man with drill
A crown blade is an important part of any steam engine. This blade can be found on any vessel that relies on a boiler or furnace to run an engine, including locomotives and steamboats. A well maintained and properly cared for corona sheet is key to minimizing the risk of injury or death whenever steam engines are used.
The steam used in a steam engine comes from a large boiler located on or near the engine. This boiler consists of a tank filled with water, which turns into steam when heated. Metal furnaces used to be placed inside the water tank of these engines. Crews could simply put wood or charcoal into the furnace through an opening in the front, while the top, bottom, and sides of the box were completely submerged in water at all times.
The steel panels that make up the firebox are known as the sheets, with the top panel being known as the crown sheet. A fire inside the box heated these sheets, which then heated the surrounding water to produce steam. As the steam traveled through the engine or out of the pipes, the water level in the tank dropped. The job of each engineer or worker was to make sure that the water level never dropped below the crown sheet and that the crown sheet was always completely covered in water.
Crews relied on a simple display located at the front of the tank to help them monitor water levels. If the water ever dropped below the level of the coronal plate, the teams knew to put out the fire immediately and let the caldera cool down. Otherwise, the crown blade may collapse, which may cause fire or even explosion. In fact, many steamboat or steam locomotive disasters can be attributed to water levels falling below the crown blade.
Some workers believed that the danger could be avoided by simply re-adding water to the tank to bring the levels back up and re-immersing the crown leaf. The entry of relatively cold water into the tank caused a rapid production of steam, which greatly increased the pressure in the boiler. This excess pressure would put too much pressure on the crown blade and would normally lead to blowouts.
Although steam engines are rarely used today, many history enthusiasts try to restore and operate old steam locomotives or steamboats. Due to the age and primitive technology used in these machines, users and bystanders should be aware of the potential danger associated with these engines. In addition to carefully monitoring water levels, operators should inspect the heater prior to use to ensure it meets operating demands.