A vertical boiler is a type of fire-tube or water-tube boiler where the boiler barrel is oriented vertically instead of the more common horizontal orientation. Vertical boilers were used for a variety of steam-powered vehicles and other mobile machines, including early steam locomotives.
Many different tube arrangements have been used. Examples include:
The main advantages of a vertical boiler are:
The main disadvantages of a vertical boiler are:
Several manufacturers produced a significant number of vertical boiler locomotives. Notable amongst these were:
The Sentinel Waggon Works also produced a range of road lorries (steam wagons) based on their high-pressure vertical boilers
The Best Manufacturing Company of San Leandro in California produced a range of steam tractors that used vertical boilers.
Certain designs of steam roller departed from the conventional traction engine style of a horizontal boiler with an engine mounted above. Vertical-boilered rollers were built around a substantial girder frame chassis, with the boiler being mounted low down between the front and rear rolls. Such designs were not common in the UK.
The traditional form of steam donkey (as a mobile winch used in the logging industry) married a vertical boiler with a steam engine on a rigid base fitted with skids for mobility. Since the ground to be traversed would be rough and rarely level, the water-level -tolerant design of the vertical boiler was an obvious choice.
Construction equipment such as steam cranes and steam shovels used vertical boilers to good effect. On a rotating base, the weight of the boiler would help to counterbalance the load suspended from the shovel bucket or crane jib, mounted on the opposite side of the pivot from the boiler. The compact boiler footprint permitted smaller designs than would have been the case for a horizontal type, thus allowing use on smaller worksites; the extra height of a vertical boiler being less critical for such a generally tall machine.