TM 5-850-1
relatively light cargoes. For example, the endless-belt
usual method is to rig the ship's off-shore boom and
cuoveyor is especially useful for side port discharge, the
winch to manipulate the up-and-down fall, and the cargo
pneumatic or air conveyor, for handling large quantities
mast and dock winch to manipulate the burtoning fall,
of dry bulk commodities; the endless pocket conveyor,
the latter being referred to as the house fall (fig. 12-1).
for handling small package units of cargo; the gravity
This system has these advantages: increased over-the-
roller conveyor, for side port handling when the endless-
side reach, sometimes being able to spot laterally the
belt powered conveyor not available or prohibited; and
entire width of the pier apron; increased height that
the screw-type conveyor, for over-the-side or for side
cargo can be worked by regular burtoning gear (being
port handling of bagged goods.
Also, the spiral
able to work second-deck levels); and since the onshore
conveyor utilizes gravity to propel cargo being worked.
boom is not employed, the danger of this boom coming
(5) Roll-on/roll-off system. There are several
in contact with the pier terminal is eliminated.
(g) Self-loading/unloading vessels. Some
ways in which containers can be handled in this type of
operation. In most cases, the method of handling
bulk carriers are fitted with self-unloading conveyors,
containers and design of the berth and layout of the port
either of the endless-belt or scraper type. A few of the
area is inextricably tied up with the design of the ship.
latest all-container vessels are fitted with self-
A large number of new ships and new berths for this
loading/unloading shipboard transporter-type cranes.
type of operation have been built or are under
Such carriers have the advantage of flexibility of
construction, which shows the importance of this type of
operation.
(3) Using floating equipment. The advantages
operation. It will undoubtedly increase throughout the
world, especially as feeder services on short sea routes
of the floating cranes are high capacity and elimination
from main container transshipment ports. Basically,
of breaking-out the ship's jumbo boom. A disadvantage
there are three methods of handling containers on a roll-
is the high cost of chartering the equipment, which may
on/roll-off service:
not be readily available. The use of floating cranes is
(a) Trailer and tractor unit drives on,
usually limited to the offshore side of a ship during calm-
remains on the ship during its voyage, and drives off at
to-moderate sea conditions.
(4) Using shore-based equipment.
the other end. This method can only be economical on
(a) Gantry cranes. Gantry cranes are
very short sea journeys because the tractor unit is idle
and burdens the ship's capacity during the sea journey.
usually large frame-supported mobile cranes, which may
No special facilities or equipment are required in the
be either rubber-tired (fig. 12-2) or railmounted (fig. 12-
port area except sufficient land for parking the trailer
while waiting to drive on.
gantry cranes directly to railway cars or tractor-trailers
(b) The trailer unit only remains on ship
are effective methods of handling materials. Gantry
during the sea journey. The tractor unit simply tows the
cranes are also used as general purpose yard cranes,
container on its trailer from the storage area onto the
stacking containers two or three high, in conjunction with
ship and drives off leaving the container on its trailer. A
other materials handling equipment. Due to the trend
further set of tractor units is required at the destination
toward containerization, most gantry cranes are now
to tow the containers off the ship and to reload the ship
being manufactured with minimum lifting capacities and
for its return journey. The trailers may be normal road
outward reaches of 40 tons and 130 feet, respectively.
(b) Fixed derricks. Fixed derricks on the
trailers suitable for driving on public roads or special
small trailers suitable only for use in the port areas. The
wharf provide heavy lift (up to 100 tons in some
former is heavier and takes up more room on the ship
commercial ports) for cargo handling (fig. 12-4). Fixed
but would be used where the container is driven some
derricks are not considered to be as efficient as mobile
distance to the port and will be driven inland some
gantry cranes.
(c) Mobile cranes.
distance to its destination. The latter would generally be
Truck or crawler-
used where the inland depot is m the port area so that
mounted cranes may be used to load and unload cargo
the container is only handled in the port area, or where
ships (fig. 12-5). Table 12-1 and figure 12-6 present the
the container is delivered by rail and transferred to the
manufacturer's rated capacities for a number of larger
trailer in the port area This type of trailer is generally
commercially available cranes. Figure 12-6 shows that
much lighter and cheaper than the normal road trailer
the large mobile cranes are not capable of lifting 40-foot
and takes up less ship capacity. For the method where
containers weighing 67,000 pounds beyond a 30-foot
the road trailer is driven on and off the ship, no special
radius.
(d) Conveyors. Conveyors are used for
equipment is required. Where the small trailer is used,
equipment may be required for transferring the
handling bulk or relatively small packaged goods, but
container from rail or road trailer to
their limited maximum lifting capacity restricts their use
to
12-2
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