Operator's cabs of portal cranes are normally located on the forward
extension of the machinery deck or on the machinery house roof. On floating
cranes, a common practice is to locate the operator's cab on, or even above, the
machinery house roof. On container cranes, the operator's cab is always attached
to the trolley to give the operator a clear view for accurate spotting of the
spreader and containers.
18.104.22.168 Open Cabs (for Indoor Cranes). Indoor OET and traveling jib (wall)
cranes may be provided with open operator's cabs. These cabs must provide adequate
visibility and physical safety for the operator.
Drive Foundations. Hoist drives, rotate drives, and travel drives of
portal, floating, and container cranes are mounted on independent structural
foundations to permit accurate shop alignment and fit-up of their mechanical
components before installation on the cranes. The foundations are required to be
rigid one-piece weldments designed to isolate the drive assembly from any
deflections of the main support structures and to maintain alignment of the
components. The foundations are shimmed and bolted to the support structures with
high strength structural bolts. Travel drives, which are shaft (wheel axle)
mounted, may only be pinned to the travel truck support structure.
22.214.171.124 Diesel Engine-Electric Generator Set Foundations. These sets are
normally obtained from commercial firms specializing in assembling such equipment.
Unlike the drive foundations, these are mounted on vibration isolators/snubbers to
prevent harmful resonance with the crane structure.
Counterweight. The counterweight is installed at the extreme rear end of
the rotating machinery deck to counteract the forward moment of the boom suspended
hook load. On older cranes it is in the form of a steel box filled with concrete.
Homogeneous scrap metal, often in the form of punchings from machine shop
operations, may be included in the concrete aggregate for increased density. The
counterweight is a permanent installation it cannot be removed nor easily
On newer cranes, the counterweight is in the form of several steel plates
or castings. The individual sections are suspended beneath the main beams of the
machinery deck with provisions for easy removal or replacement.
Ballast. Ballast is material which is emplaced in the portal base,
gantry, or barge to increase the weight of the main portion of the crane and
thereby reduces the movement of the center of gravity of the entire crane due to
the various loading conditions. It is always required on floating cranes and
sometimes on portal, gantry, and container cranes that operate on relatively
narrow rail gauges. It is normally in the form of concrete or steel slabs,
installed in the lower portion of the structure.
Ladders, Walkways, Platforms, and Stairs. All inspection and maintenance
points must have a safe means of access. Cab operated cranes require safe access
from ground level to the cab. All booms and A-frames must include walkways and
other access provisions to all sheaves, bearings, lighting fixtures, and limit
switches. Portal cranes must be provided with circular walkway around the roller
path or rotate bearing. Major closed-section structural components, sufficiently
large for interior access, must include internal ladders and platforms.