QZ Double Girder Overhead Crane

Key Features of QZ Double Girder Overhead Crane:

High Load Capacity – Suitable for heavy lifting, typically ranging from 5 tons to over 550 tons.

Double Girder Construction – Provides better stability, higher hook height, and greater span compared to single-girder cranes.

Hook Mechanism (QZ Type) – Designed with a hook lifting attachment, making it ideal for general industrial use.

Efficient Travel System –

Hoisting Mechanism: Electric wire rope hoist (common models include LH-type hoists or imported brands like Demag, KONE, ABUS).

Trolley Travel: Moves along the bridge girders.

Bridge Travel: The entire crane moves on runway beams via end trucks.

Control Options –

Pendant Control (Remote Push Button) – For manual operation.

Radio Remote Control – Wireless operation for safety and convenience.

Cabin Control – For heavy-duty or frequent use.

Safety Features –

Overload protection

Limit switches (upper/lower travel limits)

Emergency stop

Insulated or explosion-proof options (for hazardous environments)

 

Common Specifications:

Capacity: 5T – 550T+

Span: 7.5m – 35m+

Lifting Height: 6m – 30m+

Work Duty: A5 (moderate) to A7 (heavy-duty)

Power Supply: 380V/50Hz (or customized voltage)

 

A QZ double girder overhead crane consists of several key components that work together to ensure efficient and safe lifting operations. Below is a detailed breakdown of its main parts:

 

1. Bridge Girders (Main Beams)

Function: The primary load-bearing structure that spans the width of the crane bay.

Design: Two parallel girders (box-type or truss-type) made of welded steel for high strength.

Features:

Reinforced for heavy loads (5T–550T+).

Supports the trolley and hoist movement.

 

2. End Trucks (End Carriages)

Function: Allow the crane to travel along the runway rails.

Components:

Wheels & Axles – Steel wheels with bearings for smooth movement.

Buffers (Bumpers) – Absorb impact at travel limits.

Drive Motors – Power the crane's longitudinal movement (typically 2–4 motors).

3. Hoisting Mechanism

Function: Lifts and lowers the load.

Components:

Electric Hoist (e.g., wire rope hoist or chain hoist).

Hook Block – Attaches to the load (can be single/double hook).

Drum or Sheaves – For rope/chain winding.

Brake System – Prevents load slippage.

4. Trolley Assembly

Function: Moves the hoist horizontally along the bridge girders.

Components:

Trolley Frame – Supports the hoist.

Trolley Wheels & Drive – Electric motor with gearbox for cross-travel.

Guide Rollers – Keep the trolley aligned.

5. Runway System

Function: Supports the crane's movement.

Components:

Runway Beams – Installed on building columns or freestanding.

Rail Tracks – Usually PFC, CRANE, or QU120 rails.

Rail Clamps – Secures the crane when parked.

6. Electrical System

Function: Powers and controls the crane.

Components:

Main Power Supply – 380V/50Hz (or customized).

Control Panel – Includes contactors, relays, and overload protection.

Operator Controls – Pendant, remote, or cabin controls.

Festoon/Cable Reel – Delivers power to moving parts.

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7. Safety & Auxiliary Components

Limit Switches – Prevents over-travel of hoist/trolley.

Overload Protector – Cuts power if load exceeds capacity.

Emergency Stop (E-Stop) – Instantly halts crane motion.

Warning Devices – Buzzer/light for alerts.

Anti-Collision System (for multiple cranes).

 

8. Optional Add-Ons

Cabin (Operator's Cab) – For better visibility in heavy-duty use.

Magnetic/ Grab Attachments – For handling scrap, coils, or bulk materials.

Variable Frequency Drives (VFDs) – Smoother acceleration/deceleration.

Weighing System – Displays load weight in real-time.

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SKETCH

Main technical

 

The QZ double girder overhead crane is a heavy-duty lifting solution designed for industrial applications. Compared to single-girder cranes, it offers several key benefits:

1. Higher Load Capacity

Can handle 5T to 550T+, making it ideal for heavy industries like steel plants, shipbuilding, and power generation.

2. Greater Span & Hook Height

Double girder design allows for longer spans (up to 35m or more) and higher hook lift since the hoist sits between girders, maximizing vertical space.

3. Enhanced Stability & Durability

Twin girders distribute weight evenly, reducing deflection and sway during lifting.

Better suited for A5–A7 (medium to heavy-duty) work cycles compared to single-girder cranes.

4. Flexible Customization

Can be fitted with special attachments (magnets, grabs, ladles) for handling coils, scrap, molten metal, etc.

Options like explosion-proof motors, VFD controls, and cabin operation improve adaptability.

5. Smoother & More Precise Operation

Variable Frequency Drive (VFD) options allow for controlled acceleration/deceleration, reducing load swing.

Dual-hoist systems enable tandem lifting for extra-long or unbalanced loads.

6. Longer Service Life

Built with high-grade steel (Q235B/Q345B) and robust components, ensuring longevity even in harsh environments.

 

Applications of QZ Double Girder Overhead Crane

Due to its strength and versatility, this crane is widely used in industries requiring heavy, frequent, or precision lifting:

1. Steel & Metal Industry

Handling steel coils, slabs, ingots, and molds in rolling mills and foundries.

Ladle cranes for molten metal transfer (with special heat-resistant features).

2. Power Plants & Heavy Machinery

Lifting turbines, generators, and transformers.

Maintenance of boilers and large mechanical parts.

3. Shipbuilding & Ports

Assembling ship hulls, engines, and large components.

Loading/unloading heavy cargo in dry docks and warehouses.

4. Mining & Cement Plants

Moving bulk materials, crushers, and kiln parts.

Equipped with grabs or magnets for scrap handling.

5. Automotive & Aerospace

Lifting vehicle chassis, aircraft parts, and heavy machinery.

Used in assembly lines and maintenance hangars.

6. Warehousing & Logistics

For heavy pallets, containers, and machinery storage.

Often paired with radio remote control for precise positioning.

 

 

1.Design and Engineering
Requirements Gathering:

Load capacity (e.g., 10T, 50T, 100T, etc.), span, lifting height, and operational environment are defined.

Customization needs are assessed, such as control modes (pendant, wireless, cabin) and special features (e.g., anti-collision, overload protection).

Preliminary Design:

Structural engineers and crane designers create the crane's initial design, including the main beam, end carriage, lifting system, trolley system, travel mechanism, and other components.

Calculation and Simulation:

Load calculations are performed to ensure the crane can handle the specified capacity.

Finite element analysis (FEA) may be used to simulate stresses and deflections in the structure to ensure safety and stability.

Detailed Design:

After approval, detailed drawings for each part are made, including the main girder, end carriage, hoist system, motors, control systems, and safety features.

2. Material Procurement
Raw Material Selection:

High-quality materials like steel, alloyed steel, forged steel, and electrical components are sourced according to specifications.

Materials are inspected for quality certification and compliance with industry standards (e.g., ISO, CE).

Component Sourcing:

Standard components such as motors, hoists, control panels, limit switches, and safety devices are sourced from reliable suppliers.

3. Fabrication of Components
Main Girder:

Cutting and welding of steel plates to form the bridge girder.

The girder is assembled by welding or bolting sections, ensuring it meets the required strength and precision.

End Carriage Assembly:

The end carriage is fabricated and assembled to hold the crane on the runway rails.

Wheel assemblies are installed to ensure smooth travel along the rails.

Hoist and Trolley System:

The hoist unit (electric or manual) is assembled, including the drum, wire rope, hook, and motor.

The trolley system is built to transport the hoist across the bridge, including trolley wheels and drive mechanisms.

Crane Traveling Mechanism:

The crane wheels are mounted on the end carriages, ensuring smooth horizontal movement.

The drive system is installed to control travel speed.

4. Assembly of Crane
Main Beam Installation:

The assembled main girder is lifted and positioned onto the end carriages.

The girder is aligned to ensure structural integrity.

Trolley and Hoist Installation:

The trolley system is mounted onto the main girder, and the hoist is mounted to the trolley.

The load chain or wire rope is installed and tested for smooth operation.

Travel Mechanism Setup:

The crane wheels are fitted, and the drive mechanism is connected to the control system for horizontal movement.

5. Electrical and Control System Installation
Wiring and Control Panel:

The control panel is installed and wired to manage all crane movements (hoisting, trolley, crane travel).

Limit switches, emergency stop buttons, and safety alarms are integrated into the control system.

Motor and Gear Installation:

Motors for hoisting, traveling, and the trolley are installed and connected to their respective gear systems.

Testing of Control Systems:

Control systems are checked to ensure proper integration of pendant control, wireless remote, or cabin control options.

6. Testing and Quality Control
Load Testing:

The crane undergoes static load testing (to check stability) and dynamic load testing (to check operational performance under actual working conditions).

Overload protection and limit switches are tested to ensure they function correctly.

Safety System Testing:

The sound and light alarms, limit switches, emergency stop buttons, and safety devices are all tested for functionality.

Movement Testing:

All movements-hoisting, trolley movement, bridge travel, and sway control-are tested for smooth operation and precision.

Electrical Testing:

All electrical components are tested for proper wiring, grounding, and communication between systems.

Documentation and Certification:

The crane is inspected according to international safety standards and undergoes certification by relevant authorities (e.g., CE, ISO).

Test certificates for motors, cranes, and load testing are prepared.

7. Final Inspection and Painting
Visual Inspection:

A thorough inspection is carried out to ensure that the crane meets design specifications and safety requirements.

Painting:

The crane is painted with high-quality anti-corrosion coatings to protect it from environmental conditions.

Marking and Labeling:

Safety labels, warnings, and capacity markings are applied to the crane for proper identification.

8. Delivery and Installation
Shipping:

The crane is carefully disassembled into transportable parts (if needed) and shipped to the customer's location.

Installation:

The crane is installed on-site, and all connections (power, mechanical, control) are made.

Final Commissioning:

The crane is commissioned by running it through a series of operational tests to ensure it works properly.

Operator training is conducted, if necessary, for safe and efficient use.

9. Post-Installation Support
Customer Training:

Operator training on how to use the crane safely and effectively.

Maintenance Schedule:

Providing a maintenance plan for the crane's continued operation, including regular inspections, lubrication, and testing.

After-Sales Support:

Offering spare parts, troubleshooting, and repair services.

Workshop view:

The company has installed an intelligent equipment management platform, and has installed 310 sets (sets) of handling and welding robots. After the completion of the plan, there will be more than 500 sets (sets), and the equipment networking rate will reach 95%. 32 welding lines have been put into use, 50 are planned to be installed, and the automation rate of the entire product line has reached 85%.