Bridge crane upper structure

The upper structure of a bridge crane consists of the bridge girders, end carriages, trolley, hoist, and associated power and control systems, forming the main load-bearing and movement framework.

Bridge and Girders

The bridge is the primary horizontal structure spanning the workspace, supporting the trolley and hoist while moving along the runway rails. It typically consists of single or double girders, made from high-strength steel to resist bending and torsional forces. Double-girder cranes are used for heavier loads and allow the hoist to travel between the girders, maximizing lifting height.

The girders are often connected by end ties, which maintain the squareness of the bridge and prevent skewing during travel.

End Carriages

At each end of the bridge, end carriages house the wheels that allow the bridge to traverse the runway. These carriages are designed with a specific wheelbase to match the crane span and can be configured for top-running or underslung cranes. Wheel equalizer arrangements within the end carriages distribute the crane and load weight evenly across the rails, ensuring stability and smooth movement.

Trolley and Hoist

The trolley moves along the bridge girders and carries the hoist, which performs the vertical lifting and lowering of loads. Hoists can be chain, wire rope, or belt types, and their capacity ranges from a few tons to over 200 tons depending on the crane design. The trolley allows precise lateral positioning of the load across the bridge span.

Power and Control Systems

The upper structure integrates power supply systems such as festoon cables, busbars, energy chains, or cable reels to provide electricity to the bridge and hoist. Control systems can be manual, pendant, or wireless, managing bridge travel, trolley movement, and hoist operation. Variable frequency drives (VFDs) are often used to enable smooth acceleration, deceleration, and speed control.

Safety and Auxiliary Components

Additional components include limit switches to prevent overtravel, overload protection sensors, and brakes for emergency stopping. Electrical cabinets protect sensitive components from dust and moisture, ensuring reliable operation. In summary, the upper structure of a bridge crane is a coordinated assembly of girders, end carriages, trolley, hoist, and control/power systems, designed to safely lift and move heavy loads across the facility while maintaining stability, precision, and operational efficiency.