A boiler is a closed vessel where water or other liquid 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 fluid.) The warmed or vaporized fluid exits the boiler for use in a variety of processes or heating applications,[1 - [2 - including drinking water heating, central heating system, boiler-based power generation, food preparation, and sanitation.
The pressure vessel of a boiler is usually manufactured from steel (or alloy steel), or of wrought iron historically. Stainless steel, of the austenitic types especially, is not used in wetted parts of boilers thanks to stress and corrosion corrosion cracking.[3 - 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 "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 because it is more easily 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 newer 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 material used for boilermaking was the best grade of wrought iron, with assembly by rivetting. This iron was often obtained from specialist ironworks, such as at Cleator Moor (UK), observed for the high quality of their rolled plate and its own suitability for high-reliability use in critical applications, such as high-pressure boilers. In the 20th century, design practice instead transferred towards the utilization of metal, which is more powerful and cheaper, with welded building, which is quicker and requires less labour. It should be noted, however, that wrought iron boilers corrode much slower than their modern-day metal counterparts, and are less susceptible to localized pitting and stress-corrosion. This makes the durability of old wrought-iron boilers far superior to those of welded steel boilers.
Cast iron may be used for the heating 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 vapor boilers.
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The source of heat for a boiler is combustion of any of several fuels, such as wood, coal, oil, or natural gas. Electric steam boilers use level of resistance- or immersion-type heating system elements. Nuclear fission is utilized as a heat source for producing steam also, either directly (BWR) or, generally, in specialised temperature exchangers called "steam generators" (PWR). High temperature recovery vapor generators (HRSGs) use the heat rejected from other processes such as gas turbine.
there are two solutions to measure the boiler efficiency 1) direct method 2) indirect method
Direct method -direct approach to boiler efficiency test is more functional or even more common
boiler efficiency =Q*((Hg-Hf)/q)*(GCV *100 ) Q =Total vapor stream Hg= Enthalpy of saturated vapor in k cal/kg Hf =Enthalpy of give food to drinking water in kcal/kg q= level of energy 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 following parameter like
Ultimate analysis of gas (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 gasoline in kcal/kg
ash percentage in combustible fuel
GCV of ash in kcal/kg
Boilers can be classified into the following configurations:
Pot boiler or Haycock boiler/Haystack boiler: a primitive "kettle" where a fire heats a partially filled drinking water pot from below. 18th century Haycock boilers generally produced and stored large volumes of very low-pressure vapor, barely above that of the atmosphere often. These could burn off wood or most often, coal. Efficiency was suprisingly low.
Flued boiler with a couple of large flues-an early forerunner or type of fire-tube boiler.
Diagram of the fire-tube boiler
Fire-tube boiler: Here, drinking water partially fills a boiler barrel with a little volume remaining above to support the vapor (vapor space). This is the kind of boiler used in all steam locomotives nearly. Heat source is in the furnace or firebox that needs to be kept permanently surrounded by water in order to keep up the heat 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 system surface which can be further increased by causing the gases invert direction through a second parallel pipe or a bundle of multiple tubes (two-pass or come back flue boiler); alternatively the gases may be studied along the edges and then beneath the boiler through flues (3-move boiler). In case of a locomotive-type boiler, a boiler barrel stretches from the firebox and the hot gases pass through a bundle of fire pipes inside the barrel which greatly escalates the heating surface in comparison to a single tube and further improves heat transfer. Fire-tube boilers have a comparatively low rate of steam creation usually, but high steam storage capacity. Fire-tube boilers burn off solid fuels mostly, but are easily flexible to people of the liquid or gas variety.
Diagram of a water-tube boiler.
Water-tube boiler: In this kind, tubes filled with water are arranged in the furnace in a number of possible configurations. Usually the drinking water pipes connect large drums, the lower ones containing water and top of the ones water and steam; in other instances, such as a mono-tube boiler, drinking water is circulated with a pump through a succession of coils. This kind generally provides high vapor production rates, but less storage capacity than the above. Water tube boilers can be made to exploit any high temperature source and are generally 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.
Flash boiler: A flash boiler is a specialized kind of water-tube boiler where pipes are close jointly and water is pumped through them. A flash boiler differs from the kind of mono-tube steam generator in which the pipe is permanently filled up with water. Super fast boiler, the pipe 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 the two above types have been combined in the next manner: the firebox contains an assembly of water tubes, called thermic siphons. The gases go through a conventional firetube boiler then. Water-tube fireboxes were installed in many Hungarian locomotives,[citation needed - but have fulfilled with little success far away.
Sectional boiler. Inside a ensemble iron sectional boiler, sometimes called a "pork chop boiler" the water is included inside solid iron sections.[citation needed - These areas are assembled on site to produce the finished boiler.
See also: Boiler explosion
To define and secure boilers safely, some professional specialized organizations like the American Society of Mechanical Technicians (ASME) develop specifications and regulation rules. For instance, the ASME Boiler and Pressure Vessel Code is a standard providing a wide range of guidelines and directives to ensure compliance of the boilers and other pressure vessels with safety, design and security standards.[5 -
Historically, boilers were a way to obtain many serious injuries and property destruction as a consequence to badly understood engineering principles. Thin and brittle metal shells can rupture, while poorly welded or riveted seams could start, resulting in a violent eruption of the pressurized vapor. When water is converted to vapor it expands to over 1,000 times its original quantity and travels down vapor pipes at over 100 kilometres per hour. Because of this, vapor is a superb way of moving energy and temperature around a site from a central boiler house to where it is necessary, but without the right boiler feed water treatment, a steam-raising place are affected from level corrosion and formation. At best, this increases energy costs and can lead to poor quality vapor, reduced efficiency, shorter plant life and unreliable operation. At worst, it can result in catastrophic failure and lack of life. Collapsed or dislodged boiler tubes can also aerosol scalding-hot steam and smoke out of the air intake and firing chute, injuring the firemen who insert the coal into the fire chamber. Extremely large boilers providing hundreds of horsepower to operate factories could demolish entire buildings.[6 -
A boiler that has a loss of feed water and it is permitted to boil dry out can be hugely dangerous. If supply water is sent in to the vacant boiler then, the tiny cascade of inbound drinking water instantly boils on connection with the superheated metal shell and leads to a violent explosion that can't be managed even by protection vapor valves. Draining of the boiler can also happen if a leak occurs in the steam supply lines that is larger than the make-up water supply could replace. The Hartford Loop was created in 1919 by the Hartford Vapor Boiler and Insurance Company as a method to assist in preventing this condition from happening, and therefore reduce their insurance promises.[7 - [8 -
Superheated steam boiler
A superheated boiler on the steam locomotive.
Main article: Superheater
Most boilers produce vapor to be utilized at saturation heat; that is, saturated vapor. Superheated steam boilers vaporize water and additional heat the steam in a superheater then. This provides steam at much higher heat, but can decrease the overall thermal efficiency of the steam generating place because the higher steam heat range requires a higher flue gas exhaust temperature.[citation needed - 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 route, or both. There are advantages to superheated steam that may, and often will, increase overall efficiency of both vapor generation and its own utilization: benefits in input temperatures to a turbine should outweigh any cost in additional boiler problem and expense. There may also be useful limitations in using wet vapor, 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 pressure and temperature can cause serious, instantaneous injury to anyone in its path. Since the escaping steam will initially be completely superheated vapor, detection can be difficult, although the extreme heat and sound from such a leak obviously indicates its presence.
Superheater operation 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 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 warmth by rays. Others are convection type, absorbing heat from a fluid. Some are a combination of both types. Through either method, the extreme heat in the flue gas route will also temperature the superheater vapor piping and the steam within. While the heat range of the vapor in the superheater increases, the pressure of the steam will not and the pressure remains exactly like 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 charged power plant.
Main article: Supercritical steam generator
Supercritical steam generators are frequently used for the production of electric power. 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 liquid is neither liquid nor gas but a super-critical fluid. There is absolutely no era of vapor bubbles within water, because the pressure is above the critical pressure point of which steam bubbles can develop. As the fluid expands through the turbine levels, its thermodynamic condition drops below the critical point as it can work turning the turbine which converts the electrical generator from which power is eventually extracted. The liquid at that time may be considered a mixture of vapor and liquid droplets as it goes by in to the condenser. This results in somewhat less gas use and therefore less greenhouse gas production. The word "boiler" shouldn't 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 control the steam pressure in the boiler. Boilers generally have 2 or 3 3 pressuretrols: a manual-reset pressuretrol, which functions as a safety by setting the top limit of vapor pressure, the working pressuretrol, which controls when the boiler fires to keep pressure, and for boilers equipped with a modulating burner, a modulating pressuretrol which settings the amount of fire.
Safety valve: It is utilized to relieve pressure and stop possible explosion of the boiler.
Water level indications: They show the operator the level of liquid in the boiler, also known as a sight cup, water gauge or drinking water column.
Bottom blowdown valves: They offer a means for removing solid particulates that condense and lay on underneath of the boiler. As the name suggests, this valve is usually located on the bottom of the boiler, and is sometimes opened to use the pressure in the boiler to push these particulates out.
Constant blowdown valve: This allows a small level of water to flee continuously. Its purpose is to prevent water in the boiler becoming saturated with dissolved salts. Saturation would business lead to foaming and cause drinking water droplets to be carried over with the vapor - a condition known as priming. Blowdown is often used to monitor the chemistry of the boiler water also.
Trycock: a type of valve that is often use to manually check a liquid level in a tank. Most found on a drinking water boiler commonly.
Flash tank: High-pressure blowdown enters this vessel where the steam can 'flash' safely and become used in a low-pressure system or be vented to atmosphere as the ambient pressure blowdown moves to drain.
Automatic blowdown/constant heat recovery system: This system allows the boiler to blowdown only once make-up water is flowing to the boiler, thereby transferring the maximum amount of heat possible from the blowdown to the make-up water. No flash tank is normally needed as the blowdown discharged is close to the temperature of the makeup water.
Hand holes: These are metal plates installed in openings in "header" to permit for inspections & installing pipes and inspection of inner surfaces.
Steam drum internals, a series of display screen, scrubber & cans (cyclone separators).
Low-water cutoff: It really is a mechanical means (usually a float switch) that is utilized to turn off the burner or shut down gas to the boiler to prevent it from working 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 series: It provides a means for removing foam or other light-weight non-condensible chemicals that tend to float together with water inside the boiler.
Circulating pump: It is designed to circulate water back again to the boiler after it has expelled some of its heat.
Feedwater check valve or clack valve: A non-return stop valve in the feedwater range. This can be installed to the medial side of the boiler, just below water level, or to the very best of the boiler.[10 -
Top give food to: With this design for feedwater injection, the water is fed to the very best of the boiler. This can reduce boiler exhaustion caused by thermal stress. By spraying the feedwater over some trays the water is quickly heated which can reduce limescale.
Desuperheater tubes or bundles: Some tubes or bundles of pipes 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 link with add chemicals for controlling feedwater pH.
Main vapor stop valve:
Main steam stop/check valve: It is utilized on multiple boiler installations.
Gas oil system:fuel oil heaters
Other essential items
Inspectors test pressure measure attachment: