Metal and rock detection system

THE Siemens Industrial Solutions and Services Group (I&S) has received an order from RWE Power to install a metal and rock detection system on bucket-wheel excavators for open-casting mining.

THE Siemens Industrial Solutions and Services Group (I&S) has received an order from RWE Power to install a metal and rock detection system on bucket-wheel excavators for open-casting mining.

The aim is to reduce damage to the conveyor belts of the excavator extraction systems and increase their availability.

This will be done with the help of appropriate sensors.

The system functions by detecting the position of the rocks, which can then be removed by a rock crane quickly and effectively.

At the moment, the system is being used on excavators in the Garzweiler and Hambach open-cast mines.

RWE Power is the largest power producer in Germany and a leading company in the extraction of raw-materials for power generation.

RWE Power uses bucket-wheel excavators at its Garzweiler, Hambach and Inden open-cast mines to remove the overburden and the layers of coal underneath. Apart from sand, rocks of different sizes and metal is also excavated.

The overburden is loaded onto a conveyor belt by the bucket-wheel excavator and then taken away.

The detection system — developed jointly by RWE and Siemens — is directly installed in the impact area behind the bucket wheel.

Up to eight separate acceleration sensors on the impact wall, chute and festoons are able to detect when small and medium-sized rocks hit the metal. The festoon sensors mainly detect large rocks which — because of their mass — are not thrown against the metal. In addition, an integrated metal locator coil detects any metal which is present.

The system is being continually developed because — at the moment — it is not possible to find out whether the bulk material detected is made up of rocks or, for example, frozen blocks or lumps of clay.

In order to avoid an unnecessary reduction of the production equipment’s availability because of this restriction, the systems are switched on or off by the equipment operators or their sensitivity is varied when necessary.

Thanks to the rock detection function, it is possible to determine the position of the material thus found so that a rock crane can remove it.

The high rate of detection of rocks and their position saves time as they can now be removed more quickly than before.

As a result, the excavator’s availability is increased.

Damage to the belts of the conveyor systems are avoided because the detection system prevents rocks from becoming wedged in place and thus tearing the belts.

The detection system is controlled on the basis of a Siemens S7 400 automation unit.

An FM458-1 module detects connecting points and problem points on the belt and exactly detects the position of the rocks to be removed. A WinCC system is used for visualization. It shows the precise places where the material is found and then logs and archives the checking processes.

Small or large items which are detected have to be picked out by the system so that their transfer to a rock crane can be calculated and carried out.

The Siemens Industrial Solutions and Services Group (I&S)

rainer.schulze@siemens.com

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