Forno

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.

La temperatura all'interno del forno viene misurata tramite un termometro e dovrebbe essere mantenuta a un livello tale da permettere la generazione della quantità di vapore richiesta. Se la temperatura è troppo bassa, la generazione di vapore risulterà inefficiente, mentre un'eccessiva temperatura può portare a uno spreco di carburante.

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.

Per controllare più precisamente il livello di carbone all’interno del forno, il macchinista può utilizzare la pala professionale. Inoltre, è anche possibile scaricare il carbone utilizzando la leva di scarico del carbone situata accanto alla boccaporta.