e-loop energy chain safely guides arm-thick cables to the bucket-wheel excavator

The Holcim Group operates a chalk mine in the opencast mine of Lägerdorf near Itzehoe. The raw material for the neighbouring cement works is extracted here on a large scale. A bucket-wheel excavator can mine up to 4,500 tonnes of porous calcite per day in the pit. It loads the material onto the first of several conveyor wagons, which transfer the chalk along a conveyor belt route that is around two and a half kilometres long. It conveys the slurried chalk to the cement plant.

As is usual in opencast mining, the excavator is electrically powered. Two cables for the power supply, each thicker than an arm, must be guided just as safely as a control cable. The cables run from the stationary conveyor line via the conveyor wagons to the excavator. As the excavator moves while working, the cables must also be able to move flexibly. Previously, the important cables for the bucket-wheel excavator were in a hanging position. However, it also happens that they are dragged across the floor and deposited there. The problem: While they wore out quickly due to contact with rock and uneven terrain during mining, they would freeze to the ground in frosty conditions. This situation prompted the Holcim plant engineering team to look for solutions for an "ordered" and protected energy supply for the bucket-wheel excavator, which proved to be not so simple.

Obvious solutions such as a cable drum were out of the question for cable guide, as both the stacker and the reclaimer move. Every additional weight, for example on the separator arm, can cause instability. The solution: a heavy-duty energy chain that was still being extensively tested in our test laboratory at that time: the e-loop for hanging applications.

The e-loop combines the advantages of a plastic energy chain with those of a high-strength and dimensionally stable tension rope. Internal tensile forces are absorbed by the tension rope and transmitted to the structure. This ensures that all cables are strain-relieved and protected. In addition, the modular e-loop made of high-performance plastic ensures a defined minimum bend radius of the cables it protects. The plastic is wear-resistant and each element is also provided with a "cushion" of softer plastic. This increases resistance to impacts and shocks. And because the chain is modular, additional chain links can be added or removed quickly.

After we were able to see the situation on site, we determined the diameter and required length of the e-loop. The total length of 13.50 metres of energy chain was to be installed in eight hours. It was assembled in just five hours. This allowed the bucket-wheel excavator to quickly resume chalk extraction. Since its installation in May 2020, the e-loop has been operating without any problems according to Dieter Reitz from Holcim (as of 2022).
And Holcim is already planning the follow-up project: the system is now installed at the most mobile transfer point, between the conveyor belt wagon and the bucket-wheel excavator. A plan is underway to install e-loops between the conveyor belt wagons as well.