Emergency stop circuit

An emergency-stop circuit is a hardwired, fail-safe trip loop that shuts down machinery or fuel supply on demand independent of the programmable control system. It uses normally-closed contacts so a broken wire or lost power forces the safe state, and pressing any mushroom-head stop opens the loop to de-energize the run signal, close fuel valves, or trip the breaker. SOLAS requires remote emergency stops outside the machinery space for fuel and lube-oil pumps, ventilation fans, purifiers, and boiler burners, grouped at the fire-control station so a space can be isolated during a fire.