A boiler blast is a catastrophic failure of the boiler. As seen today, boiler explosions are of two kinds. One is the failure of the pressure portion of the steam and water side. There are many different causes, such as the failure of the safety valve, corrosion of the essential parts of the boiler, or low water level. Corrosion along the edge of the lap joint is a common cause of early boiler explosions.
The second type is the explosion of fuel/air in the furnace, which is more accurately described as an explosion of fire. Firebox explosions in solid-fuel boilers are rare, but explosive fuel explosions in gas or oil-fired boilers are still potentially dangerous.
Video Boiler explosion
Penyebab ledakan boiler
There are many causes of boiler explosions such as poor water treatment that cause scaling and overheating of plates, low water levels, jammed safety valves, or even furnace explosions which, in turn, if severe enough, can cause boiler explosions. Bad operator training results in negligence or other boiler handling errors that are often the cause of the explosion since the beginning of the industrial revolution. In the late 19th and early 20th centuries, inspection records of various sources in the US, UK, and Europe show that the most common cause of boiler explosion is the weakening of the boiler through simple rusting, anywhere from 2 to 5 times more than all other causes.
Prior to materials science, inspection standards, and quality control succeeded in the rapidly expanding manufacturing industry of boilers, a large number of boiler explosions could be traced directly to poor design, workmanship and undetected defects in poor quality materials. The alarming frequency of boiler failures in the US due to defects in materials and design attracted the attention of international engineering standards organizations, such as ASME, which established their first Boiler Testing Code in 1884. The boiler explosion caused Grover Shoe Factory disaster in Brockton, Massachusetts on March 10, 1905 resulting in 58 deaths and 117 injuries, and inspired the state of Massachusetts to publish its first boiler legislation in 1908.
Some written sources provide a brief description of the cause of the boiler explosion:
"The main cause of the explosion, in fact the only cause, is a lack of strength in the shell or other parts of the boiler, excessive pressure and overheating.Lower strength in the boiler may be caused by genuine defects, poor workmanship, deterioration of use or fault urus. "
Causes.-Boiler explosion is always due to the fact that some parts of the boiler, for some reason, are too weak to withstand the pressure imposed.This may be due to one of two causes: the boiler is not strong enough to bring the proper working pressure, or pressure has been allowed to rise above the usual point with the attachment of the safety valve, or some similar cause "
Maps Boiler explosion
Initial investigation of the cause of boiler explosion
While deterioration and handling errors are probably the most common cause of the explosion of boilers, the actual mechanism of catastrophic failure of the boiler was not well documented until extensive experiments were conducted by US boiler inspectors early in the century. -20. Several different attempts were made to cause the boiler to explode in various ways, but one of the most interesting experiments shows that under certain circumstances, if a sudden opening in the boiler allows to escape too quickly, water hammers can cause overall damage. pressure vessel:
"A cylindrical boiler is tested and survives with a 300 pound steam pressure unscathed." "When the [discharge] valve suddenly opens at 235 pounds pressure, the kettle gives up, the iron is twisted and torn into pieces and thrown in all directions.The reason is that the sudden steam flow from the kettle to the exhaust pipe reduces the pressure in the boiler by very quickly, this reduction in pressure causes the sudden formation of large amounts of vapor in the water, and the mass of heavy water being thrown violently towards the opening when steam is being pulled, hitting the boiler section near the opening and causing the fracture. "
Boiler explosions often occur on sinking vessels when super hot kettle touches cold sea water, because the sudden cooling of super hot metal causes it to crack; for example, when SS Ben Lomond was torpedoed by a U-boat, a torpedo and causing a boiler explosion caused the ship to descend in two minutes, leaving Poon Lim as the only survivor in the 54-crew complement.
Locomotive-type boiler blast
Boiler explosion is a special danger in fire type boiler (locomotive-type) because the top of the fire box (crown sheet) should be covered with a certain amount of water at any time; or heat of flame can weaken the crown or crown sheets remain to the point of failure, even at normal working pressure .
This was the cause of the explosion of the Gettysburg Railroad fire box near Gardners, Pennsylvania in 1995, where low water allowed the front of the crown sheet to overheat until the regular crown remained drawn through the sheets, releasing much steam and water under the pressure-filled boiler into the fire box. Fortunately, the design of the crown sheet includes several alternating fixed-key safety headlines, which limit the failure of the 5th or 6th row of the first line of conventional fixed, preventing the collapse of all the crown sheets.
However, this type of failure is not limited to rail engines, since locomotive-type boilers have been used for traction machines, portable machines, skid machines used for mining or logging, stationary machinery for sawmills and factories, for heating, and as boiler packages. providing steam for other processes. In all applications, maintaining proper water levels is critical for safe operation.
Principles
Many shell type boilers carry large baths of heated water to a higher temperature and pressure (enthalpy) than boiling water will be at atmospheric pressure. During normal operation, the water fluid remains at the bottom of the boiler due to gravity, the bubble vapor rises through the liquid water and collects at the top for use until the saturation pressure is reached, then the boil stops. If some pressure is released, boiling begins again, and so on.
If steam is released normally, say by opening the throttle valve, the action of the water bubble remains moderate and the relatively dry vapor may be withdrawn from the highest point in the vessel.
If steam is released faster, a stronger boiling action which results can throw a fine spray of upward droplets as "wet steam" which can cause damage to pipes, engines, turbines and other downstream equipment.
If a large crack or other opening in a boiler vessel allows the internal pressure to drop very abruptly, the remaining heat energy in the water will cause more of the liquid to turn into a vapor bubble, which then quickly shifts the remaining liquid. The potential energy of steam and water coming out now turns into work, as they would do in machines; with enough power to peel the material around the gap, severely damaging the shape of the plate previously held in place by a fixed, or propelled itself by its original cylindrical shape. The rapid release of steam and water can provide a very powerful explosion, and cause great damage to the property or personnel around it.
The rapidly growing vapor bubbles can also do the job by throwing a large "snail" of water inside the boiler toward the opening, and at an astonishing speed. Fast-moving masses carry a lot of kinetic energy (from inflated vapors), and colliding with the boiler's shell produces powerful destructive effects. This can greatly enlarge the initial rupture, or tear the shell in half.
Many plumbers and steam makers are aware of this phenomenon, called "water hammer". A few ounces of "slug" of water passing through the velocity line at high speed and striking the 90 degree elbow can instantly break the fitting otherwise able to handle several times the normal static pressure. Then it can be understood that a few hundred, or even several thousand pounds of water move at the same speed inside the boiler shell can easily blow a tube sheet, shut down a fire box, even throw all the surprising distance spaces through the reaction when the water comes out of the boiler, like the retreating heavy cannon that fires the ball.
Some accounts of the experimental SL-1 experimental accident clearly illustrate the very strong effect of water hammers on pressure vessels: " The expansion caused by this heating process causes water hammers as water is accelerated upward toward the head of the reactor vessel, generating about 10,000 pound per square inch (69,000 kPa) of pressure on the reactor vessel head when the water hits the head at 160 feet per second (50 m/s) "" The extreme shape of the water hammer pushes the control rod, the shield plug, and the entire reactor vessel up. then concluded that the ship weighs 26,000 pounds (12,000 kg) has jumped 9 feet 1 inch (2.77 m) and the upper control rod drive mechanism has hit the reactor building ceiling before settling back to its original location "
A steam locomotive operating at 350Ã, psi (2.4 MPa) will have a temperature of about 225Ã, Â ° C, and a specific enthalpy of 963.7 kJ/kg. Since the standard saturated water pressure has a specific enthalpy of only 418.91 kJ/kg, the difference between two specific enthalpy, 544.8 kJ/kg, is the total energy released in the explosion. So in the case of large locomotives that can accommodate as much as 10,000 kg of water under high pressure and temperature conditions, this explosion will have the same theoretical energy release of about 1,160 kg of TNT.
Firebox Explosion
In the case of a blast explosion, this usually occurs after a flameout burner. Oil, natural gas, propane, coal or other fuels can accumulate in the combustion chamber. This is especially a concern when boats are hot; the fuel will quickly volatze due to temperature. Once the lower explosive limit (LEL) is reached, any ignition source will cause a steam explosion.
A fuel explosion within the boundaries of a fire box may damage the pressure boiler pipe and the inner shell, potentially leading to structural failure, steam or water leakage, and/or secondary boiler shell failure and steam explosion.
The common form of small fire "explosion" is known as "drum" and can occur with any type of fuel. Instead of the normal "rumble" of fire, a series of "pounding" rhythms and flashes of fire under the bars and through the fireplace shows that fuel combustion takes place through a series of rapid detonations, caused by improper air./fuel mixture related to draft level available. This usually does not cause damage to locomotive type boilers, but can cause cracks in brick pairs if left to continue.
Grooving
The early locomotive boiler plates join the simple overlap of joints. This practice is quite satisfactory for the circular connection, running around the boiler, but in longitudinal connections, along the length of the boiler, overlapping of the plate is diverted the boiler cross section of the ideal circular shape. Under pressure, the boiler is strained to reach, as close as possible, a circular cross section. Because the overlap of thickness is stronger than the surrounding metal, bending and recurrence caused by pressure boiler variations cause internal cracks, or grooves (deep pitting), along the joint. Cracks offer a starting point for internal corrosion, which can accelerate failure. Finally it was found that this internal corrosion can be reduced by using a plate of sufficient size so that no connection lies beneath the surface of the water. Finally the simple lap stitch is replaced by single or double butt-strap stitches, which do not experience this defect.
Due to the constant expansion and contraction of the fire box, similar forms of "stress corrosion" can occur at the ends of the connecting plates where they enter the firebox plate, and are accelerated by poor water quality. Often referred to as "necking", this type of corrosion can reduce the strength of staybolts until they are unable to support the fire box at normal pressure.
Grooving (deep pitting, localized) also occurs near the water line, especially in boilers fed with untreated water or treated with oxygen cleaning agents. All "natural" water sources contain dissolved air, which is released as a gas when water is heated. The air (which contains oxygen) accumulates in layers near the water surface and greatly accelerates the corrosion of the boiler plates in the area.
Firebox
The complicated shape of locomotive locomotives, whether made of soft copper or from steel, can only withstand the vapor pressure on the inner walls if this is supported by sticking to the internal support beams and the outer wall. They are responsible for failure due to fatigue (because the inner and outer walls extend at different rates under heat of fire), from corrosion, or from waste because the heads that remain exposed to fire will burn out. If it still fails, the fire box will burst inside. Regular, internal and external visual inspections are used to prevent this. Even a well-kept fire box will fail explosively if the water level in the boiler is allowed to fall far enough to leave the top plate of the open fire box. This can happen when crossing a hilltop, as water flows into the front of the boiler and can expose the crown sheets of fire. The majority of the locomotive explosion is the explosion of a fire box caused by an open crown sheet.
Boiler boiler
The Pennsylvania is a wheel-side wheelchair that experienced a boiler explosion on the Mississippi River and drowned on Ship Island near Memphis, Tennessee, on June 13, 1858. Of the 450 passengers on board of over 250 ships died, including Henry Clemens, Mark's younger brother Mark Twain.
SS There Hancock, a small steamer used to move passengers and cargo to and from the large coastal steamer that stopped at San Pedro Port in the early 1860s, suffered a catastrophe when its boiler exploded violently in San Pedro Bay, the port of Los Angeles, near Wilmington, California on April 27, 1863 killed twenty-six people and injured many others from fifty-three or more passengers on board.
Steamboat Sultana was destroyed in an explosion on 27 April 1865, which resulted in the largest maritime disaster in US history. An estimated 1,549 passengers were killed when three of the four boiler vessels exploded and Sultana caught fire and sank not far from Memphis, Tennessee.
Another Steamboat US Civil War explosion was Steamer Eclipse on January 27, 1865, which brought members of the 9th Artillery of Indiana. An official Note report mentions a disaster report of 10 dead and 68 injured; a report later mentions that 27 were killed and 78 wounded. The loss of Fox Regiment reported 29 deaths.
Boiler use
The stationary steam engines used for electric machines first became famous during the industrial revolution, and in the early days there were many boiler explosions of various causes. One of the first investigators of the matter was William Fairbairn, who helped set up the first insurance company to deal with the blowout losses. He also established experimentally that the circular stress in a cylinder pressure vessel such as a boiler is twice the longitudinal voltage. Such investigations help him and others explain the importance of stress concentration in weakening the boiler.
Modern boiler
Modern boilers are designed with pumps, valves, water level monitors, fuel cutoffs, automatic controls, and excessive pressure relief valves. In addition, construction must comply with strict technical guidelines established by the relevant authorities. NBIC, ASME, and others are working to ensure safe boiler design by issuing detailed standards. The result is a boiler unit that is less susceptible to catastrophic accidents.
Also improving security is the increasing use of "boiler packages." This is a boiler built in the factory then sent as a complete unit to the work site. These usually have better quality and less problems than boilers that are assembled tube-by-tube sites. The boiler package only needs a final connection to be made (electricity, breaking, condensate path, etc.) to complete the installation.
Steam explosion
In steam locomotive boilers, as knowledge is gained by trial and error in the early days, explosive situations and explosive damage can not be avoided. However, improved design and maintenance significantly reduced the number of boiler explosions by the end of the 19th century. Further improvements continued in the 20th century.
In land-based boilers, burst pressure systems occur regularly in stationary steam boilers in the Victorian era, but are now very rare due to the various protections provided, and because of routine inspections imposed by government and industry requirements.
Water heaters can explode with shocking violence when their security devices fail.
Explosive reactor
A steam explosion can occur in any type of water heater, where sufficient quantity of energy is delivered and the resulting steam exceeds the strength of the vessel. When heat delivery is fast enough, a local super heating can occur, so the water hammer destroys the vessel. The SL-1 nuclear reactor accident is a good example.
Locomotive boiler explosion in England
Hewison (1983) provides a comprehensive report on the British boiler explosion, list 137 between 1815 and 1962. It should be noted that 122 of these were in the 19th century and only 15 in the 20th century.
The boiler explosion generally falls into two categories. The first is damage from the barrel's boiler itself, through excessive internal weakness or damage, resulting in the sudden release of steam in large areas. Stress corrosion cracking in joint laps is a common cause of early boiler explosions, possibly caused by caustic embrittlement. The water used in the boiler is not often tightly controlled, and if acid, it can corrode the wrought iron boiler plate. Galvanic corrosion is an additional problem in which copper and iron come into contact. The boiler plate has been removed up to a quarter of a mile (Hewison, Rolt). The second type is the fall of the furnace under the vapor pressure of adjacent boilers, releasing fire and hot gas into the cabin. Design and maintenance improvements almost completely eliminate the first type, but the second type is always possible if engineers and firefighters do not maintain water levels in the boiler.
Boiler barrel can explode if internal pressure becomes too high. To prevent this, the safety valve is installed to release pressure at the specified level. Early examples were springs, but John Ramsbottom created a universally-adopted tamper-proof valve. Another common cause of the explosion is the internal corrosion that weakens the boiler barrel so it can not withstand normal operating pressure. In particular, the grooves can occur along the horizontal layer (lap lap) below the water surface. Dozens of explosions occurred, but were eliminated in 1900 by the adoption of butt connections, plus better maintenance schedules and regular hydraulic testing.
Firebox is generally made of copper, although the locomotive then has a steel fire box. They are retained on the outside of the boiler with a fixed (lots of small support). Parts of the fire box in contact with the full vapor pressure must remain sealed with water, to prevent it from overheating and weakening. A common cause of the tear of fire is that the boiler water level falls too low and the top of the fire box (crown sheet) becomes revealed and overheated. This happens if firefighters fail to maintain water levels or level indicators (glass gauges) are wrong. The less common reason is the damage to a large number of stays, due to corrosion or unsuitable materials.
Throughout the 20th century, two failures of boiler barrels and thirteen fire box collapse occurred in England. Barrel boiler failures occurred in Cardiff in 1909 and Buxton in 1921; both caused by mistake mounting of the safety valve causing the boiler to exceed their design pressure. Of the 13 fire traps, four are due to breaks, one to scale scale up in a fire box, and the rest due to low water levels.
See also
- The steam explosion
- Explosive liquid vapor explosion (BLEVE)
- Boiler security
- Fusible plugs
- Grover Shoe Factory disaster
- List of boiler explosions
- List of train accidents
- William Fairbairn
- John Hick
Note
Bibliography
- Hewison, Christian H. (1983). Explosion Boiler Locomotive . David and Charles. ISBNÃ, 0-7153-8305-1. Rolt, L.T.C. (1956 (and subsequent editions)). Red for Hazard . Bodley Head/David and Charles/Pan Books.
- McEwen, Alan (2009). The Historical Steam Steam Explosion . Sledgehammer Engineering Press. ISBN: 978-0-9532725-2-5.
References
Further reading
- Bartrip, P.W.J. Country and steam boiler in England International review of social history 25, 1980, 77-105. Government intervention and the role of interest groups in Britain in the 19th century relate to stationary boilers.
- Victory, I.R. Decrease in explosive boiler locomotive in UK 1850-1900 Transactions - Newcomen Society 60, 1988-89, 73-94. Technical and other factors that reduce the incidence of explosions.
External links
Source of the article : Wikipedia
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