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. Many different tube arrangements have been used. Examples include: Fire tubes Vertical fire-tube boiler Vertical boiler with horizontal fire-tubes Water tubes Vertical cross-tube boiler Field-tube boiler Thimble tube boiler Spiral watertube boiler 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. Simpler (major) maintenance – A vertical boiler is usually mounted on a frame on the vehicle, allowing easy replacement. Horizontal boilers, such as those on railway locomotives and traction engines, form an integral part of the vehicle – the vehicle is literally built around the boiler – and hence replacement requires the dismantling of the entire vehicle. The main disadvantages of a vertical boiler are: Size – The benefits of a small footprint are compromised by the much greater height required. The presence of over-bridges limits the height of steam vehicles, and this in turn restricts the size (and hence steam production) of the boiler.