A boiler is a device used on a steam locomotive, and is a cylindrical vessel for holding and heating up water. Boiler designs have been different over the years, the most significant improvement in boiler design was the superheater header system introduced in around 1900. Steam locomotives have been know to be referred to as 'boilers' themselves.
How It WorksEdit
The boiler is filled, leaving a gap at the top, with water and the firebox is filled with fuel. When the firebox is fired, the heat from the fire travels through tubes inside the boiler and heats the water around them. The gap at the top then fills with steam from the boiling water, and the steam collects in the Steam Dome on top of the boiler.
The way these work is by recycling the steam. This is done when the steam is caught by the steam dome and sent through the main steam pipe. Instead of going into the cylinders it is sent into special superheating tubes inside the boiler, tubes like those in which the hot gases and smoke escape the firebox, but not filled with smoke and hot gases and big enough to fit tubes inside. The heat from the water around these tubes superheats the steam to give more power in the cylinders when the steam returns and is used.
Most changes have been to the outer casing on later steam locomotive types, and have prevented against boiler explosions better than how they originally were designed.