A boiler is a closed vessel in which water or other liquid is heated. The liquid does not always boil. (In North America, the term "furnace" is normally used if the purpose is never to boil the fluid.) The warmed or vaporized liquid exits the boiler for use in various procedures or heating system applications,[1 - [2 - including drinking water heating, central heating, 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 found in wetted parts of boilers thanks to stress and corrosion corrosion breaking.[3 - However, ferritic stainless is often used in superheater sections that won't come in contact with boiling water, and electrically heated stainless steel 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 easier fabricated in smaller size boilers. Historically, copper was often used for fireboxes (particularly for vapor 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 much of the Victorian "age 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), mentioned 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 steel instead, which is stronger and cheaper, with welded construction, which is quicker and requires less labour. It should be noted, however, that wrought iron boilers corrode significantly slower than their modern-day steel counterparts, and are less susceptible to localized pitting and stress-corrosion. This makes the longevity of old wrought-iron boilers considerably superior to those of welded steel boilers.
Cast iron may be used for the heating system vessel of home water heaters. Although such heaters are usually termed "boilers" in some countries, their purpose is usually to produce warm 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 steam boilers.
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The source of heating for a boiler is combustion of some of several fuels, such as wood, coal, oil, or natural gas. Electric vapor boilers use resistance- or immersion-type heating system elements. Nuclear fission is also used as a heat source for producing steam, either directly (BWR) or, in most cases, in specialised temperature exchangers called "vapor generators" (PWR). Temperature recovery steam generators (HRSGs) use heat rejected from other processes such as gas turbine.
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 useful or 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= quantity of gasoline 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 fuel 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 drinking water box from below. 18th century Haycock boilers produced and stored large amounts of very low-pressure steam generally, often hardly above that of the atmosphere. These could burn wood or frequently, 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, water partially fills a boiler barrel with a little volume remaining above to accommodate the steam (steam space). This is the kind of boiler used in all steam locomotives nearly. Heat source is in the furnace or firebox that has to be kept permanently 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 path of the hot gases, thus augmenting the heating system surface which may be further increased by causing the gases reverse direction through another parallel pipe or a bundle of multiple tubes (two-pass or come back flue boiler); alternatively the gases may be studied along the sides and then under the boiler through flues (3-pass boiler). In case of a locomotive-type boiler, a boiler barrel extends from the firebox and the hot gases go through a bundle of fire tubes inside the barrel which greatly increases the heating system surface compared to a single pipe and further increases heat transfer. Fire-tube boilers will often have a comparatively low rate of steam creation, but high steam storage capacity. Fire-tube boilers burn solid fuels mainly, but are readily adaptable to those of the gas or water variety.
Diagram of a water-tube boiler.
Water-tube boiler: In this type, tubes filled up with drinking water are arranged inside a furnace in a genuine quantity of possible configurations. Often the drinking water tubes connect large drums, the low ones filled with 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 kind generally provides high steam production rates, but less storage capacity than the above. Water tube boilers can be designed to exploit any warmth source and are generally preferred in high-pressure applications since the high-pressure drinking water/steam is included within small diameter 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 collectively and water is pumped through them. A flash boiler differs from the kind of mono-tube vapor generator where the pipe is permanently filled with water. Super fast boiler, the pipe is kept so hot that water feed is quickly flashed into steam and superheated. Flash boilers had 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 next manner: the firebox includes an set up of water pipes, called thermic siphons. The gases pass through a conventional firetube boiler then. Water-tube fireboxes were installed in many Hungarian locomotives,[citation needed - but have fulfilled with little success in other countries.
Sectional boiler. Within a solid iron sectional boiler, sometimes called a "pork chop boiler" the water is contained inside cast iron areas.[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 such as the American Society of Mechanical Technical engineers (ASME) develop criteria and regulation rules. For example, the ASME Boiler and Pressure Vessel Code is a typical providing a wide range of rules and directives to ensure compliance of the boilers and other pressure vessels with security, security and design standards.[5 -
Historically, boilers were a source of many serious injuries and property destruction as a consequence 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 converted to vapor it expands to over 1,000 times its original travels and volume down steam pipes at over 100 kilometres per hour. Because of this, steam is a great way of moving energy and warmth around a niche 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 level development and corrosion. At best, this boosts energy costs and can result in poor quality steam, reduced efficiency, shorter plant life and unreliable operation. At worst, it can lead to catastrophic reduction and failure of life. Collapsed or dislodged boiler pipes can also spray scalding-hot vapor and smoke out of the air intake and firing chute, injuring the firemen who insert the coal in to the fire chamber. Extremely large boilers providing a huge selection of horsepower to use factories can potentially demolish entire structures.[6 -
A boiler which has a loss of give food to water and is permitted to boil dry out can be hugely dangerous. If nourish water is sent into the empty boiler then, the tiny cascade of incoming drinking water instantly boils on connection with the superheated metal shell and leads to a violent explosion that can't be controlled even by protection steam valves. Draining of the boiler can also happen if a leak occurs in the steam source lines that is bigger than the make-up drinking water supply could replace. The Hartford Loop was created in 1919 by the Hartford Steam Boiler and Insurance Company as a strategy to assist in preventing this condition from taking place, and therefore 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 used at saturation temperature; that is, saturated steam. Superheated steam boilers vaporize the water and additional heat up the steam in a superheater then. This provides steam at much higher temp, but can decrease the overall thermal efficiency of the steam generating plant because the higher steam heat range takes a higher flue gas exhaust temp.[citation needed - There are several ways to circumvent this issue, by giving an economizer that heats the give food to water typically, a combustion air heating unit in the hot flue gas exhaust route, or both. There are benefits to superheated steam that may, and often will, increase overall efficiency of both vapor generation and its own utilization: benefits in input temp to a turbine should outweigh any cost in additional boiler problem and expense. There could be useful restrictions in using wet steam 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 flee, the ruthless and temperature can cause serious, instantaneous harm to anyone in its path. Since the escaping steam will at first be completely superheated vapor, detection can be difficult, although the extreme heat and sound from such a leak indicates its existence 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 temp 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 high temperature by rays. Others are convection type, absorbing temperature from a fluid. Some are a combination of both 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 range of the vapor in the superheater goes up, the pressure of the vapor does 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 power seed.
Main article: Supercritical steam generator
Supercritical steam generators are frequently used for the production of energy. They operate at supercritical pressure. As opposed 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 liquid is neither water nor gas but a super-critical liquid. There is no era of vapor bubbles within water, because the pressure is above the critical pressure point at which vapor bubbles can form. As the fluid expands through the turbine phases, its thermodynamic state drops below the critical point as it does work turning the turbine which turns the power generator from which power is eventually extracted. The liquid at that time may be a mixture of steam and liquid droplets as it goes by in to the condenser. This leads to slightly less gasoline use and for that reason less greenhouse gas production. The term "boiler" should not 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 basic safety by setting the top limit of vapor pressure, the operating pressuretrol, which handles when the boiler fires to keep up pressure, and for boilers outfitted with a modulating burner, a modulating pressuretrol which settings the quantity of fire.
Protection valve: It is used to alleviate pressure and stop possible explosion of the boiler.
Water level signals: They show the operator the amount of fluid in the boiler, known as a sight cup also, water gauge or drinking water column.
Bottom blowdown valves: They offer a means for removing solid particulates that condense and lay on the bottom of the boiler. As the name suggests, this valve is usually located directly on the bottom of the boiler, and is sometimes opened up to use the pressure in the boiler to drive these particulates out.
Constant blowdown valve: This allows a small level of water to escape continuously. Its purpose is to avoid water in the boiler becoming saturated with dissolved salts. Saturation would lead to foaming and cause drinking water droplets to be transported 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. 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 as the ambient pressure blowdown flows to drain.
Automatic blowdown/constant heat recovery system: This technique 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 container is generally needed as the blowdown discharged is near to the heat range of the makeup water.
Hand openings: These are steel plates installed in openings in "header" to allow for inspections & installation of pipes and inspection of internal surfaces.
Steam drum internals, some display, 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 fuel to the boiler to prevent it from running once the drinking water moves below a certain point. If a boiler is "dry-fired" (burned without drinking water in it) it can cause rupture or catastrophic failure.
Surface blowdown line: It offers a means for removing foam or other lightweight non-condensible substances that tend to float on top of the water inside the boiler.
Circulating pump: It really 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 series. This may be fitted to the relative side of the boiler, below water level just, or to the top of the boiler.[10 -
Top give food to: Within this design for feedwater injection, the water is fed to the top of the boiler. This may reduce boiler exhaustion triggered by thermal stress. By spraying the feedwater over some trays water is quickly warmed which can reduce limescale.
Desuperheater pipes or bundles: A series of pipes or bundles of pipes in water drum or the vapor drum designed to cool superheated steam, in order to provide 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 can be used on multiple boiler installations.
Gasoline oil system:fuel oil heaters
Other essential items
Inspectors test pressure gauge attachment: