Liebherr has developed the SX boom system for its 750-tonne LR 1750/2 and LG 1750 lattice cranes for erecting wind turbines with hub heights of up to 165 meters and component weights of up to 120 tonnes. Previously, only cranes in the 1,000-tonne class and above could erect these late-generation turbines.
The SX system is different from previous boom systems because its 3.5-meter-wide lattice sections are used in the bottom area of the boom, which increases the lateral stability of the boom and delivers a higher load capacity. The weight of the lattice sections also has been reduced, which means the boom length can now be raised up to 165 meters, comprising the main boom plus the fixed lattice jib.
An additional increase in lifting capacity is achieved with an innovative extension to the SX system. Instead of 3.5-meter-wide lattice sections, the system can have two lattice sections that are each 14 meters long (SX2 system) or three lattice sections that each 14 meters long (SX3 system) and 6 meters wide installed in the lowest area of the main boom. This provides additional rigidity to the boom system and an increase in load capacity.
The challenge for developing the 6-meter wide lattice sections was economically transporting them on public roads. Liebherr solved the problem by designing wide boom sections made up of two halves that can be bolted together in the center and separated again quickly. To transport them, the individual halves are slightly offset longitudinally and then joined so that they mesh together like teeth. This means that a practical transport width of 3.5 meters can be achieved.