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A boiler is a closed vessel where drinking water or other fluid is heated. The liquid does not always boil. (In THE UNITED STATES, the term "furnace" is normally used if the reason is not to boil the fluid.) The heated or vaporized fluid exits the boiler for use in various processes or heating applications,[1 - [2 - including drinking water heating, central heating system, boiler-based power era, 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 elements of boilers credited to corrosion and stress corrosion breaking.[3 - However, ferritic stainless is often found in superheater sections that won't come in contact with boiling 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 easier fabricated in smaller size boilers. Historically, copper was often used for fireboxes (especially for vapor locomotives), due to 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 steel) are used instead.
For much of the Victorian "age group of steam", the only materials used for boilermaking was the highest quality of wrought iron, with assembly 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 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 structure, which is quicker and requires less labour. It should be observed, however, that wrought iron boilers corrode significantly slower than their modern-day steel counterparts, and are less vunerable to localized stress-corrosion and pitting. This makes the durability of older wrought-iron boilers significantly more advanced than those of welded metal boilers.
Cast iron might be used for the heating system vessel of domestic drinking water heaters. Although such heaters are usually termed "boilers" in some countries, their purpose will be 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 vapor boilers.
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The source of heating for a boiler is combustion of any of several fuels, such as wood, coal, oil, or natural gas. Electric vapor boilers use resistance- or immersion-type heating elements. Nuclear fission is utilized as a heat source for generating steam also, either straight (BWR) or, in most cases, in specialised heat exchangers called "steam generators" (PWR). Heat recovery vapor generators (HRSGs) use the heat rejected from other procedures such as gas turbine.
there are two methods to gauge the boiler efficiency 1) direct method 2) indirect method
Immediate method -immediate method of boiler efficiency test is more usable or more common
boiler efficiency =Q*((Hg-Hf)/q)*(GCV *100 ) Q =Total vapor movement Hg= Enthalpy of saturated vapor 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 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 gasoline 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 fire heats a partially filled drinking water container from below. 18th century Haycock boilers generally produced and stored large quantities of very low-pressure steam, hardly above that of the atmosphere often. These could burn wood or frequently, 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 remaining above to support the vapor (steam space). This is the kind of boiler used in almost all steam locomotives. Heat source is inside a furnace or firebox that has to be kept completely surrounded by the water in order to maintain 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 may 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 sides and then under the boiler through flues (3-pass boiler). In case of a locomotive-type boiler, a boiler barrel expands from the firebox and the hot gases go through a lot of money of fire tubes inside the barrel which greatly increases the heating system surface in comparison to a single tube and further boosts heat transfer. Fire-tube boilers usually have a comparatively low rate of steam creation, but high vapor storage capacity. Fire-tube boilers burn off solid fuels mainly, but are readily adaptable to those of the gas or liquid variety.
Diagram of the water-tube boiler.
Water-tube boiler: In this type, pipes filled with drinking water are arranged in the furnace in a number of possible configurations. Usually the water pipes connect large drums, the lower ones filled with drinking water and the upper ones steam and water; 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 creation rates, but less storage space capacity than the above. Water pipe boilers can be made to exploit any temperature source and tend to be preferred in high-pressure applications because the high-pressure drinking water/steam is included 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 in which tubes are close collectively 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 had some use in automobiles in the 19th century and this use continued in to 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 following manner: the firebox contains 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. In a cast iron sectional boiler, sometimes called a "pork chop boiler" the water is contained inside ensemble iron areas.[citation needed - These sections 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 Designers (ASME) develop criteria and regulation rules. For instance, the ASME Boiler and Pressure Vessel Code is a typical providing a wide range 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 way to obtain many serious injuries and property destruction due to badly understood engineering principles. Thin and brittle metal shells can rupture, while badly welded or riveted seams could open up, leading to a violent eruption of the pressurized steam. 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, vapor is a superb way of moving energy and high temperature around a niche 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 are affected from range 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 loss and failure of life. Collapsed or dislodged boiler pipes can also aerosol scalding-hot steam and smoke from the air intake and firing chute, injuring the firemen who fill the coal into the open fire chamber. Extremely large boilers providing a huge selection of horsepower to use factories could demolish entire buildings.[6 -
A boiler that has a loss of feed water and it is permitted to boil dry can be extremely dangerous. If give food to water is sent into the bare boiler then, the small cascade of incoming water instantly boils on connection with the superheated metal shell and leads to a violent explosion that cannot be managed even by security 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 drinking water supply could replace. The Hartford Loop was invented in 1919 by the Hartford Steam Boiler and Insurance Company as a method to assist in preventing 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 temp; that is, saturated vapor. Superheated steam boilers vaporize the water and further heat the steam in a superheater then. This provides vapor at much higher temp, but can decrease the overall thermal efficiency of the vapor generating vegetable because the bigger vapor temp requires a higher flue gas exhaust temperatures.[citation needed - There are many ways to circumvent this issue, by giving an economizer that heats the feed drinking water typically, a combustion air heater in the hot flue gas exhaust path, or both. A couple of advantages to superheated vapor that may, and will often, increase overall efficiency of both vapor generation and its own utilization: increases in input heat to a turbine should outweigh any cost in additional boiler complication 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 temperature and pressure 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 clearly indicates its presence.
Superheater procedure 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 path in the boiler furnace. The heat in this area is normally between 1,300 and 1,600 °C (2,372 and 2,912 °F). Some superheaters are radiant type; that is, they absorb warmth by radiation. Others are convection type, absorbing temperature from a liquid. Some are a mixture of the two types. Through either method, the extreme heat in the flue gas path will also high temperature the superheater vapor piping and the steam within. While the temperatures of the steam in the superheater goes up, the pressure of the steam 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 prevent damage to the turbine blading and associated piping.
Supercritical steam generator
Boiler for a power plant.
Main article: Supercritical steam generator
Supercritical steam generators are generally used for the production of electric power. 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 that occurs; the fluid is neither water nor gas but a super-critical liquid. There is absolutely no generation of steam 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 phases, its thermodynamic condition drops below the critical point as it can work turning the turbine which changes the power generator from which power is ultimately extracted. The fluid at that point may be a mixture of vapor and liquid droplets as it passes in to the condenser. This leads to less fuel use and for that reason less greenhouse gas production slightly. 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 2 or 3 3 pressuretrols: a manual-reset pressuretrol, which functions as a basic safety by setting the upper limit of steam pressure, the operating pressuretrol, which handles when the boiler fires to keep up pressure, as well as for boilers equipped with a modulating burner, a modulating pressuretrol which handles the amount of fire.
Security valve: It can be used to alleviate pressure and prevent possible explosion of a boiler.
Water level indications: They show the operator the level of fluid in the boiler, also known as a view cup, water gauge or drinking water column.
Bottom blowdown valves: They provide a way for removing solid particulates that condense and lay on the bottom of the boiler. As the name indicates, this valve is usually located on underneath of the boiler, and is sometimes opened to use the pressure in the boiler to drive these particulates out.
Continuous blowdown valve: This allows a small level of water to flee continuously. Its purpose is to avoid water in the boiler becoming saturated with dissolved salts. Saturation would business lead to foaming and cause water droplets to be transported over with the steam - a condition 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 water level in a tank. Most commonly found on a water boiler.
Flash tank: High-pressure blowdown enters this vessel where the steam can 'flash' safely and be found 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 technique allows the boiler to blowdown only when 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 normally needed as the blowdown discharged is near to the heat range of the makeup water.
Hand holes: They may be metal plates installed in openings in "header" to allow for inspections & installation of pipes and inspection of inner 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 used to turn from the burner or shut off gasoline to the boiler to prevent it from running once the water runs 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 substances that tend to float on top of 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 may be fitted to the side of the boiler, below the 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 exhaustion triggered by thermal stress. By spraying the feedwater over a series of trays the water is quickly heated and this can reduce limescale.
Desuperheater tubes or bundles: A series of tubes or bundles of pipes in water drum or the vapor drum designed to cool superheated vapor, in order to supply auxiliary equipment that does not need, or may be damaged by, dry steam.
Chemical substance injection line: A connection to add chemicals for controlling feedwater pH.
Main vapor stop valve:
Main vapor stop/check valve: It is utilized on multiple boiler installations.
Fuel oil system:gasoline oil heaters
Other essential items
Inspectors test pressure gauge attachment: