Выставка: Индустрия моды - 2009
JamesFen [07.11.2017 19:21:26]
A boiler is a closed vessel where water or other liquid is heated. The fluid will not boil. (In North America, the word "furnace" is normally used if the reason is never to boil the fluid.) The warmed or vaporized fluid exits the boiler for use in various heating system or procedures applications,[1 - [2 - including water heating, central heating system, boiler-based power era, cooking, and sanitation.
The pressure vessel of the boiler is usually manufactured from steel (or alloy steel), or historically of wrought iron. Stainless steel, of the austenitic types especially, is not used in wetted parts of boilers due to stress and corrosion corrosion cracking.[3 - However, ferritic stainless steel is often found in superheater sections that won't be exposed to boiling drinking water, and electrically heated stainless steel shell boilers are allowed under the European "Pressure Equipment Directive" for creation of steam for sterilizers and disinfectors.[4 -
https://en.wikipedia.org/wiki/Boiler - https://en.wikipedia.org/wiki/Boiler
In live steam models, copper or brass is often used since it is more easily fabricated in smaller size boilers. Historically, copper was often used for fireboxes (especially for vapor locomotives), due to its better formability and higher thermal conductivity; however, in more recent times, the high price of copper often makes this an uneconomic choice and cheaper substitutes (such as steel) are used instead.
For a lot of the Victorian "age of vapor", the only material used for boilermaking was the best quality of wrought iron, with set up by rivetting. This iron was extracted from specialist ironworks, such as at Cleator Moor (UK), observed for the high quality of their rolled plate and its suitability for high-reliability use in critical applications, such as high-pressure boilers. In the 20th century, design practice shifted towards the utilization of steel instead, which is more powerful and cheaper, with welded building, which is quicker and requires less labour. It ought to be noted, however, that wrought iron boilers corrode far slower than their modern-day metal counterparts, and are less vunerable to localized stress-corrosion and pitting. This makes the longevity of older wrought-iron boilers considerably more advanced than those of welded metal boilers.
Cast iron can be utilized for the heating system vessel of local water heaters. Although such heaters are usually termed "boilers" in a few countries, their purpose is usually to produce hot water, not steam, and so they run at low pressure and stay away from boiling. The brittleness of cast iron helps it be impractical for high-pressure steam boilers.
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The source of heating for a boiler is combustion of any of several fuels, such as wood, coal, oil, or natural gas. Electric steam boilers use resistance- or immersion-type heating elements. Nuclear fission is used as a heat source for producing steam also, either straight (BWR) or, generally, in specialised warmth exchangers called "steam generators" (PWR). Temperature recovery vapor generators (HRSGs) use heat rejected from other processes such as gas turbine.
there are two solutions to gauge the boiler efficiency 1) direct method 2) indirect method
Direct method -direct method of boiler efficiency test is more useful or more common
boiler efficiency =Q*((Hg-Hf)/q)*(GCV *100 ) Q =Total steam movement Hg= Enthalpy of saturated vapor in k cal/kg Hf =Enthalpy of give food to drinking water in kcal/kg q= quantity of fuel use in kg/hr GCV =gross calorific value in kcal/kg like family pet coke (8200 kcal/KG)
indirect method -to gauge the boiler efficiency in indirect method, we are in need of a following parameter like
Ultimate analysis of fuel (H2,S2,S,C moisture constraint, ash constraint)
percentage of O2 or CO2 at flue gas
flue gas temperature at outlet
ambient temperature in deg c and humidity of air in kg/kg
GCV of energy in kcal/kg
ash percentage in combustible fuel
GCV of ash in kcal/kg
Boilers can be classified in to the following configurations:
Pot boiler or Haycock boiler/Haystack boiler: a primitive "kettle" where a fireplace heats a partially filled drinking water pot from below. 18th century Haycock boilers generally produced and stored large quantities of very low-pressure steam, barely above that of the atmosphere often. These could burn wood or most often, coal. Efficiency was suprisingly low.
Flued boiler with a couple of large flues-an early type or forerunner of fire-tube boiler.
Diagram of the fire-tube boiler
Fire-tube boiler: Here, water partially fills a boiler barrel with a little volume left above to support the vapor (steam space). This is the type of boiler used in all steam locomotives nearly. Heat source is in the furnace or firebox that needs to be kept completely surrounded by the water in order to keep the heat of the heating system surface below the boiling point. The furnace can be situated at one end of the fire-tube which lengthens the road of the hot gases, thus augmenting the heating surface which may be further increased by making the gases reverse direction through another parallel tube or a bundle of multiple pipes (two-pass or return flue boiler); additionally the gases may be taken along the edges and then under the boiler through flues (3-move boiler). In case of a locomotive-type boiler, a boiler barrel expands from the firebox and the hot gases go through a bundle of fire pipes inside the barrel which greatly increases the heating surface compared to a single pipe and further boosts heat transfer. Fire-tube boilers have a comparatively low rate of vapor production usually, but high steam storage capacity. Fire-tube boilers burn solid fuels mainly, but are readily adaptable to people of the gas or water variety.
Diagram of the water-tube boiler.
Water-tube boiler: In this kind, pipes filled up with water are arranged in the furnace in a number of possible configurations. The water pipes connect large drums Often, the lower ones containing water and the upper ones water and steam; in other cases, like a mono-tube boiler, water is circulated with a pump through a succession of coils. This kind provides high steam production rates generally, but less storage space capacity than the above. Water pipe boilers can be made to exploit any high temperature source and tend to be preferred in high-pressure applications because the high-pressure drinking water/steam is included within small size pipes which can withstand the pressure with a thinner wall structure.
Flash boiler: A flash boiler is a specialized kind of water-tube boiler in which tubes are close jointly and water is pumped through them. A flash boiler differs from the kind of mono-tube vapor generator where the pipe is permanently filled up with water. Super fast boiler, the pipe is held so hot that the water give food to is quickly flashed into vapor and superheated. Flash boilers had some use in automobiles in the 19th century and this use continued into the early 20th century. .
1950s design vapor locomotive boiler, from a Victorian Railways J class
Fire-tube boiler with Water-tube firebox. Sometimes the two above types have been combined in the next manner: the firebox consists of an set up of water pipes, called thermic siphons. The gases go through a typical firetube boiler then. Water-tube fireboxes were installed in many Hungarian locomotives,[citation needed - but have met with little success in other countries.
Sectional boiler. Within a cast iron sectional boiler, sometimes called a "pork chop boiler" water is contained inside solid iron sections.[citation needed - These areas are assembled on site to generate the finished boiler.
See also: Boiler explosion
To define and secure boilers safely, some professional specialized organizations such as the American Society of Mechanical Engineers (ASME) develop specifications and regulation codes. For example, the ASME Boiler and Pressure Vessel Code is a typical providing an array of guidelines and directives to ensure compliance of the boilers and other pressure vessels with safety, security and design standards.[5 -
Historically, boilers were a way to obtain many serious injuries and property destruction due to badly understood engineering principles. Thin and brittle steel shells can rupture, while welded or riveted seams could start badly, resulting in a violent eruption of the pressurized vapor. When drinking water is changed into vapor it expands to over 1,000 times its original travels and volume down steam pipes at over 100 kilometres per hour. Because of this, vapor is a superb way of moving energy and high temperature around a niche site from a central boiler house to where it is needed, but with no right boiler give food to water treatment, a steam-raising herb are affected from level formation and corrosion. At best, this increases energy costs and can result in poor quality steam, reduced efficiency, shorter vegetation and unreliable procedure. At worst, it can lead to catastrophic reduction and failing of life. Collapsed or dislodged boiler pipes can also aerosol scalding-hot vapor and smoke from the air intake and firing chute, injuring the firemen who weight the coal into the open fire chamber. Extremely large boilers providing hundreds of horsepower to operate factories can potentially demolish entire structures.[6 -
A boiler which has a loss of give food to drinking water and it is permitted to boil dry can be hugely dangerous. If supply drinking water is sent in to the unfilled boiler then, the small cascade of incoming water instantly boils on contact with the superheated metal shell and leads to a violent explosion that can't be controlled even by basic safety vapor valves. Draining of the boiler can also happen if a leak occurs in the vapor supply lines that is larger than the make-up water supply could replace. The Hartford Loop was developed in 1919 by the Hartford Vapor Boiler and Insurance Company as a method to assist in preventing this problem from happening, and thus reduce their insurance claims.[7 - [8 -
Superheated steam boiler
A superheated boiler on the steam locomotive.
Main article: Superheater
Most boilers produce steam to be used at saturation heat range; that is, saturated vapor. Superheated steam boilers vaporize water and additional heat the steam in a superheater then. This provides vapor at much higher temperature, but can reduce the overall thermal efficiency of the vapor generating vegetable because the bigger vapor temp requires a higher flue gas exhaust heat.[citation needed - There are several ways to circumvent this issue, typically by giving an economizer that heats the feed water, a combustion air heater in the hot flue gas exhaust path, or both. You can find benefits to superheated steam that may, and often will, increase overall efficiency of both steam generation and its own utilization: increases in input heat to a turbine should outweigh any cost in additional boiler complication and expense. There may also be practical restrictions in using moist steam, as entrained condensation droplets will damage turbine blades.
Superheated steam presents unique safety concerns because, if any system component fails and allows steam to escape, the high temperature and pressure can cause serious, instantaneous harm to anyone in its path. Since the escaping steam will be completely superheated vapor, detection can be difficult, although the intense heat and sound from such a leak clearly indicates its presence.
Superheater procedure is similar to that of the coils on an fresh air conditioning unit, although for a different purpose. The vapor piping is directed through the flue gas route in the boiler furnace. The heat range in this area is between 1 typically,300 and 1,600 °C (2,372 and 2,912 °F). Some superheaters are radiant type; that is, they absorb high temperature by rays. Others are convection type, absorbing heat from a fluid. Some are a mixture of the two types. Through either method, the extreme heat in the flue gas path will heat the superheater steam piping and the steam within also. While the temperatures of the vapor in the superheater increases, the pressure of the vapor will not and the pressure remains the same as that of the boiler.[9 - Almost all steam superheater system designs remove droplets entrained in the steam to prevent harm to the turbine blading and associated piping.
Supercritical steam generator
Boiler for a power plant.
Main article: Supercritical steam generator
Supercritical steam generators are used for the production of energy frequently. They operate at supercritical pressure. In contrast to a "subcritical boiler", a supercritical vapor generator operates at such a higher pressure (over 3,200 psi or 22 MPa) that the physical turbulence that characterizes boiling ceases to occur; the liquid is neither liquid nor gas but a super-critical liquid. There is absolutely no generation of vapor bubbles within the water, because the pressure is above the critical pressure point of which vapor bubbles can form. As the liquid expands through the turbine levels, its thermodynamic state drops below the critical point as it can work turning the turbine which changes the power generator from which power is eventually extracted. The fluid at that point may be considered a mixture of vapor and liquid droplets as it goes by in to the condenser. This leads to somewhat less gas use and therefore less greenhouse gas creation. The term "boiler" should not be used for a supercritical pressure vapor generator, as no "boiling" occurs in this product.
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Boiler fittings and accessories
Pressuretrols to regulate the vapor pressure in the boiler. Boilers generally have 2 or 3 3 pressuretrols: a manual-reset pressuretrol, which functions as a protection by setting top of the limit of vapor pressure, the operating pressuretrol, which controls when the boiler fires to maintain pressure, as well as for boilers equipped with a modulating burner, a modulating pressuretrol which handles the amount of fire.
Safety valve: It can be used to alleviate pressure and prevent possible explosion of the boiler.
Water level indicators: They show the operator the level of liquid in the boiler, also called a view glass, water measure or water column.
Bottom level blowdown valves: They offer a means for removing solid particulates that condense and lie on underneath of the boiler. As the name implies, this valve is usually located on the bottom of the boiler, and is sometimes opened to use the pressure in the boiler to press these particulates out.
Continuous blowdown valve: This allows a small level of water to escape continuously. Its purpose is to avoid water in the boiler becoming saturated with dissolved salts. Saturation would lead to foaming and cause drinking water droplets to be carried over with the steam - a condition known as priming. Blowdown is also often used to monitor the chemistry of the boiler water.
Trycock: a kind of valve that is often use to manually check a water level in a tank. Most entirely on a drinking water boiler commonly.
Flash tank: High-pressure blowdown enters this vessel where the steam can 'flash' safely and become found in a low-pressure system or be vented to atmosphere as the ambient pressure blowdown flows to drain.
Automatic blowdown/continuous heat recovery system: This system allows the boiler to blowdown only once make-up water is moving to the boiler, thereby transferring the maximum amount of heat possible from the blowdown to the makeup water. No flash tank is normally needed as the blowdown discharged is near to the heat range of the make-up water.
Hand holes: They are metal plates installed in openings in "header" to permit for inspections & installing tubes and inspection of internal surfaces.
Steam drum internals, some display screen, scrubber & cans (cyclone separators).
Low-water cutoff: It is a mechanical means (usually a float change) that is utilized to turn off the burner or shut off energy to the boiler to avoid it from jogging once the water goes below a certain point. If a boiler is "dry-fired" (burned without drinking water in it) it can cause rupture or catastrophic failing.
Surface blowdown line: It offers a means for removing foam or other lightweight non-condensible substances that tend to float on top of the water inside the boiler.
Circulating pump: It is designed to circulate water back to the boiler after they have expelled a few of its heat.
Feedwater check valve or clack valve: A non-return stop valve in the feedwater collection. This may be installed to the side of the boiler, just below water level, or to the very best of the boiler.[10 -
Top feed: In this design for feedwater injection, water is fed to the top of the boiler. This can reduce boiler exhaustion caused by thermal stress. By spraying the feedwater over a series of trays water is quickly heated which can reduce limescale.
Desuperheater tubes or bundles: A series of tubes or bundles of tubes in water drum or the vapor drum made to cool superheated steam, in order to supply auxiliary equipment that will not need, or may be damaged by, dry out steam.
Chemical substance injection line: A connection to add chemicals for controlling feedwater pH.
Main steam stop valve:
Main steam stop/check valve: It is utilized on multiple boiler installations.
Energy oil system:fuel oil heaters
Other essential items
Inspectors test pressure gauge attachment: