1. Restoring a safe state. Functional safety in machinery usually means systems that safely monitor and, when necessary, override the machine applications to ensure safe operation. A safety-related system thus implements the required safety functions by detecting hazardous conditions and bringing operation to a safe state, ensuring that a desired action, such safe stopping, takes place.
2. Detecting deviations. Safety system monitoring can include machine speed, direction of movement, stopping and standstill. When executing a safety function, such as monitoring a crawl speed that deviates from the expected value (such as too fast), the safety system detects this deviation and actively returns machine operation to a safe state by stopping the machine safely and removing the torque from the motor shaft.
3. Human response required. In a hydraulic press machine, as another example, human safety was achieved by using a light curtain at the job press' work area to hold the press for any human interrupt. The press can only resume operation when the operator comes out of the working area and acknowledges the action.
4. Safety modules. Safety inputs are monitored with special modules that detect input discrepancies and they are processed in a safety controller, which generates safety code.
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