Anyone can create steam with a little water and heat. You do it every time you heat water to make spaghetti or tea, but steam can actually serve a useful purpose, too. Of course, you can't power a train with your tea kettle, but industrial applications of the same general principle enable people to create steam in massive quantities so that they can power industrial equipment, move locomotives and even generate electricity! There are different types of boilers that can be used, each with distinct advantages and disadvantages, but if you know how they work from the inside out, you understand the secret of their incredible potential.
Fire and Water
Two of the most distinctly different types of boilers are fire tube and water tube boilers. In a fire tube boiler, burning fuel creates hot gas that travels through a series of tubes inside the boiler. The tubes actually course through a tank of water, and as the hot gas circulates in the tubes, heat passes through the walls of those tubes and heat the water. As the water heats, it evaporates into steam, which exits the boiler to provide power in whatever capacity it needs.
Compare this to a water tube boiler, which operates in a manner that is both remarkably similar and fundamentally different. Like a fire tube boiler, this model has a series of tubes and a fuel burner that creates hot gas. Instead of the gas circulating through the tubes, though, in this model, water circulates through the tubes. The hot gas fills the air outside the tubes, and heats the water from the outside in. Hot water rises to the tops of the tubes, where the steam collects and flows out of the boiler while cooler water circulates back down.
While water tube boilers first appeared in the 1700's, they did not become particularly popular for at least 100 years. This is because these types of boilers were, at the time, quite revolutionary—they were so advanced and complex that engineers struggled to perfect the design. They were not the...