Firebox

Fireboxes are chambers found on steam vehicles , where fuel is burned in order to boil water in boilers . A firebox is positioned such that it is partly inside a boiler. It also features a cluster of heating tubes extending through the boiler, to a chimney at the other end, where the hot air and smoke pass through.

Coal-powered fireboxes have a firedoor in the vehicle's cab , which can be opened to shovel coal inside. The door should be kept closed otherwise, to prevent blowback. Blowback is a dangerous event where exhaust flow is reversed, drawing fire into the cab, potentially catastrophically harming the crew. It happens upon entering tunnels with the firedoor open.

To ignite coal, use a lighter .

In order to boil water, fireboxes need to be hot. Firebox temperature is measured by a temperature gauge. Fireboxes should be kept only as hot as needed to create the required amount of steam. Overheating them all the time wastes fuel .

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 airflow is key, and depends on whether there is steam being admitted to the cylinders , but can also be adjusted by the blower and damper controls.

Having the firebox full to the brim with coal 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 the chimney before fully burning. This is what makes the exhaust dark. When coal amount is proportional to available airflow, however, coal burns cleaner and the exhaust color is more bright.

Different types of shovels have different characteristics when it comes to feeding the firebox.

Coal in fireboxes can be dumped manually, with the coal dump lever found next to the firedoor.