Safety Relays
Safety Relays : Safety relays must be used in all control circuits for safeguarding devices such as interlocks, emergency stops, lights screens, safety mats and two hand controls to comply with the control reliability requirement. Safety relays have positive guided or captive contacts which are very different from conventional "ice cube" relays. The actuator (mechanical linkage) for the positive-guided relay is place much closer to the contacts than on the conventional relay. This placement of the actuator and the lack of gap tolerance on the positive-guided relay insures a consistent relationship between the normally-open contacts and the normally-closed contacts. The positive-guided relay is guaranteed to maintain a minimum .5 mm distance between its normally-closed contacts when the normally-open contact is held closed. This characteristic makes the positive-guided relay a preferred relay when designing safety circuits for generating a safe output. A control reliable circuit requires three positive-guided relays to provide redundancy and monitoring
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