Water-tube boiler
Overview
 
A water tube boiler is a type of boiler
Boiler (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...

 in which water circulates in tubes heated externally by the fire. Fuel is burned inside the furnace, creating hot gas which heats 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
Steam
Steam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...

.

The heated water then rises into the steam drum
Steam drum
A steam drum is a standard feature of a water-tube boiler. It is a reservoir of water/steam at the top end of the water tubes. The drum stores the steam generated in the water tubes and acts as a phase-separator for the steam/water mixture...

.
Encyclopedia
A water tube boiler is a type of boiler
Boiler (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...

 in which water circulates in tubes heated externally by the fire. Fuel is burned inside the furnace, creating hot gas which heats 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
Steam
Steam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...

.

The heated water then rises into the steam drum
Steam drum
A steam drum is a standard feature of a water-tube boiler. It is a reservoir of water/steam at the top end of the water tubes. The drum stores the steam generated in the water tubes and acts as a phase-separator for the steam/water mixture...

. Here, saturated steam is drawn off the top of the drum. In some services, the steam will reenter the furnace through a superheater
Superheater
A superheater is a device used to convert saturated steam or wet steam into dry steam used for power generation or processes. There are three types of superheaters namely: radiant, convection, and separately fired...

 to become superheated. Superheated steam is defined as steam that is heated above the boiling point at a given pressure. Superheated steam is a dry gas and therefore used to drive turbines, since water droplets can severely damage turbine blades.

Cool water at the bottom of the steam drum returns to the feedwater drum via large-bore 'downcomer tubes', where it pre-heats the feedwater supply. (In 'large utility boilers', the feedwater is supplied to the steam drum and the downcomers supply water to the bottom of the waterwalls). To increase economy of the boiler, exhaust gases are also used to pre-heat the air blown into the furnace and warm the feedwater supply. Such water tube boilers in thermal power station
Thermal power station
A thermal power station is a power plant in which the prime mover is steam driven. Water is heated, turns into steam and spins a steam turbine which drives an electrical generator. After it passes through the turbine, the steam is condensed in a condenser and recycled to where it was heated; this...

 are also called steam generating units.

The older fire-tube boiler
Fire-tube boiler
A fire-tube boiler is a type of boiler in which hot gases from a fire pass through one or more tubes running through a sealed container of water...

 design – in which the water surrounds the heat source and the gases from combustion pass through tubes through the water space – is a much weaker structure and is rarely used for pressures above 350 psi (2.4 MPa). A significant advantage of the water tube boiler is that there is less chance of a catastrophic failure: there is not a large volume of water in the boiler nor are there large mechanical elements subject to failure.

Stationary

Modern boilers for power generation are almost entirely water-tube designs, owing to their ability to operate at higher pressures. Where process steam is required for heating or as a chemical component, then there is still a small niche for fire-tube boilers.

Marine

Their ability to work at higher pressures has led to marine boilers being almost entirely water-tube. This change began around 1900, and traced the adoption of turbine
Steam turbine
A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion. Its modern manifestation was invented by Sir Charles Parsons in 1884....

s for propulsion rather than reciprocating (i.e. piston) engines – although water tube boilers were also used with reciprocating engines.

Railway

There has been no significant adoption of water-tube boilers for railway locomotives. A handful of experimental designs were produced, but none of these were successful or led to their widespread use. Most water-tube railway locomotives, especially in Europe, used the Schmidt system. Most were compounds, and a few uniflow
Uniflow steam engine
The uniflow type of steam engine uses steam that flows in one direction only in each half of the cylinder. Thermal efficiency is increased in the compound and multiple expansion types of steam engine by separating expansion into steps in separate cylinders; in the uniflow design, thermal efficiency...

s. The Norfolk and Western Railway
Norfolk and Western Railway
The Norfolk and Western Railway , a US class I railroad, was formed by more than 200 railroad mergers between 1838 and 1982. It had headquarters in Roanoke, Virginia for most of its 150 year existence....

's Jawn Henry was an exception, as it used a steam turbine
Steam turbine
A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion. Its modern manifestation was invented by Sir Charles Parsons in 1884....

 combined with an electric transmission.
  • LMS 6399 Fury
    LMS 6399 Fury
    The London Midland and Scottish Railway 6399 Fury was an unsuccessful British experimental express passenger locomotive. The intention was to save fuel by using high-pressure steam, which is thermodynamically more efficient than low-pressure steam....

Rebuilt completely after a fatal accident
  • LNER 10000 "Hush hush"
    LNER Class W1
    The LNER W1 No. 10000 was an experimental steam locomotive fitted with a high pressure water-tube boiler...

Using a Yarrow boiler
Yarrow boiler
Yarrow boilers are an important class of high-pressure water-tube boilers. They were developed byYarrows and were widely used on ships, particularly warships....

, rather than Schmidt. Never successful and re-boilered with a conventional boiler.

Hybrids

A slightly more successful adoption was the use of hybrid water-tube / fire-tube systems. As the hottest part of a locomotive boiler is the firebox, it was an effective design to use a water-tube design here and a conventional fire-tube boiler as an economiser (i.e. pre-heater) in the usual position.

One famous example of this was the USA Baldwin
Baldwin Locomotive Works
The Baldwin Locomotive Works was an American builder of railroad locomotives. It was located in Philadelphia, Pennsylvania, originally, and later in nearby Eddystone, Pennsylvania. Although the company was very successful as a producer of steam locomotives, its transition to the production of...

 4-10-2
4-10-2
Under the Whyte notation for the classification of steam locomotives, 4-10-2 represents the wheel arrangement of four leading wheels on two axles , ten powered and coupled driving wheels on five axles, and two trailing wheels on one axle...

 No. 60000
Baldwin 60000
Baldwin 60000 is an experimental steam locomotive built by the Baldwin Locomotive Works in Eddystone, Pennsylvania in 1926, during the height of the railroading industry. It received its number for being the 60,000th locomotive built by Baldwin....

, built in 1926. Operating as a compound at a boiler pressure of 350 psi it covered over 100,000 successful miles. After a year though, it became clear that any economies were overwhelmed by the extra costs and it was retired to become a stationary plant. A series of twelve experimental locomotives were constructed at the Baltimore and Ohio Railroad
Baltimore and Ohio Railroad
The Baltimore and Ohio Railroad was one of the oldest railroads in the United States and the first common carrier railroad. It came into being mostly because the city of Baltimore wanted to compete with the newly constructed Erie Canal and another canal being proposed by Pennsylvania, which...

's Mt. Clare shops under the supervision of George H. Emerson, but none of them was replicated in any numbers.

The only railway use of water-tube boilers in any numbers was the Brotan boiler, invented in Austria in 1902 by Johann Brotan
Johann Brotan
Johann Brotan was an Austrian mechanical engineer, specialising in locomotive construction.-Biography:Johann Brotan was born in Klattau, now Klatovy in the Czech Republic. He studied at the Imperial-Royal Polytechnic Institute Johann Brotan (24 June 1843 – 20 November 1918) was an Austrian...

 and found in rare examples throughout Europe. Hungary, though, was a keen user and had around 1,000 of them. Like the Baldwin, this combined a water-tube firebox with a fire-tube barrel. The original characteristic of the Brotan was a long steam drum running above the main barrel, making it resemble a Flaman boiler in appearance.

Road

While the traction engine
Traction engine
A traction engine is a self-propelled steam engine 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 traction engine is to draw a load behind it...

 was usually built using its locomotive boiler as its frame, other types of steam road vehicles such as lorries
Steam wagon
A steam wagon is a steam-powered road vehicle for carrying freight. It was the earliest form of lorry and came in two basic forms: overtype and undertype – the distinction being the position of the engine relative to the boiler...

 and cars
Steam car
A steam car is a light car powered by a steam engine.Steam locomotives, steam engines capable of propelling themselves along either road or rails, developed around one hundred years earlier than internal combustion engine cars although their weight restricted them to agricultural and heavy haulage...

 have used a wide range of different boiler types. Road transport pioneers Goldsworthy Gurney
Goldsworthy Gurney
Sir Goldsworthy Gurney was a surgeon, chemist, lecturer, consultant, architect, builder and prototypical British gentleman scientist and inventor of the Victorian period....

 and Walter Hancock
Walter Hancock
Walter Hancock was an English inventor of the Victorian period. He is chiefly remembered for his steam powered road vehicles, but also received a patent for preparing and cutting indiarubber into sheets...

 both used water-tube boilers in their steam carriages around 1830.

Most undertype wagons
Steam wagon
A steam wagon is a steam-powered road vehicle for carrying freight. It was the earliest form of lorry and came in two basic forms: overtype and undertype – the distinction being the position of the engine relative to the boiler...

 used water-tube boilers. Many manufacturers used variants of the vertical cross-tube boiler, including Atkinson
Seddon Atkinson
Seddon Atkinson Vehicles Limited, a manufacturer of large goods vehicles based in Oldham, Greater Manchester, England, was formed in mid 1970 when Atkinson Vehicles Limited of Preston was acquired by Seddon Diesel Vehicles Limited of Oldham...

, Clayton
Clayton & Shuttleworth
Clayton & Shuttleworth was an engineering company located at Stamp End Works, Lincoln, Lincolnshire. The company was established in 1842 when Nathaniel Clayton formed a partnership with his brother-in-law, Joseph Shuttleworth .-History:...

, Garrett
Richard Garrett & Sons
Richard Garrett & Sons was a manufacturer of agricultural machinery, steam engines and trolleybuses. Their factory was Leiston Works, in Leiston, Suffolk, United Kingdom.The company was active under its original ownership between 1778 and 1932....

 and Sentinel
Sentinel Waggon Works
Sentinel Waggon Works Ltd was a British company based in Shrewsbury, Shropshire that made steam-powered lorries, railway locomotives, and later, diesel engined lorries and locomotives.-Alley & MacLellan, Sentinel Works, Jessie Street Glasgow:...

. Other types include the Clarkson 'Thimble tube' and the Foden O-type pistol-shaped boiler
Pistol boiler
A pistol boiler is a design of steam boiler used in light steam tractors and overtype steam wagons. It is noted for the unusual shape of the firebox, a circular design intended to be self-supporting without the use of firebox stays....

.

Steam fire-engine makers such as Merryweather
Merryweather & Sons
Merryweather & Sons of Clapham, later Greenwich, London, were builders of steam fire engines and steam tram engines.The founder was Moses Merryweather of Clapham, who was joined by his son Richard Moses .-Fire appliances:...

 usually used water-tube boilers for their rapid steam-raising capacity.

Many steam cars used water-tube boilers, and the Bolsover Express company even made a water-tube replacement for the Stanley Steamer
Stanley Steamer
The Stanley Motor Carriage Company was a manufacturer of steam-engine vehicles; it operated from 1902 to 1924. The cars made by the company were colloquially called Stanley Steamers, although several different models were produced.-Early history:...

 fire-tube boiler.

D-type boiler

The 'D-type' is the most common type of small- to medium-sized boilers, similar to the one shown in the schematic diagram. It is used in both stationary and marine applications. It consists of a large steam drum vertically connected to a smaller water drum (a.k.a. "mud drum") via multiple steam-generating tubes. These are surrounded by walls made up of larger water-filled tubes, which make up the furnace.
M-Type Boilers
Two fireboxes with a control super-heater

Low Water Content

The 'Low Water Content' boiler has a lower and upper header connected by water tubes that are directly impinged upon from the burner. This is a "furnace-less" boiler that can generate steam and react quickly to changes in load.

Babcock & Wilcox boiler

Designed by the American firm of Babcock and Wilcox
Babcock and Wilcox
The Babcock & Wilcox Company is a U.S.-based company that provides design, engineering, manufacturing, construction and facilities management services to nuclear, renewable, fossil power, industrial and government customers worldwide. B&W's boilers supply more than 300,000 megawatts of installed...

, this type has a single drum, with feedwater drawn from the bottom of the drum into a header that supplies inclined water-tubes. The water tubes supply steam back into the top of the drum. Furnaces are located below the tubes and drum.
  • Foster-Wheelers
  • Combustion Engineering


This type of boiler was used by the Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...

's Leander class
Leander class frigate
The Leander class, or Type 12I frigates, comprising twenty-six vessels, was among the most numerous and long-lived classes of frigate in the Royal Navy's modern history. The class was built in three batches between 1959 and 1973...

 frigate
Frigate
A frigate is any of several types of warship, the term having been used for ships of various sizes and roles over the last few centuries.In the 17th century, the term was used for any warship built for speed and maneuverability, the description often used being "frigate-built"...

s.

Stirling boiler

The Stirling boiler
Stirling boiler
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.- Design :...

 has near-vertical, almost-straight watertubes that zig-zag between a number of steam and water drums. Usually there are three banks of tubes in a "four drum" layout, but certain applications use variations designed with a different number of drums and banks.

They are mainly used as stationary boilers, owing to their large size, although the large grate area does also encourage their ability to burn a wide range of fuels. Originally coal-fired in power stations, they also became widespread in industries that produced combustible waste and required process steam. Paper pulp mills could burn waste bark, sugar refineries their bagasse
Bagasse
Bagasse is the fibrous matter that remains after sugarcane or sorghum stalks are crushed to extract their juice. It is currently used as a biofuel and as a renewable resource in the manufacture of pulp and paper products and building materials....

 waste.

Yarrow

Named after its designers, the then Poplar
Poplar, London
Poplar is a historic, mainly residential area of the East End of London in the London Borough of Tower Hamlets. It is about east of Charing Cross. Historically a hamlet in the parish of Stepney, Middlesex, in 1817 Poplar became a civil parish. In 1855 the Poplar District of the Metropolis was...

-based Yarrow Shipbuilders
Yarrow Shipbuilders
Yarrow Limited , often styled as simply Yarrows, was a major shipbuilding firm based in the Scotstoun district of Glasgow on the River Clyde...

, this type has three drums in a delta
Delta (letter)
Delta is the fourth letter of the Greek alphabet. In the system of Greek numerals it has a value of 4. It was derived from the Phoenician letter Dalet...

 formation connected by water tubes. The drums are linked by straight water tubes, allowing easy tube-cleaning. This does however mean that the tubes enter the drums at varying angles, a more difficult joint to caulk. Outside the firebox, a pair of 'cold-leg' pipes between each drum act as 'downcomers'.

Due to its three drums, the Yarrow boiler has a greater water capacity. Hence, this type is usually used in older marine
Steamboat
A steamboat or steamship, sometimes called a steamer, is a ship in which the primary method of propulsion is steam power, typically driving propellers or paddlewheels...

 boiler applications. Its compact size made it attractive for use in transportable power generation units during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. In order to make it transportable, the boiler and its auxiliary equipment (fuel oil heating, pumping units, fans etc.), turbines, and condensers
Condenser (steam turbine)
A surface condenser is a commonly used term for a water-cooled shell and tube heat exchanger installed on the exhaust steam from a steam turbine in thermal power stations. These condensers are heat exchangers which convert steam from its gaseous to its liquid state at a pressure below atmospheric...

 were mounted on wagons to be transported by rail
Rail transport
Rail transport is a means of conveyance of passengers and goods by way of wheeled vehicles running on rail tracks. In contrast to road transport, where vehicles merely run on a prepared surface, rail vehicles are also directionally guided by the tracks they run on...

.

White-Forster

The White-Forster type is similar to the Yarrow, but with tubes that are gradually curved. This makes their entry into the drums perpendicular, thus simpler to make a reliable seal.

Thornycroft

Designed by the shipbuilder John I. Thornycroft & Company
John I. Thornycroft & Company
John I. Thornycroft & Company Limited, usually known simply as Thornycroft was a British shipbuilding firm started by John Isaac Thornycroft in the 19th century.-History:...

, the Thornycroft type features a single steam drum with two sets of water tubes either side of the furnace. These tubes, especially the central set, have sharp curves. Apart from obvious difficulties in cleaning them, this may also give rise to bending forces as the tubes warm up, tending to pull them loose from the tubeplate and creating a leak. There are two furnaces, venting into a common exhaust, giving the boiler a wide base tapering profile.

Other types

  • O-type
  • A-type
  • Flex-Tube Boiler
  • 'M-Type- Control superheater

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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