Safety relays prevent dangerous movements of machinery and equipment that may be triggered by the failure of a relay contact. Such a failure is caused, for example, by the heat generated during switching operations. This heat can lead to contacts melting together. If this is the case, a machine can no longer be stopped by actuating the emergency stop switch.
The positively driven contacts of safety relays ensure that this situation cannot occur. At least 2 relays connected in series with positively driven contacts are always installed in safety control systems: If a relay with a welded normally open contact fails, its normally closed contact shall remain open so that the error is recognised. The normally open contacts of the other relays shall then safely turn off the machine and shut it down.
Hengstler has decades of experience in the production of relays with positively driven contacts. In 1983, the company acquired E. Haller GmbH, which invented this electromechanical switching device. In 1976, its engineer, Ralf-Eberhard Kirsch, developed it together with colleagues. Today, Hengstler supplies 15 series of safety relays for various applications all over the world.