SX boom system helps to increases lifting capacity and lifting height of Liebherr 750-tonne lattice boom cranes to the 1,000 tonne class for erecting wind turbines.
Beating Larger Capacity Class Crawlers
Liebherr has developed a completely new boom system in 2017, designated as SX for its own 750-tonne lattice boom LG1750/2 and LG1750 for erecting the latest generation of wind turbines. The 750-tonne crawlers are able to erect wind turbines with a hub height of up to 165m and components weighing up to 120 tonnes when equipped with this system. Prior to the development of such a boom system, only 1000-tonne class or above crawler cranes are able to perform such lift.
Design of SX Boom System
It differs from Liebherr’s previous boom systems by the fact that 3.5-metre wide lattice sections are used in the bottom area of the boom rather than sections measuring just 3 metres wide. The extended lattice sections increase the lateral stability of the boom and therefore deliver a higher load capacity. Furthermore, the weight of the lattice sections has been reduced. This means that the boom length can now be raised up to 165 metres comprising the main boom plus the fixed lattice jib.
An additional 30% increase in lifting capacity is achieved by a particularly innovative extension to the SX system: instead of 3.5-metre wide lattice sections, two lattice sections every 14 metres in length (SX2 system) or three lattice sections every 14 metres in length (SX3 system) with a width of 6 metres are installed in the lowest area of the main boom. This provides additional rigidity to the boom system, thus increasing its load capacity.
In order to install the 6-metre wide lattice sections in the boom, there is an extension adapter from 3 metres to 6 metres on the pivot section for the turntable. At the top, the width of 6 metres is reduced to 3.5 metres by a second adapter. When designing this system extension, Liebherr focused on ensuring it was highly economical. This means that crane operators only have to buy the 6 metre wide sections and the adapters in addition to the SX system.
Making It Fit For Transport
The challenge for the development of the 6-metre wide lattice sections, however, was the question of how they could be transported economically on public roads. Liebherr created something completely new to solve this problem: the wide boom sections made up of two halves which can be bolted together in the centre and separated again very 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 metres can be achieved.
Interchangeable With Its Model
The complete SX system can be interchanged between the LR 1750/2 crawler crane and the LG 1750 mobile crane. To enable the higher lifting capacities of the SX system to be used, Liebherr has also developed a new fixed jib specially enhanced for this system. A runner is included and the head sheaves and a new hook block are designed so as to prevent the hook block becoming twisted.