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  • A boiler is a closed vessel where drinking water or other fluid is heated. The fluid will not necessarily boil. (In THE UNITED STATES, the term "furnace" is generally used if the purpose is not to boil the fluid.) The warmed or vaporized liquid exits the boiler for use in various processes or heating system applications,[1 - [2 - including drinking water heating, central heating, boiler-based power generation, 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 found in wetted parts of boilers thanks to stress and corrosion corrosion breaking.[3 - However, ferritic stainless is often used in superheater sections that will not be exposed to boiling drinking water, and electrically heated stainless steel shell boilers are allowed under the Western european "Pressure Equipment Directive" for production 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), 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 group of vapor", the only material used for boilermaking was the highest quality of wrought iron, with set up by rivetting. This iron was often obtained from specialist ironworks, such as at Cleator Moor (UK), noted 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 moved towards the use of steel, which is stronger and cheaper, with welded structure, which is quicker and requires less labour. It should be mentioned, however, that wrought iron boilers corrode far slower than their modern-day steel counterparts, and are less susceptible to localized stress-corrosion and pitting. This makes the longevity of old wrought-iron boilers much more advanced than those of welded metal boilers.

    Cast iron may be used for the heating vessel of home drinking water heaters. Although such heaters are usually termed "boilers" in a few countries, their purpose is usually to produce warm 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 heat for a boiler is combustion of some of several fuels, such as wood, coal, oil, or natural gas. Electric steam boilers use level of resistance- or immersion-type heating elements. Nuclear fission is used as a heat source for producing steam also, either straight (BWR) or, in most cases, in specialised high temperature exchangers called "vapor generators" (PWR). Temperature recovery steam generators (HRSGs) use heat rejected from other processes such as gas turbine.

    Boiler efficiency
    there are two methods to gauge the boiler efficiency 1) direct method 2) indirect method

    Immediate method -immediate approach to boiler efficiency test is more functional or more common

    boiler efficiency =Q*((Hg-Hf)/q)*(GCV *100 ) Q =Total vapor flow Hg= Enthalpy of saturated steam in k cal/kg Hf =Enthalpy of feed water in kcal/kg q= quantity of energy use in kg/hr GCV =gross calorific value in kcal/kg like family pet coke (8200 kcal/KG)

    indirect method -to measure 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 fuel 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" where a fireplace heats a partially filled water container from below. 18th century Haycock boilers generally produced and stored large amounts 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 one or two large flues-an early forerunner or type of fire-tube boiler.

    Diagram of the fire-tube boiler
    Fire-tube boiler: Here, water partially fills a boiler barrel with a small volume left above to accommodate the vapor (vapor space). This is the type of boiler used in almost all steam locomotives. The heat source is in the furnace or firebox that has to be held permanently surrounded by water in order to keep up the heat range 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 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); additionally the gases may be studied along the sides and then beneath 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 pass through a bundle of fire pipes inside the barrel which greatly increases the heating surface compared to a single tube and further increases heat transfer. Fire-tube boilers have a comparatively low rate of vapor production usually, but high vapor storage capacity. Fire-tube boilers burn off solid fuels mainly, but are readily adjustable to those of the liquid or gas variety.

    Diagram of the water-tube boiler.
    Water-tube boiler: In this kind, tubes filled with water are arranged inside a furnace in several possible configurations. Usually the water pipes connect large drums, the low ones containing water and the upper ones water and steam; in other situations, like a mono-tube boiler, water is circulated by a pump through a succession of coils. This kind generally gives high vapor production rates, but less storage space capacity than the above. Water tube boilers can be designed 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 structure.
    Flash boiler: A flash boiler is a specialized type of water-tube boiler where tubes are close together and water is pumped through them. A flash boiler differs from the type of mono-tube vapor generator in which the tube is permanently filled up with water. In a flash boiler, the pipe is held so hot that the water give food to is quickly flashed into vapor and superheated. Flash boilers acquired some use in cars in the 19th century which use continued into 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 combined in the next manner: the firebox includes an assembly 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 solid iron sectional boiler, sometimes called a "pork chop boiler" water is included inside ensemble iron areas.[citation needed - These sections are assembled on site to make the finished boiler.
    See also: Boiler explosion
    To define and secure boilers safely, some professional specialized organizations such as the American Culture of Mechanical Designers (ASME) develop criteria and regulation codes. For instance, the ASME Boiler and Pressure Vessel Code is a standard providing an array of guidelines and directives to ensure compliance of the boilers and other pressure vessels with basic safety, design and security standards.[5 -

    Historically, boilers were a source of many serious injuries and property destruction due to badly understood engineering principles. Thin and brittle metallic shells can rupture, while badly welded or riveted seams could start, leading to a violent eruption of the pressurized vapor. When water is converted to vapor it expands to over 1,000 times its original volume and travels down vapor pipes at over 100 kilometres each hour. Because of this, vapor is a great way of moving energy and warmth 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 place are affected from scale 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 lead to catastrophic loss and failing of life. Collapsed or dislodged boiler pipes can also spray scalding-hot vapor and smoke from the air intake and firing chute, injuring the firemen who fill the coal in to the fireplace chamber. Extremely large boilers providing a huge selection of horsepower to operate factories could demolish entire buildings.[6 -

    A boiler which has a loss of feed water and it is permitted to boil dry out can be extremely dangerous. If supply drinking water is sent in to the bare boiler then, the small cascade of inbound drinking water instantly boils on connection with the superheated metallic shell and leads to a violent explosion that can't be managed even by security 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 drinking water source could replace. The Hartford Loop was invented in 1919 by the Hartford Vapor Boiler and Insurance Company as a method to help prevent this condition from happening, and thereby reduce their insurance promises.[7 - [8 -

    Superheated steam boiler

    A superheated boiler on a steam locomotive.
    Main article: Superheater
    Most boilers produce vapor to be utilized at saturation temperature; that is, saturated vapor. Superheated steam boilers vaporize water and further heat the steam in a superheater then. This provides vapor at much higher temperatures, but can reduce the overall thermal efficiency of the vapor generating plant because the higher vapor heat requires a higher flue gas exhaust temp.[citation needed - There are many ways to circumvent this issue, by giving an economizer that heats the feed water typically, a combustion air heater in the hot flue gas exhaust route, or both. You can find advantages to superheated vapor that may, and often will, increase overall efficiency of both steam generation and its own utilization: increases in input temperature to a turbine should outweigh any cost in additional boiler problem and expense. There can also be practical restrictions in using moist vapor, 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 extreme heat and sound from such a leak clearly indicates its presence.

    Superheater operation is similar to that of the coils on an fresh air conditioning unit, although for a different purpose. The steam piping is directed through the flue gas route 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 glowing type; that is, they absorb high temperature by radiation. Others are convection type, absorbing warmth from a fluid. Some are a mixture of both types. Through either method, the extreme temperature in the flue gas path will also high temperature the superheater steam piping and the steam within. While the heat of the vapor in the superheater rises, the pressure of the steam will not and the pressure remains exactly like that of the boiler.[9 - Virtually all steam superheater system designs remove droplets entrained in the steam to avoid harm to the turbine blading and associated piping.

    Supercritical steam generator

    Boiler for a charged power place.
    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 steam generator operates at such a high pressure (over 3,200 psi or 22 MPa) that the physical turbulence that characterizes boiling ceases to occur; the fluid is liquid nor gas but a super-critical fluid neither. There is no era of vapor bubbles within the water, because the pressure is above the critical pressure point of which vapor bubbles can develop. As the liquid expands through the turbine stages, its thermodynamic condition drops below the critical point as it can work turning the turbine which converts the electrical generator from which power is ultimately extracted. The liquid at that point may be a mixture of vapor and liquid droplets as it goes by into the condenser. This results in somewhat less gasoline use and for that reason less greenhouse gas creation. The term "boiler" shouldn't be used for a supercritical pressure steam generator, as no "boiling" occurs in this device.
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    Boiler fittings and accessories
    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 basic safety by setting the upper limit of vapor pressure, the working pressuretrol, which controls when the boiler fires to keep up pressure, and for boilers equipped with a modulating burner, a modulating pressuretrol which handles the quantity of fire.
    Safety 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 liquid in the boiler, known as a sight glass also, water measure or water column.
    Bottom level blowdown valves: They provide a means for removing solid particulates that condense and rest on underneath of the boiler. As the name suggests, this valve is located directly on underneath of the boiler usually, and is occasionally opened to use the pressure in the boiler to force these particulates out.
    Continuous blowdown valve: This enables a small quantity of water to escape continuously. Its purpose is to avoid the 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 liquid level in a tank. Mostly entirely on a drinking water boiler.
    Flash tank: High-pressure blowdown enters this vessel where the vapor can 'flash' safely and be found in a low-pressure system or be vented to atmosphere as the ambient pressure blowdown moves to drain.
    Automatic blowdown/continuous heat recovery system: This system allows the boiler to blowdown only once makeup water is moving to the boiler, thereby transferring the utmost amount of heat possible from the blowdown to the make-up water. No flash tank is generally needed as the blowdown discharged is near to the heat of the make-up water.
    Hand holes: They may be steel plates installed in openings in "header" to allow for inspections & installing pipes and inspection of inner surfaces.
    Steam drum internals, some screen, scrubber & cans (cyclone separators).
    Low-water cutoff: It is a mechanical means (usually a float switch) that can be used to turn off the burner or shut off gas to the boiler to avoid it from running once the drinking water goes below a certain point. If a boiler is "dry-fired" (burnt without drinking water in it) it can cause rupture or catastrophic failure.
    Surface blowdown collection: It provides a means for removing foam or other lightweight non-condensible chemicals that tend to float together with water inside the boiler.
    Circulating pump: It really is designed to circulate water back again to the boiler after they have expelled some 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 side of the boiler, below water level just, or to the very best of the boiler.[10 -
    Top give food to: With this design for feedwater injection, water is fed to the top of the boiler. This can reduce boiler fatigue caused by thermal stress. By spraying the feedwater over some trays water is quickly warmed and this can reduce limescale.
    Desuperheater tubes or bundles: Some tubes or bundles of tubes in water drum or the vapor drum designed to cool superheated vapor, in order to provide auxiliary equipment that does not need, or may be damaged by, dry out steam.
    Chemical substance injection line: A connection to add chemicals for controlling feedwater pH.
    Steam accessories
    Main steam stop valve:
    Steam traps:
    Main steam stop/check valve: It can be used on multiple boiler installations.
    Combustion accessories
    Gasoline oil system:gas oil heaters
    Gas system:
    Coal system:
    Soot blower
    Other essential items
    Pressure gauges:
    Feed pumps:
    Fusible plug:
    Inspectors test pressure measure attachment:
    Name plate:
    Registration plate:

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