The Haystack-boiler

The first boilers as used by Savery and Newcomen were inspired by the well known model in the kitchen, the kettle.

This boiler was called the "Haystack"-boiler, also known as "Balloon" or "Beehive" boiler. All these names are obvious according to the shape of the boiler.

The first boilers were made of copper sheets riveted together with little copper rivets. The top was made out of a sheet of led. Obviously this boiler was very vulnerable, not capable of holding any pressure and easy to deform. Many boilers simply "burned away" as the temperatures of the fire got much higher than the copper material could stand. Therefore this boilers were only good for pressures up to 5 p.s.i.

Haystack boilerWhen these boilers were build there was not much more technical knowledge than that possessed by the coppersmiths. Only in later times the used materials changed to iron.

In the beginning the boiler was used as is, but later on the boiler was enclosed in masonry. Inside were spaces to make the fumes to get in touch with the heated surface of the boiler as much as possible.

Newcomen had the strange idea that, to increase the steam-production, you just had to increase the water-volume. Therefore the boilers got higher and higher. The engines therefore were often under-boilered. It had to wait until Watt before the problem was solved by building boilers in another shape.

Nowadays you can still find little, strange sheds in the countryside, used as shelter for cattle, and at a better look it then shows to be an old haystack-boiler!