New switchgear series installed at Rhein-Umschlag / On-site testing at gravel works: robust emergency pull-wire switches

At the Vennebeck gravel works in Porta Westfalica, Rhein-Umschlag is currently testing a new series of heavy-duty emergency pull-wire switches with anti-corrosive thermoset enclosures in cooperation with steute.

At the major bend in the River Weser near Porta Westfalica, the Rhein-Umschlag Group excavates Weser gravel, rich in sandstone and quartz and deposited during the Ice Age. This gravel is not particularly reactive, making it suitable for processing as a raw material for concrete. And it is also popular with landscape gardeners because it is more colourful than, for example, Rhine gravel: each particle has its own individual colouration.

Using a floating-grab excavator, the fine gravel is dredged from a depth of over 20 metres and first moved on to dry land, then transported over several hundred metres via a conveyor system to a screen and from there to a raw gravel tip for processing and grading.

The responsible persons at Rhein-Umschlag attach great importance to state-of-the-art technology and efficient plant operation, shown for example by their retrofit investment in load-dependent grading control. It adapts the operation mode of the plant, and thus also the power consumption, to the scale of the gravel. The result is a saving in energy.

Regarding safety at its gravel plants, Rhein-Umschlag also welcomes new ideas. All conveyor belts are safeguarded with emergency pull-wire switches which can prevent the worst from happening in a hazardous situation: one pull of the wire, and the belt stops. Along the central conveyor belt from the shore-side loading point towards the processing plant, steute has now – in agreement with Rhein-Umschlag – installed a brand new emergency pull wire switch for test purposes, the ZS 92 KST switch from the steute "Extreme" range.

This safety switch has been especially developed for heavy-duty applications, including in the extraction industry, which is clear not only from its size and obviously robust design, but also from its thermoset enclosure. The new emergency pull wire switch is considerably more corrosion-resistant than the already available ZS 92 versions featuring die-cast aluminium enclosures with multiple coatings.

The mounting dimensions are compatible with those of other commercially available emergency pull wire switches, simplifying the retrofitting or replacement of existing systems with this new series – as has occurred at Rhein-Umschlag. Using the same connection diagram, mounting is possible from below or behind the switch. One advantage from the standpoint of the user is the low release force and travel necessary to actuate the emergency stop function. This simplifies operation of the safety switch, while making it reliably compliant with all relevant international standards (e.g. for electrical emergency stop devices with a mechanical latching function).

This means that the latest variant of the ZS 92 with its robust plastic housing is also ideally suited for all bulk goods transportation and processing applications. The thermoset emergency pull-wire switches are now passing first tests in practice in heavy-duty conditions at the Vennebeck gravel works, observed by Rhein-Umschlag and steute - to date without any adverse events.