Forced Guide Contact Relays

Force guided contact relays have sets of contacts linked mechanically so that if one set is open, another is closed. If one set of contacts (typically the contacts carrying power to some king of actuator) becomes welded, neither set changes state when the relay coil is energized or de-energized.

This means that in a safety-critical application, the state of the contacts mechanically linked to the power contacts can be monitored to verify that the relay is operating correctly.

Typically two such relays would be used in series with the load. There is a very small probability that the contacts in both would become welded at the same time, and by monitoring the state of the relays with the linked contacts, a failure of one relay can be detected (by e.g. a Safety relay or Safety PLC) and the system can be put in a safe state, with no operation possible until the failed relay has been repaired or replaced.

GA.

Something like this from Rockwell?