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How a spreader used to lift containers- Various container handling safety technics

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The daily operations involved in a busy container terminal can be termed as one of the most complex environments within the transport sector. Progress of modern container terminals is one of the lifeblood of global trade. Coping with increasing container volumes, the capability of such terminals often comes under pressure. To improve productivity in cargo handling, most terminal operators employ equipment such as straddle carriers and gantries for moving containers into and out of the terminal stack and positioning beneath a portainer crane for lifting onboard the ship.

Cranes must have sufficient outreach to access the containers on the outboard side of the largest ships, which may be stowed up to 24 across. They are fitted with telescopic spreaders so that either 20ft or 40ft units can be lifted easily. Some cranes also fitted with spreaders capable of twin-lifting 20ft containers. Such equipment can usually only operate if containers of the same height are paired. The spreader is fitted with twist locks that enter the apertures in the container's top corner castings and engage when it is turned 90.

Lifting of a container with ships' gear (by crane or derrick) should properly be carried out using a spreader to ensure that a vertical lift is applied to each top corner casting of the unit. The twist locks of such spreaders may be activated remotely by the crane driver with a sophisticated system or by moving the locking lever on the side of the spreader frame, usually through a rope hanging from the lever. This latter system is referred to as "semi-automatic." The more sophisticated spreader system may also be self-leveling and maintain a parallel line to the ship as the crane, or derrick swings the container on board.

A-container-spreader

An essential spreader may consist of a steel frame with a wide leg and a hook suspended from each corner. The four hooks can be inserted into the corner castings of a container. It works in such a way that the hook protrudes from the casting. It provides maximum support from the seat of the hook and makes for ease of unhooking when the container is in position. It is a slow labor-intensive procedure as stevedores need to be on top of the container or a ladder against the container in order to hook on and unhook. Consequently, it is also an inherently dangerous operation but may be the norm in unsophisticated ports. A container should never be lifted by direct wire slings from top corner castings without a spreader to prevent the wires pinching and thus causing damage to the unit.

Forklift trucks may be used for handling both empty and full containers on terminals/quaysides and when loading/discharging Ro-Ro vessels. Trucks must be capable of handling loaded containers with a mast height suitable for operating within the confines of a Ro-Ro vessel. Lifting with a forklift truck may be by top-lifting spreader, using the forklift pockets or, in some cases, by side-lifting frame, although the latter method is not suitable over uneven terrain. Containers should not be lifted (empty or full) by end frames as this will inevitably damage the container.

Two containers may be lifted together, one on top of the other, by a fork lift truck of adequate capacity in certain circumstances (e.g. the weather deck stowage on board a Ro-Ro vessel with no overhead gear available) to obtain a three-high stow. However, the lifting of two containers, coupled together by twist- locks or similar, by overhead gear is dangerous and should not be attempted unless the system has been properly tested and approved.

container-handling-technics
container handling methods

Container Terminal Operations

With the capacity of some cellular container ships now exceeding 20,000 Teu and exchange of several thousand containers taking place in a particular port, it would be impossible for ship's staff to plan the discharge and loading, taking into account the short turn round time of a ship, constantly changing information, containers arriving up to the last minute, and the requirement for overall knowledge of future container movements (including empties). Thus, planning of the container exchange is normally undertaken by the container terminal under the guidance of a centralized unit controlled by the ship or service operator, which has information available for the whole round voyage and can provide much more effective planning.

Terminal planners are provided with guidelines on the optimum stowage to be planned, taking into account stability, deadweight, port rotation, movement of empties, forecasts of future cargo, and the special requirements of IMDG, out-of-gauge, containerized and refrigerated cargoes. However, planning activity remote from the ship does not detract from the Master's responsibility for the safety of his vessel and the ship's officers must always check stability and stress calculations.

While it is impossible to check all containers being loaded, ships' officers should be alert to the possibility of container damage, the correct stowage position, and labeling of Dangerous Goods containers. The securing of cargo can be seen (e.g., on flat racks), and the declared contents of refrigerated containers should be checked for correct temperature settings. Tank containers should be scrutinized for any sign of leakage or damage to valves. Random checks, either on the terminal or onboard, may provide evidence of any short-comings. Close liaison with shore planners is necessary to up-date stowage positions, weights and, when required, contents, so that stability, etc., can be monitored and checked before departure.

Containers in Non-cellular Ships

The carriage of containers in a non-cellular ship requires much more active input from ships' officers as, unless it is a full container cargo, it is unlikely that shore planners will be involved. While a container may appear to be a substantial unit, care must be taken to protect containers loaded in a compartment with other cargo types, i.e., unitized or breakbulk, to ensure that the doors, roof, and sides are not damaged. If it is necessary to over-stow a container with breakbulk cargo (not a recommended practice) only the lightest of cargo should be used.

Stuffed containers loaded without door seals (or locks) should be queried with the shore staff and a seal fitted with and a note made of the number and the circumstances.

Containers should preferably be stowed in the fore and aft line and be lashed with wire and bottle screws from the top lifting castings to substantial D-rings in the deck unless the ship is fitted with suitable deck twist-lock pockets and rod lashings.

If containers are stowed more than one high, the block of containers should consist of equal height, i.e., avoid mixing 8ft 6 ins and 9ft six ins high containers in the stow, so that an easily secured block is formed. It may be possible to stow a 40ft unit on top of two 20ft units if the position and securing arrangements permit, but two 20ft containers should never be stowed immediately over a 40ft unit unless a specially constructed frame or platform takes the weight.

The weight of a container is supported through its four bottom corner castings, and the calculation of deck loadings must consider this. Some ships are constructed with strengthened points on the deck or the tank-top to support loaded containers. Care must be taken to ensure that they are correctly positioned over these points, and that maximum permitted stack weights are not exceeded.

It is preferable that containers with side canvas tilts, which might be damaged by high winds or heavy spray, are not stowed on the outboard side of the stack on deck. When animals are carried, the stowage position should be such that the crew can gain easy access to them for feeding or watering or, if the worst occurs, for removing an animal carcass at sea.



Related Information

Details Of various Container Types

Safe navigation in a seaway

Hull strength & stability requirement for containerships

Cargo cranes operation, maintenance & safety matters

Cargo stowage and planning in containership

Cargo care at sea

Containership hull strength and stability

Securing arrangement in containerships

Cargo securing in containership requirements

Safe cargo operation in containership

Containerships cargo carrying advantages










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