|A boiler is a closed vessel in which drinking water or other fluid is heated. The fluid will not necessarily boil. (In THE UNITED STATES, the word "furnace" is generally used if the reason is not to boil the liquid.) The warmed or vaporized fluid exits the boiler for use in a variety of heating or processes applications, including drinking water heating, central heating, boiler-based power era, food preparation, and sanitation. |
The pressure vessel of a boiler is usually made of steel (or alloy steel), or of wrought iron historically. Stainless steel, especially of the austenitic types, is not found in wetted elements of boilers due to corrosion and stress corrosion cracking. However, ferritic stainless steel is often used in superheater sections that won't be exposed to boiling drinking water, and electrically heated stainless shell boilers are allowed under the Western european "Pressure Equipment Directive" for creation of steam for sterilizers and disinfectors.
In live steam models, copper or brass is often used because it is easier fabricated in smaller size boilers. Historically, copper was often used for fireboxes (especially for steam locomotives), because of 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 metal) are used instead.
For a lot of the Victorian "age of vapor", the only materials used for boilermaking was the best grade of wrought iron, with assembly by rivetting. This iron was often 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 instead relocated towards the utilization of steel, which is stronger and cheaper, with welded building, which is quicker and requires less labour. It should be mentioned, however, that wrought iron boilers corrode much slower than their modern-day steel counterparts, and are less susceptible to localized pitting and stress-corrosion. This makes the longevity of older wrought-iron boilers far more advanced than those of welded steel boilers.
Cast iron might be used for the heating system vessel of home drinking water heaters. Although such heaters are usually termed "boilers" in some countries, their purpose is usually to produce hot water, not steam, and they also run at low pressure and stay away from boiling. The brittleness of cast iron helps it be impractical for high-pressure vapor boilers.
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The foundation of heating for a boiler is combustion of any of several fuels, such as wood, coal, oil, or gas. Electric vapor boilers use resistance- or immersion-type heating elements. Nuclear fission can be used as a heat source for producing steam also, either straight (BWR) or, generally, in specialised high temperature exchangers called "vapor generators" (PWR). Heat recovery steam 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 -immediate approach to boiler efficiency test is more useful or more common
boiler efficiency =Q*((Hg-Hf)/q)*(GCV *100 ) Q =Total vapor circulation Hg= Enthalpy of saturated steam in k cal/kg Hf =Enthalpy of give food to water in kcal/kg q= level 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 need a subsequent parameter like
Ultimate analysis of gasoline (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 gas in kcal/kg
ash percentage in combustible fuel
GCV of ash in kcal/kg
Boilers can be classified into the following configurations:
Container boiler or Haycock boiler/Haystack boiler: a primitive "kettle" in which a fire heats a partially filled water box from below. 18th century Haycock boilers produced and stored large quantities of very low-pressure steam generally, hardly above that of the atmosphere often. These could burn off wood or frequently, coal. Efficiency was very low.
Flued boiler with one or two large flues-an early type or forerunner of fire-tube boiler.
Diagram of a fire-tube boiler
Fire-tube boiler: Here, drinking water partially fills a boiler barrel with a small volume remaining above to accommodate the steam (steam space). This is the type of boiler used in all steam locomotives nearly. The heat source is inside a furnace or firebox that needs to be held permanently surrounded by the water in order to keep the temperatures of the heating system surface below the boiling point. The furnace can be situated at one end of a fire-tube which lengthens the road of the hot gases, thus augmenting the heating surface which may be further increased by causing the gases invert direction through a second parallel tube or a bundle of multiple tubes (two-pass or return flue boiler); on the other hand the gases may be taken along the edges and then beneath the boiler through flues (3-move boiler). In case there is a locomotive-type boiler, a boiler barrel stretches from the firebox and the hot gases pass through a lot of money of fire pipes inside the barrel which greatly escalates the heating surface in comparison to a single tube 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 mostly, but are easily versatile to the people of the liquid or gas variety.
Diagram of a water-tube boiler.
Water-tube boiler: In this type, tubes filled with water are arranged in the furnace in a number of possible configurations. Water tubes connect large drums Often, the lower ones including water and top of the ones vapor and drinking water; in other instances, like a mono-tube boiler, water is circulated with a pump through a succession of coils. This type generally gives high vapor production rates, but less storage capacity than the above mentioned. Water pipe boilers can be designed to exploit any heat source and tend to be preferred in high-pressure applications since the high-pressure water/vapor is contained within small size pipes which can withstand the pressure with a thinner wall structure.
Flash boiler: A flash boiler is a specialized type of water-tube boiler where pipes are close together and drinking water is pumped through them. A flash boiler differs from the kind of mono-tube steam generator where the pipe is permanently filled up with water. In a flash boiler, the tube is held so hot that water give food to is quickly flashed into vapor and superheated. Flash boilers got some use in cars in the 19th century which use continued in to the early 20th century. .
1950s design steam locomotive boiler, from a Victorian Railways J class
Fire-tube boiler with Water-tube firebox. Sometimes both above types have been mixed in the following manner: the firebox consists of an set up of water pipes, called thermic siphons. The gases then go through a typical firetube boiler. Water-tube fireboxes were installed in many Hungarian locomotives, but have fulfilled with little success far away.
Sectional boiler. In a cast iron sectional boiler, sometimes called a "pork chop boiler" the water is included inside cast iron areas. 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 like the American Society of Mechanical Engineers (ASME) develop requirements and regulation codes. For example, the ASME Boiler and Pressure Vessel Code is a typical providing a wide range of guidelines and directives to ensure compliance of the boilers and other pressure vessels with safety, design and security standards.
Historically, boilers were a way to obtain many serious injuries and property destruction as a consequence to poorly understood engineering principles. Thin and brittle metal shells can rupture, while poorly welded or riveted seams could start, leading to a violent eruption of the pressurized vapor. When water is changed into steam it expands to over 1,000 times its original quantity and travels down vapor pipes at over 100 kilometres per hour. Because of this, steam is a great way of moving energy and high temperature around a 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 will suffer from level formation and corrosion. At best, this boosts energy costs and can result in poor quality steam, reduced efficiency, shorter vegetation and unreliable procedure. At worst, it can lead to catastrophic failure and lack of life. Collapsed or dislodged boiler tubes can also aerosol scalding-hot vapor and smoke out of the air intake and firing chute, injuring the firemen who fill the coal into the fire chamber. Extremely large boilers providing a huge selection of horsepower to operate factories can potentially demolish entire structures.
A boiler that has a loss of give food to water and it is permitted to boil dry out can be extremely dangerous. If feed drinking water is sent into the vacant boiler then, the small cascade of inbound drinking water instantly boils on connection with the superheated steel shell and leads to a violent explosion that can't be controlled even by protection vapor valves. Draining of the boiler can also happen if a leak occurs in the vapor supply lines that is bigger than the make-up water source could replace. The Hartford Loop was invented in 1919 by the Hartford Vapor Boiler and INSURANCE PROVIDER as a method to help prevent this problem from happening, and thus reduce their insurance statements.
Superheated steam boiler
A superheated boiler on the steam locomotive.
Main article: Superheater
Most boilers produce vapor to be utilized at saturation temperature; that is, saturated steam. Superheated steam boilers vaporize water and then further temperature the steam in a superheater. This provides vapor at higher temp, but can decrease the overall thermal efficiency of the steam generating plant because the higher vapor heat takes a higher flue gas exhaust temp. There are several ways to circumvent this problem, typically by giving an economizer that heats the feed water, a combustion air heating unit in the hot flue gas exhaust path, or both. There are advantages to superheated vapor that may, and often will, increase overall efficiency of both vapor generation and its utilization: increases in input temperatures to a turbine should outweigh any cost in additional boiler complication and expense. There could be practical limitations in using wet vapor also, as entrained condensation droplets will damage turbine blades.
Superheated steam presents unique safety concerns because, if any operational system component fails and allows steam to escape, the high pressure and temperature can cause serious, instantaneous injury 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 indicates its existence clearly.
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 path in the boiler furnace. The temperatures in this field is between 1 typically,300 and 1,600 ∞C (2,372 and 2,912 ∞F). Some superheaters are glowing type; that is, they absorb warmth by radiation. Others are convection type, absorbing high temperature 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 heat of the vapor in the superheater rises, the pressure of the vapor will not and the pressure remains exactly like that of the boiler. Virtually all steam superheater system designs remove droplets entrained in the steam to prevent damage to the turbine blading and associated piping.
Supercritical steam generator
Boiler for a power vegetable.
Main article: Supercritical steam generator
Supercritical steam generators are used for the production of electric power frequently. They operate at supercritical pressure. As opposed 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 that occurs; the fluid is neither water nor gas but a super-critical liquid. There is no era of steam bubbles within the water, because the pressure is above the critical pressure point of which vapor bubbles can develop. As the fluid expands through the turbine levels, its thermodynamic state drops below the critical point as it can work turning the turbine which turns the power generator from which power is ultimately extracted. The liquid at that time may be considered a mixture of vapor and liquid droplets as it goes by into the condenser. This results in less fuel use and for that reason less greenhouse gas production slightly. The term "boiler" should not be used for a supercritical pressure steam generator, as no "boiling" occurs in this device.
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Boiler accessories and fittings
Pressuretrols to control the vapor pressure in the boiler. Boilers generally have two or three 3 pressuretrols: a manual-reset pressuretrol, which functions as a protection by setting the top limit of vapor pressure, the working pressuretrol, which settings when the boiler fires to keep pressure, as well as for boilers equipped with a modulating burner, a modulating pressuretrol which controls the quantity of fire.
Security valve: It can be used to relieve pressure and prevent possible explosion of the boiler.
Water level indicators: They show the operator the level of fluid in the boiler, also known as a sight cup, water gauge or drinking water column.
Bottom blowdown valves: They offer a way for removing solid particulates that condense and rest on underneath of a boiler. As the name indicates, this valve is usually located on underneath of the boiler, and is sometimes opened up to use the pressure in the boiler to force these particulates out.
Constant blowdown valve: This allows a small level of water to escape continuously. Its purpose is to avoid the water in the boiler becoming saturated with dissolved salts. Saturation would business lead to foaming and cause water droplets to be transported over with the steam - a disorder known as priming. Blowdown is also often used to monitor the chemistry of the boiler water.
Trycock: a type of valve that is often use to manually check a liquid level in a container. Most entirely on a drinking water boiler commonly.
Flash tank: High-pressure blowdown enters this vessel where in fact the vapor can 'flash' safely and be used in a low-pressure system or be vented to atmosphere while the ambient pressure blowdown moves to drain.
Automatic blowdown/continuous heat recovery system: This system allows the boiler to blowdown only when make-up water is moving to the boiler, thereby transferring the utmost amount of heat possible from the blowdown to the makeup water. No flash container is normally needed as the blowdown discharged is near to the temperature of the makeup water.
Hand holes: They may be steel plates installed in openings in "header" to permit for inspections & installing pipes and inspection of internal surfaces.
Steam drum internals, a series of display, scrubber & cans (cyclone separators).
Low-water cutoff: It really is a mechanical means (usually a float change) that is used to turn from the burner or shut down energy to the boiler to avoid it from running once the water goes below a certain point. If a boiler is "dry-fired" (burnt without water in it) it can cause rupture or catastrophic failing.
Surface blowdown range: It offers a means for removing foam or other lightweight non-condensible substances that tend to float on top of water inside the boiler.
Circulating pump: It really is designed to circulate drinking 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 line. This can be suited to the comparative part of the boiler, just below the water level, or to the very best of the boiler.
Top feed: In this design for feedwater injection, water is fed to the top of the boiler. This may reduce boiler fatigue triggered by thermal stress. By spraying the feedwater over a series of trays the water is quickly warmed which can reduce limescale.
Desuperheater tubes or bundles: A series of pipes or bundles of tubes in the water drum or the vapor drum made to cool superheated steam, in order to provide auxiliary equipment that will not need, or may be damaged by, dry steam.
Chemical injection line: A connection to add chemicals for controlling feedwater pH.
Main vapor stop valve:
Main vapor stop/check valve: It is used on multiple boiler installations.
Gasoline oil system:energy oil heaters
Other essential items
Inspectors test pressure measure attachment: