Rubber-Tired Overhead Gantry Crane (RTG), Halterm Terminal, Halifax
The purpose of a container overhead gantry crane is to position containers
along a linear stacking yard. Although the yard's length can in theory
be unlimited, the width of the stacking depends on the width of the
crane, but six containers in width is a common configuration. Depending
on the length of the terminal yard, several gantry cranes can operate
along a stack. Containers are usually stacked up to three in height,
which enables to minimize rehandlings. A common
stacking problem is the repositioning of containers within the stack,
particularly when it concerns cargo bound inland. Trucks are coming
somewhat randomly to pick an individual container, up to until demurrage
expires (4 to 5 days). This implies the need to continuously take containers
out of the stack as customers come to pick up their containers. If the
required container is at the bottom of the stack, those above it have
to be removed, which involves non revenue generating moves.
On the above photo, there are two rubber-tired overhead cranes
a stack with a capacity of six containers in width by three in height.
The space on the left under the crane is used to load or unload a container
from a chassis. The overhead crane has 40 tons in design capacity which
comfortably exceeds the maximum of 34 tons containers may have. It was
manufactured by the Chinese company ZPMC, which is the world's largest.