Double Girder Clamshell Grab Bucket Overhead Crane

Double Girder Bridge

Two robust girders span the crane runway, offering higher lifting capacity (typically 5–550 tons) and better hook height compared to single girder cranes.

Ideal for heavy-duty applications and long spans.

Clamshell Grab Bucket

A hinged bucket with two or more shells that close to grab material and open to dump it.

Operated via wire rope or hydraulic system (mechanical grabs use ropes; hydraulic grabs offer precise control).

Common types: Rope-operated (2/4-rope) or Motorized (hydraulic/electric).

Hoist Mechanism

Equipped with dual hoists:

One for lifting/lowering the grab.

Another for opening/closing the bucket.

May include a rotating mechanism for precise material placement.

Trolley & End Trucks

The trolley moves along the bridge girders, carrying the hoist and grab.

End trucks with wheels facilitate crane movement along the runway.

Control System

Pendant control, radio remote control, or cabin-operated for precise handling.

Optional automation for repetitive tasks (e.g., loading/unloading ships or stockpiles).

 

Comparison with Other Grab Bucket Cranes

Feature	Double Girder Clamshell Crane	Single Girder Clamshell Crane
Capacity	5–550+ tons	1–20 tons
Span	Long spans (up to 40m+)	Shorter spans (<25m)
Lifting Height	Higher due to double girder design	Limited
Durability	Heavy-duty, long lifespan	Light to medium-duty
Cost	Higher initial cost	More economical

 

Core Components：Bearing, Gearbox, Motor, Pump

Place of Origin：Henan, China

Warranty：1 Year

Weight (KG)：2000 kg

Video outgoing-inspection：Provided

Machinery Test Report：Provided

Design：Double beam

Effectiveness：high efficiency

Operating speed：High speed operation

Stability：Anti-swing function

Color：Optional

Power Source：110V/220V/230V/380V/440V,customized

Span：7.5-31.5m

 

 

A double girder clamshell grab bucket overhead crane consists of several critical components working together to efficiently handle bulk materials. Below is a detailed breakdown of its key parts:

 

1. Bridge Structure (Double Girder)

Main Girders (2) – Heavy-duty steel beams that span the crane runway, providing high load capacity (typically 5–550+ tons) and long-span support.

End Trucks – Located at each end of the bridge, equipped with wheels for longitudinal movement along the runway rails.

Cross Beams & Bracing – Reinforce the bridge for stability and rigidity.

2. Hoisting & Grab Mechanism

a) Hoist Unit (Main & Auxiliary Hoists)

Main Hoist – Handles the lifting and lowering of the grab bucket.

Auxiliary Hoist – Controls the opening/closing of the clamshell bucket (for rope-operated grabs).

Wire Ropes & Drums – High-strength steel ropes wound on drums for lifting and grab operation.

b) Clamshell Grab Bucket

Shells (2 or more) – Hinged buckets that close to grab material and open to release it.

Types of Grabs:

Rope-Operated (2/4-Rope Grabs) – Uses separate hoists for lifting and opening/closing.

Motorized (Hydraulic/Electric Grabs) – Self-contained power for precise control.

Material Options – Heavy-duty steel, abrasion-resistant liners, or stainless steel for corrosive environments.

 

 

3. Trolley Assembly

Trolley Frame – Moves along the bridge girders, carrying the hoist and grab.

Wheels & Drive Motors – Electric motors with gearboxes for smooth trolley travel.

Guide Rollers – Ensure proper alignment on the girders.

4. Runway System

Runway Beams – Support the crane's movement (top-running or underhung).

Rail Tracks – Installed on the runway beams for crane travel.

Buffers & End Stops – Prevent over-travel collisions.

5. Power & Control System

Festoon System / Cable Reel – Delivers power to the crane and trolley.

Control Options:

Pendant Control – Handheld wired controller.

Radio Remote Control – Wireless operation for flexibility.

Operator Cabin – For cabs with joystick/button controls (common in heavy-duty applications).

Variable Frequency Drives (VFDs) – Ensure smooth acceleration/deceleration.

6. Safety & Auxiliary Components

Limit Switches – Prevent over-hoisting or over-travel.

Overload Protection – Sensors to avoid exceeding rated capacity.

Anti-Sway System – Minimizes grab bucket swing for precise dumping.

Lubrication System – Automatic greasing for gears and bearings.

.

Optional Features

Grab Rotation System – Allows 360° rotation for precise material placement.

Weighing System – Built-in load cells for measuring material weight.

Dustproof & Corrosion Protection – For harsh environments (ports, chemical plants).

Automation & PLC Control – For programmed loading/unloading cycles.

Key Differences vs. Single Girder Cranes

✔ Higher Capacity – Double girders handle heavier loads.
✔ Better Hook Height – More space under the crane.
✔ Greater Durability – Suitable for intensive use.

 

SKETCH

Main technical

 

 

High Load Capacity (5–550+ Tons)

Double girder design provides superior strength, making it ideal for heavy bulk materials like coal, ore, and scrap metal.

Efficient Material Handling

The clamshell grab bucket allows quick grabbing, lifting, and dumping of loose materials, reducing manual labor and increasing productivity.

Versatility in Applications

Works with a wide range of materials: dry (grain, sand), wet (sludge, waste), and abrasive (ore, gravel).

Precise Control & Automation Options

Smooth operation via pendant, remote, or cabin control.

Can be integrated with PLC systems for automated loading/unloading cycles.

Durable & Low Maintenance

Robust construction with abrasion-resistant grabs and corrosion protection for harsh environments (ports, mines, steel plants).

Better Hook Height & Span Coverage

Double girders allow more lifting height compared to single girder cranes, useful in tall storage facilities.

Safety Features

Overload protection, anti-sway systems, and limit switches ensure safe operation.

 

1. Ports & Shipyards

Unloading bulk cargo (coal, grain, fertilizers) from ships.

Stacking and transferring materials in storage yards.

2. Mining & Metallurgy

Handling iron ore, coal, limestone, and scrap metal.

Loading/unloading raw materials in smelting plants.

3. Waste Management & Recycling

Grabbing MSW (municipal solid waste), industrial waste, and recyclables.

Used in landfills, incineration plants, and recycling centers.

4. Agriculture & Food Processing

Transporting grain, feed, soybeans, and sugar in silos or processing plants.

5. Construction & Cement Industry

Moving sand, gravel, cement, and fly ash in batching plants.

6. Power Plants

Handling coal, biomass, and ash in thermal power stations.

7. Chemical & Fertilizer Plants

Managing powdered chemicals, fertilizers, and raw materials.

 

 

1. Engineering & Design
Load analysis, duty classification (FEM/ISO/GB), and span calculation

Selection of key specifications: lifting capacity, lifting height, span, speed

CAD drawings and structural analysis (Finite Element Method if needed)

Electrical and control system schematics

Preparation of Bill of Materials (BOM)

2. Material Preparation
Procurement of Q235B / Q345B steel plates, I-beams, rails, etc.

Surface treatment (sandblasting, pickling) to remove rust and impurities

Cutting of steel parts using CNC plasma or laser cutting machines

Material inspection and marking

3. Fabrication of Main Components
A. Main Girders (Double Beams)
Assembly of top flanges, bottom plates, and web plates

Full-length welding using automatic welding machines

Welding inspection (UT/RT) and stress relief if required

Internal stiffeners and mounting brackets installation

Cambering the beams to compensate for deflection

B. End Carriages
Fabrication of box or plate-type structures

Installation of wheel seats and axle holders

Machining of joint faces to precise tolerances

C. Trolley Frame
Fabrication of the trolley steel structure

Mounting of hoisting mechanism (drum, motor, gearbox)

Assembly of trolley wheels, buffers, and drive units

D. Hoisting Mechanism
Machining of drum, gearbox, sheaves, and hook block

Assembly of motor, brake, coupling, and rope drum

Winding of steel wire rope and hook block installation

4. Machining & Precision Processing
Key components like drums, shafts, and sheaves are CNC machined

Boring of shaft holes, gear fitting, and alignment checking

Dynamic balancing of rotating elements (if needed)

5. Electrical System Assembly
Wiring of control panels, frequency inverters, contactors, and relays

Programming of PLC or remote control units (if automated)

Installation of limit switches, alarms, and sensor systems

6. Assembly and Pre-testing
Crane main girders, end carriages, and trolley are assembled on ground

Alignment and bolting of joints

Electrical connection of motors, brakes, and control units

Dry run test: travel motors, trolley, and hoist checked without load
7. Load Testing & Quality Inspection
No-load test: Verify all functions-lifting, traveling, braking, limit switches

Rated load test (100%) and overload test (usually 125%)

Functionality test of emergency stop, limit switches, alarms

Deflection check of girders (should be within specified limits)

Inspection report signed off by QA team

8. Surface Treatment & Painting
Anti-corrosion treatment (e.g., zinc-rich primer)

Painting according to project specification (commonly yellow or orange)

Logo or nameplate installation

9. Packing and Delivery
Disassembly into transportable sections (main girders, end trucks, trolley)

Packed using steel frames, shrink wrap, or wood cases for export

Delivery arranged by road, rail, or sea as required
10. On-site Installation & Commissioning (Optional)
Assembly on customer site

Final alignment, wiring, and load testing

Operator training and maintenance guidance

Handover with full documentation: manual, certificate, test report, wiring diagram

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%.