Container
Ships
During recent years an important development has taken place
in the handling and transport of rail, road and seaborne freight
with the introduction of the container /or unit/ system. A completely
integrated system has been evolved based on the use of standard
ISO (International Standard Organization) box units of agreed
dimensions: 2.44m high and wide; and 6.06, 9.12 and 12.19m long.
The 6- and 12-m (resp. 20 and 40 ft) containers are those in
general use. The majority of containers are designed for general
dry cargo, but specialized units can take liquid, powder or
refrigerated cargoes. Specially designed road vehicles, railway
wagons, ships and dockside equipment handle these units in a
coordinated way with speed and efficiency, and a minimum of
manpower, providing door-to-door service.
Like tankers, container ships are characterized by the absence
of cargo handling gear. Unlike the tanker, they require large
hatches in the deck for stowing the cargo. Below decks, the
ship is equipped with a cellular grid of compartments opening
to the weather deck. Vertical guide rails divide the cargo holds
into cells sized precisely to hold stacks of containers. Labour
within the hold is almost eliminated - no need of dunnage, packing
and lashing necessary to secure the usual break-bulk cargoes.
The ship is filled to the deck level with containers, the hatches
are closed, and one or two layers of containers, depending upon
the size and stability of the ship, are loaded on the hatch
covers on deck.
In a few hours the ship can be filled with containers destined
for another port and can be under way. An additional economy
is the low cost of the ship’s crew while it is in port
awaiting loading or unloading. Further, because each ship can
make more trips than before, container fleets require fewer
vessels. There is also less pilferage and, hence, lower insurance
rates.
Container ships are moderate-size merchant vessels with a high
freeboard and the superstructure either right aft or three-quarter
aft. The deck is unobstructed so that containers can be stacked
on it in addition to those stowed below in the holds. This type
of ships is built for speeds of greater than about 20 knots.
Small, compact, diesel power plants are used to provide more
space for containers. Special equipment includes mooring winches
to ensure accurate positioning of the ship under cranes in port
and special tanks to list and trim the ship to permit a symmetrical
loading or unloading without excessive list or trim. Cranes
and lifting gear designed for handling the standard-size containers
are usually part of the terminal but not of the typical container
ship.
