Mg-u Type Double Girder Gantry Cranes

 

DEFINITION & CORE CONCEPT

MG-u Type Double Girder Gantry Cranes are a standardized series of high-capacity, universal gantry cranes designed according to specific industrial standards (typically Russian GOST or similar Eastern European norms). The designation breaks down as:

MG = Mostovoy Gantry (Bridge Gantry)

u = Universal/General Purpose

Double Girder = Two main load-bearing beams

These are rail-mounted, outdoor gantry cranes with legs that run on ground-level tracks, forming a movable "gate" structure capable of spanning large work areas without requiring building support.

 

DEFINITION & CORE CONCEPT

MG-u Type Double Girder Gantry Cranes are a standardized series of high-capacity, universal gantry cranes designed according to specific industrial standards (typically Russian GOST or similar Eastern European norms). The designation breaks down as:

MG = Mostovoy Gantry (Bridge Gantry)

u = Universal/General Purpose

Double Girder = Two main load-bearing beams

These are rail-mounted, outdoor gantry cranes with legs that run on ground-level tracks, forming a movable "gate" structure capable of spanning large work areas without requiring building support.

 

Typical Technical Parameters

Lifting Capacity: 20–500 t

Span: 18–50 m (customizable)

Lifting Height: 10–30 m

Working Duty: A5–A7

Control Mode: Cabin / Pendant / Remote

 

1. MAIN METAL STRUCTURE COMPONENTS

1.1 Bridge (Main) Structure

Main Girders (2x): Primary load-carrying beams.

Construction: Welded box girders with internal stiffening plates/diaphragms

Material: S355JR steel (or equivalent GOST St3/St4 steel)

Features: Cambered for deflection compensation (typically L/1000)

End Connections: Machined surfaces with high-strength bolt connections to end frames

Girder Connecting Beams: Transverse beams at each end connecting the two main girders

Trolley Rails: P43 or QU-type rails mounted on top of main girders

Rail Fasteners: Bolt-type or welded clips to secure rails

Rail Joints: Ground smooth for seamless trolley travel

 

1.2 End Frames (Leg Structures)

Rigid Legs (2x): Vertical or slightly inclined columns

Construction: Box section or lattice design

Bracing: Diagonal cross-bracing for stability

Ladder/Access: Fixed ladders with safety cages for maintenance access

Leg-to-Girder Connection: High-strength bolted flange connection with alignment pins

Machined Pads: Precision surfaces for accurate girder mounting

1.3 End Carriages (Travel Bogies)

Travel Bogie Frames: Structural frames housing wheels and drives

Wheel Assemblies (per bogie):

Wheels: Forged steel wheels with double flanges

Wheel Axles: Solid steel shafts with keyways

Bearings: Tapered roller bearings in sealed housings

Wheel Covers: Protective covers against debris

Buffer Plates: Mounted at ends of end carriages

Rail Sweepers: Angled plates ahead of wheels to clear debris from rails

.

2. HOISTING MECHANISM COMPONENTS

2.1 Hoist Assembly (Mounted on Trolley)

Hoist Motor: AC induction motor (wound rotor or squirrel cage)

Power: 7.5-150 kW depending on capacity

Insulation: Class F or H for thermal endurance

Mounting: Foot-mounted with flexible coupling

Hoist Gearbox: Two-stage helical gear reducer

Gear Ratio: Typically 40:1 to 80:1

Housing: Cast iron or welded steel

Lubrication: Oil bath with sight glass

Brake System:

Main Brake: Electromagnetic thruster brake on high-speed shaft

Emergency/Safety Brake: Spring-loaded mechanical brake

Brake Wheel/Lining: Replaceable friction material

Rope Drum:

Construction: Welded steel with machined grooves

Rope Layers: Designed for multiple rope layers

Drum Ends: Flanged with rope anchor points

Drum Shaft: Supported by heavy-duty bearings

Rope Guide: Helical groove follower to ensure proper spooling

2.2 Rope System

Wire Rope: 6x36WS or 6x19S construction

Diameter: 11-32mm depending on capacity

Grade: 1770 N/mm² or higher

Lubrication: Pre-lubricated during manufacture

Rope Anchorage: Wedge-type or clamp-type anchors on drum

Sheaves/Pulleys:

Head Sheave: Grooved cast steel sheave on trolley frame

Equalizing Sheaves: For multiple fall reeving

Bearings: Sealed roller bearings in each sheave

Hook Block:

Hook: Forged steel hook with safety latch

Swivel: Thrust bearing assembly for 360° rotation

Sheave Assembly: Multiple sheaves for rope reeving

Load Cell Pocket: (Optional) for weight measurement

 

3. TROLLEY COMPONENTS

3.1 Trolley Frame

Main Frame: Welded steel frame with cross-bracing

Wheel Assemblies (4 or 8 wheels):

Wheels: Double-flanged steel wheels

Axle Boxes: Cast steel housings with bearings

Wheel Balancing: Dynamic balancing performed

Bumpers: Rubber or spring buffers at trolley ends

Skirt Plates: Safety plates around moving parts

3.2 Trolley Drive Mechanism

Drive Motor: AC motor with brake

Drive Gearbox: Helical gear reducer

Drive Wheels: One or two driven wheels

Coupling: Flexible or gear-type coupling

3.3 Trolley Platforms & Walkways

Maintenance Platform: Grid steel platform around mechanisms

Handrails: 1m high with kick plates

Access Ladder: From main girder walkway

4. GANTRY TRAVEL MECHANISM

4.1 Long Travel Drives

Travel Motors (2 or 4 total):

Power: 3-30 kW each

Mounting: Vertical or horizontal configuration

Brakes: Spring-set brakes on each motor

Travel Gearboxes:

Type: Parallel shaft or right-angle gear reducers

Mounting: Directly to bogie frame

Drive Wheels: Flanged wheels keyed to gearbox output

Coupling: Gear-type or rigid coupling

4.2 Rail System Components

Crane Rails: QU70, QU80, QU100, or P43/P50 rails

Rail Fasteners: Fish plates, bolts, and clips

Rail Pads: Neoprene or steel pads under rails

Rail Joints: Welded or bolted with smooth transition

Rail Anchors: To prevent rail creeping

Rail Lubricators (Optional): Automatic flange lubricators

5. ELECTRICAL SYSTEM COMPONENTS

5.1 Power Supply System

Conductor System (One of these):

Conductor Bars: Enclosed copper or steel conductor bars

Festoon System: Cables in festoon carriers

Cable Reel: Spring- or motor-driven cable drum

Collector Shoes/Carriages: Current collection devices

Main Circuit Breaker: Air circuit breaker in main panel

Disconnect Switch: Manual isolation switch

5.2 Control & Protection

Control Panel:

Contactors: AC3 duty contactors for motor control

Overload Relays: Thermal or electronic motor protection

Timer Relays: For acceleration/deceleration control

Terminal Blocks: DIN-rail mounted with labeling

Operator's Cabin:

Cabin Structure: Welded steel with safety glass

Control Devices: Master controllers or joysticks

Instrumentation: Ammeters, indicator lights

Heating/AC: Climate control systems

Seat: Adjustable operator seat

Resistor Banks (for wound rotor motors):

Resistor Grids: Cast iron or steel grid resistors

Enclosure: Ventilated steel cabinet

Mounting: Isolated from structure

5.3 Safety & Limit Devices

Limit Switches:

Hoist Upper/Lower: Rotary cam or lever type

Trolley Limits: At both ends of girder

Gantry Travel Limits: At rail ends

Overload Protection:

Load Cell (electronic) or Load Limiter (mechanical)

Display Unit: In operator's cabin

Anti-Collision System (for multiple cranes):

Sensors: Ultrasonic or laser distance sensors

Control Unit: Programmable controller

Emergency Stop Buttons:

Cabin: Red mushroom buttons

Local Stations: At strategic locations on structure

 

6. SAFETY & AUXILIARY COMPONENTS

6.1 Safety Equipment

Audible Warning: Electric horn or siren

Visual Warning: Rotating beacon lights (red/amber)

Wind Monitoring (for outdoor):

Anemometer: Cup-type with transmitter

Display: Wind speed indicator in cabin

Alarm: Audio-visual alarms at set points

Rail Clamps:

Manual or Hydraulic: For parking in high winds

Activation: Manual lever or electric pump

Fire Extinguishers: CO₂ or dry powder type in cabin and on structure

First Aid Kit: Standard industrial first aid supplies

6.2 Maintenance & Access Features

Walkways: Full-length catwalks along main girder

Decking: Steel grating or chequer plate

Handrails: 1.1m high with mid-rails

Toeboards: 100mm high at edges

Access Ladders: From ground to platforms

Safety Cages: For ladders over 6m

Rest Platforms: Every 6-9m of vertical climb

Lighting:

Flood Lights: For work area illumination

Path Lights: Along walkways for night maintenance

Lifting Lugs: For component replacement

Drain Holes: In box sections to prevent water accumulation

6.3 Paint & Protection System

Surface Preparation: Shot blasting to Sa 2.5 standard

Primer: Zinc-rich epoxy primer (50-75μm)

Intermediate Coat: Epoxy build coat (100-125μm)

Top Coat: Polyurethane enamel (50-75μm)

Color Coding:

Main Structure: Light gray or orange

Moving Parts: Yellow warning stripes

Handrails: Yellow or black/white

Corrosion Protection: Anodic protection in critical areas

.

7. OPTIONAL COMPONENTS

7.1 Enhanced Control Systems

Variable Frequency Drives (VFDs):

Hoist VFD: For precise speed control

Travel VFDs: For smooth acceleration

Programmable Logic Controller (PLC):

Main Processor: Modular PLC system

I/O Modules: Digital and analog inputs/outputs

HMI: Touch screen display in cabin

Remote Control:

Radio Remote: Pendant or belt-pack transmitter

Infrared Control: For hazardous areas

Automation Systems:

Auto Positioning: Pre-set position memory

Anti-Sway Control: Load sway damping system

7.2 Monitoring & Data Systems

Weight Measurement:

Load Cells: Strain gauge sensors in rope system

Display: Digital readout with data logging

Condition Monitoring:

Vibration Sensors: On motors and gearboxes

Temperature Sensors: For bearings and brakes

Maintenance Management:

Hour Meters: For each major mechanism

Lift Counter: Records number of cycles

7.3 Special Attachments

Magnet Systems:

DC Lifting Magnet: With cable reel

Control Panel: Magnet control in cabin

Grapple Attachments:

Rotator: 360° rotation device

Hydraulic Power Pack: For hydraulic attachments

Spreader Beams:

Adjustable: Telescopic or link-adjustable

Multi-Lift: For simultaneous handling of multiple loads

8. FOUNDATION & SUPPORT COMPONENTS

8.1 Rail Support System

Rail Sleepers/Beams: Concrete or steel sleepers

Fastening Systems: Rail clips, bolts, and anchors

Rail Alignment Tools: For installation and maintenance

8.2 Electrical Infrastructure

Power Feed Points: Along the runway length

Grounding System: Copper ground grid under rails

Lightning Protection: For outdoor installations

 

Sketch

 

 

 

Advantages of MG-U Type Double Girder Gantry Cranes

1. High Load Capacity

Designed for medium to ultra-heavy lifting

Typical capacity range: 20–500 tons

Suitable for heavy steel structures and large components

2. U-Type Structure for Higher Lifting Height

U-shaped double girders allow the trolley to run inside the girder

Maximizes usable lifting height

Ideal for handling tall or bulky loads

3. Excellent Structural Stability

Double girder box structure offers:

High rigidity

Strong torsional resistance

Improved wind resistance

Stable operation even under high loads

4. Large Span & Wide Working Area

Suitable for long spans and wide yards

Covers large storage or production areas with minimal crane quantity

5. Smooth & Reliable Operation

Independent crane and trolley traveling mechanisms

Optional frequency inverter (VFD) control for smooth speed regulation

Low vibration and precise positioning

6. Flexible Lifting Configurations

Can be equipped with:

Electric winch trolley

Grab bucket

Electromagnetic lifter

Customized lifting beams or spreaders

7. Designed for Outdoor Use

Equipped with:

Wind alarms

Rail clamps

Weather-resistant electrical components

Reliable performance in harsh environments

8. Multiple Control Options

Operator cabin with wide visibility

Pendant push-button control

Wireless remote control (optional)

 

Applications of MG-U Type Double Girder Gantry Cranes

The MG-U gantry crane is widely used in heavy industry and outdoor material handling.

1. Steel Plants & Steel Yards

Handling steel plates, beams, coils, and billets

Loading and unloading heavy steel products

2. Shipyards & Dockyards

Lifting ship components and steel blocks

Assembly and maintenance operations

3. Construction & Bridge Yards

Handling precast concrete girders and bridge segments

Transporting large construction components

4. Power Plants & Heavy Equipment Factories

Installation and maintenance of heavy machinery

Handling generators, transformers, and turbines

5. Cargo & Industrial Storage Yards

Bulk cargo handling

Large material storage and transfer operations

 

MG-U Type Double Girder Gantry Crane – Production Process

The MG-U Type Double Girder Gantry Crane is a heavy-duty lifting system manufactured under strict quality control to ensure high load capacity, structural stability, and long-term reliability. Production complies with GB/T, FEM, ISO, and CE standards.

 

1. Engineering Design & Technical Confirmation

Confirm:

Lifting capacity

Span and lifting height

Working duty (A5–A7)

Trolley type (winch / grab / magnet)

Structural strength and deflection calculation

Wind load and seismic design for outdoor use

Electrical and safety system configuration

2. Raw Material Selection & Inspection

High-strength structural steel (Q235B / Q345B or equivalent)

Material certificate verification

Ultrasonic testing (UT) for plates and key parts

Shot blasting or surface cleaning before fabrication

3. CNC Cutting & Component Preparation

CNC flame or plasma cutting of:

U-type main girder plates

Gantry leg panels

End beam components

Stiffeners and diaphragms

Edge beveling for welding

Dimensional inspection and marking

4. U-Type Main Girder Fabrication

4.1 Assembly

Assembly of U-shaped box girders using special fixtures

Camber control to meet design requirements

4.2 Welding

Submerged arc welding for main seams

CO₂ gas-shielded welding for secondary structures

4.3 Straightening & Stress Relief

Mechanical straightening after welding

Vibration or thermal stress relief (if required)

4.4 Weld Inspection

Visual inspection

Ultrasonic testing (UT)

Magnetic particle testing (MT) on critical welds

5. Gantry Legs & End Beam Manufacturing

Fabrication of rigid leg and flexible leg

Welding of box-type or tubular structures

CNC machining of wheel seats and connection surfaces

Assembly of end beams with bearing housings

6. Traveling Mechanism Assembly

Installation of:

Crane traveling motors

Gear reducers

Braking systems

Assembly of crane wheels

Alignment and smooth-travel testing

7. Trolley (Winch) Manufacturing & Installation

Assembly of electric winch trolley:

Lifting motor

Gearbox

Drum

Wire rope

Hook block

Installation of trolley rails inside U-type girders

Trolley traveling mechanism assembly

8. Electrical System Assembly

Installation of main electrical control cabinet

Wiring of lifting, trolley, and crane traveling systems

Installation of:

Overload limiter

Limit switches

Emergency stop system

Optional VFD installation for smooth speed control

9. Safety System Installation

Rail clamps and wind alarm

Buffers and anti-collision devices

Grounding and lightning protection system

Safety signage and warning lights

10. Surface Treatment & Painting

10.1 Shot Blasting

Steel surface treatment to Sa2.5 standard

10.2 Painting System

Epoxy zinc-rich primer

Epoxy intermediate coating

Polyurethane topcoat

Paint thickness and color per customer requirement

11. Factory Assembly & Testing

Full crane assembly or modular assembly

No-load operation test

Static load test (125% rated load)

Dynamic load test (110% rated load)

Functional testing of all safety devices

12. Packing & Transportation

Electrical components packed in wooden crates

Trolley and motors protected against moisture

Steel structures wrapped for safe transportation

13. On-Site Installation & Commissioning

Installation of ground rails and crane structure

Electrical connection and grounding

On-site testing and commissioning

Operator training and safety instruction

14. Final Inspection & Acceptance

Performance and safety acceptance

Delivery of:

Quality certificates

Test reports

Operation & maintenance manuals

Warranty and after-sales service support

 

 

 

Material Inspection

Quality Inspection: Strict quality inspection is carried out on the purchased raw materials to ensure that they meet the design requirements and national standards.

Material Storage: Qualified materials are stored according to classification to prevent corrosion or damage.

Cutting and Forming

Steel Cutting: Use plasma cutting, laser cutting or flame cutting and other technologies to cut the steel according to the size of the design drawing.

Forming Processing: Form the steel plate through bending, rolling, welding and other processes to manufacture the main beam, end beam and other structural parts.

Welding

Component Welding: The cut and formed steel parts are welded into the main structures such as the main beam, end beam and trolley. The welding process needs to be strictly controlled to ensure the structural strength and welding quality.

Weld Inspection: Use non-destructive testing technology (such as ultrasonic testing, radiographic testing) to inspect the welds to ensure that there are no cracks or other defects.

Machining

Precision Machining: Precision machining is performed on the key components of the crane, such as wheel sets, bearing seats, pulleys, etc., to ensure their dimensional accuracy and surface quality.

Assembly of the whole machine

General assembly: On the basis of pre-assembly, the overall assembly of the crane is carried out, including the final installation of the main beam, end beam, lifting mechanism, walking mechanism, etc.

Commissioning and testing

Under dynamic conditions, the operating performance of the crane is tested, including the testing of lifting, walking, steering and other functions. The overall size of the assembled bridge crane is checked to ensure that all dimensions meet the design requirements.

Spraying and anti-corrosion treatment

Surface treatment Rust removal: Rust removal on the surface of the crane, common methods include sandblasting, pickling, etc. Primer spraying: Spray anti-corrosion primer on the treated surface to prevent metal oxidation and corrosion. Topcoat spraying Color spraying: Spray topcoat according to customer requirements or industry standards to give the crane a protective and decorative effect. Marking: After spraying, mark the crane's identification information in accordance with the specifications, such as model, rated load, etc.

Factory and installation

Packaging and transportation

Packaging protection: Protectively package the key components of the crane to prevent damage during transportation. Transportation arrangement: According to the equipment size and transportation conditions, select a suitable transportation method to transport the crane to the customer's site.

Acceptance and delivery

Customer acceptance

On-site acceptance: The customer conducts on-site acceptance of the crane according to the contract requirements and technical specifications to check the performance and quality of the equipment.

Problem rectification: If any problems are found, the manufacturer needs to rectify them in time to ensure that the equipment fully meets the customer's requirements. Delivery and use Operation training: The manufacturer usually trains the customer's operators to ensure that they can operate the crane correctly and safely.

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