Why use a safety relay

Safety Relays for Functional Safety: Monitoring, Diagnostics and Reliability in Industrial Applications

Safety relays are designed to perform safety-related functions in industrial applications. When a hazardous condition occurs, they initiate a predefined response to bring a process or machinery to a safe state.
While a standard relay can switch a load on or off, safety-critical applications require more. The device responsible for a safety function must operate reliably when required and, depending on the application, provide monitoring and diagnostic capabilities to help ensure the integrity of the safety loop.

Prevention and safe operation
Prevention is at the core of Functional Safety. Safety relays work behind devices such as emergency stop buttons, safety switches and light curtains to ensure that the required safety action is performed correctly. For example, a safety relay can monitor a safety gate and enable machine operation only when the required conditions are met. When an emergency stop is activated, it can interrupt power and bring the application to a safe state. In other applications, the safety function may require activating a sounder or beacon to warn personnel of a hazardous event.

Monitoring and diagnostics
Many safety functions remain dormant during normal operation and are activated only when hazardous conditions occur. Their ability to operate correctly must therefore be monitored over time. Depending on their design, safety relays can detect welded contacts, relay coil faults, field power loss, short circuits and open circuits. Advanced devices can also provide internal diagnostics and communicate their operating status to the control system. Some safety relays are also compatible with pulse-test signals generated by safety PLC output cards, filtering these signals during normal operation while maintaining fault detection capabilities.

Functional Safety and reliability
In a Safety Instrumented System (SIS), sensors, logic solvers and final elements work together to perform a Safety Instrumented Function (SIF). When a safety relay is part of this chain, its reliability contributes directly to achieving or maintaining the required safe state.
Safety relays may incorporate redundant internal channels and diagnostic circuitry to reduce the probability that a single failure prevents the required safety action. Their selection should therefore consider not only switching characteristics, but also architecture, diagnostics and certified safety performance, including applicable SIL or PL requirements. Periodic maintenance and proof testing also help ensure that the required safety performance is maintained throughout the installation lifecycle.
Ultimately, a safety relay provides much more than switching: reliable operation, monitoring, diagnostics and redundancy help ensure that the required safety action is available when it is needed.

Want to learn more about safety relays? Read the full article on GMI website: https://gminternational.com/blog/why-use-a-safety-relay