Box girder assembly machine with mobile gantry: clamps the plates onto the diaphragms before electroslag welding, for 5–12 m parts. 60-month warranty.
| Cover plate (flange) width | 200–1000 mm |
| Cover plate (flange) thickness | 6–40 mm |
| Web height | 300–1000 mm |
| Web thickness | 6–40 mm |
| Workpiece length | 5000–12000 mm |
| Total power | 22 kW |
| Weight | 13 t |
| Equipment dimensions | 28 m × 3.5 m × 3 m |
A box girder assembly machine becomes necessary as soon as a steel structure plant moves from H-beams to closed-section girders, for heavy columns, overhead cranes or infrastructure. On a box girder, the four outer plates must be clamped tightly onto the internal diaphragms, and this can no longer be done properly with clamps, wedges and the overhead crane.
In the production flow, UZL sits after plate cutting and diaphragm fitting and before welding the main seams and electroslag welding of the diaphragms. It replaces manual assembly on trestles, which is slow and hard to control dimensionally, with a machine operation that behaves consistently and needs less manual intervention. See all LAZIRON machines for H-beam and box girder fabrication, from assembly to welding and straightening.
• Mobile gantry, suited to discontinuous diaphragms: the diaphragms in a box girder are not continuous along the full length, but spaced apart. The gantry travels along the part and clamps the plates exactly at each diaphragm.
• Tight clamping on four sides: the cover plates and webs sit tightly against the diaphragms. During electroslag welding, the molten slag has nowhere to run out, so the weld forms correctly.
• Automated alignment: a box girder assembly machine positions the components precisely and repeatably, and the joints come out solid and accurate, without repeated hammer adjustments.
• Less manual work: the control system takes over many of the manoeuvres that would otherwise require two or three people and the overhead crane for each plate.
• Wide range of sections: cover plates of 200–1000 mm, webs of 300–1000 mm, thicknesses of 6–40 mm, so the same machine covers columns, crane runway girders and bridge elements.
• Low installed power: 22 kW total power, which makes the machine easy to supply in an existing hall.
• Good geometry for the next operations: a correctly assembled box girder is easier to weld, distorts less and comes closer to the nominal dimensions at inspection.
| Parameter | Value |
|---|---|
| Model | LAZIRON UZL |
| Cover plate (flange) width | 200–1000 mm |
| Cover plate (flange) thickness | 6–40 mm |
| Web height | 300–1000 mm |
| Web thickness | 6–40 mm |
| Workpiece length | 5000–12000 mm |
| Total power | 22 kW |
| Weight | 13 t |
| Equipment dimensions | 28 m × 3.5 m × 3 m |
With dimensions of 28 m × 3.5 m × 3 m and a weight of 13 t, the machine needs a dedicated hall bay, but not special foundations for a large press or an enclosed cell.
Box girders appear where an open section is no longer enough: columns for tall steel buildings and multi-storey buildings, crane runway girders for heavy overhead cranes, main girders for trestles and footbridges, elements for bridges and for energy structures. For a steel construction fabricator, a box girder assembly machine turns these parts from a special order that blocks the workshop for days into series production with predictable times.
The difference from steel beams with an H section lies in how the section behaves. A box girder resists torsion and loads in two directions much better, which is why it is preferred for columns with large moments, for girders carrying eccentric loads and for long spans. The price of this performance is more demanding fabrication: the closed section must be assembled correctly from the start, because once the last plate is welded you no longer have access to the inside.
The machine suits steel structure plants working on infrastructure projects and large-scale construction, where girder strength matters and where the internal diaphragms are electroslag welded. Tight clamping of the plates is the condition for this weld to come out right. The equipment is delivered with CE-certified components, in line with the requirements of the Machinery Directive 2006/42/EC.
Demand for box girders comes from road and rail infrastructure projects, from industrial extensions with heavy overhead cranes and from tall buildings with a steel frame. For open-section beams in the same flow, see also the H-beam assembly machine and the beam welding gantry.
The flow on a box girder assembly machine with mobile gantry follows the natural order of building a closed section:
1. Preparing the components: cover plates, webs and diaphragms are cut to size, and the diaphragms are fitted on the base plate at the spacings in the design.
2. Placing the side plates: the webs are brought next to the diaphragms and positioned along the full length of the part, 5–12 m.
3. Clamping with the mobile gantry: the gantry travels along the girder and clamps the plates onto the diaphragms, exactly at each one.
4. Tack welding: the aligned components are tacked so that the section keeps its geometry during welding.
5. Closing the section: the top cover plate is clamped and tacked onto the diaphragms, on all four sides.
6. Discharge: the assembled box girder moves on to welding of the main seams and electroslag welding of the diaphragms.
The gain shows especially in electroslag welding. If a gap remains between plate and diaphragm, the molten slag runs out, the weld comes out incomplete, and repairing a closed box girder is difficult and expensive. Tight assembly from the start avoids exactly this scenario.
The second gain concerns assembly time. On trestles, with clamps and wedges, a long box girder can keep a whole team busy for a day. With UZL, the gantry does the clamping, and people handle tacking and inspection. This frees the overhead crane for other operations and makes the time per girder predictable, which matters when you promise deadlines to a general contractor.
The third gain is dimensional quality at acceptance. A bent or twisted box girder is very hard to correct once the section is closed, because you no longer have access to the inside. A box girder assembly machine fixes the geometry before welding, while corrections are still cheap. For the client, this means girders that are erected on site without adjustments, and for you, fewer complaints and fewer hours lost on rework.
• Delivery, installation and commissioning, with operator training on your own parts.
• 60-month warranty and service with on-site response in under 24 hours in Romania (24–72 hours in other countries).
• Technical documentation for EU-funded, PNRR and public procurement projects.
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