Behind and below the boiler, the crown sheet arches over the firebox, exposing in-flowing feedwater to the heat of the combustion for the first time. Other mechanical and hydraulic processes draw the water further into the boiler and super-heater tubes, where it becomes saturated steam. The crown sheet is a critical element of the locomotive, and the fireman's primary duty is to keep all parts of it completely covered with water (not an easy task since it is built against gravity)—otherwise the exposed metal will overheat and fail.
Quick facts
Accident prone
Still happens
Safety features