and trim characteristics for various conditions of loading .
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  13. Broken stowage? Cargo ships guideline

  14. The access shall be separate from the hatchway opening, and shall be by a stairway if possible. A fixed ladder, or a line of fixed rungs, shall have no point where they fill a reverse slope .
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  15. Ship type, design and facilities for cargo

  16. Cargo gear is designed for speed and flexibility for handling breakbulk, palletized, or container cargo. Various combinations of derricks, winches, and deck cranes are used for the handling of cargo. Cranes are fitted on many vessels to reduce manpower requirements. Some ships have special heavy-lift derricks that may serve one or more holds. Booms are rigged for either yard and stay (burton) or swinging-boom operation.
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  17. Cargo ships structural plans- how to use them

  18. Structural plans, sometimes called scantlings plans, show dimensions of the ships framing and plating. The midships section drawing, generally available for all ships
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