Dongqi 75/20 Ton Double Girder Overhead Crane: A Robust Core for Heavy-Duty Construction Projects

In the fields of large-scale steel structure erection, precast component installation, and heavy equipment handling, efficient and safe material handling solutions are critical to ensuring project timelines and safety. The Dongqi 75/20 Ton Double Girder Overhead Crane (QD Type) is engineered precisely for such demanding, high-capacity construction environments. Integrating a robust structure, powerful lifting capacity, and flexible operability, this crane is designed to be a pillar of support for modern construction sites, precast factories, and large industrial plant installation areas.

Core Structure & Design Advantages

The heart of this crane lies in its double girder bridge structure. Compared to a single girder design, the two parallel main girders provide superior structural strength and rigidity. This design delivers multiple direct benefits:

• Enhanced Stability & Safety: The double girder configuration effectively distributes stress and deflection under heavy loads, ensuring smooth operation even at the full 75-ton capacity and significantly reducing load swing. This creates a stable foundation for precise installation work.
• Greater Lifting Height: As the hoist trolley travels on rails atop the main girders, space above the bridge is utilized efficiently. This allows for a greater usable hook height within the same building clearance, facilitating the handling of tall components.
• Stronger Adaptability: The double girder structure provides a solid platform for housing the heavy-duty main and auxiliary hook system. It can also readily accommodate large spans (customizable beyond 30 meters), ensuring comprehensive coverage of wide work areas.

Powerful Main & Auxiliary Hook System

The “75/20 ton” capacity rating underscores the versatility of this crane, designed for complex lifting tasks.

• Main Hook (75 tons): Handles the core heavy-lifting duties, such as moving and installing large steel roof trusses, heavy factory columns, large precast concrete beams, or heavy construction modules.
• Auxiliary Hook (20 tons): Serving as an efficient complement to the main hook, the auxiliary hoist typically operates at higher speeds. It is used for frequent handling of lighter materials or works in tandem with the main hook for tilting and precise positioning of components. This configuration significantly boosts overall workflow efficiency, combining “heavy-duty precision lifting” with “light-duty rapid transport.”

Performance Features Tailored for Construction

1. Robust Drive Mechanism: The bridge and trolley travel drives typically employ integrated “three-in-one” drive units (combining motor, reducer, and brake) coupled with frequency control systems. This enables smooth acceleration, stepless speed variation, and precise stopping, effectively controlling load sway and ensuring accurate placement.
2. Reliable Safety Assurance: Safety systems are paramount in the design. Standard features include:
   • Independent overload limiters for both the main and auxiliary hoists.
   • Hoisting height limiters and travel limiters.
   • Emergency stop buttons.
   • End buffer stops and anti-collision devices (optional).
   • Key electrical components with suitable ingress protection ratings for dusty site environments.
3. Flexible Operation Modes: Control can be provided via remote radio control, cabin operation, or pendant station, based on site conditions and customer preference. Wireless remote control, in particular, offers the operator optimal visibility and mobility, allowing for safer and more intuitive load command in complex sites.
4. Robust Construction & Durability: Main structural components are fabricated from high-quality steel, undergoing strict welding procedures and stress relief treatment. Surfaces are shot-blasted and coated with high-performance anti-corrosion paint to withstand the challenging conditions of construction sites.

Typical Technical Parameters Reference

Parameter	Specification
Rated Capacity	Main Hook: 75 Tons
Duty Class	A5 (Heavy) or A6 (Very Heavy) as per FEM/ISO standards
Span (S)	Customizable based on actual building dimensions (e.g., 22.5m, 25.5m, 28.5m, 31.5m, etc.)
Lifting Height	Customizable for Main/Auxiliary Hooks (Aux. hook typically higher)
Lifting Speed	Main Hook: ~1.5-3.0 m/min
Bridge Travel Speed	~20-40 m/min (VF controlled)
Trolley Travel Speed	~10-20 m/min (VF controlled)
Power Supply	3 Phase, 380V/400V/415V, 50/60Hz

Primary Application Scenarios

• Steel Structure Erection: Handling and installation of steel columns, beams, and trusses for factories, power plants, stadiums, and other large structures.
• Precast Concrete Installation: Transport and placement of large precast wall panels, floor slabs, bridge segments, and utility tunnels.
• Heavy Equipment Installation: Positioning of large machinery, generators, pressure vessels, etc., within buildings or plants under construction.
• Material Handling Yards: Systematic stacking and transfer of heavy materials in precast yards or onsite storage areas.
• Major Infrastructure Projects: Suitable for heavy-duty environments like bridge precasting yards and port machinery assembly workshops.

Conclusion

The Dongqi 75/20 Ton Double Girder Overhead Crane is more than just lifting equipment; it is an integrated solution designed to enhance the heavy-lifting capabilities of major construction projects. We understand deeply what equipment reliability, safety, and efficiency mean in a construction context. Therefore, we focus on delivering excellence at every stage—from professional consultation and customized design to rigorous manufacturing and comprehensive after-sales support.

If you are seeking a reliable lifting solution for your next significant construction project, the technical team at Dongqi Crane is ready to provide detailed consultation and project-specific planning, ensuring the equipment you receive is perfectly matched to your unique requirements and challenges.