The Waggon-boiler

Waggon boiler

The next type of boiler was the Waggon-boiler as designed by Watt. The boiler had a concave bottom which made the heated gases to circulate under the boiler. The transfer of the heat was reasonably good. The bottom part of the boiler was enclosed in masonry.

Instead of copper only iron was used

Not just the shape was different from the boilers that Newcomen used, there was a lot of new auxiliary instruments attached, like waterlevel sight-glasses, safety valves and a kind of water regulator. Used materials and maximum pressure didn't really change, but that was not a problem for Watt, since he didn't appreciate higher pressures. So these boilers were sufficient for his needs.