The boiler of a steam engine uses the heat from both fire and the hot gases produced by fire to boil water and produce steam. The efficiency of this process can be greatly improved if the contact area between the hot gases and the water vessel is very large. Instead of just having a kettle-type boiler sitting on a fire, a multiple-tube boiler passes the fire gases through the boiler along a series of narrow tubes. Cornish boilers had one tube, Lancashire boilers two, and marine and locomotive boilers had many tubes, which sometimes were passed back and forward through the boiler.
The first two-pass multi-tube boiler was invented in 1828 by the French engineer Mark Seguin (1786- 1875). This quickly led to a considerable improvement in the power and speed of early railway engines and was a major factor in the success of George Stephenson's Rocket in the Rainhill Trials on the Liverpool and Manchester railway, in October 1829.
Multiple-tube boilers such as these are known as fire-tube boilers. They are relatively compact and enable a working steam pressure to be built up quickly. As well as i» locomotives, multiple-tube boilers generated steam power for anything from stationary industrial engines to steam boats.
In the modern era, boilers working at higher pressures incorporate a multiple water-tube system. Here, narrow tubes carry water and steam directly through the hot furnace, and forced convection is often used to speed the transit of the fluids in the tubes. The steam can also be superheated for use in driving turbines. Multiple water-tube systems are safer than fire-tube boilers. They are less likely to suffer catastrophic failures, and thus have an important role in the generation of nuclear power.
