Long Span Double Girder Gantry Crane with Hook Grab

1. Box Beam Structure

The main girders of a double girder gantry crane adopt a robust box-beam structure featuring a closed “square box” cross-section. This design provides exceptional rigidity, superior bending resistance, and excellent torsional stability, allowing the crane to handle heavy loads with minimal deformation. High-strength steel plates such as Q345B or Q235B are typically used to ensure durability and long service life. Each panel of the box beam is joined through precision welding to guarantee structural integrity. Reinforcement ribs are strategically added at key stress points to further enhance strength, ensuring safe and reliable operation under demanding industrial conditions.

2. Drive Mechanism

The operating mechanism of the double girder gantry crane utilizes an integrated three-in-one drive system consisting of a motor, reducer, and brake. This compact system improves reliability, reduces maintenance, and enhances overall efficiency. A three-phase AC variable-frequency motor provides stable power, allowing smooth acceleration and deceleration. The hard-tooth-surface reducer ensures high transmission efficiency and long service life. The braking system uses an electromagnetic brake equipped with asbestos-free brake pads and high-strength brake discs, delivering fast response, strong braking force, and increased operational safety.

3. Electrical Control System

The crane’s electrical system is designed for precise control and easy operation. Through a frequency converter, users can achieve adjustable running speeds, micro-speed functions, and dual-speed lifting, providing smooth and accurate material handling. The control box features a clean, logical layout that simplifies inspection and maintenance. With a protection rating of up to IP55, the electrical components are safeguarded against dust and moisture, ensuring consistent performance even in harsh environments. Various main power supply configurations are available according to customer requirements.

4. Wheel and Traveling Components

The wheels of the double girder gantry crane are manufactured from high-grade 40Cr or 42CrMo alloy steel, heat-treated to achieve high hardness and excellent wear resistance. These wheels support heavy loads while maintaining long service life. Self-aligning bearings ensure smooth rotation and reduced friction. The wheel assembly often includes an angular box structure, shock-absorbing buffers, and a modular design, allowing customization for different track conditions and operational needs.

1. Overload & Short Circuit Protection: A master air switch protects the main power circuit, while small air switches or fuses safeguard the control circuits. Every electrical cabinet is equipped with overcurrent and overload protection, ensuring stable and safe operation even under heavy working conditions.

2. Zero-Position Protection: For safety during restart, all operating handles of the double girder gantry crane must return to the zero (neutral) position. The master contactor will only activate once all controls are reset, preventing accidental startup after power failure or fault recovery.

3. Multi-Level Limit Protection: The lifting mechanism uses limit switches to stop the hook before reaching upper and lower limits. Trolley and crane travel mechanisms also include limit switches to halt movement at boundary positions, allowing travel only in the opposite direction. Additional limit switches are installed on the operator cabin door and balustrades, ensuring master power can only be activated when all access points are securely closed.

4. Overload Limiter System: An advanced overload limiter is integrated into the lifting mechanism. When the load exceeds the rated capacity, the system automatically cuts off power, activates audible and visual alarms, and displays overload data, ensuring maximum operational safety.