Vertical cross-tube boiler
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A cross-tube boiler was the most common for of small vertical boiler. They were widely used, in the age of steam, as a small donkey boiler, for the independent power of winches, steam cranes etc.[1][2][3]
The boiler has the advantage of simple robust construction, in particular requiring little regular maintenance. It is relatively inefficient, which was not a serious drawback to the purposes for which it was used. However it was also of limited heating surface, thus sustained output power, compared to other boiler designs. For that reason it was rarely used when significant power was required continuously, such as for locomotives. As the boiler is of relatively large internal volume relative to its power, this acts as a transient reserve of steam. Applications such as cranes require steam intermittently, allowing the boiler to recover pressure between lifts.
Construction
The boiler consists of a cylindrical vertical external shell, with a large firebox inside this, filling perhaps half of the total height. A single large vertical flue or uptake leads to an external chimney. Some boilers use vertical rod stays between the firebox crown and top of the boiler shell.
The main evaporative surface is provided by a pair of large water-filled cross-tubes across this firebox and directly exposed to the radiant heat of the fire. As these tubes are large in diameter they remain mostly filled with water, rather than filling with steam, and so the boiler is not classed amongst the usual water-tube boilers. These tubes are horizontal,[1] or slightly inclined[2] so as to encourage circulation in a single direction without turbulence.
As usual, there is a manhole in the upper part of the shell for internal access and inspection. The boiler may be distinguished externally from other types of vertical boiler by the additional presence of two smaller handholes, in line with the end of each tube and used for internal cleaning.
References
- ^ a b Prof. William Ripper, Sheffield Univ. d.1937 (1913 edition of 1909 book. Originally published in 1889 as "Steam", but later expanded to cover internal combustion engines and so re-titled.). Heat Engines. London: Longmans. pp. 196–197.
{{cite book}}: Check date values in:|date=(help)CS1 maint: numeric names: authors list (link) - ^ a b Milton, J. H. (1961) [1953]. Marine Steam Boilers (2nd ed.). Newnes. pp. 70–77.
- ^ Stokers Manual ((1912 edition) ed.). Admiralty, via HMSO, via Eyre & Spottiswoode. 1901.
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