20m Span Overhead Crane

Structural Design Considerations
Girder Type:
Box girder (common for heavy loads).
I-beam girder (lighter loads, cost-saving).
Support Structure:
Rail-mounted for precision movement.
Rubber-tired (RTG) for portability.
Finite Element Analysis (FEA):
Used to optimize stress distribution in 20m spans

 

Key Specifications for 20m Span Cranes

Parameter	Single-Girder	Double-Girder
Max. Load	≤20 tons	Up to 800+ tons
Lifting Height	3–16m	16–28m
Lifting Speed	0.7–8 m/min	Adjustable (VFD)
Control Method	Pendant/Remote	Cabin/Remote
Duty Class	A3–A5	A6–A8 (heavy-duty)

 

• Capacity: 5-800/50ton
• Span length: 4-35m
• Lifting height: 3-50m
• Work duty: A4, A5, A6,A7
• Raged voltage: 220V~690V, 50-60Hz, 3ph AC
• Work environment temperature: -25℃～+50℃, relative humidity ≤85%
• Crane control mode: Floor control / Remote control / Cabin room

 

Components of a 20m Span Overhead Crane
A 20m span overhead crane consists of several critical components that ensure safe and efficient lifting operations. Below is a detailed breakdown of its key parts, along with their functions and industry applications.

1. Bridge/Girder (Main Load-Bearing Structure)
Function: Supports the trolley and hoist, spanning the 20m work area.
Types:
Single-Girder: Lighter loads (up to ~20 tons), cost-effective.
Double-Girder: Heavy-duty (up to 500+ tons), higher stability.
Material: High-strength steel or aluminum (for corrosion resistance in harsh environments).

 

 

2. Trolley & Hoist Assembly
Trolley: Moves horizontally along the girder, carrying the hoist.
Can be manual or motor-driven.
Hoist: The lifting mechanism (electric chain or wire rope).
Open Winch: Used for heavy-duty applications (e.g., 250–500 tons).
Integrated Controls: Adjustable speeds for precision handling.

 

3. End Trucks & Runway System
End Trucks: Wheeled assemblies at each end of the girder.
Top-Running: Moves on rails mounted on runway beams.
Underhung: Suspended from ceiling structures (for low headroom).
Runway Rails: Guide the crane's movement (standard or curved for specialized paths).

 

4. Drive Mechanism
Travel Motors: Power longitudinal movement along the runway.
Gearboxes & Brakes: Ensure smooth acceleration/deceleration.
Variable Frequency Drives (VFDs): Enable precise speed control.

 

 

5. Control System
Pendant Control: Handheld wired remote for operator safety.
Radio Remote/Wireless: Flexible operation in large facilities.
Automation Options: Programmable logic controllers (PLCs) for smart warehousing.

 

6. Safety Components
Limit Switches: Prevent over-travel of the trolley or bridge.
Overload Protection: Sensors halt operation if capacity is exceeded.
Anti-Collision Systems: Essential for multi-crane setups.

 

7. Electrical & Power Supply
Festoon Systems/Cable Reels: Manage power and signal cables.
Busbars: Deliver uninterrupted power in high-duty cycles.

8. Optional Attachments
Magnets/Vacuum Lifters: For steel sheets or fragile loads.
Spreader Beams: Container handling in ports.
Weighing Systems: Real-time load monitoring.

 

SKETCH

 

 

 

 

Key Advantages:

Large Coverage Area

The 20m span provides extensive coverage, ideal for wide workspaces like factories, warehouses, and shipyards

Eliminates need for multiple cranes in large facilities

Heavy Lifting Capacity

Double girder versions can handle up to 500+ tons

Single girder models suitable for 1-20 ton loads

Robust construction ensures stability during heavy lifts

Space Optimization

Clears floor space by operating overhead

Underhung versions maximize vertical space in low-clearance facilities

Precision Handling

Variable frequency drives enable smooth acceleration/deceleration

Fine-control options for delicate positioning

Customizable Configurations

Available in top-running or underhung designs

Options for explosion-proof, high-temperature, or corrosion-resistant models

Cost Efficiency

Lower long-term costs compared to multiple smaller cranes

Reduced labor requirements for material handling

 

 

Primary Applications:

1. Heavy Manufacturing

Automotive plants: Moving vehicle chassis and large components

Steel mills: Handling coils, plates, and structural beams

Machinery production: Positioning heavy equipment parts

2. Logistics & Warehousing

Large distribution centers: Pallet and container handling

Port facilities: Container stacking and movement (using RTG variants)

3. Construction & Infrastructure

Precast concrete plants: Moving large concrete elements

Bridge construction: Positioning structural components

4. Energy Sector

Power plants: Turbine and generator maintenance

Renewable energy: Wind turbine component handling

5. Shipbuilding & Repair

Dry docks: Moving ship sections and heavy marine components

Assembly areas: Positioning large hull segments

6. Aerospace Industry

Aircraft assembly: Moving fuselage sections and wings

Engine maintenance: Handling heavy propulsion systems

 

Specialized Applications:

Foundries: Special high-temperature models for molten metal

Mining: Heavy-duty versions for ore processing equipment

Nuclear Facilities: Radiation-resistant designs for containment areas

 

 

1. Design & Engineering
Requirements Analysis: Determine load capacity, span, lifting height, and operating environment.

CAD Modeling: Create 3D designs and structural calculations (stress analysis, deflection, etc.).

Material Selection: Choose suitable casting materials (typically cast steel or ductile iron) for key components like girders, end carriages, and hooks.

Regulatory Compliance: Ensure designs meet standards (ISO, DIN, FEM, or ASME).

2. Pattern Making & Mold Preparation
Pattern Creation: Wood or metal patterns are made for casting molds.

Sand Mold Preparation:

Use resin-bonded sand or green sand for mold cavities.

Cores (for hollow sections) are prepared separately.

3. Casting Process
Melting & Pouring:

Metal (e.g., carbon steel, alloy steel) is melted in a furnace.

Molten metal is poured into molds under controlled conditions.

Cooling & Solidification: Allow the casting to cool slowly to avoid defects.

Shakeout & Cleaning: Remove sand molds, and clean castings (shot blasting, grinding).

4. Machining & Finishing
Rough Machining: Remove excess material (gates, risers).

Precision Machining: CNC machining for critical dimensions (bearing seats, bolt holes).

Surface Treatment: Painting, galvanizing, or anti-corrosion coatings.

5. Fabrication of Bridge Girder & End Carriages
Welding/Assembly:

Fabricate box girders or I-beams (if hybrid design).

Weld/bolt end carriages (with wheels for movement).

Stress Relief Heat Treatment (if needed) to reduce residual stresses.

6. Assembly of Crane Components
Hoist & Trolley Installation: Mount electric hoist or wire rope system.

Rail & Runway Setup: Install crane rails on supporting structure.

Electrical System Integration: Wire motors, controls, limit switches, and safety devices.

7. Testing & Quality Control
Dimensional Inspection: Verify tolerances per design specs.

Non-Destructive Testing (NDT):

Ultrasonic, magnetic particle, or dye penetrant testing for cracks.

Load Testing:

Static Load Test: 125% of rated capacity.

Dynamic Load Test: 110% of rated capacity with movements.

Functional Test: Check braking, lifting, and travel operations.

8. Painting & Corrosion Protection
Apply primer and corrosion-resistant paint.

Markings (capacity, serial number, warnings) as per standards.

9. Packaging & Delivery
Disassemble (if needed) for shipping.

Protect critical components during transit.

10. Installation & Commissioning (On-Site)
Reassemble on the customer's runway.

Final alignment and calibration.

Operator training and handover.

 

 

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