20ton Single Girder Overhead Crane

A 20-ton single girder overhead crane is composed of several main assemblies and sub-components that work together to provide safe and efficient material handling. The major components are listed below.

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1. Bridge Structure (Main Girder)

The bridge is the primary load-bearing structure of the crane.

Main Girder: A single box-type welded beam made of Q235B or Q345B steel plates. It supports the hoist and carries the lifting load across the span.

Reinforcing Ribs: Internal stiffeners welded inside the girder to increase strength and prevent deformation.

Girder Connections: Bolted or welded joints connecting the main girder to the end carriages.

2. End Carriages (End Trucks)

Located at both ends of the main girder, the end carriages support the bridge and allow it to travel along the runway rails.

End Carriage Frame: Welded steel structure housing the wheels and bearings.

Travel Wheels: Forged or cast steel wheels that run on the runway rails.

Wheel Bearings: Sealed bearings for smooth rotation and reduced friction.

Travel Drive Unit: Consists of a motor, reducer, and brake for long travel motion.

Buffer Blocks: Rubber or polyurethane buffers to absorb impact at the end of travel.

 

3. Lifting Mechanism (Electric Hoist)

The hoist is mounted on the main girder and performs the lifting and lowering of loads.

Wire Rope Electric Hoist: The main lifting unit, rated for 20 tons.

Hoisting Motor: Drives the drum to raise and lower the load.

Wire Rope Drum: Grooved drum that winds the wire rope.

Wire Rope: High-tensile steel rope for lifting.

Hook Block: Includes the hook, pulley block, and safety latch.

Brake System: Electromagnetic or hydraulic brake for holding loads securely.

Reducer/Gearbox: Reduces motor speed and increases torque.

4. Trolley / Cross Travel Mechanism

Allows the hoist to move horizontally along the main girder.

Trolley Frame: Supports the hoist and travel wheels.

Cross Travel Wheels: Run along the bottom flange of the main girder.

Cross Travel Motor: Drives the trolley movement.

Cross Travel Reducer: Controls speed and torque.

Cross Travel Brake: Stops the trolley safely.

 

5. Runway and Rails

The runway supports the entire crane and allows long travel movement.

Runway Beams: Structural beams (usually steel) mounted on building columns.

Runway Rails: Steel rails (QU70, QU80, etc.) on which the end carriage wheels travel.

Rail Clamps: Secure the rails to the runway beams.

Hook Block

Used to connect the crane with lifting slings or other lifting accessories.

Designed according to the rated lifting capacity.

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6. Electrical System

Provides power and control for all crane movements.

Main Power Supply: Typically 380V/50Hz/3Ph or customized.

Festoon System / Cable Reel: Supplies power to the moving crane and trolley.

Control Panel / Electrical Cabinet: Houses contactors, relays, and overload protection.

Motors: For hoisting, cross travel, and long travel.

Limit Switches: For hoisting, cross travel, and long travel limits.

Overload Limiter: Prevents lifting loads beyond rated capacity.

Emergency Stop: Immediately cuts power in case of danger.

 

7. Control System

Allows the operator to control crane movements.

Pendant Control Station: Push-button box suspended from the crane.

Radio Remote Control: Wireless operation for greater flexibility.

Cabin Control: Enclosed operator cabin for harsh or high-frequency environments.

Control Cables: Connect the control devices to the electrical panel.

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8. Safety Devices

Essential for safe operation and protection of personnel and equipment.

Overload Limiter

Travel Limit Switches (long travel, cross travel, hoisting)

Buffers and Anti-Collision Devices

Emergency Stop Button

Protective Earthing

Insulation Monitoring Device

Warning Light and Buzzer (optional)

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9. Optional Components

Available based on specific application requirements.

Explosion-Proof Electrical Equipment (for hazardous environments)

Low Headroom Trolley (for limited space)

Anti-Sway System

Weighing Device / Load Display

Cabin with Air Conditioning

Rain Cover (for outdoor use)

 

 

Sketch

 

Safety Protection Devices

Include overload limiter, upper/lower lifting limit switches, travel limit switches, emergency stop, buffers, and other safety devices.

Runway Wheels and Rails

The crane traveling wheels run on the workshop runway rails.

The runway system provides the supporting path for longitudinal crane movement.

 

 

 

Main technical

 

Advantages of a 20 Ton Single Girder Overhead Crane

A 20-ton single girder overhead crane offers a practical balance between lifting capacity, cost, and efficiency. Below are its main advantages.

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1. Cost-Effective Investment

Lower purchase price compared to double girder cranes of the same capacity.

Reduced manufacturing cost due to simpler structure and fewer components.

Lower installation cost because of lighter overall weight and simpler assembly.

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2. Lightweight and Compact Structure

Single main girder design significantly reduces the crane's dead weight.

Lower wheel load on the runway beams, reducing requirements for building columns and foundations.

Compact dimensions allow better use of available workshop space.

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3. Lower Headroom Requirement

The hoist is mounted under the main girder, which maximizes the effective lifting height.

Ideal for buildings with limited vertical clearance.

A low-headroom version is also available for extremely tight spaces.

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4. Simple and Reliable Design

Fewer mechanical and electrical components means fewer potential failure points.

Proven technology widely used in light to medium-duty applications.

Stable and dependable performance with minimal downtime.

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5. Easy Installation and Maintenance

Modular structure allows quick on-site assembly.

Bolted connections between the main girder and end carriages simplify transport and installation.

Accessible lubrication points and standardized parts reduce maintenance time and cost.

Readily available spare parts in most markets.

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6. Flexible Operation Options

Supports pendant control, radio remote control, or cabin operation.

Can be adapted to different operator preferences and working environments.

Smooth starting and stopping for precise load positioning.

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7. Wide Range of Applications

Suitable for manufacturing workshops, warehouses, logistics centers, steel fabrication, and outdoor yards.

Available in explosion-proof versions for hazardous environments.

Can be customized with different spans, lifting heights, and speeds.

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8. Energy Efficiency

Lighter crane weight means less power required for long travel motion.

Efficient motor and reducer combinations reduce energy consumption.

Lower inertia allows faster acceleration and deceleration with less energy loss.

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9. Good Return on Investment

Lower initial cost and low operating cost result in a short payback period.

Long service life with proper maintenance.

High uptime improves overall productivity.

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10. Compliance with Standards

Manufactured in accordance with GB/T 14405, FEM, ISO, and other international standards.

Equipped with comprehensive safety devices for reliable and safe operation.

Certified quality gives users confidence and meets regulatory requirements.

 

Applications of a 20 Ton Single Girder Overhead Crane

The 20-ton single girder overhead crane is a versatile lifting solution widely used in light to medium-duty material handling. Its combination of adequate lifting capacity, compact design, and cost efficiency makes it suitable for a broad range of industries and working environments.

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1. Manufacturing and Assembly Workshops

Machinery manufacturing: Lifting and positioning heavy machine parts, castings, and assemblies.

Automotive industry: Handling engines, chassis components, and body parts during assembly.

Electrical and electronics: Moving heavy equipment and production materials.

General assembly lines: Transferring components between workstations.

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2. Warehouses and Logistics Centers

Loading and unloading: Moving goods onto and off trucks and containers.

Storage handling: Transferring heavy pallets, crates, and bulk materials.

Order picking: Assisting in the movement of heavy items in high-bay storage.

Distribution centers: Supporting efficient material flow and inventory management.

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3. Steel Structure and Metal Fabrication

Steel fabrication plants: Lifting steel plates, beams, and welded structures.

Metal processing: Handling raw materials, semi-finished, and finished products.

Cutting and welding shops: Positioning heavy workpieces during processing.

Pipe and tube handling: Moving long or bulky metal sections.

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4. Construction and Precast Concrete

Precast concrete plants: Lifting molds, precast panels, and concrete elements.

Construction sites: Handling building materials and structural components.

Bridge and tunnel construction: Moving heavy segments and equipment.

Temporary lifting solutions: Providing flexible lifting capacity on site.

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5. Power Plants and Energy Industry

Thermal and hydro power plants: Handling turbines, generators, and auxiliary equipment.

Wind power manufacturing: Lifting tower sections, nacelles, and blades.

Nuclear facilities: Moving heavy components with strict safety requirements.

Maintenance operations: Supporting overhaul and repair work.

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6. Chemical, Petrochemical, and Pharmaceutical

Chemical plants: Handling reactors, vessels, and process equipment.

Petrochemical facilities: Moving pipes, valves, and heavy machinery.

Pharmaceutical industry: Lifting equipment in clean or controlled environments.

Explosion-proof applications: Using LB-type explosion-proof cranes in hazardous areas.

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7. Paper, Cement, and Building Materials

Paper mills: Handling paper rolls, pulp, and machinery.

Cement plants: Moving clinker, grinding media, and equipment.

Building materials: Lifting bricks, blocks, and prefabricated components.

Glass industry: Handling glass sheets and molds.

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8. Outdoor Storage Yards

Steel yards: Lifting and stacking steel plates, beams, and pipes.

Timber yards: Handling logs and timber products.

Container yards: Moving containers and heavy cargo.

Equipment storage: Transferring machinery and spare parts.

Note: For outdoor use, proper weather protection and corrosion-resistant treatment are recommended.

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9. Maintenance and Repair Workshops

Vehicle maintenance: Lifting engines, transmissions, and heavy parts.

Equipment repair: Handling large components during overhaul.

Railway maintenance: Moving wheelsets, bogies, and locomotive parts.

Marine and shipyard: Handling marine engines and ship components.

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10. Specialized and Custom Applications

Explosion-proof environments: Chemical, oil, and gas facilities requiring ExdⅡBT4 or ExdⅡCT4 protection.

Low headroom buildings: Workshops with limited vertical space.

Clean rooms: Pharmaceutical and electronics production.

High-temperature environments: Metallurgical and foundry applications (with special modifications).

Corrosive environments: Chemical plants and coastal areas (with anti-corrosion treatment).

 

Crane Production Procedure

The manufacturing of a 20-ton single girder overhead crane follows a rigorous sequence of engineering, fabrication, assembly, and testing steps. Each stage is subject to strict quality control to ensure safety, performance, and compliance with standards such as GB/T 14405, FEM, and ISO.

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Phase 1: Design and Engineering

1. Customer Requirement Analysis

The process begins with a detailed review of the customer's lifting needs, including:

Rated capacity and span requirements

Lifting height and work duty (A5/A6)

Operating environment (indoor/outdoor, explosion-proof, corrosive, etc.)

Control method preference (pendant, remote, or cabin)

2. Site Survey and Technical Confirmation

For customized orders, engineers may conduct an on-site survey to measure:

Actual span and rail-to-rail distance

Available headroom and building clearance

Runway beam capacity and structural condition

Power supply specifications

3. Design and Drawing Approval

Based on confirmed parameters, the engineering team prepares:

General arrangement drawings

Structural calculations for the main girder (strength, stiffness, camber)

Electrical schematics and control system design

Component selection and Bill of Materials (BOM)

Drawings are submitted to the customer for approval before production begins .

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Phase 2: Material Preparation

4. Steel Plate Inspection and Pre-Treatment

Steel plates (typically Q235B or Q345B) are inspected for quality and then undergo:

Shot blasting to remove rust and scale

Primer spraying to prevent corrosion during fabrication

Drying before cutting

This pre-treatment ensures better paint adhesion and longer service life .

5. CNC Cutting

Steel plates are cut to precise dimensions using:

CNC plasma cutting machines for high-speed, high-precision cutting (deviation controlled within 1mm)

Flame cutting for thicker plates

Whole-plate cutting is preferred over using offcuts to ensure material consistency .

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Phase 3: Main Girder Fabrication

The main girder is the most critical structural component and requires the most careful fabrication.

6. Component Assembly

The girder is typically assembled from:

U-shaped channel steel (upper section)

I-beam (lower section)

Diaphragms and stiffeners (internal reinforcement)

The assembly is performed on a level platform using an inverted assembly method to control deformation .

7. Welding

Welding is performed in a controlled sequence to minimize distortion:

Internal welds: MAG welding with Ar+CO₂ mixed shielding gas

External welds: Automatic submerged arc welding (SAW)

Longitudinal joints: Submerged arc fillet welding

Welding parameters (current, voltage, speed) are strictly controlled to reduce heat input and prevent warping .

8. Camber Formation

The main girder must have a specified upward camber (typically Lk/1000, where Lk is the span) to compensate for deflection under load. Camber is achieved through:

Pre-setting during assembly

Controlled welding sequence

Tensioning systems (for large spans)

The camber curve is automatically formed and checked against standards .

9. Weld Inspection

All critical welds undergo non-destructive testing:

Radiographic inspection (X-ray) for butt welds

Ultrasonic flaw detection for fillet and full-penetration welds

Weld quality must meet specified acceptance criteria .

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Phase 4: End Carriage Fabrication

10. End Carriage Welding and Machining

End carriages are fabricated from rectangular steel tubes or welded steel plates. After welding:

The structure undergoes stress-relieving annealing to eliminate internal stresses

CNC machining is performed in a single setup to ensure dimensional accuracy and fit tolerances .

11. Wheel Assembly

Travel wheels are:

Forged or cast from high-strength steel

Heat-treated (quenching and tempering) for wear resistance

Fitted with anti-friction bearings

Installed with buffer blocks and anti-derailment devices .

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Phase 5: Surface Treatment and Painting

12. Shot Blasting

After welding, the entire girder and end carriages are shot-blasted to Sa2.5 grade to:

Remove welding scale and rust

Eliminate surface stress

Improve paint adhesion .

13. Painting

The crane receives a multi-layer protective coating:

Epoxy zinc-rich primer (one or two coats)

Intermediate coat (epoxy or polyurethane)

Topcoat (epoxy or polyurethane, color per customer requirement)

Total dry film thickness is typically 120μm or more .

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Phase 6: Assembly and Electrical Installation

14. Mechanical Assembly

Main girder and end carriages are connected using 10.9-grade high-strength bolts to ensure structural precision and easy transport .

The electric hoist and trolley are mounted on the main girder.

The travel drive units (motor, reducer, brake) are installed on the end carriages.

15. Electrical System Installation

Control panel and electrical cabinet are mounted

Power supply system (festoon cable or conductor rail) is installed

All wiring is completed and labeled with identification numbers

Limit switches, overload limiter, and safety devices are connected .

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Phase 7: Testing and Quality Control

16. No-Load Test

The crane is tested without load to verify:

All movements (hoisting, trolley travel, long travel) function correctly

Limit switches operate properly

Brakes engage and release correctly

Control system responds accurately

17. Load Test

Load testing is performed in accordance with standards:

Static load test: 125% of rated capacity

Dynamic load test: 110% of rated capacity

The crane is checked for structural deformation, brake performance, and overall stability .

18. Final Inspection and Documentation

Dimensional inspection

Painting thickness measurement

Safety device verification

Preparation of quality certificates, test reports, and operation manuals

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Phase 8: Delivery and Installation Support

19. Packing and Shipping

Main girder and end carriages are separated for transport

Components are packed with protection against moisture and damage

Shipping documents and installation instructions are provided

20. On-Site Installation and Commissioning

Installation team surveys the site and prepares the runway

Crane is assembled on-site

Final adjustments and commissioning are performed

Load test is conducted at the customer's site

Operator training and documentation handover .

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%.