Container ship operation: Common reasons for stow collapse
Container stows often fail due to container stacks being too heavy and too high overall, exposing the lower containers to excessive transverse racking and compressive forces due to the tipping effect. Such an anomaly may occur if the ship is unable to calculate the forces acting on stow with precision. The Cargo/Container Securing Manual is limited in this respect as the examples of container weight distributions shown may not cover all permutations and eventualities. Software programs have the advantage of taking into account all known variables.
The wind force acting on the outboard stacks not being taken into account.
Loose lashings allowing the stacks to tilt and arrest sharply as the slack is taken up. This causes the securing system to experience a sudden shock load which may exceed safe working limits by a considerable margin.
• Two 20 foot containers placed in a 40 foot slot, leaving insufficient space for lashing rods to be fitted to the inward facing ends. This arrangement should be avoided unless the containers are either lightly loaded or empty and the stack height is low, or if the Cargo / Container Securing Manual allows.
Fig: improper lashing caused container stowfall
• Rogue twist locks (e.g. right-hand locking mechanism) finding their way aboard a vessel equipped entirely with twistlocks of a different type (e.g. left-hand locking mechanism).
• If manual twist locks are used, screening checks should be carried out whenever possible in order to ensure that rogue devices are not present.
• High cube boxes stowed cumulatively, resulting in the highest container extending well above the top of the cell guides.
• Wherever possible, the vessel should scrutinize pre-plan details for the presence of non-standard containers. If the pre-plan shows that out of gauge boxes are to be loaded in unacceptable positions, more suitable stowage options should be discussed and agreed with the terminal as soon as possible.
• Securing equipment not applied correctly, not tightened or not applied at all, contrary to the provisions of the Cargo/Container Securing manual.
• Stevedores should be given detailed instructions regarding the positioning of the lashings and equipment to be used and, as far as practicable all arrangements should be checked thoroughly by the crew before sailing.
• Portable and/or fixed securing equipment in damaged or worn condition.
• Extreme weather conditions.
• The movement of inadequately secured heavy cargo within a container during adverse weather, resulting in damage to the container walls and/or framework and leading to the eventual collapse of the stack.
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Containership operation : Cargo Securing There are six degrees of motion at sea that a ship may have to encounter in a voyage. However, pitching, heaving, and rolling are three major forces that impact most on a containership's lashing arrangement. Lateral rolling motion factors the greatest challenge for piles of containers. If containers are to be carried safely on the deck of a container vessel, they must be tightly connected to the ship. It is done with the aid of devices known as twist locks.
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Containership operation : Common reasons for stowfall
Container stows often fail due to container stacks being too heavy and too high overall, exposing the lower containers to excessive transverse racking and compressive forces due to the tipping effect. Such an anomaly may occur if the ship is unable to calculate the forces acting on stow with precision. The Cargo/Container Securing Manual is limited in this respect as the examples of container weight distributions shown may not cover all permutations and eventualities. Software programs have the advantage of taking into account all known variables........
Containership operation: Cargo hold ventilation
Cargo holds ventilation onboard a containership is very important as it minimizes the risk of harm or damage to cargo. A proper ventilation system assures the quality of the transported goods by preventing the formation of condensation in cargo spaces, reducing the harmful heating of the shipment, and removing potential hazardous gases from cargo spaces........
Containership operation: Safety of personnel
In port stevedores board the vessel for lashing, unlashing and cargo operations and their safety whilst on board is the vessels responsibility. It is important to understand that any injury caused to stevedores or shore personnel due to a condition on board being unsafe, can result in very large claims to the vessel.
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Containership operation: wet damage in cargo hold When water entered into a ship's cargo, hold it may cause wet damage to the cargo inside containers especially to those stowed on the bottom stack, unless the bilge water is drained in a proper and swift manner. The regular sounding of bilge well or monitoring bilge alarm must be one of the very important or rather essential routine jobs on board. However, this job requires special attention on board. All bilge alarm need to be tested regularly......
Reefer cargo care at sea Unlike permanent cold stores or refrigerated ships, where robust equipment is under constant care by qualified personnel, the ISO refrigerated container may travel by several different modes and be in the care of many and varied people. Before being despatched to load refrigerated cargo (usually at shippers' premises), the container and its machinery should be subjected to a rigorous examination.......
Containership cargo stowage and planning Master and officers of all vessels require a good working knowledge of the various kinds of cargo they are likely to carry their peculiar characteristics, liability to damage, decay, or deterioration, their measurement, and the usual methods of packing, loading and discharging, stowage, dunnage, etc., as the Master is responsible for the safe loading of his vessel and the proper storage of the cargo......
Stacking Weights Restrictions
rior loading cargo, stacking weights of containers must be checked against the allowable stack weights on board the vessel both on deck and under deck. Neglecting above may cause serious damage to ships structure, hull and eventually overall stabilty of ship may get affected. Maximum allowable stack weights of Tank tops, Hatch covers and Decks shall not be exceeded at any time......
Lashing strength calculation Lashing strength of deck cargo shall be ascertained by using the appropriate lashing strength calculation software where provided. All resulting values for lashing strength must be within the tolerance limits prescribed by the vessels classification society......
Dangerous goods stowage and segregation Clear guidelines apply to the stowage and segregation of Dangerous Goods and in some cases may require particular commodities to be carried in completely separate holds. The interaction of two cargoes will not occur if the packaging of that cargo remains intact. However, the Master must always consider the possible effect should the cargo escape for any reason and should not restrict his consideration to those cargoes which are listed in the IMDG Code......
Reefer Container Stowage
Reefer containers proposed for stowage must be accompanied by a reefer manifest. This reefer manifest should contain Container No., Stow position, Commodity, Temperature, and Ventilation status......
Out of Gauge Container Stowage
It is essential that, during out of gauge cargo operations, a careful watch is kept for any damage caused to the vessel, her equipment, or to containers. Notice of any damage must be immediately brought to the attention of the Stevedore's representative, the Port Captain/Supercargo and Charterers Agent. Damage reports must be completed in all cases giving the full and comprehensive details of damage caused......
Special Container Stowage After receiving stowage plan ships, Chief Officer must ensure that all Deck Officers are aware of any specialized containers due to be worked, such as reefers, vents, over-heights, over-widths, flat racks, etc. and their unique requirements.....
20 or 40 or 45 feet Compulsory Stowage Locations
Most cargo securing manual provide a guideline for different container types. These stow positions of 20 feet,40 feet, or 45 feet are also incorporated in a ship-specific stowage planning software and highlight errors if any violations occur......
Irregular Stowage of Containers
The Terminal Planner shall present the pre-loading plan to the Chief Officer to obtain his approval/comments. The Chief Officer, in turn, enters the cargo data in the loading computer and must ensure that the required criteria, concerning stack weights, trim/stability/stresses/ visibility limitations, DG cargo segregation, and specialized container requirements, are met. He should allow the bunker/freshwater consumption during the voyage and all possibilities of ballasting / deballasting. The completed loading plan must be presented to the ship's Master for approval.....
Over-stow of Containers With a closed roof, the hardtop the container offers the same reliable protection as provided by a standard box. Hardtop containers have more lashing points than other container types. This guaran- tees reliable and convenient securing of cargo.
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Other matters regarding cargo stowage as necessary Bulk products carried in a closed container might include malt, grain, seed, polythene granules, chemically inert powders, brake fluid, detergent, fruit juice, wine, non-hazardous oils, sodium silicate, fatty acids and maple syrup amongst many others......
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