As described in NFPA
79, Emergency Stops
should be designed to do the following:
- Be initiated by a single human action
- Override all other functions and operations in all other modes
- Remove power to machine actuators quickly and without creating other hazards
- Function as either a Category 0 or Category 1 stop, depending on the machine
Additionally, the following requirements apply:
- In all situations, regardless of the type of stop, the reset of the stop function must not initiate a hazardous situation. Only a "start" procedure after the reset of the stop can initiate the machine cycle.
- Emergency stop that function as a Category 0 should have only hard-wired electromechanical components.
Emergency Stop: (Machine Safety) A control function initiated by a single human action to arrest dangerous machine motion, or otherwise avert or reduce existing hazards to persons, damage to machinery or to work in progress.