Water-tube boiler
A high pressure watertube boiler
The heated water/steam mixture then rises into the
Saturated water at the bottom of the steam drum returns to the lower 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
The older fire-tube boiler design, in which the water surrounds the heat source and gases from combustion pass through tubes within the water space, is typically a much weaker structure and is rarely used for pressures above 2.4 MPa (350 psi). A significant advantage of the watertube 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.
A water-tube boiler was patented by Blakey of England in 1766 and was made by Dallery of France in 1780.[2]
Applications
"The ability of watertube boilers to be designed without the use of excessively large and thick-walled pressure vessels makes these boilers particularly attractive in applications that require dry, high-pressure, high-energy steam, including steam turbine power generation".[3]
Owing to their superb working properties, the use of watertube boilers is highly preferred in the following major areas:
- Variety of process applications in industries
- Chemical processing divisions
- Pulp and Paper manufacturing plants
- Refining units
Besides, they are frequently employed in power generation plants where large quantities of steam (ranging up to 500 kg/s) having high pressures i.e. approximately 16 megapascals (160 bar) and high temperatures reaching up to 550 °C are generally required. For example, the Ivanpah solar-power station uses two Rentech Type-D watertube boilers for plant warmup, and when operating as a fossil-fueled power station.[4]
Stationary
Modern boilers for power generation are almost entirely water-tube designs, owing to their ability to operate at higher pressures. Where
Marine
Their ability to work at higher pressures has led to marine boilers being almost entirely watertube. This change began around 1900, and traced the adoption of turbines for propulsion rather than reciprocating (i.e. piston) engines – although watertube boilers were also used with reciprocating engines, and firetube boilers were also used in many marine turbine applications.
Railway
There has been no significant adoption of water-tube boilers for railway locomotives. A handful of experimental designs were produced, but none of them were successful or led to their widespread use.
- Rebuilt completely after a fatal accident
- Using a Yarrow boiler, rather than Schmidt. Not successful and re-boilered with a conventional boiler.[7]
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
One famous example of this was the USA Baldwin 4-10-2 No. 60000, built in 1926. Operating as a compound at a boiler pressure of 2,400 kilopascals (350 psi) it covered over 160,000 kilometres (100,000 mi) successfully. After a year though, it became clear that any economies were overwhelmed by the extra costs, and it was retired to a museum display at the Franklin Institute in Philadelphia, Pennsylvania.[8] A series of twelve experimental locomotives were constructed at the Baltimore and Ohio Railroad's Mt. Clare shops under the supervision of George H. Emerson, but none of them was replicated in any numbers.[9]
The only railway use of water-tube boilers in any numbers was the Brotan boiler, invented by
Road
While the
Most
Steam
Many steam cars used water-tube boilers, and the Bolsover Express company even made a water-tube replacement for the
Design variations
This section needs additional citations for verification. (October 2020) |
D-type boiler
The '
M-type boilers
The M-type boilers were used in many US World War II warships including hundreds of Fletcher-class destroyers. Three sets of tubes form the shape of an M, and create a separately fired superheater that allows better superheat temperature control. In addition to the mud drum shown on a D-type boiler, an M-type has a water-screen header and a waterwall header at the bottom of the two additional rows of vertical tubes and downcomers.
Low water content
The low water content boiler has a lower and upper header connected by watertubes 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 & Wilcox, this type has a single drum, with feedwater drawn from the bottom of the drum into a header that supplies inclined water-tubes. The watertubes supply steam back into the top of the drum. Furnaces are located below the tubes and drum.
This type of boiler was used by the Royal Navy's Leander-class frigates and in United States Navy New Orleans-class cruisers.
Stirling boiler
The Stirling boiler 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 waste. It is a horizontal drum type of boiler.
Yarrow
Named after its designers, the then
Due to its three drums, the Yarrow boiler has a greater water capacity. Hence, this type is usually used in older
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.[14]
Thornycroft
Designed by the shipbuilder John I. Thornycroft & Company, the Thornycroft type features a single steam drum with two sets of watertubes 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.[14]
Forced circulation boiler
In a forced circulation boiler, a pump is added to speed up the flow of water through the tubes.[15]
Other types
- O-type boiler
- A-type boiler
- Flex-tube boiler
- M-type control superheater
See also
- Three-drum boiler
- Clarkson thimble tube boiler
- Corner tube boiler
- Internally rifled boiler tubes (also known as serve tubes)
References
- ^ "Recommended Guidelines for the Care of Power Boilers" (PDF). Archived from the original (PDF) on 2016-10-11. Retrieved 2013-11-21.
- ISBN 9783845712871– via Google Books.
- ^ "Boiler Efficiency: Water Tube Boilers". Archived from the original on 2016-03-09. Retrieved 2014-06-15.
- ^ "eCRMS" (PDF). Docketpublic.energy.ca.gov. Retrieved 2018-09-24.
- ^ "High Pressure Steam Locomotive Technology". Loco Locomotive gallery. Archived from the original on 2018-07-22. Retrieved 2010-09-14.
- ^ "The Jawn Henry". Trains Magazine. Retrieved 2008-10-28.
- ^ "LNER 10000 High Pressure Locomotive". Loco Locomotive gallery D&H 1402 James Archibald. Archived from the original on 2018-07-22. Retrieved 2010-09-14.
The Delaware and Hudson E7 class of water tube boiler locomotives consisted of three examples 1400-1402
- ^ "Baldwin 60000". Loco Locomotive gallery.
- ^ See chapter on "Experimentals" in Sagle, Lawrence W. (1964). B&O Power. Staufer. p. 288 ff.
- ^ "Brotan". Loco Locomotive gallery. Archived from the original on 2018-07-22. Retrieved 2010-09-14.
- ^ "Brotan".
- ISBN 0-900404-16-7.
- OL 8281488M.
- ^ (PDF) from the original on 15 March 2021. Retrieved 28 June 2021 – via Friends of the Cerberus.
- ^ Newest on Process Equipments (2012-11-25). "Boilers circulation systems: natural circulation and forced circulation". Enggcyclopedia. Retrieved 2013-09-30.
External links
- Robertson, Leslie Stephen (10 October 2018) [1901]. Water-Tube Boilers: Based on a Short Course of Lectures Delivered at University College, London. .