Qz Series Double Girder Grab Bucket Overhead Cranes

A QZ Series Double Girder Grab Bucket Overhead Crane is a double-girder bridge crane equipped with a grab bucket instead of a standard hook. The crane travels along overhead runway rails, and the integrated grab (clamshell, orange-peel type, etc.) allows the crane to grab, lift, and transport bulk or loose materials efficiently.

 

Advantages

✔ Higher load capacity and stability due to double-girder design - suitable for heavy operations compared to single-girder cranes.
✔ Efficient bulk material handling with grab buckets (clamshell/orange peel). 
✔ Multiple control modes (cabin, remote, automated). 
✔ Comprehensive safety features: overload protection, limit switches, emergency stops. 
✔ Adaptable to indoor/outdoor environments with a wide operating temperature range.

 

COMPARISON WITH OTHER GRAB CRANE TYPES

Aspect	QZ Series	European Grab Cranes	Custom Grab Cranes
Design Standard	Chinese GB/T	FEM/ISO	Project-specific
Cost	Medium	High	Variable
Delivery Time	12-20 weeks	20-32 weeks	24-40 weeks
Component Availability	Excellent in Asia	Good globally	Limited
Customization	Limited options	Extensive options	Fully customizable
Technology Level	Good	Advanced	Project-dependent

 

Parameter                  Typical Values
Lifting capacity： 5 – 20 ton (some variants up to ~50 t+)
Span (bridge width)： ~10.5 – 34.5 m
Lifting height： ~6 – 20+ m (application-dependent)
Operating temperature： ~-20 °C to +60 °C
Working duty/class： Heavy duty A5–A6 (frequent use)
Typical speeds：Lifting ~30–45 m/min, trolley ~40–50 m/min, crane travel ~80–110 m/min

The QZ Series Double Girder Grab Bucket Overhead Crane is made up of several key components that work together to ensure efficient operation for handling bulk materials. Here's a breakdown of the major components in this type of crane:

1. Main Girder (Bridge Frame)

Purpose: Forms the primary load-bearing structure of the crane.

Design: Typically a double girder design, meaning there are two horizontal beams (girders) on either side that support the crane's load.

Material: Often made of steel to ensure strength and durability.

Function: The bridge travels across the runway tracks and supports the trolley (or hoist) and the grab bucket.

2. Grab Bucket

Purpose: Used to pick up, lift, and transport bulk materials like coal, ore, sand, or scrap.

Design: Commonly comes in two types:

Clamshell Bucket: A two-part bucket with jaws that open and close.

Orange Peel Bucket: A bucket with multiple claws (typically 4–8), designed for grabbing materials like scrap metal.

Control Mechanism: The grab can be controlled by electric motors (for opening/closing) or hydraulic systems.

3. Trolley

Purpose: Carries the hoist mechanism (for lifting the bucket) along the girder, moving it horizontally across the crane's span.

Functionality: The trolley moves from left to right across the girder, allowing the crane to reach different parts of the workspace.

Drive: Powered by electric motors, typically with gears to control the movement speed.

4. Hoist Mechanism

Purpose: Lifts and lowers the grab bucket (and materials) vertically.

Components:

Drum or Sheave: For winding the lifting ropes or chains.

Ropes/Chains: Steel cables or chains to raise and lower the bucket.

Motor: Usually electric, providing the necessary power to raise and lower the load.

5. Runway and Rails

Purpose: Provides the tracks on which the crane's girder moves horizontally.

Design: Rails are installed on the floor of the workspace (often overhead) for the crane bridge to travel along.

Rails: Made of high-strength steel for durability and smooth operation.

6. Cabin or Remote Control (Operator Control System)

Purpose: To control the crane's operations (lifting, lowering, moving the bucket, etc.).

Options:

Cabin Control: The operator sits inside a cabin attached to the crane for direct control.

Wireless Remote Control: Allows the operator to control the crane from a distance, offering more flexibility.

Control Panel: Typically includes buttons or joysticks for precise control of lifting, lowering, and moving the grab bucket.

 

7. Electrical System

Purpose: Powers all the components like motors, hoists, and control systems.

Components:

Power Supply: Usually connected to a three-phase power source.

Switchgear & Circuit Breakers: Protect the crane's electrical components from overload or faults.

PLC (Programmable Logic Controller): For automated operations and precise control of the crane's movements.

 

8. Safety Features

Overload Protection: Prevents the crane from lifting more than its rated capacity, protecting the structure and operators.

Limit Switches: These prevent over-travel of the trolley, hoist, or bucket.

Emergency Stop: Allows the operator to stop all crane movements in case of a problem.

Anti-collision Device: Prevents accidental collisions between parts of the crane or nearby structures.

Wind Speed Monitor: In outdoor applications, the crane may have sensors that detect high winds to ensure safe operation.

 

9. Counterweight

Purpose: Ensures the stability of the crane during lifting operations by balancing the load on the grab bucket.

Location: Mounted on the opposite side of the crane bridge to offset the weight of the load.

Material: Typically made from steel or concrete for added weight and stability.

10. End Carriages

Purpose: These are the wheels and frames that sit at the end of the crane bridge, enabling it to travel along the runway rails.

Design: Each carriage has wheels mounted on bearings to reduce friction and ensure smooth movement across the rails.

Drive Mechanism: Driven by motors, often with gearboxes to control the speed and direction of the crane's travel.

Optional Components (Depending on Specific Applications):

Rotary Systems – For rotating the grab bucket.

Hydraulic or Pneumatic Systems – Used to operate the grab mechanism if it's a hydraulic grab bucket.

Dust Suppression Systems – To reduce airborne particles, especially in environments like ports or steel plants.

Load Monitoring Systems – To monitor the weight of the materials being lifted for real-time tracking and safety.

Sketch

Main technical

 

 

Advantages of QZ Series Double Girder Grab Bucket Overhead Cranes

The QZ Series Double Girder Grab Bucket Overhead Crane offers several advantages that make it suitable for heavy-duty operations, especially in industries dealing with bulk materials. Here are some of the key advantages:

1. High Lifting Capacity

The double girder design allows for greater load capacity compared to single girder cranes. This makes the QZ series ideal for lifting heavy, bulk materials such as coal, ore, scrap, and sand.

Typical lifting capacities range from 5 tons to 20 tons, with some models able to lift more depending on the design.

2. Increased Stability and Safety

Double girder configuration offers superior stability and rigidity when handling heavy loads.

Safety features like overload protection, limit switches, and anti-collision devices ensure that the crane operates safely, even in high-risk environments.

The design of the grab bucket allows for better load control, minimizing the risk of spills or accidents during material handling.

3. Efficient Bulk Material Handling

The grab bucket mechanism is specifically designed to handle bulk and loose materials such as coal, sand, scrap metal, and grain, making it highly effective in industrial settings like ports, power plants, and metal factories.

The clamshell or orange peel grab can efficiently collect and move large quantities of materials in a single cycle, significantly reducing operational time.

4. Versatility in Operation

QZ cranes offer a wide range of control options:

Cabin control for operator comfort and precise control.

Wireless remote control for more flexibility and safety, allowing the operator to move freely.

Automatic control systems for precise and efficient lifting, lowering, and moving materials.

Can be adapted to different operational needs depending on the type of grab bucket used (e.g., clamshell, orange peel).

5. Durability and Long Service Life

The double girder design and high-strength materials used in construction ensure long-lasting performance, even under heavy use.

Corrosion-resistant coatings are often applied, especially in harsh environments like coastal areas or steel plants.

6. Adaptable to Different Environments

Indoor and outdoor operation: Suitable for both indoor and outdoor environments, with the ability to withstand temperature variations from -20°C to +60°C.

Weather-resistant features like wind speed monitors and anti-sway systems make it ideal for outdoor environments such as ports and steel mills.

7. Smooth Operation with Reduced Wear and Tear

The trolley and hoist systems are designed to move smoothly, reducing friction and wear on components.

Efficient lubrication systems and high-quality bearings help minimize downtime for maintenance.

8. Increased Productivity

The combination of high lifting capacity, precise control, and efficient material handling significantly boosts productivity in material-heavy industries.

Quick load cycles reduce the time required to move large amounts of material, making the crane an asset for high-volume operations.

 

Applications of QZ Series Double Girder Grab Bucket Overhead Cranes

The QZ Series Double Girder Grab Bucket Overhead Crane is typically used in industries and environments where bulk materials need to be moved efficiently. Here are some common applications:

1. Ports and Terminals

Bulk Cargo Handling: The QZ crane is ideal for handling bulk cargo such as coal, grain, ore, and fertilizers. The grab bucket can pick up large amounts of material and load them onto ships or barges for transport.

Unloading of Bulk Ships: The crane can unload bulk ships quickly and efficiently, reducing port turnaround times.

Storage Yard Management: It can also be used to transport materials within the storage yards at ports, transferring materials from stockpiles to transport vehicles.

2. Power Plants

Coal Handling: In power plants that use coal as a fuel, the QZ crane is used to move coal from stockpiles to boilers or conveyors.

Ash Handling: It is also used in handling ash by lifting and transporting it to disposal areas or ash storage facilities.

Scrap Material: In some plants, the crane can be used to handle scrap metal or other waste materials for recycling or disposal.

3. Steel and Metallurgical Plants

Ore and Coke Handling: Steel mills use these cranes to handle raw materials such as iron ore, coke, and scrap metal used in the production of steel.

Scrap Steel Handling: The grab bucket's ability to handle irregularly shaped and bulky materials makes it ideal for moving scrap steel to furnaces for melting.

Waste Handling: After the steel production process, the crane can be used to transport slag or other waste products from the production area.

4. Construction and Building Materials

Sand, Gravel, and Stone: In construction sites, the crane can handle materials like sand, gravel, and crushed stone, moving them from stockpiles to loading areas or construction equipment.

Cement Handling: In cement plants, QZ cranes can move raw materials like limestone, gypsum, or coal into processing areas.

5. Warehouse and Storage Yards

Bulk Material Handling: These cranes are commonly used in warehouses or storage yards to manage bulk materials, such as agricultural products (e.g., grains), chemicals, or fertilizers.

Stacking and Repacking: The grab bucket can handle large quantities of material, which can then be stacked or repacked as needed for further processing or shipment.

6. Recycling and Scrap Metal Industry

Scrap Metal Handling: These cranes are commonly used in scrap yards for collecting and moving scrap metal, waste, and recyclable materials like old cars, machinery, and steel.

Shredding and Sorting: The crane can move materials to shredders or sorting areas, helping streamline recycling operations.

7. Shipbuilding and Heavy Industry

Material Transport: In shipbuilding yards, the QZ crane can move materials like steel plates, beams, and other heavy components from one area to another.

Steel Plate Handling: It can also be used for lifting and transporting steel plates used in the fabrication of ships and other large industrial projects.

8. Mining

Handling Ore and Waste: In mining operations, these cranes are used to handle materials such as mineral ore, coal, and waste rock.

Transporting Materials: The grab bucket can help load raw materials onto trucks or conveyors for further processing.

 

The production process of a QZ Series Double Girder Grab Bucket Overhead Crane involves several key stages, from initial design and material selection to assembly, testing, and final delivery. The manufacturing process is highly detailed and requires precise engineering to ensure the crane is durable, reliable, and capable of handling the heavy loads typical in bulk material handling applications. Below is a step-by-step overview of the production process:

 

1. Design and Engineering

Conceptual Design: The first step is designing the QZ Series crane based on the specific needs of the client or intended use. This involves discussions with the customer to understand the working environment, load capacity, span, lifting height, and control systems needed.

Detailed Engineering: Once the concept is finalized, engineers develop detailed designs for each component, including:

The bridge frame (double girder structure).

The grab bucket (clamshell or orange peel).

Hoist mechanism and trolley systems.

Electrical control systems.

Safety features like overload protection and limit switches.

Structural Calculations: Engineers perform rigorous calculations to ensure the crane meets the required strength and stability standards, especially considering the heavy loads it will carry.

 

2. Material Selection

High-Quality Steel: Materials used in the crane are typically high-strength steel, which provides durability and safety under heavy loads.

Steel Plates for Girder Frame: Used to fabricate the main bridge girder and cross beams.

Steel for Trolley and Hoist: The trolley and hoist components require materials with high wear resistance and structural strength.

Grab Bucket Materials: The grab bucket is usually made from high-strength steel or alloy steel for durability, especially when handling abrasive materials.

Motors and Electrical Components: For the hoisting mechanism, trolley, and control systems, the motors and electrical components must be of high quality to ensure efficient and reliable operation.

 

3. Manufacturing and Fabrication

CNC Cutting and Welding:

Steel plates are cut using CNC cutting machines to the precise dimensions needed for each part (such as the girder beams, frame structure, and support brackets).

Welding is done to join these components into larger structures like the double girder frame and trolley frame. Precision welding techniques are used to ensure the parts are strong and properly aligned.

Machining: Parts like hoist drums, shaft supports, and gears are machined to meet exact specifications, ensuring smooth and reliable movement.

Casting and Forging:

Some critical parts, like gears, bearings, and certain components of the grab bucket, may be cast or forged to achieve the necessary strength and resistance to wear.

Grab Bucket Fabrication:

The grab bucket is often assembled separately, with the clamshell jaws or orange peel claws welded and fitted with the hydraulic or mechanical controls that open and close the grab.

The bucket is then tested to ensure proper functioning before being integrated with the hoist mechanism.

 

4. Assembly

Girder Assembly: The two girders that make up the double girder design are assembled and aligned. These are the primary load-bearing components, and the alignment must be precise to ensure smooth crane operation.

Trolley and Hoist Assembly:

The trolley is attached to the bridge frame and is fitted with the hoisting mechanism.

The hoist (which includes the drum, ropes, and lifting motor) is installed on the trolley to lift and lower the grab bucket.

The trolley wheels are mounted to ensure smooth horizontal movement along the girder.

Grab Bucket Installation: The grab bucket is mounted on the hoist ropes and integrated with the hoist system. Depending on the crane design, hydraulic or electric motors control the opening and closing of the grab.

End Carriages and Wheels: The end carriages are assembled and fitted with wheels, which allow the entire crane to travel along the runway rails. These carriages are essential for smooth movement.

 

5. Electrical and Control Systems Installation

Electrical Wiring: The crane's electrical systems (motors, limit switches, lights, etc.) are installed, and all wiring is tested to ensure it meets safety standards.

Control Panel Assembly:

The operator control panel (if a cabin is used) or wireless remote controls are installed.

The PLC (Programmable Logic Controller) is programmed to automate and control the crane's movements, ensuring smooth operation with precise control over lifting, lowering, and horizontal travel.

Safety Systems: The crane's safety features (e.g., overload protection, limit switches, emergency stop buttons, wind monitoring systems) are tested and configured.

 

6. Painting and Finishing

Surface Treatment: The crane components are typically subjected to surface treatment processes like shot blasting or sandblasting to remove rust and debris.

Painting: After surface treatment, the crane components are painted with high-quality industrial paint that provides protection against corrosion, especially in outdoor or harsh environments.

Coating for Grab Bucket: The grab bucket is also coated to resist corrosion, especially if it's going to be used in wet or highly abrasive environments like ports or steel plants.

 

7. Testing and Quality Control

Pre-Assembly Testing: Individual components like the hoist mechanism, grab bucket, and electrical systems are tested for functionality before final assembly.

Full System Testing:

The completed crane undergoes a series of rigorous tests, including:

Load tests to ensure the crane can handle the specified weight without any issues.

Safety system checks to verify that all limit switches, emergency stops, and overload protection devices are working properly.

Operational tests for both manual and automatic control systems to ensure smooth operation and correct functionality of all movements (lifting, lowering, horizontal travel, etc.).

Final Inspection: Once testing is complete, the crane is subjected to a final quality control check to ensure everything meets the design and safety standards.

 

8. Packaging and Delivery

Disassembly (if needed): Some larger cranes may be disassembled for easier transport. Components like the girder, trolley, and grab bucket may be separated into smaller sections.

Packaging: Smaller parts and sensitive components are carefully packaged to avoid damage during transport.

Shipping: The crane is shipped to the customer's site, either as a pre-assembled unit or in parts that will be reassembled onsite. The delivery includes documentation, installation instructions, and warranty details.

 

9. Installation and Commissioning

Once the crane arrives at the customer's site, installation is carried out by trained technicians, who will:

Assemble any parts that were disassembled during transport.

Install the crane on the runway rails and connect the electrical systems to the power supply.

Commissioning involves running the crane through a series of test operations to ensure everything is working as expected before being handed over for regular use.

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%.