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A boiler is a closed vessel where drinking water or other liquid is heated. The fluid will not necessarily boil. (In North America, the word "furnace" is generally used if the purpose is not to boil the fluid.) The heated or vaporized liquid exits the boiler for use in various procedures or heating system applications,[1][2] including drinking water heating, central heating system, boiler-based power generation, cooking food, and sanitation.
Materials
The pressure vessel of the boiler is usually manufactured from steel (or alloy steel), or historically of wrought iron. Stainless steel, especially of the austenitic types, is not found in wetted parts of boilers credited to corrosion and stress corrosion breaking.[3] However, ferritic stainless is often used in superheater sections that will not come in contact with boiling water, and electrically heated stainless shell boilers are allowed under the Western "Pressure Equipment Directive" for production of steam for sterilizers and disinfectors.[4]
https://en.wikipedia.org/wiki/Boiler
In live steam models, copper or brass is often used since it is more fabricated in smaller size boilers easily. 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 metal) are used instead.
For a lot of the Victorian "age of steam", the only material used for boilermaking was the highest quality 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 transferred towards the utilization of metal instead, which is stronger and cheaper, with welded structure, which is quicker and requires less labour. It ought to be mentioned, however, that wrought iron boilers corrode much slower than their modern-day metal counterparts, and are less susceptible to localized stress-corrosion and pitting. This makes the durability of older wrought-iron boilers considerably superior to those of welded metal boilers.
Cast iron might be used for the heating vessel of local water heaters. Although such heaters are usually termed "boilers" in a few countries, their purpose is to produce hot water usually, not steam, and so they run at low pressure and stay away from boiling. The brittleness of cast iron makes it impractical for high-pressure vapor boilers.
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Energy
The foundation of heating for a boiler is combustion of some of several fuels, such as wood, coal, oil, or natural gas. Electric vapor boilers use level of resistance- or immersion-type heating elements. Nuclear fission is also used as a heat source for producing steam, either straight (BWR) or, in most cases, in specialised temperature exchangers called "vapor generators" (PWR). High temperature recovery steam generators (HRSGs) use the heat rejected from other procedures 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 usable or even more common
boiler efficiency =Q*((Hg-Hf)/q)*(GCV *100 ) Q =Total vapor flow Hg= Enthalpy of saturated vapor in k cal/kg Hf =Enthalpy of give food to water in kcal/kg q= quantity of fuel use in kg/hr GCV =gross calorific value in kcal/kg like pet coke (8200 kcal/KG)
indirect method -to measure the boiler efficiency in indirect method, we need a subsequent 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 gas in kcal/kg
ash percentage in combustible fuel
GCV of ash in kcal/kg
Configurations
Boilers can be classified in to the following configurations:
Pot boiler or Haycock boiler/Haystack boiler: a primitive "kettle" where a fire heats a partially filled water container from below. 18th century Haycock boilers produced and stored large volumes of very low-pressure vapor generally, often hardly above that of the atmosphere. These could burn off wood or frequently, coal. Efficiency was very low.
Flued boiler with one or two large flues-an early forerunner or kind of fire-tube boiler.
Diagram of a fire-tube boiler
Fire-tube boiler: Here, water partially fills a boiler barrel with a little volume left above to accommodate the vapor (vapor space). This is the type of boiler used in all steam locomotives nearly. Heat source is inside a furnace or firebox that needs to be kept completely surrounded by water in order to keep the heat range of the heating 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 making the gases reverse direction through another parallel pipe or a lot of money of multiple tubes (two-pass or return flue boiler); alternatively the gases may be studied along the edges and then under the boiler through flues (3-move boiler). In case of a locomotive-type boiler, a boiler barrel extends 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 enhances heat transfer. Fire-tube boilers have a comparatively low rate of steam production usually, but high steam storage capacity. Fire-tube boilers mostly burn solid fuels, but are readily adaptable to people of the gas or water variety.
Diagram of the water-tube boiler.
Water-tube boiler: In this kind, tubes filled up with drinking water are arranged inside a furnace in a true quantity of possible configurations. Usually the drinking water pipes connect large drums, the lower ones including drinking water and the top ones steam and water; in other situations, like a mono-tube boiler, water is circulated by a pump through a succession of coils. This type generally gives high vapor production rates, but less storage 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 since the high-pressure water/vapor is included within small diameter pipes which can withstand the pressure with a thinner wall.
Flash boiler: A flash boiler is a specialized kind of water-tube boiler where tubes are close jointly and drinking water is pumped through them. A flash boiler differs from the kind of mono-tube steam generator in which the tube is permanently filled with water. Super fast boiler, the tube is held so hot that water feed is quickly flashed into vapor and superheated. Flash boilers acquired some use in cars 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 both above types have been mixed in the next manner: the firebox includes an set up of water pipes, called thermic siphons. The gases then pass through a typical firetube boiler. Water-tube fireboxes were installed in many Hungarian locomotives,[citation needed] but have fulfilled with little success in other countries.
Sectional boiler. Inside a ensemble iron sectional boiler, sometimes called a "pork chop boiler" water is contained inside cast iron areas.[citation needed] These sections are assembled on site to create the finished boiler.
Safety
See also: Boiler explosion
To define and secure boilers safely, some professional specialized organizations such as the American Culture of Mechanical Technicians (ASME) develop specifications and regulation rules. For example, the ASME Boiler and Pressure Vessel Code is a standard providing a wide range of rules and directives to ensure compliance of the boilers and other pressure vessels with basic safety, design and security standards.[5]
Historically, boilers were a way to obtain many serious injuries and property destruction due to badly understood engineering principles. Thin and brittle metal shells can rupture, while welded or riveted seams could start poorly, leading to a violent eruption of the pressurized steam. 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 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 give food to water treatment, a steam-raising herb will suffer from range corrosion and formation. At best, this boosts energy costs and can lead to poor quality vapor, reduced efficiency, shorter vegetation and unreliable operation. At worst, it can lead to catastrophic reduction and failing of life. Collapsed or dislodged boiler tubes can also spray 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 use factories could demolish entire structures.[6]
A boiler that has a loss of feed drinking water and it is permitted to boil dry out can be extremely dangerous. If give food to drinking water is then sent in to the vacant boiler, the small cascade of inbound water instantly boils on connection with the superheated metallic shell and leads to a violent explosion that cannot be controlled even by protection vapor valves. Draining of the boiler can also happen if a leak occurs in the steam source lines that is bigger 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 strategy to assist in preventing this condition from happening, and thus reduce their insurance statements.[7][8]
Superheated steam boiler
A superheated boiler on the steam locomotive.
Main article: Superheater
Most boilers produce vapor to be utilized at saturation temp; that is, saturated steam. Superheated steam boilers vaporize the water and additional heat the steam in a superheater then. This provides vapor at much higher temperatures, but can reduce the overall thermal efficiency of the steam generating vegetable because the higher steam heat range takes a higher flue gas exhaust temperature.[citation needed] There are several ways to circumvent this issue, typically by providing an economizer that heats the give food to water, a combustion air heater in the hot flue gas exhaust route, or both. You can find advantages to superheated steam that may, and will often, increase overall efficiency of both steam generation and its own utilization: benefits in input heat to a turbine should outweigh any cost in additional boiler complication and expense. There can also be practical limitations in using wet steam, as entrained condensation droplets will harm 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 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 indicates its presence clearly.
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 path in the boiler furnace. The heat in this area is typically between 1,300 and 1,600 °C (2,372 and 2,912 °F). Some superheaters are glowing type; that is, they absorb heat by rays. Others are convection type, absorbing warmth from a fluid. Some are a mixture of both types. Through either method, the extreme high temperature in the flue gas path will also high temperature the superheater vapor piping and the steam within. While the temperature of the vapor in the superheater increases, the pressure of the vapor does 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 power vegetable.
Main article: Supercritical steam generator
Supercritical steam generators are used for the production of energy 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 to occur; the fluid is liquid nor gas but a super-critical fluid neither. There is no era of vapor bubbles within water, because the pressure is above the critical pressure point of which steam bubbles can form. As the liquid expands through the turbine phases, its thermodynamic condition drops below the critical point as it can work turning the turbine which turns the electrical generator that power is ultimately extracted. The fluid at that time may be considered a mix of vapor and liquid droplets as it passes in to the condenser. This results in slightly less gasoline use and for that reason less greenhouse gas production. The term "boiler" shouldn't be used for a supercritical pressure vapor generator, as no "boiling" occurs in this device.
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Accessories
Boiler fittings and accessories
Pressuretrols to control 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 the upper limit of vapor pressure, the operating pressuretrol, which settings when the boiler fires to keep pressure, and for boilers outfitted with a modulating burner, a modulating pressuretrol which controls the amount of fire.
Security valve: It can be used to relieve pressure and prevent possible explosion of a boiler.
Water level signals: They show the operator the level of fluid in the boiler, also known as a view glass, water gauge or drinking water column.
Bottom blowdown valves: They offer a means for removing solid particulates that condense and rest on the bottom of the boiler. As the name suggests, this valve is situated directly on the bottom of the boiler usually, and is occasionally opened up to use the pressure in the boiler to push these particulates out.
Constant blowdown valve: This allows a small quantity of water to flee continuously. Its purpose is to prevent the water in the boiler becoming saturated with dissolved salts. Saturation would lead to foaming and cause water droplets to be carried over with the steam - a disorder known as priming. Blowdown is often used to monitor the chemistry of the boiler drinking water also.
Trycock: a type of valve that is often use to manually check a liquid level in a container. Mostly found on a drinking water boiler.
Flash container: High-pressure blowdown enters this vessel where the steam 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/constant heat recovery system: This system allows the boiler to blowdown only when make-up water is flowing to the boiler, thereby transferring the utmost 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 temp of the make-up water.
Hand openings: They are metal plates installed in openings in "header" to allow for inspections & installing tubes and inspection of internal surfaces.
Steam drum internals, a series of display 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 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 water in it) it can cause rupture or catastrophic failure.
Surface blowdown line: It provides a way for removing foam or other lightweight non-condensible chemicals that have a tendency to float together with the water inside the boiler.
Circulating pump: It really 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 line. This can be suited to the comparative aspect of the boiler, below the water level just, or to the very best of the boiler.[10]
Top give food to: Within this design for feedwater injection, water is fed to the very best 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 heated which can reduce limescale.
Desuperheater pipes or bundles: Some pipes or bundles of tubes in the water drum or the vapor drum designed to cool superheated steam, in order to supply auxiliary equipment that does not need, or may be damaged by, dry out vapor.
Chemical injection line: A link with add chemicals for controlling feedwater pH.
Steam accessories
Main vapor stop valve:
Steam traps:
Main vapor stop/check valve: It is used on multiple boiler installations.
Combustion accessories
Fuel oil system:fuel oil heaters
Gas system:
Coal system:
Soot blower
Other essential items
Pressure gauges:
Feed pumps:
Fusible plug:
Inspectors test pressure gauge attachment:
Name dish:
Registration plate: -
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