Vertical boiler with horizontal fire-tubes

Last updated
Cochran boiler Cochran boiler, section (Bentley, Sketches of Engine and Machine Details).jpg
Cochran boiler

A vertical boiler with horizontal fire-tubes is a type of small vertical boiler, used to generate steam for small machinery. It is characterised by having many narrow fire-tubes, running horizontally.

Contents

Boilers like this have been widely used on ships as either auxiliary or donkey boilers. [lower-roman 1] Smaller examples, particularly the Robertson type have been used for steam wagons.

Parallel tube boilers

Cochran boiler Cochran boiler, Coalbrookdale.jpg
Cochran boiler

Parallel tube boilers place all of their fire-tubes in a single parallel group, running from side to side of the boiler shell. The best known of these is the Cochran design.

Cochran boiler

The Cochran boiler was produced by Cochran & Co. of Annan, Scotland. [2] It is widely used in marine practice, either fired directly by coal or oil fuels, or else used for heat recovery from the exhaust of large diesel engines. [3] Where such a boiler may be heated either by the exhaust gases of the main propulsion plant, or else separately fired when in port (usually by oil rather than coal) it is referred to as a composite boiler. [4]

The boiler is a cylindrical vertical water drum with a hemispherical domed top. This domed shape is strong enough not to require staying. The firebox is another hemispherical dome, riveted to the base foundation ring to give a narrow waterspace.

The fire-tubes are arranged in a single horizontal group above this, mounted between two flat vertical plates that are inset into the boiler barrel. The first of these plates forms a shallow combustion chamber and is connected to the firebox by a short diagonal neck. The combustion chamber is of the "dry back" form and is closed by a steel and firebrick plate, rather than a water jacket. The exhaust from the fire-tubes is into an external smokebox and a vertical flue. For maintenance access to the tubes, a manhole is provided in the hemispherical dome.

A typical Cochran boiler, as illustrated, [5] might be 15 feet (4.57 m) high and 7 feet (2.13 m) in diameter, giving a heating surface of 500 square feet (46.45 m2), and a grate area of 24 square feet (2.23 m2). Working pressure is between 100 and 125 psi (6.9 and 8.6 bar; 690 and 860 kPa).

Where composite firing is used, [4] there are several possible arrangements for the heating gases. [6] Most use a double-pass tube arrangement where another dry back combustion chamber routes the gases from one tube bank to return through the other. Some arrangements use a separate tube bank for the heat recovery exhaust gases or the direct firing gases, others pass the exhaust gases into the top of the (unlit) firebox. A pure heat-recovery boiler may have no firebox at all, other than a shallow domed plate for strength. [6]

GNSR railmotor Railway and locomotive engineering - a practical journal of railway motive power and rolling stock (1906) (14755699541).jpg
GNSR railmotor

Cochran also offer a modified "Sinuflo" fire-tube, which is claimed to offer better heat transfer from the gases. This is bent into a number of horizontal sinusoidal waves, rather than being straight. [6]

The Cochran boiler was not applied to locomotives, but was used for a pair of experimental steam railmotors built for the GNSR by Andrew Barclay in 1905. [7] These were not successful and were scrapped after a few years, although one coach body survives in a poor state. [8]

Clarke Chapman boiler

Clarke Chapman 'wet back' "Victoria" boiler Renwick copper mine - geograph.org.uk - 494637.jpg
Clarke Chapman 'wet back' "Victoria" boiler

The Clarke Chapman boiler is similar to the Cochran type, with the difference that the top of the boiler shell is a shallow dome rather than a hemisphere. This dome shape is still sufficiently strong to withstand the pressure, but there is now a sharp corner between the shell and the top plate. This corner requires the support of gusset stays.

Clarke Chapman boilers are made in both 'dry back' (as for the Cochran) and 'wet back' forms. [9] The wet back or "Victoria" [10] (illustrated) has the combustion chamber entirely surrounded by water. This increases the heating surface and reduces lost heat, but it also makes the boiler more complex to manufacture and makes tube cleaning more difficult.

Radial horizontal tube boilers

Robertson "autocar" boiler Robertson autocar boiler, section (Rankin Kennedy, Modern Engines, Vol III).jpg
Robertson "autocar" boiler

Radial horizontal tube boilers avoid the flat tubeplate of the Cochran boiler in favour of a circular firebox, a shape that better resists pressure. They thus have their tubes arranged radially, so as to seat more easily by entering the firebox perpendicular to the plate.

Robertson boiler

The design by Robertson of Fleetwood, Lancashire, was originally used in steam wagons. It was often used in similar situations to the Sentinel boiler, but has fire-tubes rather than watertubes. It is best known from its popularity in model engineering, as a multi-tube boiler that's relatively easy to construct.

The boiler consists of two concentric drums with a waterspace between them. Fire-tubes pass through this drum, arranged symmetrically around the diameter. The entire boiler is wrapped in a cylindrical smokebox. The top of the inner drum is not water-jacketed and is only closed by a steel plate. The outer drum is a parallel cylinder but the inner drum is usually stepped in three diameters: wide around the fire grate to provide the most grate area and to promote rapid boiling in its waterjacket, the central section carries the inner ends of the fire-tubes, and the upper section is narrowed to reduce the unjacketed surface area and to provide an open steam space above the waterline. [9] [11] This upper space is deliberately oversized so that when fitted to a road vehicle, any tilting during hill climbing will still leave an adequate depth of water cover above the tubes.

The top plate is unjacketed so that it may contain a hatch and a firing chute. Where the boiler is used for steam wagons it is often coke-fired with a deep firebed, and coke is merely poured down this chute rather than carefully distributed. This means of firing is acceptable with coke, but with coal would lead to a thick, dull fire that blocked with clinker. It is also less distracting when trying to drive a steam vehicle. Avoiding coal also reduces the risk of volatile gases flaring out of the firing chute when it is opened.

The boiler is sometimes superheated by a semi-radiant element arranged as a coil inside the upper part of the central drum. [11]

Other designs

Blake boiler Blake vertical boiler, section (Rankin Kennedy, Modern Engines, Vol VI).jpg
Blake boiler

Blake boiler

The Blake boiler has features of both the Clarke Chapman and the Robertson designs. The combustion chamber is set entirely within the water space so that all of it can provide heating surface, and it is made cylindrical for strength. The tubes are arranged radially rather than in a parallel group, so as to enter the combustion chamber perpendicularly. This makes expanding their ends a simpler operation and gives better sealing. The smokebox is larger and partially wraps around the outside of the boiler drum. [12]

Harris "Economic" boiler

The Harris "Economic" boiler [13] is a design for a model engineering-sized boiler. Similar to the Blake, but symmetrical with a centrally placed combustion chamber and fire-tubes around the entire circumference.

Riley Brothers

Similar boilers, both fire-tube to 'Meredith's Patent' and water-tube boilers of their own design, were also produced by Riley Brothers of Stockton-on-Tees from around 1890 to WWI. [14]

Related Research Articles

<span class="mw-page-title-main">Boiler</span> Closed vessel in which fluid is heated

A boiler is a closed vessel in which fluid 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 heating, boiler-based power generation, cooking, and sanitation.

<span class="mw-page-title-main">Steam locomotive components</span> Glossary of the main components of a typical steam locomotive

Main components found on a typical steam locomotive include:

<span class="mw-page-title-main">Fire-tube boiler</span> Type of 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 the water and ultimately creating steam.

<span class="mw-page-title-main">Water-tube boiler</span> Type of furnace generating steam

A high pressure watertube boiler 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-generating tubes. In smaller boilers, additional generating tubes are separate in the furnace, while larger utility boilers rely on the water-filled tubes that make up the walls of the furnace to generate steam.

<span class="mw-page-title-main">Firebox (steam engine)</span>

In a steam engine, the firebox is the area where the fuel is burned, producing heat to boil the water in the boiler. Most are somewhat box-shaped, hence the name. The hot gases generated in the firebox are pulled through a rack of tubes running through the boiler.

<span class="mw-page-title-main">Heat recovery steam generator</span> Energy recovery heat exchanger that recovers heat from a hot gas stream

A heat recovery steam generator (HRSG) is an energy recovery heat exchanger that recovers heat from a hot gas stream, such as a combustion turbine or other waste gas stream. It produces steam that can be used in a process (cogeneration) or used to drive a steam turbine.

<span class="mw-page-title-main">Smokebox</span>

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 exhausted to the atmosphere through the chimney. Early locomotives had no smokebox and relied on a long chimney to provide natural draught for the fire but smokeboxes were soon included in the design for two specific reasons. Firstly and most importantly, the blast of exhaust steam from the cylinders, when directed upwards through an airtight smokebox with an appropriate design of exhaust nozzle, effectively draws hot gases through the boiler tubes and flues and, consequently, fresh combustion air into the firebox. Secondly, the smokebox provides a convenient collection point for ash and cinders ("char") drawn through the boiler tubes, which can be easily cleaned out at the end of a working day. Without a smokebox, all char must pass up the chimney or it will collect in the tubes and flues themselves, gradually blocking them.

<span class="mw-page-title-main">Boiler (power generation)</span> High pressure steam generator

A boiler or steam generator is a device used to create steam by applying heat energy to water. Although the definitions are somewhat flexible, it can be said that older steam generators were commonly termed boilers and worked at low to medium pressure but, at pressures above this, it is more usual to speak of a steam generator.

<span class="mw-page-title-main">Scotch marine boiler</span> Design of steam boiler best known for its use on ships

A "Scotch" marine boiler is a design of steam boiler best known for its use on ships.

<span class="mw-page-title-main">Flued boiler</span> Type of boiler used to make steam

A shell or flued boiler is an early and relatively simple form of boiler used to make steam, usually for the purpose of driving a steam engine. The design marked a transitional stage in boiler development, between the early haystack boilers 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 flues containing the furnace. 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.

<span class="mw-page-title-main">Rocket mass heater</span>

A rocket mass heater (RMH), also known as rocket stove mass heater, is a form of slow-release radiant heating system, designed to primarily heat people and secondarily to warm areas in line of sight around it. Variations of RMH can also be extended for the functions of cooking, heating water, and producing warm air for distribution.

<span class="mw-page-title-main">Yarrow boiler</span> Obsolete class of high-pressure water-tube boilers widely used on ships

Yarrow boilers are an important class of high-pressure water-tube boilers. They were developed by Yarrow & Co. (London), Shipbuilders and Engineers and were widely used on ships, particularly warships.

<span class="mw-page-title-main">Stirling boiler</span>

The Stirling boiler is an early form of water-tube boiler, used to generate steam in large land-based stationary plants. Although widely used around 1900, it has now fallen from favour and is rarely seen.

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.

A Field-tube boiler is a form of water-tube boiler where the water tubes are single-ended. The tubes are closed at one end, and they contain a concentric inner tube. Flow is thus separated into the colder inner flow down the tube and the heated flow upwards through the outer sleeve. As Field tubes are thus dependent on thermo-syphon flow within the tube, they must thus always have some vertical height to encourage the flow. In most designs they are mounted near-vertically, to encourage this.

<span class="mw-page-title-main">Three-drum boiler</span> Compact furnace with two side water drums and one steam drum above

Three-drum boilers are a class of water-tube boiler used to generate steam, typically to power ships. They are compact and of high evaporative power, factors that encourage this use. Other boiler designs may be more efficient, although bulkier, and so the three-drum pattern was rare as a land-based stationary boiler.

<span class="mw-page-title-main">Transverse boiler</span>

A transverse boiler is a boiler used to generate steam to power a vehicle. Unlike other boilers, its external drum is mounted transversely across the vehicle.

<span class="mw-page-title-main">Vertical cross-tube boiler</span> Small, vertical water boiler

A cross-tube boiler was the most common form 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.

<span class="mw-page-title-main">Vertical fire-tube boiler</span> Steam boiler powered by vertical fire tubes

A vertical fire-tube boiler or vertical multitubular boiler is a vertical boiler where the heating surface is composed of multiple small fire-tubes, arranged vertically.

<span class="mw-page-title-main">High-pressure steam locomotive</span>

A high-pressure steam locomotive is a steam locomotive with a boiler that operates at pressures well above what would be considered normal for other locomotives. In the later years of steam, boiler pressures were typically 200 to 250 psi. High-pressure locomotives can be considered to start at 350 psi (2.41 MPa), when special construction techniques become necessary, but some had boilers that operated at over 1,500 psi (10.34 MPa).

References

  1. An auxiliary boiler supplies steam that is not used for main propulsion, but is necessary for some part of the essential propulsion machinery. A donkey boiler is used, often when in port, to supply non-essential steam for 'hotel' services such as heating or lighting. [1]
  1. Milton & Marine Steam Boilers.
  2. Cochran
  3. Milton, J. H. (1961) [1953]. Marine Steam Boilers (2nd ed.). Newnes. pp. 63–66.
  4. 1 2 Milton & Marine Steam Boilers, pp. 119–121.
  5. Bentley, Wallace (1918). Sketches of Engine and Machine Details. p. 106.
  6. 1 2 3 Milton & Marine Steam Boilers, pp. 133–135.
  7. Jenkinson, David (1996). "15: Alternatives to convention". The History of British Railway Carriages 1900–1953. Vol. I (2nd ed.). Pendragon. p. 266. ISBN   1-899816-03-8.
  8. "GNSR Steam Railmotor Saloon (body only)". Vintage Carriages Trust.
  9. 1 2 Kennedy, Modern Engines, Vol III
  10. Milton, James Tayler; Horner, Joseph Gregory (1911). "Boiler"  . In Chisholm, Hugh (ed.). Encyclopædia Britannica . Vol. 04 (11th ed.). Cambridge University Press. pp. 141–153, see page 143, fig. 6.
  11. 1 2 Harris, K. N. (1974). Model Boilers and Boilermaking. MAP. pp. 52–53. ISBN   0-85242-377-2.
  12. Kennedy, Rankin (1905). The Book of Modern Engines and Power Generators. Vol. VI. London: Caxton. p. 31.
  13. Harris, Model Boilers, pp. 158-159
  14. "Riley Brothers". Grace's Guide .