In mechanical engineering, functional safety control systems help to cover the requirements of health and safety protection in accordance with the Machinery Directive (2006/42/EC). The starting point here is the risk analysis and risk estimation based on EN ISO 12100. This standard describes fundamental hazards and helps the design engineer to identify relevant and significant hazards, which are reduced to an acceptable residual risk through risk-reducing measures.
Protective measures in accordance with EN ISO 13849-1 and/or IEC 62061
If control protection measures are used, manufacturers will design these in accordance with EN ISO 13849-1 and/or IEC 62061. Technical documentation will contain guidelines for constructing these measures, their safety-related reliability and intended use.
Safe state in functional safety
Today's functional safety control systems are designed so that their safe state is one of de-energisation. In other words: all hazardous movements are stopped. This is the right choice for all plant and machinery on which removal of power, and therefore a stop, is the safe state.
However, increased availability is required or demanded for increasingly more plant and machinery, in the context of Industrie 4.0, for example. Also, a "hard stop" may lead to further hazards, which need to be considered in the risk analysis. So the dogma of removing power, as the only reaction in the case of a fault, is no longer up to date.