Liebherr has developed a boom system, designated SX, for its 750t lattice boom cranes: the LR 1750/2 and LG 1750, to allow them to erect wind turbines beyond the normal limits of their weight class.
Using the SX system, the 1750 models can now erect turbines with a hub height of up to 165m and component weights of up to 120t – a scope that was previously the preserve of 1,000t-class cranes.
The SX system uses fixed lattice jib sections of up to 6m in width, and sections of up to 3.5m in width in the lowest sections of the boom, compared to 3m-wide sections in previous boom systems.
The extended lattice sections increase the lateral stability of the boom and therefore deliver a higher load capacity and lifting heights of up to 165m. The weight of the lattice sections has also been reduced.
In order to install the 6m-wide lattice sections in the boom, there is an extension adapter from 3m to 6m on the pivot section for the turntable, while at the top the width of 6m is reduced to 3.5 metres by a second adapter.
Liebherr focused on designing a system that is highly economical, meaning that crane operators only have to buy the 6m-wide sections and the adapters for the boom and jib to employ the SX system.
The fixed jib adaptations include a runner, head sheaves and a new hook block designed to prevent the device from becoming twisted.
The main challenge for the development of the 6m-wide lattice sections was the question of how they could be transported economically on public roads.
The solution is that the wide boom sections are made up of two halves that are bolted together in the centre and which can be assembled or disassembled very quickly.
During transport, the unbolted section can then be overlapped and a practical transport width of 3.5m achieved.
In March, Dammam-based Gulf Haulage Heavy Lift Company erected the very first commercial wind turbine in Saudi Arabia, on behalf of Saudi Aramco, using a Liebherr LR 1750 crawler crane.