A boiler is a closed vessel where drinking water or other liquid is heated. The fluid does not boil. (In North America, the term "furnace" is normally used if the reason is never to boil the liquid.) The heated or vaporized liquid exits the boiler for use in a variety of processes or heating applications,[1 - [2 - including water heating, central heating, boiler-based power generation, 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 used in wetted elements of boilers due 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 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 since it is easier fabricated in smaller size boilers. Historically, copper was often used for fireboxes (particularly 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 group of vapor", the only material used for boilermaking was the best 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 relocated towards the utilization of steel instead, which is stronger and cheaper, with welded construction, which is quicker and requires less labour. It ought to be observed, 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 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 water heaters. Although such heaters are usually termed "boilers" in a few countries, their purpose is to produce warm water usually, 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 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 gas. Electric steam boilers use resistance- or immersion-type heating system elements. Nuclear fission is utilized as a heat source for generating steam also, either directly (BWR) or, generally, in specialised warmth exchangers called "vapor generators" (PWR). Temperature recovery vapor generators (HRSGs) use heat rejected from other procedures such as gas turbine.
there are two solutions to measure the boiler efficiency 1) direct method 2) indirect method
Immediate method -direct approach to boiler efficiency test is more functional or even more common
boiler efficiency =Q*((Hg-Hf)/q)*(GCV *100 ) Q =Total steam circulation Hg= Enthalpy of saturated steam in k cal/kg Hf =Enthalpy of feed drinking water in kcal/kg q= level of gas 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 are in need of a subsequent 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 energy in kcal/kg
ash percentage in combustible fuel
GCV of ash in kcal/kg
Boilers can be classified in to the following configurations:
Container boiler or Haycock boiler/Haystack boiler: a primitive "kettle" in which a open fire heats a partially filled water pot from below. 18th century Haycock boilers generally produced and stored large quantities of very low-pressure vapor, hardly above that of the atmosphere often. These could burn wood or frequently, coal. Efficiency was very 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 still left above to support the vapor (vapor space). This is the type of boiler used in almost all steam locomotives. The heat source is inside a furnace or firebox that needs to be held completely surrounded by water in order to keep the temp of the heating system surface below the boiling point. The furnace can be situated at one end of a fire-tube which lengthens the path of the hot gases, thus augmenting the heating system surface which may be further increased by making the gases reverse direction through a second parallel pipe or a lot of money 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 go through a bundle of fire tubes inside the barrel which greatly escalates the heating system surface compared to a single tube and further enhances heat transfer. Fire-tube boilers will often have a comparatively low rate of steam creation, but high vapor storage capacity. Fire-tube boilers burn solid fuels mostly, but are easily adjustable to people of the liquid or gas variety.
Diagram of the water-tube boiler.
Water-tube boiler: In this kind, pipes filled with water are arranged in the furnace in a genuine quantity of possible configurations. Often the drinking water tubes connect large drums, the lower ones made up of drinking water and the top ones vapor and drinking water; in other cases, such as a mono-tube boiler, water is circulated by a pump through a succession of coils. This kind generally gives high steam creation rates, but less storage space capacity than the above mentioned. Water pipe boilers can be designed to exploit any high temperature source and tend to be preferred in high-pressure applications because the high-pressure drinking 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 type of water-tube boiler where pipes are close collectively and drinking water is pumped through them. A flash boiler differs from the kind of mono-tube steam generator where the tube is permanently filled up with water. In a flash boiler, the pipe is kept so hot that the 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 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 following manner: the firebox includes an assembly of water pipes, 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" 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 Society of Mechanical Technicians (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 basic safety, security and design standards.[5 -
Historically, boilers were a source of many serious injuries and property destruction due to poorly understood engineering principles. Thin and brittle steel shells can rupture, while poorly welded or riveted seams could start, leading to a violent eruption of the pressurized vapor. When drinking water is changed into vapor it expands to over 1,000 times its original quantity and moves down vapor pipes at over 100 kilometres per hour. As a result of this, vapor is a superb way of moving energy and temperature around a site from a central boiler house to where it is needed, but without the right boiler give food to water treatment, a steam-raising flower are affected from size development and corrosion. At best, this raises energy costs and can result in poor quality vapor, reduced efficiency, shorter vegetation 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 vapor and smoke out of the air intake and firing chute, injuring the firemen who load the coal into the fire chamber. Extremely large boilers providing hundreds of horsepower to use factories can potentially demolish entire structures.[6 -
A boiler which has a loss of feed water and it is permitted to boil dry out can be hugely dangerous. If supply drinking water is sent in to the clear 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 basic safety steam valves. Draining of the boiler can also happen if a leak occurs in the vapor source lines that is bigger 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 taking place, and therefore 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 used at saturation temperature; that is, saturated vapor. Superheated steam boilers vaporize water and then further heat the vapor in a superheater. This provides steam at higher temperatures, but can decrease the overall thermal efficiency of the steam generating vegetable because the higher steam temperatures takes a higher flue gas exhaust temp.[citation needed - There are many ways to circumvent this problem, typically by providing an economizer that heats the give food to water, a combustion air heater in the hot flue gas exhaust path, or both. There are benefits to superheated steam that may, and will often, increase overall efficiency of both vapor generation and its utilization: increases in input heat range to a turbine should outweigh any cost in additional boiler problem and expense. There could be useful restrictions in using moist vapor also, as entrained condensation droplets will harm turbine blades.
Superheated steam presents unique safety concerns because, if any operational 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 intense heat and sound from such a leak indicates its presence clearly.
Superheater operation is similar to that of the coils on an air conditioning unit, although for a different purpose. The vapor piping is directed through the flue gas route in the boiler furnace. The heat 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 heat by radiation. Others are convection type, absorbing warmth from a liquid. Some are a mixture of the two types. Through either method, the extreme temperature in the flue gas path will also high temperature the superheater steam piping and the vapor within. While the temperatures of the steam in the superheater goes up, the pressure of the steam does 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 charged power flower.
Main article: Supercritical steam generator
Supercritical steam generators are frequently used for the production of energy. They operate at supercritical pressure. In contrast to a "subcritical boiler", a supercritical vapor 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 absolutely no generation of vapor bubbles within the water, because the pressure is above the critical pressure point of which steam bubbles can develop. As the fluid expands through the turbine phases, its thermodynamic state drops below the critical point as it does work turning the turbine which changes the power generator that power is ultimately extracted. The fluid at that point may be considered a mixture of steam and liquid droplets as it passes in to the condenser. This leads to somewhat less gasoline use and therefore 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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Boiler fittings and accessories
Pressuretrols to regulate the steam pressure in the boiler. Boilers generally have two or three 3 pressuretrols: a manual-reset pressuretrol, which functions as a safety by setting top of the limit of vapor pressure, the operating pressuretrol, which settings when the boiler fires to keep up pressure, and for boilers outfitted with a modulating burner, a modulating pressuretrol which controls the quantity of fire.
Security valve: It is utilized to relieve pressure and stop possible explosion of a boiler.
Water level signals: They show the operator the amount of fluid in the boiler, also known as a sight cup, water measure or water column.
Bottom blowdown valves: They provide a means for removing solid particulates that condense and lie on the bottom of the boiler. As the name implies, this valve is usually located directly on underneath of the boiler, and is sometimes opened to use the pressure in the boiler to push these particulates out.
Constant blowdown valve: This enables a small quantity of water to escape 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 transported 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 water boiler.
Flash container: High-pressure blowdown enters this vessel where in fact the steam can 'flash' safely and be 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 makeup water is moving to the boiler, thereby transferring the utmost 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 temp of the makeup water.
Hand holes: They may be metal plates installed in openings in "header" to permit for inspections & installing tubes and inspection of internal surfaces.
Vapor drum internals, some screen, scrubber & cans (cyclone separators).
Low-water cutoff: It really is a mechanical means (usually a float switch) that is utilized to turn from the burner or shut down gasoline to the boiler to prevent it from working once the drinking water moves below a certain point. If a boiler is "dry-fired" (burned without water in it) it can cause rupture or catastrophic failing.
Surface blowdown range: It offers a means for removing foam or other light-weight non-condensible chemicals that have a tendency to float on top of water inside the boiler.
Circulating pump: It 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 range. This can be installed to the medial side 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, 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 water is quickly warmed and this can reduce limescale.
Desuperheater tubes or bundles: Some pipes or bundles of pipes in the 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 vapor.
Chemical substance injection line: A connection to add chemicals for controlling feedwater pH.
Main vapor stop valve:
Main steam stop/check valve: It is utilized on multiple boiler installations.
Gasoline oil system:fuel oil heaters
Other essential items
Inspectors test pressure measure attachment: