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Electronic overspeed switch for fault rectification with no time lost


Electronic overspeed switch for fault rectification with no time lost

Minimizing downtimes and safety hazards in heavy industry.

“Safety Limited Speed”, slip control and maintenance work carried out under voltage are operating conditions found in heavy industry which present particular safety challenges for people in the immediate environs of a plant. The operators of heavy industry plants face downtimes and increased maintenance costs when it comes to servicing and maintenance work, and the elimination of faults. Johannes Huebner GmbH is responding to these challenges with the newly developed electronic overspeed switch EGS(H)® 41: Attachable to existing encoders, this safety solution is suitable for applications ranging from steelworks and rolling mills to mining, crane systems and nuclear power plants.

First overspeed switch with SIL certification

Huebner’s innovation spells considerable time savings for industrial system operators in fault remediation. When an incident occurs, the operator of the system can use the switch to transition to “Safety Limited Speed” or “Zero Rotation” and commence servicing and repair immediately. “Without the EGS(H)® 41, an electrician would have to come and disconnect the system, costing the operator time and money,” explains Bernhard Herbst, project engineer at Huebner. The EGS(H)® 41 also benefits operators of industrial systems by increasing occupational safety. The overspeed switch is the only one of its kind worldwide which is certified to the international IEC 61508 standard for use in safety-oriented applications up to Safety Integrity Level (SIL) 2 and to Performance Level (PL) d in accordance with German industry standard DIN EN ISO 13849. The Giessen-based company is thus setting standards worldwide in the field of functional safety, consolidating its leading position as a manufacturer of data, encoder and traction technology for heavy industry.

Assured diagnosis, high-precision switching

The device comes as standard with two separate, galvanically isolated switches for rotation speed monitoring, each independently programmable for over- and underspeed from a value of 0.5 min-1. The EGS(H)® 41 possesses functions for integrated downtime and slip monitoring and a diagnostic switch for monitoring the device’s safety functions. The device features impressively high-precision switching and allows users to control the switch status (open/closed) of the non-wearing electronic switch contacts. “Our new overspeed switch minimises safety hazards such as a system suddenly going into operation or abrupt increases in rotation speed during maintenance and setting-up work,” confirms Bernhard Herbst.


As used at ThyssenKrupp Steel Europe AG

The safe operations and overspeed switching independent of rotation speed regulation made possible by the product have impressed long-term Huebner customer ThyssenKrupp Steel Europe AG. Germany’s largest steel manufacturer uses the EGS(H)® 41 in combination with the absolute encoder ASPAH60, likewise recently launched by Huebner, in applications such as the frames of its cogging train in its hot-rolled strip plant 2 at its Duisburg site. Bernhard Herbst comments: “ThyssenKrupp was the first customer whose attention we drew to this solution in the context of technical consulting services; they responded by deciding to purchase the EGS 41.” ThyssenKrupp has since been joined by other customers from the heavy industry sector.

Further benchmark data on the EGS(H)® 41 electronic overspeed switch:


  • Supply voltage: 12 ... 30 VDC or 100 ... 240 VAC
  • Switching voltage: 0 ... 30 VDC (max 500 mA) or 30 ... 230 VAC/VDC (max. 250 mA)
  • Configurations: B5 (flange) and B35 (flange and foot) EGS 41 or hollow shaft EGSH 41
  • Protection classes: IP65, IP66, IP66 / IP67
  • Four programmable switch outputs (two terminal boxes)
  • Second shaft extension for device combinations