Principles of shipping container stowage
  • 14 Jun 2017

Modo Contain factory yard always has over 200 containers, stowage is usually needed. Here is some principles should be borne in mind when stowage:

• a deck stack of containers is only as strong as the weakest component in that stack. Premature failure of a component can cause loss of an entire stack. During loading, containers should be inspected for damage and, if damaged, they should be rejected

• twistlocks limit vertical and transverse movement. Diagonal crossed lashing rods, placed at the ends of a container, can withstand large tensile loads

• outside lashings are sometimes used. These are lashings that lead away from a container. However, although this arrangement provides a more rigid stow than a combination of crossed lashings and twistlocks, it is less common

• containers exposed to wind loading need additional or stronger lashings. When carried in block stowage, it is the outer stacks that are exposed to wind loading. However, when carried on a partially loaded deck, isolated stacks and inboard containers can also be exposed to wind, in which case, additional lashings need to be applied

• if containers of non-standard length, that is, 45, 48 or 53 feet are carried, the ship arrangement will need to be specially adapted

• 45-foot containers fitted with additional corner posts at 40-foot spacing can be stowed on top of 40-foot containers. Lashings can be applied in the normal way. It should be noted, however, that the additional corner posts may not be suitable for carrying the required loads, either from the container itself or from those stowed above. Lashings should not be applied to the overhang. The container specification and the Cargo Securing Manual should be consulted

• 40-foot containers may be stowed on top of 45-foot containers. However, this arrangement of stowage will present difficulties in fastening/unfastening twistlocks, and it will not be possible to apply lashings to the 40-foot containers

• when carrying over-width containers, for example 45-foot or 53-foot containers with width 8'-6", adaptor platforms may be used. These must be certified by a class society or an appropriate recognised body. The arrangement must be defined and approved in the ship’s Cargo Securing Manual

• twistlocks should always be locked, even when the ship is at anchor, except during container loading and unloading. Lashing rods should be kept taut and, where possible, have even tension. Lashing rods should never be loose nor should they be overtightened. Turnbuckle locking nuts should be fully tightened

• as a ship rolls, pitches and heaves in a seaway, tension, compression and racking forces are transmitted through the container frames, lashings and twistlocks to the ship’s structure. However, clearances between securing components and the elasticity of the container frame and lashing equipment produce a securing system that forms a flexible structure. Thus, a deck stow of containers will move.

• containers can be held by only twistlocks when two or three tiers are carried on deck, depending upon container weights

• arrangements with automatic and semi-automatic twistlocks are used to reduce time spent securing the stow and to eliminate the need for lashers to climb the stacks Checks and tests during discharge and loading

• regularly examine lashing components, looking for wear and tear, damage or distortion. Check that left-hand and right-hand locking twistlocks are not being mixed in the same storage bin. Remove from the ship any lashing component found to be worn, damaged or distorted

• make arrangements for some damaged or distorted lashing components to be sent for non-destructive testing. This will determine their strength and help to establish replacement criteria carefully check twistlocks that stevedores return to the ship as the locks might not originate from your ship, that is, their strength and locking direction could differ

• discourage stevedores from treating lashing equipment roughly as this can induce weakness

• examine dovetail foundations, D rings and pad-eyes for damage. Repair if damage is found

• observe the loading of containers to determine if stowage is in accordance with the stowage plan and that best practice is always

• observe the application of lashings to make sure that they are correctly applied in accordance with the requirements set out in the Cargo Securing Manual

Professional shipping container supplier

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