The Steamboating Forum

Steam Technology - The Basics

Generating Steam
Basic Engine Principle
Boiler Theory and Designs
Engine Theory and Designs
Pipes & Fittings

Generating Steam

How does steam work? Not very well if you haven't got any to begin with.

In a steam boat, a steam generator, typically called a Boiler, produces steam by boiling water from a heat source such as burning coal. Although there are many different types of boiler, they all use the same basic principle of passing hot gasses around or through a metal body containing water.

The image below shows a simple horizontal fire tube type boiler. In this instance, the fire is at one end of the boiler and the hot gasses produced by the flames travel through tubes running inside the cylinder of water. The hot gasses carry on upwards out of the flue.

As the hot gasses heat the metal pipes which in turn heats the water. Bubbles of steam rise to the top and the steam collects above the water. Convection currents in the water keep the water moving around in the boiler's pressure vessel which help to transfer the hot water away from the tubes so cooler water can be heated up.

The steam output pipe will take the steam out of the boiler and transfer it to the engine and other parts requiring steam.

Of course with a working boiler things aren't quite so straightforward. As you take steam out, this uses up the water. The water has to be replaced as it is being used. It is most important that the tubes do not dry out as they will overheat and eventually the boiler will fail. Fortunately on a boat you are rarely far from any water. There are many way of putting water into a boiler, most of which can be seen on the Pumps page.

Basic Engine Principle

Once you have a boiler full of steam, it is not much use unless you can convert the steam into a useful form of energy. On a boat this energy is usually a rotational force to drive a propeller in the water. An Engine does just that, converts energy (pressure and heat contained in the steam) into a rotational force, almost but not quite like a car engine.

The typical engine design for a boat is based around a piston being pushed up and down by the steam which in turn is connected to a crank to rotate a shaft.

The picture below shows a very simple engine.

*Artist on strike*



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