Photo 4


It is when such items are packed into ordinary cargo containers that disasters occur.


As the Atlantic Container Lines booklet says to shippers: “When you have finally packed your cargo into the container, sealed the doors and dispatched the unit, it is extremely difficult to correct an inadequate stow. If your load has not been properly secured or if the packaging is unsuitable the risks of damage to your cargo will increase during transit.”


Containers in stack


Most ISO containers are designed and constructed to allow nine-high stacking when empty. They should be placed and must stand on the four lower and four upper corner castings, alone, with the appropriate stacking/ locking components between. The bottom and top side rails, the front and rear sills and headers, and the underside floor bearers should remain free of vertical stacking contact at all times if transient wracking stresses are to be avoided.


A variety of securing systems sometimes create problems where ships’ officers/charterers’ superintendents familiar with one specific system fail to update themselves when faced with something different. It is not possible within the scope of this article to examine the many different fully approved and highly efficient systems in current use, but the Club cannot stress firmly enough the need to comply with, and to fully implement the requirements of, the stowage and securing system formally approved and planned for a particular vessel. All too often, container stack wracking failures occur in non purpose-built vessels because charterers insist on stacking containers in the holds and on the weather-deck in a manner which would not be approved even in a purpose-built ship. Unfortunately, stack collapses within the holds, and within weather-deck stacks, occur just as frequently in purpose-built vessels.


Independent of casualties arising from lack of securing arrangements and use of inappropriate containers as indicated earlier, container stack failures seem to arise from three prime causes, all of which involve unacceptable wracking stresses in one form or another.


5


Firstly, it is found that container stacks have failed because a fully-approved and fully adequate securing system has become downgraded with time. That is to say, after the casualty all concerned aboard the vessel insist that “we always secure them that way” when what proves to be the case is that, over time, one small recommended aspect after another has been omitted incrementally and successively without casualty until the day that circumstances conspire to subject the stacks to the maximum stress which the system was designed to withstand. Damage and loss result. A chain is only as strong as its weakest link, and a container stack securing system is only as effective as its least efficient component. Do not omit from a container stack securing system any single component which comprises the full and approved arrangement.


Photo 5


Secondly, and with disturbing frequency, it is found that container structural collapse has occurred due to excessive


superincumbent weight in stack. This occurs mostly in chartered vessels where charterers neglect to consult, or deliberately ignore, the stack weight restrictions set out in the approved stacking plans. It is most unusual for ships to be approved for on-deck and under-deck stacks of 4, 5 or 6 units high in the absence of very rigorous unit-weight restrictions. In other words, an approved stacking plan for 5 or 6 units high may well specify a sliding decrease in weight per unit up to 4 high, with tiers 5 and 6 required to be empty. Time and again, casualty investigation reveals a blatant disregard for these restrictions.


A very large, purpose-built, container vessel was slot- chartered on her maiden voyage to a number of


Fig I. A recipe for disaster. Adjacent corner castings should never be loop-lashed like this, or similar.


Source: Lashing & Securing of Deck Cargoes


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