Principles of container stowage- container handling good practices
Containers are rectangular box-shaped units of cargo. It is easy to stow them in classical
block stowage both on and below deck.
Containers are carried on deck. Ships loading manual is required to be classification society approved for on deck loading and lashing arrangements. All boxes on deck are secured with twist locks and lashings. These usually consist of
steel rods and turnbuckles.
When containers are carried below deck, the containers are slotted into cell guides on a cellular
container ship, or sit on the tanktop, joined together with stacking cones, in the holds of a dry
cargo ship. Containers can easily be stowed in box-shaped holds; it is more difficult to carry
them in the holds of a dry cargo ship fitted with side hopper tanks, in which case, buttresses
may be fitted.
When carried within a cell guide framework, no further external support is generally required.
When 20-foot containers are stowed below deck in 40-foot cell guides, it may be beneficial to
overstow the 20-foot containers with a 40-foot container. The Cargo Securing Manual should be
consulted before loading.
Containers carried on deck may be secured by twist locks alone, provided the stack is not more
than two containers high. When containers are carried three high, twist locks alone may be
sufficient depending on the weight of the containers.
The horizontal movement of a deck stow is resisted by the twist locks or cones. Lifting of containers in
extreme seas is prevented by the pull-out strength of the twist locks. The limitation of a twist-lock only
stow is often the racking strength of the containers. For stows of more than three containers
high, lashing rods are fitted because they provide additional racking strength.
In the early days of containerization, lashings were fitted vertically to resist tipping. However,
it soon became clear that it is more effective to arrange the lashings diagonally so that the
container and the lashings work together to resist racking.
The usual arrangement is to fit one tier of lashings, placed diagonally within the
container width, with the tops of the lashing rods placed in the bottom corner castings of the second-tier
containers. It is called ‘cross-lashing.’ An alternative arrangement, with the lashing rods
located outside of the width of the box, is called ‘external lashing.’ It is often used for high
stacks which are lashed from a two-tier lashing bridge.
Fig below highlights container handling many good practices
Container handling good practice
Visibility issue- Higher tears stowage on deck - Container ship Fore-ward visibility criteria:
Higher tears stowage on deck, especially in ships forward, shall cause the blind zone against ships ahead visibility.
Visibility from Navigation Bridge must conform with the IMO requirements and additionally to special needs like those for Panama Canal, etc., as applicable.
If the Master observes deviating from the above criteria, even though applying the best Trim adjustment, the Terminal planner / Central planner must be informed and cargo stow plan appropriately modified.
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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