tons. It is a common practice to provide a load beam with one or several hooks,
which can be readily installed in place of the spreader for handling bulk cargo.
Figure 9 shows a typical container crane.
General Description. The primary structural components of container
cranes are the gantry, horizontal main beams, luffing boom, and an overrunning or
underrunning trolley with an adjacent operator's cab. When in use, the boom is
lowered to the horizontal position in line with the main beam and above the
container ship deck. The boom length is designed to reach across the entire width
of the stacked containers on the ship. The horizontal main beams form a rearward
extension of the boom over the container storage area on the wharf or pier. These
cranes have non-rotating upperworks; they must reposition themselves on the rails
to be in line for each row of containers to be handled. The boom is luffed up to
clear any ship superstructure before the crane moves along the rails. When the
container crane is not in use, the boom is locked in a nearly vertical position.
The containers are engaged by twist locks located in the corners of the
lifting frame (spreader). The spreaders may be of fixed length designed to engage
only one size of containers, or they may be telescoping to fit any length of
container. The standard dimensions of containers are 8 feet high, 8 feet wide,
and 20 to 40 feet long. The spreaders are readily disengageable from the hoist
The hoist may be located either on the trolley with the wire ropes
descending downward from the wire rope drum to the four sheaves in the corner of
the head block frame, or in the machinery house with the wire ropes routed
horizontally to the trolley and downward to the head block frame sheaves. The
four wire ropes are independent (non-equalized). The head block is designed
for quick mechanical and electrical connection to its counterpart on the spreader.
Electric power is delivered to the spreader hydraulic devices via a suspended
coiled power cable.
Distinctive Features. The structure is a rigid traveling gantry with a
fixed main beam and a luffing boom. When the boom is in the horizontal
(operating) position, it is supported by steel stays, which are attached to the
top of the A-frame. The machinery house and an integral or separate diesel
engine-generator set enclosure are installed on top of the main beam, and both are
equipped with a built-in service crane (either OET or underrunning type) of
adequate capacity to handle the heaviest components which may require removal.
The machinery house and enclosure floors have removable hatches through which the
service crane hooks can reach the ground level.
These cranes are designed specifically for handling standard containers
at a rapid rate (up to 35 per hour) and a high degree of safety.
Industry Standards. There are no industry standards specifically for the
design of container cranes. Structurally these cranes are designed to comply with
the applicable requirement of Manual of Steel Construction, published by the
American Institute of Steel Construction, Inc.
ASME B30.24 (under development), Container Cranes, will be published by
the American Society of Mechanical Engineers. This standard focuses primarily on
the safety aspects of the design and operation of the cranes.