Casting director

Spanning 43.3m and with hook heights about 11m above the ground, the new crane at Belgian concrete caster Marmorith's plant is the biggest of its 30-odd gantry cranes. Marmorith's mammoth runs on its own 220m railtrack, alongside a new casting shed adjacent to the main building. It moves concrete sections from a production facility into storage areas and onto transport trailers.

The crane was procured after Marmorith, based in Houthalen, Belgium, won a contract to supply pre-cast bridge sections for a new high-speed train line between Brussels and Cologne. If it could produce larger sections, occasionally weighing as much as 90t, then it could maximise profits. Although more difficult to handle, larger pre-cast sections simplify assembly and cut labour costs on site. Marmorith decided it was time to make an investment.

In some ways, the lifting requirements eased the problem of designing the right crane. Outside, the crane is not restricted by headroom or hemmed in by other cranes. As it would only be used about 10 times a day, and only during the daytime, crane engineer and manufacturer Kurt Deman specified two FEM 2M SWF hoists, each rated 25t capacity. For the rare occasion when a 90t section needed lifting, the firm would hire in a mobile crane to lift the far end of the load.

But the size of the crane, and its location outside, pushed Deman to its limit. The 31.8t girder was the largest the company can produce in its factory. Any larger and the crane would have had to be built on site. Deman says he had to choose between a box section and lattice-section girder structure. He went with box-section because it was cheaper and faster to produce. But there was another reason that cuts to the essence of long-term maintenance: paint. A box girder would be easier to repaint than a lattice boom girder.

Paint is no trivial issue. As the crane is exposed to the elements year-round, a good surface treatment is essential for the long-term structural health of the crane. The painting cost more than 10% of the e30,000 value of the crane. Deman says that now the surface treatment should last 20 years.

A downside of the crane's box girder is that its surface can act as a sail and catch the wind. Deman compensated by beefing up the drive systems. Each of the crane's eight 630mm-diameter wheels has its own 9.7kW Demag motor.

Running parallel to the new crane is a smaller 12.5t SWL Yamaha gantry crane. The new crane's left cantilever overhangs the smaller crane by 9m. Handy though this may be for passing loads through the splayed legs of the Deman crane, it can also result in collision with ropes, loads or girders. To avoid collision in poor weather, such as fog, Deman added a 10,000 euros laser collision-avoidance system from German manufacturer Sick.