Firebox/en

Firebox is a chamber onboard a steam vehicle, where the fuel is burned in order to heat up the water inside the boiler. Coal powered fireboxes have a firedoor, which the engineer can keep open while shoveling coal inside. The door should be kept closed whenever possible. Even though its effect on firebox temperature is minimal, keeping the door open can cause blowback when entering tunnels, a reversal of the exhaust flow that can draw fire into the cab and be catastrophic for the crew. Blowback can be prevented by keeping the door closed, or by maintaining intense airflow when entering a tunnel.

Temperature inside of the firebox is measured by a temperature gauge. It should be kept only as hot as needed to create the required amount of steam. Having it too cold will not generate enough steam, and overheating it can cause inefficiency with fuel consumption.

Firebox temperature is controlled by the amount of coal and airflow inside it. Simply having no more coal to burn will cause the firebox to cool down, and adding more coal will warm it up if the airflow is sufficient. The amount of draft depends on whether the steam is being admitted to the cylinders, but can also be adjusted by the blower and damper controls.

Having the firebox full to the brim is not always the best choice. Too much coal with too little airflow negatively affects fuel efficiency, resulting in a lot of coal particles getting spewed out of the chimney before they’re fully burned. This is what makes the smoke dark. When there’s less coal in the firebox it burns cleaner, making the smoke color closer to white.

To control the level of coal in the firebox more precisely, the driver can use the expert shovel. They’re also able to dump coals using the coal dump lever next to the firedoor.

See also: Shovel, Blower & Damper, Driving Efficiency, Regulator, Cutoff, Fees, Firebox