Component of prime mover in boiler machine

The steam generator or boiler is an integral component of a steam engine when considered as a prime mover; however it needs be treated separately, as to some extent a variety of generator types can be combined with a variety of engine units. A boiler incorporates a Firebox or Furnace in order to burn the fuel and generate heat; the heat is initially transferred to water to make steam: this produces saturated steam at ebullition temperature saturated steam which can vary according to the pressure above the boiling water.

The higher the furnace temperature, the faster the steam production. The saturated steam thus produced can then either be used immediately to produce power via a turbine and alternator , or else may be further superheated to a higher temperature; this notably reduces suspended water content making a given volume of steam produce more work and creates a greater temperature gradient in order to counter tendency to condensation due to pressure and heat drop resulting from work plus contact with the cooler walls of the steam passages and cylinders and wire-drawing effect from strangulation at the regulator. Any remaining heat in the combustion gases can then either be evacuated or made to pass through an economiser, the role of which is to warm the feed water before it reaches the boiler.