1. Rail-Mounted Gantry Crane (MG Type, Rail-Track Gantry Crane)
Commonly known as a rail-mounted gantry crane, the gantry travels along dedicated steel rails on the ground. It features a double-main-girder gantry structure and is the most common type in beam yards.
- Power: 380V external power supply;
- Features: Stable operation, low cost, simple maintenance; requires laying gantry rails, and movement is constrained by the rails;
- Applications: Fixed precast beam yards, 900t high-speed railway box girders, highway small box girders, and T-beams.
2. Rubber-Tyred Gantry Crane (MGLT / TTB Rubber-Tyred Beam Transporter)
Rail-free, equipped with heavy-duty rubber-tyred bogies, self-powered by a diesel generator set, and fully hydraulically driven.
- Travel modes: Straight travel, transverse travel, crab steering, and spot turning;
- Features: No rail laying required, flexible and maneuverable, can be relocated between multiple beam yards; ground needs to be hardened due to high ground bearing pressure;
- Applications: Beam yards requiring flexible site relocation or with irregular layouts.
Note: A gantry crane is not the same as a bridge erecting machine; the gantry crane operates within the beam yard, while the bridge erecting machine places girders on bridge piers.
Main Components of the Complete Machine
1. Metal structure: Double main girders, rigid/flexible legs, and upper crossbeam, made of Q355B high-strength steel, with modular pin-and-bolt assembly; 2. Hoisting mechanism: Two hoisting trolleys and a dedicated box girder spreader; high-speed railway models are equipped as standard with four-point lifting and three-point balancing to protect the concrete girder from torsion; 3. Gantry travel mechanism: Rail-mounted type uses wheel bogies; rubber-tyred type uses hydraulic suspension bogies; 4. Power system: Rail-mounted type uses external 380V power; rubber-tyred type is equipped with a diesel generator set; 5. Electrical system: PLC variable frequency control, cab operation, with safety monitoring for attitude, wind speed, and torque.
II. Meaning of Main Model Designations
- MG450‑42: Rail-mounted gantry crane, rated capacity 450t, clear span of gantry 42m;
- MGLT450‑42: Rubber-tyred gantry crane, rated capacity 450t, clear span of gantry 42m;
For 900t high-speed railway box girders, two 450t gantry cranes are commonly used for tandem lifting; a single 900t integrated gantry crane is also available.
