Vertical boiler
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.
Design considerations
Tube arrangements
Many different tube arrangements have been used. Examples include:
Vertical fire-tube boiler
Vertical boiler with horizontal fire-tubes
Vertical cross-tube boiler
Field-tube boiler
Thimble tube boiler
Spiral watertube boiler
Advantages
The main advantages of a vertical boiler are:
Small footprint – where width and length constraints are critical, use of a vertical boiler permits design of a smaller machine.
Water-level tolerance – The water level in a horizontal boiler must be maintained above the crown (top) of the firebox at all times, or the crownplate could overheat and buckle, causing a boiler explosion. For a vehicle application expected to traverse hills, such as a railway locomotive or steam wagon, maintaining the correct water level when the vehicle itself is not level is a skilled task, and one that occupies much of the fireman's time. In a vertical boiler, the water is all sitting on the top of the firebox, and the boiler would need to be extremely low on water before a gradient could cause a risk by uncovering the firebox top.
