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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.
When containers are carried on deck, the ship is required to be approved for that purpose and the containers themselves are secured with twistlocks 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 twistlocks alone, provided the stack is not more than two containers high. When containers are carried three high, twistlocks alone may be sufficient depending on the weight of the containers.

Horizontal movement of a deck stow is resisted by the twistlocks or cones. Lifting of containers in extreme seas is prevented by the pull-out strength of the twistlocks. The limitation of a twistlockonly 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 containerisation, 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 width of the container, with the tops of the lashing rods placed in the bottom corner castings of the secondtier containers. This is called ‘cross-lashing’. An alternative arrangement, with the lashing rods located outside of the width of the container, is called ‘external lashing’. This 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
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 requirements 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.

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