In a steam engine
, the firebox
is the area where the fuel
is burned, producing heat to boil the water in the boiler
. Most are somewhat box-shaped, hence the name.
Railway locomotive firebox
In the standard steam locomotive
firetube type boiler, the firebox is surrounded by water space on five sides. The underside is not so surrounded. If the engine burns solid fuel, there is a grate
covering most of the bottom of the firebox to hold the fuel. An ashpan collects the solid combustion waste below. Combustion air generally enters at the base, and the airflow is usually controlled by damper doors.
There is a large brick arch (made from fire brick
) at the front of the box which directs heat and flames back towards the firedoor at the rear. Without the arch, flames would be sucked straight into the firetubes, and only the front of the box would receive heat. The brick arch and the bars of the grate require periodic replacement due to the extreme heat they endure.
Firetubes are attached to one wall of the firebox (the front wall for a longitudinal boiler, the top for a vertical boiler) and carry the hot gaseous products of combustion through the boiler water, heating it, before they escape to the atmosphere.
Sheets and stays
The metal walls of the firebox are normally called sheets
, which are separated by stays
. Since any corrosion is hidden, the stays may have longitudinal holes, called tell-tales
, drilled in them which leak before they become... Read More