QZ Grab Overhead Crane

Overview

The QZ grab crane consists of a double-girder bridge, trolley with grab, end carriages, and an electrical control system. It is engineered for loading, unloading, transferring, and feeding loose materials such as:

Sand, gravel, coal, mineral ore

Grain, biomass, fertilizer

Scrap metal and waste

Bulk chemicals

This crane operates with high precision and reliability, making it essential equipment for ports, power plants, steel mills, and material yards.

 

Technical Features

High working duty: A6–A8 according to FEM/ISO standards

Continuous and fast cycle times for loading & unloading

Dual-motor independent control of lifting and closing

Automatic grab control for efficient material handling

Smooth travel with variable frequency drive (optional)

High anti-sway performance when handling heavy grabs

 

Span: 10.5–31.5 m or customized

Lifting capacity: 5t–25t (grab weight included)

Lifting height: Up to 30 m

Working duty: A6–A8

Grab type: Clamshell, orange-peel, hydraulic, four-rope

Control: Cabin, wireless remote, VFD control

Power supply: 380V/400V/415V 50/60 Hz or customized

The QZ type overhead crane is equipped with a grab bucket for bulk material handling. Its structure and systems are designed for heavy-duty, continuous operation. Below are the complete components:

1. Bridge (Double Girder Structure)

Welded box-type double girders

High-strength structural steel

Walkways, platforms, handrails

Girder end diaphragms for load distribution

Rail installation for trolley travel

2. End Carriages (Crane Traveling Mechanism)

Side beam structure

Driven wheels and idle wheels

Wheel bearings and shafts

Travel motors (single-speed or VFD control)

Gear reducers

End buffers, rail sweepers, derailment prevention plates

3. Grab Trolley Frame

Trolley steel structure (box or plate welded)

Mounting base for motors, drums, and control panels

Rails for grab mechanism

Maintenance platform

4. Lifting Mechanism (Hoisting System)

Includes the components responsible for lifting the grab:

Hoist motor

Reducer/gearbox

Drum and rope drum shaft

Wire ropes (lifting ropes)

Lifting pulleys/sheaves

Braking system (electromagnetic or hydraulic)

Lifting limit switch

Load sensor / overload limiter

 

5. Grab Opening & Closing Mechanism

Independent mechanism for grab bucket operation:

Separate motor for opening/closing

Gear reducer

Opening/closing drum

Wire ropes (closing ropes)

Synchronization sheaves

Grab control unit

Mechanical or hydraulic clutch (optional)

6. Grab Bucket (Material Handling Tool)

Different types depending on material:

Clamshell grab (sand, grain, fertilizer)

Orange-peel grab (scrap metal, waste)

Hydraulic grab (sticky materials)

Four-rope mechanical grab (standard type)

High-strength wear-resistant plates

Teeth or cutting edges depending on material

Grab capacity: 0.5–20 m³

 

7. Crane Traveling System

Crane travel motors

Gear reducers

Wheel assemblies with hardened tread

VFD control for smooth acceleration

Positioning sensors (optional)

8. Electrical Control System

Main control panel

Trolley and crane junction boxes

Power supply via festoon system or conductor bars

Electrical cables and limit switches

Frequency inverters (optional)

Control modes: cabin / remote-control / dual-control

PLC for synchronized grab control (optional)

9. Operator Cabin (Optional)

Closed or open cabin

Air-conditioning/heating (optional)

Joystick control console

Safety glass with wide viewing window

Ergonomic chair and emergency stop

10. Safety Devices

Overload limiter

Upper/lower lifting limits

Trolley and crane travel limit switches

Anti-sway system (optional)

Emergency stop system

Rail sweeper

Anti-collision sensors (dual crane operation)

Overheat and phase failure protection

11. Power Supply System

Conductor rails / busbar system

Cable festoon system

Isolator and grounding system

Power distribution cabinet

Sketch

Main technical

 

 

Advantages of QZ Grab Double Girder Overhead Crane

1. High Efficiency for Bulk Material Handling

Specially designed to grab, lift, transport, and discharge loose bulk materials.

Short operating cycle time increases productivity.

Ideal for unloading and feeding production lines.

2. Heavy-Duty & High Working Class (A6–A8)

Robust double-girder construction provides high load capacity.

Suitable for continuous operations and harsh environments such as power plants and ports.

3. Independent Lifting and Grab Mechanisms

Separate motors and drums for lifting and opening/closing.

Ensures smooth, precise control of grab operations.

Increases reliability and reduces downtime.

4. Stable and Reliable Performance

Four-rope grab design ensures stability during lifting.

High-quality motors, reducers, brakes ensure long service life.

Less affected by wind or load swing compared to other lifting tools.

5. Versatile Grab Options

Clamshell, orange-peel, four-rope mechanical, or hydraulic grab available.

Allows easy adaptation to different materials and industries.

6. Flexible Operation Modes

Cabin control, wireless remote control, or dual control.

PLC and VFD control systems available for precise operation.

7. Excellent Safety Features

Overload limiter

Buffer and rail sweeper

Travel limit switches

Emergency stop system

Anti-sway and anti-collision systems (optional)

Ensures safe operation even in busy material yards.

8. Low Maintenance and Easy Access

Modular structure for easier replacement of rope drums, motors, and sheaves.

Walkways and maintenance platforms allow safe inspection access.

 

Applications of QZ Grab Double Girder Overhead Crane

The QZ grab crane is widely used for bulk material handling in various industries. Typical materials include: coal, sand, ore, grain, fertilizer, biomass, scrap metal, and waste.

1. Power Plants

Coal feeding systems

Ash handling

Biomass loading and unloading

2. Steel Mills & Foundries

Scrap yard feeding

Charge handling

Raw material loading

3. Ports & Terminals

Bulk cargo handling (coal, grain, ore, sand, fertilizer)

Ship unloading and storage yard management

4. Cement & Building Materials Plants

Limestone, clinker, gypsum, and aggregates handling

Feeding raw materials to production lines

5. Mining & Mineral Processing

Ore loading/unloading

Mineral concentrate transfer

Stockyard operations

6. Waste & Recycling Plants

Garbage grab cranes (waste-to-energy plants)

Scrap metal sorting and loading

7. Chemical & Fertilizer Industry

Handling granular or powder bulk materials

Feeding production bins and silos

QZ Grab Double Girder Overhead Crane Production Process

The production of a QZ Grab Double Girder Overhead Crane follows a strict, standardized manufacturing process to ensure strength, reliability, and long service life. Below is the complete process from raw materials to final installation.

 

1. Raw Material Preparation

Select high-quality Q235B/Q345B structural steel plates

Ultrasonic testing for internal defects

Material cutting lists prepared by engineering department

Steel plates cleaned (shot blasting) to remove rust and scale

 

2. Girder Fabrication (Double Box Girders)

2.1 Cutting & Forming

CNC plasma cutting of web plates and flanges

Bending/forming of side plates if needed

2.2 Assembly & Welding

Assembly of inner diaphragm plates

CO₂ gas-shielded automatic welding

Longitudinal seams welded by gantry welding machine

2.3 Stress Relief & Straightening

Girder placed in a stress-relieving furnace or treated by vibration stress relief

Girder straightening to correct deformation and camber

2.4 Non-Destructive Testing

Ultrasonic testing (UT) and magnetic particle testing (MT)

Weld seam inspection to DIN/ISO standards

 

3. End Carriage Manufacturing

CNC machining of wheel holes and motor mounting surfaces

Wheel assemblies (forged or cast-steel wheels) installed

Motors, reducers, brakes assembled

Final alignment check

 

4. Trolley & Grab Mechanism Production

4.1 Trolley Frame Welding

Box-type frame fabricated with precision fixtures

Robot or semi-automatic welding ensures strength

4.2 Lifting Mechanism Assembly

Lifting motor

Reducer/gearbox

Drum and rope drum shaft

Brake system

Wire ropes and lifting pulley block

4.3 Opening & Closing Mechanism

Separate motor and reducer assembly

Clamshell or orange-peel grab bucket installation

Alignment of opening/closing ropes

4.4 Grab Bucket Fabrication

Wear-resistant steel plates cut and formed

Bucket plates welded

Pins, hinges, and teeth installed

Load test before painting

 

5. Electrical System Production

Control cabinet assembly with Siemens/Schneider components

Wiring for power, signal, and control circuits

PLC programming (optional) for synchronized grab operation

Load protection and interlock testing

 

6. Surface Treatment (Painting)

6.1 Shot Blasting

Entire girder blasted to Sa2.5 standard

Ensures paint adhesion and corrosion resistance

6.2 Primer & Topcoat

Typical system:

1 layer epoxy zinc-rich primer

1 layer epoxy intermediate paint

1 layer polyurethane topcoat
Color customized upon request

 

7. Assembly & Pre-Assembly

Crane assembled on workshop test bay

End carriages connected to girders

Trolley placed on the crane bridge

Cable festoon system or busbar system installed

Limit switches, sensors, safety devices connected

Online test for electrical control

 

8. Factory Testing (FAT – Factory Acceptance Test)

Test Items Include:

No-load running test

Load test (static test at 125% and dynamic test at 110%)

Travel speed test

Grab opening/closing test

Brake performance test

Safety device operation test

Testing ensures compliance with ISO, FEM, GB/T, and CE standards.

 

9. Packing & Delivery

Motors, electrical components packed in wooden cases

Grab bucket protected with steel frame

Girders wrapped with moisture-proof packaging

Container or bulk shipment depending on size

 

10. On-Site Installation & Commissioning

Crane bridge and end carriages installed on runway beams

Trolley and grab assembled and wired

Rail alignment and wheel calibration

On-site control system debugging

Operator training and safety instruction

 

11. Final Acceptance

Final load test performed onsite

Inspection report provided

Warranty documents issued

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%.