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Encyclopedia > Steam explosion

A steam explosion (also called a littoral explosion, or fuel-coolant interaction, FCI) is a violent boiling or flashing of water into steam, occurring when water is either superheated, or rapidly heated by fine hot debris produced within it. Pressure vessels that operate at above atmospheric pressure can also provide the proper conditions for a steam explosion. The water changes from a liquid to a gas with extreme speed, increasing dramatically in volume. A steam explosion sprays steam and boiling-hot water and the hot medium that heated it in all directions (if not otherwise confined, e.g. by the walls of a container), creating a danger of scalding and burning. Steam explosions are not normally chemical explosions, although a number of substances will react chemically with steam (for example, zirconium reacts with steam to give off hydrogen, which burns violently in air) so that chemical explosions and fires may follow. Some steam explosions appear to be special kinds of Boiling Liquid Expanding Vapor Explosion, and rely on release of stored superheat. But many large-scale events (eg 'Foundry Accidents') show evidence of an energy-release front propagating through the material (see description of FCI below), where the forces created fragment and mix the hot phase into the cold volatile one; the rapid heat transfer at the front sustains the propagation. A littoral is the region near the shoreline of a body of fresh or salt water. ... It has been suggested that this article be split into articles entitled steam and water vapor, accessible from a disambiguation page. ... In physics, superheating (sometimes referred to as boiling retardation, boiling delay, or defervescence) is the phenomenon in which a liquid is heated to a temperature higher than its standard boiling point, without actually boiling. ... This page deals with the type of injury called burns; for other meanings of burn see burn (disambiguation) In medicine, a burn is a type of injury to the skin caused by heat, electricity, chemicals, or radiation (an example of the latter is sunburn). ... This article is concerned solely with chemical explosives. ... General Name, Symbol, Number zirconium, Zr, 40 Chemical series transition metals Group, Period, Block 4, 5, d Appearance silvery white Standard atomic weight 91. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... A BLEVE erupting from a tanker. ...


Steam explosions are often encountered where hot lava meets sea water. A dangerous steam explosion can be created when liquid water encounters hot, molten metal. As the water explodes into steam, it splashes the burning hot liquid metal along with it, causing an extreme risk of severe burns to anyone located nearby and creating a fire hazard. Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary. ...


Events of this general type are also possible if, under extreme circumstances, the fuel of a liquid-cooled nuclear reactor becomes molten. Such explosions are known as fuel-coolant interactions or FCI. In these events the passage of the pressure wave through the predispersed material creates flow forces which further fragment the melt, resulting in rapid heat transfer, and thus sustaining the wave. Much of the destruction in the Chernobyl accident is thought to have been due to such a steam explosion. The nuclear power plant at Chernobyl prior to the completion of the sarcophagus. ...


In a full-fledged nuclear meltdown, the most severe outcomes would be those leading to early containment failure. Two possibilities are the ejection at high pressure of molten fuel into the containment, causing rapid heating; or an in-vessel steam explosion causing ejection of a missile (eg. the upper head) into, and through, the containment. Less onerous but still significant would be that the molten mass of fuel and reactor core melts through the floor of the reactor building and reaches ground water; a steam explosion might occur, but the debris would probably be contained, and would in fact, being dispersed, probably be more easily coolable. See WASH-1400 for details. Three Mile Island Nuclear Generating Station consisted of two pressurized water reactors manufactured by Babcock & Wilcox each inside its own containment building and connected cooling towers. ... Groundwater is any water found below the land surface. ... WASH-1400, Reactor Safety Study was produced by a committee of specialists under Professor Norman Rasmussen in 1975 for the USNRC. It is thus often referred to as the Rasmussen Report. ...


Other rapid boiling phenomena

High steam generation rates are possible under other circumstances, such as boiler-drum failure, or at a quench front (for example when water re-enters a hot dry boiler). Though potentially damaging, they are usually less energetic than events in which the hot ('fuel') phase is molten and so can be finely fragmented within the volatile ('coolant') phase. Some examples follow:-


Steam explosions are naturally produced by certain volcanos especially a stratovolcano and are a major cause of human fatalities in volcanic eruptions. For other uses, see Volcano (disambiguation). ... A cutaway diagram of a stratovolcano Mount Damavand, a stratovolcano in Māzandarān, Iran Mount St. ...


When a pressurized container such as the waterside of a steam boiler ruptures, it is always followed by some degree of steam explosion. A common operating temperature and pressure for a marine boiler is around 950 P.S.I. (6.55 MPa) and 850 °F (454 °C) at the outlet of the superheater. A steam boiler has an interface of steam and water in the steam drum, which is where the water is finally evaporating due to the heat input, usually oil-fired burners. When a water tube fails due to any of a variety of reasons, it will cause the water in the boiler to expand out of the opening into the furnace area that is only a few P.S.I. above atmospheric pressure. This will likely extinguish all fires and expands over the large surface area on the sides of the boiler. To decrease the likelihood of a devastating explosion, boilers have gone from the "fire-tube" designs, where the heat was added by passing hot gasses through tubes in a body of water, to "water-tube" boilers that have the water inside of the tubes and the furnace area is around the tubes. Old "fire-tube" boilers were known to fail due to poor build quality or lack of maintenance (such as corrosion of the fire tubes, or fatigue of the boiler shell due to constant expansion and contraction). A failure of fire tubes forces largew volumes of high pressure, high temperature steam back down the fire tubes in a fraction of a second and often blows the burners off the front of the boiler, whereas a failure of the pressure vessel surrounding the water would lead to a full and entire evacuation of the boiler's contents in a large steam explosion. On a marine boiler, this would certainly destroy the ship's propulsion plant and possibly the corresponding end of the ship. A boiler is a closed vessel in which water or other fluid is heated under pressure. ... A fire-tube boiler is a type of boiler in which hot gases from the fire pass through one or more tubes within the boiler. ... Schematic diagram of a marine-type water tube boiler A water-tube boiler is a type of boiler in which water circulates in tubes which are heated externally by the fire. ... This article is about a computer game. ...


In a more domestic setting, steam explosions can be a result of incorrectly handled chip pan fires. When oil in a pan is on fire, the natural impulse is to extinguish it with water. However, doing so will cause the water to become superheated by the hot oil. Upon turning to steam, it will disperse upwards and outwards rapidly and violently in a spray also containing the ignited oil. It is for this reason that the correct course of action for dealing with such fires is to use a damp cloth to help deprive the fire of oxygen as well as serve to cool it down. Alternatively, a non-volatile purpose designed fire retardant agent or simply a fire blanket can be used instead. A chip pan is a deep cooking pan used to fry chips, where the pan is filled with oil or fat, and the sliced potatoes added. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... A fire retardant is a substance that helps to delay or prevent combustion. ... A fire blanket is a safety device, made from flameproof fabric (typically fibreglass) usually made available along with other fire safety equipment such as fire extinguishers, which can be used to help extinguishing accidental fires. ...


See also


  Results from FactBites:
 
Steam - Engineering - A Wikia wiki (483 words)
Steam is a pure, completely invisible gas (for mist see below), which at standard atmospheric pressure has a temperature of around 100 degrees Celsius, and occupies about 1,600 times the volume of liquid water (steam can of course be much hotter than the boiling point of water; such steam is usually called superheated steam).
Steam is a capacious reservoir for energy because of water's high heat of vaporization.
Steam is used in saunas and steam showers to produce warmth and therapeutic effects in human beings.
steam explosion: Information from Answers.com (941 words)
A steam explosion (also called a littoral explosion, or fuel-coolant interaction, FCI) is a violent boiling or flashing of water into steam, occurring when water is either superheated, or rapidly heated by fine hot debris produced within it.
Steam explosions are not normally chemical explosions, although a number of substances will react chemically with steam (for example, zirconium reacts with steam to give off hydrogen, which burns violently in air) so that chemical explosions and fires often follow.
To decrease the likelihood of a devastating explosion, boilers have gone from the "firetube" designs, where the heat was added by burning inside of the tubes as the pressure vessel of water surrounded the tubes, to "watertube" boilers that have the water inside of the tubes and the furnace area is around the tubes.
  More results at FactBites »

 
 

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