![Trevithick high pressure engine of 1806](https://upload.wikimedia.org/wikipedia/commons/5/54/Trevithick_high_pressure_engine_of_1806.jpg)
A shell or flued boiler is an early and relatively simple form of
boiler
A boiler is a closed vessel in which fluid (generally water) is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, central h ...
used to make
steam
Steam is a substance containing water in the gas phase, and sometimes also an aerosol of liquid water droplets, or air. This may occur due to evaporation or due to boiling, where heat is applied until water reaches the enthalpy of vaporization ...
, usually for the purpose of driving a
steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force can be trans ...
. The design marked a transitional stage in boiler development, between the early
haystack boiler
There have been a vast number of designs of steam boiler, particularly towards the end of the 19th century when the technology was evolving rapidly. A great many of these took the names of their originators or primary manufacturers, rather than a ...
s and the later multi-tube
fire-tube boilers. A flued boiler is characterized by a large cylindrical boiler shell forming a tank of water, traversed by one or more large
flue
A flue is a duct, pipe, or opening in a chimney for conveying exhaust gases from a fireplace, furnace, water heater, boiler, or generator to the outdoors. Historically the term flue meant the chimney itself. In the United States, they are ...
s containing the
furnace
A furnace is a structure in which heat is produced with the help of combustion.
Furnace may also refer to:
Appliances Buildings
* Furnace (central heating): a furnace , or a heater or boiler , used to generate heat for buildings
* Boiler, used t ...
. These boilers appeared around the start of the 19th century and some forms remain in service today. Although mostly used for static steam plants, some were used in early steam vehicles, railway locomotives and ships.
Flued boilers were developed in an attempt to raise steam pressures and improve engine efficiency. Early haystack designs of
Watt
The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James Wa ...
's day were mechanically weak and often presented an unsupported flat surface to the fire.
Boiler explosion
A boiler explosion is a catastrophic failure of a boiler. There are two types of boiler explosions. One type is a failure of the pressure parts of the steam and water sides. There can be many different causes, such as failure of the safety valve ...
s, usually beginning with failure of this firebox plate, were common. It was known that an arched structure was stronger than a flat plate and so a large circular flue tube was placed inside the boiler shell. The fire itself was on an iron grating placed across this flue, with a shallow ashpan beneath to collect the non-combustible residue. This had the additional advantage of wrapping the heating surface closely around the furnace, but that was a secondary benefit.
Although considered as low-pressure (perhaps ) today, this was regarded as high pressure compared to its predecessors. This increase in pressure was a major factor in making locomotives (i.e. small self-moving vehicles) such as
Trevithick's into a practical proposition.
Centre-flue boilers
![Blenkinsop's rack locomotive, 1812 (British Railway Locomotives 1803-1853)](https://upload.wikimedia.org/wikipedia/commons/c/c0/Blenkinsop%27s_rack_locomotive%2C_1812_%28British_Railway_Locomotives_1803-1853%29.jpg)
The simplest boiler for locomotives had a single straight flue. It was widely used by many of the early locomotive makers, including
Blenkinsop's locomotives for the
Middleton railway
The Middleton Railway is the world's oldest continuously working railway, situated in the English city of Leeds. It was founded in 1758 and is now a heritage railway, run by volunteers from The Middleton Railway Trust Ltd. since 1960.
The rail ...
and Stephenson's
Locomotion
Locomotion means the act or ability of something to transport or move itself from place to place.
Locomotion may refer to:
Motion
* Motion (physics)
* Robot locomotion, of man-made devices
By environment
* Aquatic locomotion
* Flight
* Locomo ...
.
This type of boiler is simple to manufacture and strong enough to support "high pressure" (for the period) steam with
expansive working in the cylinders. There is also good gas flow through the large flue, so that the fire receives sufficient
draught from the action of a tall
chimney
A chimney is an architectural ventilation structure made of masonry, clay or metal that isolates hot toxic exhaust gases or smoke produced by a boiler, stove, furnace, incinerator, or fireplace from human living areas. Chimneys are typic ...
alone. However it also has little heating area, so is inefficient and burns a large amount of coal.
Return-flue boilers
![Puffing Billy steam engine](https://upload.wikimedia.org/wikipedia/commons/4/4e/Puffing_Billy_steam_engine.JPG)
A simple flue must be long if it is to offer adequate heating area. In a short boiler shell, such as required for a
steam locomotive
A steam locomotive is a locomotive that provides the force to move itself and other vehicles by means of the expansion of steam. It is fuelled by burning combustible material (usually coal, oil or, rarely, wood) to heat water in the locomot ...
, this may be done by using a U-shaped ''return flue'' that bends back on itself.
Richard Trevithick
Richard Trevithick (13 April 1771 – 22 April 1833) was a British inventor and mining engineer. The son of a mining captain, and born in the mining heartland of Cornwall, Trevithick was immersed in mining and engineering from an early age. He w ...
had already used a return flue with his first 1802
Coalbrookdale
Coalbrookdale is a village in the Ironbridge Gorge in Shropshire, England, containing a settlement of great significance in the history of iron ore smelting. It lies within the civil parish called the Gorge.
This is where iron ore was first s ...
locomotive design and 1804
Pen-y-darren
: ''For Trevithick's Pen-y-darren locomotive, see Richard Trevithick.''
Penydarren is a community and electoral ward in Merthyr Tydfil County Borough in Wales.
Description
The area is most notable for being the site of a 1st-century Roman fort, a ...
engine.
These boilers were heavily built of
cast iron
Cast iron is a class of iron–carbon alloys with a carbon content more than 2%. Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its color when fractured: white cast iron has carbide impuriti ...
, short and flat-ended. His 1804/5 "
Newcastle Newcastle usually refers to:
*Newcastle upon Tyne, a city and metropolitan borough in Tyne and Wear, England
*Newcastle-under-Lyme, a town in Staffordshire, England
*Newcastle, New South Wales, a metropolitan area in Australia, named after Newcastle ...
" locomotive (actually built in
Gateshead
Gateshead () is a large town in northern England. It is on the River Tyne's southern bank, opposite Newcastle upon Tyne, Newcastle to which it is joined by seven bridges. The town contains the Gateshead Millennium Bridge, Millennium Bridge, Sage ...
) began to show one characteristic feature of the return-flued boiler, a prominent dome shape to resist steam pressure in the solid end opposite both furnace and chimney. In this case, the boilermaking, now of
wrought iron
Wrought iron is an iron alloy with a very low carbon content (less than 0.08%) in contrast to that of cast iron (2.1% to 4%). It is a semi-fused mass of iron with fibrous slag Inclusion (mineral), inclusions (up to 2% by weight), which give it a ...
plates, must have been complicated by Trevithick's single long-travel horizontal cylinder ( diameter×stroke) which emerged through this domed end.
This did make work easier for the fireman though, as he was no longer trying to reach a
firedoor
Boilers for generating steam or hot water have been designed in countless shapes, sizes and configurations. An extensive terminology has evolved to describe their common features. This glossary provides definitions for these terms.
Terms which re ...
beneath the long crosshead of the piston.
William Hedley
William Hedley (13 July 1779 – 9 January 1843) was born in Newburn, near Newcastle upon Tyne. He was one of the leading industrial engineers of the early 19th century, and was instrumental in several major innovations in early rail transpor ...
used this pattern of boiler for his 1813 locomotives ''
Puffing Billy'' and ''
Wylam Dilly
''Wylam Dilly'' is the second oldest surviving rail transport, railway locomotive in the world; it was built circa 1815 by William Hedley and Timothy Hackworth for Christopher Blackett, the owner of Wylam colliery, west of Newcastle upon Tyne ...
''. Through the
Wylam
Wylam is a village and civil parish in the county of Northumberland. It is located about west of Newcastle upon Tyne.
It is famous for the being the birthplace of George Stephenson, one of the early railway pioneers. George Stephenson's Birth ...
colliery and its owner
Christopher Blackett
Christopher Blackett (1751 – 25 January 1829) owned the Northumberland colliery at Wylam that built ''Puffing Billy'', the first commercial adhesion steam locomotive. He was also the founding owner of ''The Globe'' newspaper in 1803.
Lif ...
, Hedley would have been familiar with Trevithick's engine.
Timothy Hackworth
Timothy Hackworth (22 December 1786 – 7 July 1850) was an English steam locomotive engineer who lived in Shildon, County Durham, England and was the first locomotive superintendent of the Stockton and Darlington Railway.
Youth and early work ...
's 0-6-0 ''
Royal George'' of 1827 also used a return-flued boiler, although it is best known for its pioneering use of a deliberate
blastpipe The blastpipe is part of the exhaust system of a steam locomotive that discharges exhaust steam from the cylinders into the smokebox beneath the chimney in order to increase the draught through the fire.
History
The primacy of discovery of the ...
to encourage draught on the fire.
His lighter weight 0-4-0 version for the
Rainhill Trials, ''
Sans Pareil
''Sans Pareil'' is a steam locomotive built by Timothy Hackworth which took part in the 1829 Rainhill Trials on the Liverpool and Manchester Railway, held to select a builder of locomotives. The name is French and means 'peerless' or 'withou ...
'' was very similar.
Even though they appeared antiquated as soon as the Trials were over, the Canadian ''
Samson
Samson (; , '' he, Šīmšōn, label= none'', "man of the sun") was the last of the judges of the ancient Israelites mentioned in the Book of Judges (chapters 13 to 16) and one of the last leaders who "judged" Israel before the institution o ...
'' of this pattern was built in 1838 and still in service in 1883.
Huber boilers
The last return-flue boilers constructed (other than some stationary boilers) are often considered to be those built by the
Huber
Huber is a German-language surname. It derives from the German word ''Hube'' meaning hide, a unit of land a farmer might possess, granting them the status of a free tenant. It is in the top ten most common surnames in the German-speaking world, ...
Co. of
Marion, Ohio
Marion is a city in and the county seat of Marion County, Ohio, Marion County, Ohio, United States. The municipality is located in north-central Ohio, approximately north of Columbus, Ohio, Columbus.
The population was 35,999 at the 2020 United S ...
for their "New Huber"
traction engine
A traction engine is a steam engine, steam-powered tractor used to move heavy loads on roads, plough ground or to provide power at a chosen location. The name derives from the Latin ''tractus'', meaning 'drawn', since the prime function of any t ...
s, from 1885 to 1903.
These were not, however, return-''flue'' boilers in the sense used here, but rather ''return-tube'' boilers. They had a single large cylindrical furnace tube, a combustion chamber external to the boiler's pressure shell, then ''multiple, narrow''
fire-tubes returning to a horseshoe-shaped
smokebox
A smokebox is one of the major basic parts of a steam locomotive exhaust system. Smoke and hot gases pass from the firebox through tubes where they pass heat to the surrounding water in the boiler. The smoke then enters the smokebox, and is e ...
above and around the firedoor. The proximity of this smokebox to the fireman led to their nickname of "belly burners". Their design thus has more in common with the horizontal
launch-type boiler
A launch-type, gunboat or horizontal multitubular boiler is a form of small steam boiler. It consists of a cylindrical horizontal shell with a cylindrical furnace and fire-tubes within this.
Their name derives from the boiler's popular use at ...
s (as used by
Sir Arthur Heywood
Sir Arthur Percival Heywood, 3rd Baronet (25 December 1849 – 19 April 1916) is best known today as the innovator of the fifteen inch minimum gauge railway, for estate use.
Early life
He was the eldest son of Sir Thomas Percival Heywood ...
) or the
Scotch marine boiler
A "Scotch" marine boiler (or simply Scotch boiler) is a design of steam boiler best known for its use on ships.
The general layout is that of a squat horizontal cylinder. One or more large cylindrical furnaces are in the lower part of the boiler ...
than they do with the simple single-flue boiler.
By this time, the
locomotive boiler
A fire-tube boiler is a type of boiler in which hot gases pass from a fire through one or more tubes running through a sealed container of water. The heat of the gases is transferred through the walls of the tubes by thermal conduction, heating t ...
had become ubiquitous for traction engines. Compared to this, the advantage of the Huber boiler was that the firetubes could be replaced more easily, without needing to work from within an enclosed firebox.
Cornish boiler
![Moonta historic copper mines 1](https://upload.wikimedia.org/wikipedia/commons/5/5d/Moonta_historic_copper_mines_1.JPG)
The simplest form of flued boiler was
Richard Trevithick
Richard Trevithick (13 April 1771 – 22 April 1833) was a British inventor and mining engineer. The son of a mining captain, and born in the mining heartland of Cornwall, Trevithick was immersed in mining and engineering from an early age. He w ...
's "high-pressure" Cornish boiler, first installed at
Dolcoath mine
Dolcoath mine ( kw, Bal Dorkoth) was a copper and tin mine in Camborne, Cornwall, England, United Kingdom. Its name derives from the Cornish for 'Old Ground', and it was also affectionately known as ''The Queen of Cornish Mines''. The site is ...
in 1812. This is a long horizontal cylinder with a single large flue containing the fire. As the furnace relied on natural
draught, a tall
chimney
A chimney is an architectural ventilation structure made of masonry, clay or metal that isolates hot toxic exhaust gases or smoke produced by a boiler, stove, furnace, incinerator, or fireplace from human living areas. Chimneys are typic ...
was required at the far end of the flue to encourage a good supply of air (oxygen) to the fire.
For efficiency, Trevithick's innovation was to encase beneath the boiler with a
brick
A brick is a type of block used to build walls, pavements and other elements in masonry construction. Properly, the term ''brick'' denotes a block composed of dried clay, but is now also used informally to denote other chemically cured cons ...
-built chamber. Exhaust gases passed through the central flue and then routed outside and around the iron boiler shell. To keep the chimney clear of the firing space, the brick flue passed first underneath the centre of the boiler to the front face, then back again along the sides and to the chimney.
Cornish boilers had several advantages over the preceding
wagon boilers: they were composed of mostly curved surfaces, better to resist the pressure. Their flat ends were smaller than the flat sides of the wagon boiler and were
stayed by the central furnace flue, and sometimes by additional long
rod stays. A less obvious advantage was that of boiler scale. Wagon or haystack boilers were heated from beneath and any scale or impurities that formed a sediment settled upon this plate, insulating it from the water. This reduced heating efficiency and could ''in extremis'' lead to local overheating and failure of the boiler plates. In the flued boiler, any sediment fell past the furnace flue and settled out at the bottom of the boiler shell, where it had less effect.
In
model engineering
Model engineering is the pursuit of constructing proportionally-scaled miniature working representations of full-sized machines. It is a branch of metalworking with a strong emphasis on artisanry, as opposed to mass production. While now mainly a ...
, the Cornish boiler, particularly when fitted with Galloway tubes (''see Lancashire Boiler, below''), is an excellent choice for gas-fired boilers and model steam boats. It is simple to build and as efficient as any small-scale boiler.
Butterley boiler
![Butterley boiler - Fairbairn - On Boiler Explosions](https://upload.wikimedia.org/wikipedia/commons/3/3f/Butterley_boiler_-_Fairbairn_-_On_Boiler_Explosions.jpg)
The Butterley or "whistle mouth" boiler is a little-known design derived from the Cornish pattern, produced by the noted Butterley boilerworks of Derbyshire. It is basically a Cornish boiler with the lower half of the shell around the furnace removed, so as to permit a large fire to be lit. This made it popular in the textile mills of the
Pennines
The Pennines (), also known as the Pennine Chain or Pennine Hills, are a range of uplands running between three regions of Northern England: North West England on the west, North East England and Yorkshire and the Humber on the east. Commo ...
, where the hard Northern coal was of less calorific value than the Welsh coal used in the South West and required a larger fire. Alternatively it may be considered as a shortened Cornish boiler with a
wagon boiler placed in front of it with a larger fire beneath that. It suffers the same drawback as the wagon boiler: the concave firebox plate is mechanically weak and this either limits the working pressure or requires extra mechanical
staying.
Lancashire boiler
![Lancashire boiler, Pinchbeck Pumping station - geograph](https://upload.wikimedia.org/wikipedia/commons/1/1d/Lancashire_boiler%2C_Pinchbeck_Pumping_station_-_geograph.org.uk_-_1157301.jpg)
The Lancashire boiler is similar to the Cornish, but has two large flues containing the fires instead of one. It is generally considered to be the invention of
William Fairbairn
Sir William Fairbairn, 1st Baronet of Ardwick (19 February 1789 – 18 August 1874) was a Scottish civil engineer, structural engineer
Structural engineers analyze, design, plan, and research structural components and structural systems ...
and John Hetherington in 1844, although their patent was for the method of firing the furnaces alternately, so as to reduce smoke, rather than the boiler itself.
[ in ] Stephenson's early
0-4-0 locomotive ''"
Lancashire Witch
''Lancashire Witch'' was an early steam locomotive built by Robert Stephenson and Company in Newcastle-upon-Tyne in 1828. It was a development of ''Locomotion''.
Description
''Lancashire Witch'' was an 0-4-0 locomotive with rear mounted cy ...
"'' had already demonstrated the use of twin furnace tubes within a boiler 15 years earlier.
Fairbairn had made a theoretical study of the thermodynamics of more efficient boilers, and it was this that had led him to increase the
furnace
A furnace is a structure in which heat is produced with the help of combustion.
Furnace may also refer to:
Appliances Buildings
* Furnace (central heating): a furnace , or a heater or boiler , used to generate heat for buildings
* Boiler, used t ...
grate area relative to the volume of water. A particular reason for this was the so-far poor adoption of the Cornish boiler in the cotton mills of Lancashire, where the harder local coal couldn't be burned satisfactorily in the smaller furnace, in favour of the older low-pressure wagon boiler and its large grate.
The difficulties of the Cornish boiler were that a boiler of any particular power would require a known area of furnace tube as the heating area. Longer tubes required a longer and more expensive boiler shell. They also reduced the ratio of grate area relative to the heating area, making it difficult to maintain an adequate fire. Increasing the tube diameter reduced the depth of water covering the furnace tube and so increased the need for accurate control of water level by the fireman, or else the risk of
boiler explosion
A boiler explosion is a catastrophic failure of a boiler. There are two types of boiler explosions. One type is a failure of the pressure parts of the steam and water sides. There can be many different causes, such as failure of the safety valve ...
. Fairbairn's studies of hoop stress in cylinders also showed that smaller tubes were stronger than larger tubes. His solution was simple: to replace one large furnace tube with two smaller ones.
The patent
showed another advantage of twin furnaces. By firing them alternately and closing the firebox door between firings, it was also possible to arrange a supply of air past the furnace (in the case of a Lancashire boiler, through the ashpan beneath the grate) which would encourage the
flue gases
Flue gas is the gas exiting to the atmosphere via a flue, which is a pipe or channel for conveying exhaust gases from a fireplace, oven, furnace, boiler or steam generator. Quite often, the flue gas refers to the combustion exhaust gas produced ...
produced by the fire to burn more completely and cleanly, thus reducing smoke and pollution. A key factor in this was the distinctive shuttered rotating air damper in the door, which became a feature from the 1840s.
The use of two flues also has a strengthening effect, acting as two long
rod stays that support the end plates.
Later developments added
Galloway tube
W & J Galloway and Sons was a British manufacturer of steam engines and boilers based in Manchester, England. The firm was established in 1835 as a partnership of two brothers, William and John Galloway. The partnership expanded to encompass t ...
s (after their inventor, patented in either 1848
or 1851) crosswise water tubes across the flue, thus increasing the heated surface area. As these are short tubes of large diameter and the boiler continues to use a relatively low pressure, this is still not considered to be a
water-tube boiler
A high pressure watertube boiler (also spelled water-tube and water tube) is a type of boiler in which water circulates in tubes heated externally by the fire. Fuel is burned inside the furnace, creating hot gas which boils water in the steam-gene ...
. The tubes are tapered to make their installation through the flue easier.
Lancashire boilers often show
corrugated flues, which absorb thermal expansion without straining the riveted seams. Another development was the "
kidney
The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blood ...
flue" or
Galloway boiler, where the two furnaces join together into a single flue, kidney-shaped in cross-section. This widened and flat-topped flue was
stayed by the use of Galloway tubes.
Its maximum pressure is 20 bar. The maximum diameter of the boiler is 3m, has two fire tubes of length varying from 6-10m and diameter of 0.8-1m
Although the Lancashire boiler is considered to be an antiquated design, provided that the flue is long enough it can be reasonably efficient. This does lead to a bulky boiler though, particularly for its length, and this has always limited its use to stationary installations. It was the standard boiler in Lancashire
cotton mill
A cotton mill is a building that houses spinning (textiles), spinning or weaving machinery for the production of yarn or cloth from cotton, an important product during the Industrial Revolution in the development of the factory system.
Althou ...
s.
Fairbairn's five-tube boiler
William Fairbairn
Sir William Fairbairn, 1st Baronet of Ardwick (19 February 1789 – 18 August 1874) was a Scottish civil engineer, structural engineer
Structural engineers analyze, design, plan, and research structural components and structural systems ...
's work on the Lancashire boiler had demonstrated the efficiency virtues of multiple furnaces relative to a reduced water volume. It was also widely understood that higher steam pressures improved the efficiency of engines. Fairbairn's research on the strength of cylinders led him to design another improved boiler, based around far-smaller tube diameters, which would thus be able to operate at higher pressures, typically . This was the "five tube" boiler, whose five tubes were arranged in two nested pairs as water drum and furnace, with the remaining tube mounted above them as a separate steam drum.
The water volume was extremely low compared to previous boiler designs, as the furnace tubes almost filled each of the water drums.
The boiler was successful according to its goals and provided two large furnaces in a small water capacity. The separate steam drum also aided the production of "dry" steam, without the carryover of water and risk of priming. However it was also complex to manufacture, and did not offer a great deal of heating area for the work involved. It was soon superseded by
multi-tube boilers such as the
Fairbairn-Beeley and the
Scotch boilers.
See also
*
Scotch marine boiler
A "Scotch" marine boiler (or simply Scotch boiler) is a design of steam boiler best known for its use on ships.
The general layout is that of a squat horizontal cylinder. One or more large cylindrical furnaces are in the lower part of the boiler ...
Further reading
*
*
References
{{steam engine configurations, state=collapsed
Early steam locomotives
Fire-tube boilers