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

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

As is usual in open-cast mining, the excavator is electrically driven. Two cables more than arm-thick for the power supply have to be routed just as safely as a control cable. The cable runs from the stationary conveyor line via the belt carriages to the excavator. As the excavator moves during work, the cables must also be able to move flexibly. Previously, the important cables for the bucket wheel excavator were in a suspended position. However, they are also sometimes dragged across the ground and deposited there. The problem with this was that while they quickly wore out during mining due to contact with rock and uneven terrain, they froze to the ground in frosty conditions. This situation prompted Holcim's plant engineering department to look for solutions for an "organised" and protected energy supply for the bucket wheel excavator, which proved to be no easy task.

Obvious solutions such as a cable drum were out of the question as a cable guide, as both the spreader and the excavator move. Any additional weight, for example on the spreader arm, could cause instability. The solution: a heavy-duty energy chain, which was still undergoing extensive testing in our test laboratory at the time: The e-loop® for suspended applications.

The e-loop® combines the advantages of a plastic-energy chain with those of a high-strength and dimensionally stable tension cable. Internal tensile forces are absorbed by the tension cable and transferred to the structure. In this way, 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 additionally provided with a "cushion" made of softer plastic. This increases resistance to shocks and impacts. And because the chain is modular, additional chain links can be quickly added or removed.

After we were able to see the situation on site, we determined the diameter and required length of the e-loop. The energy chain, which is 13.50 metres long in total, was to be installed in eight hours. It was installed after just five hours. This allowed the bucket wheel excavator to quickly resume chalk extraction. According to Dieter Reitz from Holcim, the e-loop® has been proving itself without any problems since it was installed in May 2020 (trade show status 2022).
And Holcim is already planning the follow-up project: the system is now installed at the most mobile transfer point, between the belt wagon and bucket wheel excavator. There are also plans to install e-loops between the belt wagons.