A boiler is a closed vessel where drinking water or other liquid is heated. The fluid does not necessarily boil. (In THE UNITED STATES, the word "furnace" is normally used if the purpose is never to boil the fluid.) The warmed or vaporized liquid exits the boiler for use in a variety of processes or heating applications, including water heating, central heating system, boiler-based power generation, food preparation, and sanitation.
The pressure vessel of the boiler is usually made of steel (or alloy steel), or historically of wrought iron. Stainless steel, especially of the austenitic types, is not used in wetted parts of boilers due to corrosion and stress corrosion breaking. However, ferritic stainless is often used in superheater sections that won't be exposed to boiling drinking water, and electrically heated stainless shell boilers are allowed under the Western "Pressure Equipment Directive" for production of steam for sterilizers and disinfectors.
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 (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 steel) are used instead.
For a lot of the Victorian "age of vapor", the only materials used for boilermaking was the highest quality of wrought iron, with set up by rivetting. This iron was 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 instead relocated towards the use of metal, which is more powerful and cheaper, with welded construction, which is quicker and requires less labour. It ought to be mentioned, however, that wrought iron boilers corrode considerably slower than their modern-day steel counterparts, and are less susceptible 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 utilized for the heating 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 try to avoid boiling. The brittleness of cast iron makes it 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 used as a heat source for producing steam also, either directly (BWR) or, in most cases, in specialised warmth exchangers called "vapor generators" (PWR). Warmth 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 approach to boiler efficiency test is more functional or more common
boiler efficiency =Q*((Hg-Hf)/q)*(GCV *100 ) Q =Total vapor movement Hg= Enthalpy of saturated steam in k cal/kg Hf =Enthalpy of give food to drinking water in kcal/kg q= quantity of fuel 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 are in need of a subsequent parameter like
Ultimate analysis of energy (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:
Pot boiler or Haycock boiler/Haystack boiler: a primitive "kettle" where a fire heats a partially filled water pot from below. 18th century Haycock boilers produced and stored large quantities of very low-pressure vapor generally, often barely above that of the atmosphere. These could burn off 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 a fire-tube boiler
Fire-tube boiler: Here, water partially fills a boiler barrel with a little volume left above to support the steam (vapor space). This is the type of boiler used in all steam locomotives nearly. The heat source is in the furnace or firebox that has to be kept completely surrounded by the water in order to maintain the heat of the heating 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 making 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-move boiler). In case there is a locomotive-type boiler, a boiler barrel stretches from the firebox and the hot gases pass through a lot of money of fire tubes inside the barrel which greatly increases the heating surface compared to a single pipe and further improves heat transfer. Fire-tube boilers have a comparatively low rate of steam production usually, but high steam storage capacity. Fire-tube boilers burn solid fuels mainly, but are easily adaptable to the people of the liquid or gas 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 variety of possible configurations. The water tubes connect large drums Often, the lower ones filled with water and top of the ones vapor and drinking water; in other cases, such as a mono-tube boiler, water is circulated with a pump through a succession of coils. This kind generally provides high vapor production rates, but less storage space capacity than the above mentioned. Water tube boilers can be designed to exploit any heat source and tend to be preferred in high-pressure applications since the high-pressure drinking water/steam is contained within small diameter 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 jointly and water is pumped through them. A flash boiler differs from the kind of mono-tube steam generator where the tube is permanently filled with water. Super fast boiler, the tube is kept so hot that water give food to is quickly flashed into vapor and superheated. Flash boilers got some use in cars 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 the two above types have been mixed in the next manner: the firebox consists of 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, but have fulfilled with little success far away.
Sectional boiler. In a cast iron sectional boiler, sometimes called a "pork chop boiler" the water is included inside cast iron areas. These areas are assembled on site to generate the finished boiler.
See also: Boiler explosion
To define and secure boilers safely, some professional specialized organizations like the American Society of Mechanical Engineers (ASME) develop standards 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, security and design standards.
Historically, boilers were a source of many serious injuries and property destruction due to badly understood engineering principles. Thin and brittle steel shells can rupture, while welded or riveted seams could open up badly, resulting in a violent eruption of the pressurized vapor. When drinking water is changed into steam it expands to over 1,000 times its original travels and volume down steam pipes at over 100 kilometres each hour. As a result of this, vapor is a great 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 herb are affected from size formation and corrosion. At best, this increases energy costs and can lead to poor quality steam, reduced efficiency, shorter plant life and unreliable procedure. At worst, it can lead to 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 a huge selection of horsepower to use factories could demolish entire buildings.
A boiler which has a loss of feed drinking water and is permitted to boil dry out can be extremely dangerous. If give food to drinking water is sent into the clear boiler then, the small cascade of inbound drinking water instantly boils on contact with the superheated metal shell and leads to a violent explosion that can't be managed even by protection vapor valves. Draining of the boiler can also happen if a leak occurs in the vapor supply lines that is bigger than the make-up drinking water supply could replace. The Hartford Loop was developed in 1919 by the Hartford Steam Boiler and Insurance Company as a method to assist in preventing this problem from happening, and thereby reduce their insurance claims.
Superheated steam boiler
A superheated boiler on the steam locomotive.
Main article: Superheater
Most boilers produce steam to be used at saturation heat; that is, saturated steam. Superheated steam boilers vaporize the water and further heating the steam in a superheater then. This provides steam at higher temp, but can reduce the overall thermal efficiency of the vapor generating place because the higher steam heat range requires a higher flue gas exhaust temperature. There are many ways to circumvent this issue, typically by giving an economizer that heats the give food to water, a combustion air heating unit in the hot flue gas exhaust route, or both. There are advantages to superheated vapor that may, and will often, increase overall efficiency of both steam generation and its utilization: benefits in input heat to a turbine should outweigh any cost in additional boiler problem and expense. There can also be practical limitations in using damp 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 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 indicates its existence clearly.
Superheater operation is similar to that of the coils on an 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 field 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 liquid. Some are a combination of both types. Through either method, the extreme heat in the flue gas route will also warmth 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. 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 herb.
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 that occurs; the fluid is liquid nor gas but a super-critical fluid neither. There is absolutely no era of steam bubbles within water, because the pressure is above the critical pressure point at which vapor bubbles can develop. As the liquid expands through the turbine phases, its thermodynamic state drops below the critical point as it does work turning the turbine which converts the electrical generator that power is ultimately extracted. The fluid at that point may be considered a mixture of steam and liquid droplets as it passes into the condenser. This leads to somewhat less gasoline use and for that reason less greenhouse gas creation. The word "boiler" should not be used for a supercritical pressure steam generator, as no "boiling" occurs in this product.
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Boiler accessories and fittings
Pressuretrols to control the steam pressure in the boiler. Boilers generally have two or three 3 pressuretrols: a manual-reset pressuretrol, which functions as a protection by setting the upper limit of vapor pressure, the operating pressuretrol, which controls when the boiler fires to keep up pressure, as well as for boilers equipped with a modulating burner, a modulating pressuretrol which settings the amount of fire.
Security valve: It is utilized to alleviate pressure and prevent possible explosion of a boiler.
Water level signals: They show the operator the level of liquid in the boiler, also known as a sight glass, water measure or drinking water column.
Bottom blowdown valves: They offer a way for removing solid particulates that condense and rest on underneath of the boiler. As the name indicates, this valve is located straight on underneath of the boiler usually, and is occasionally opened to use the pressure in the boiler to drive these particulates out.
Continuous blowdown valve: This enables a small level of water to escape continuously. Its purpose is to prevent water in the boiler becoming saturated with dissolved salts. Saturation would business lead to foaming and cause drinking water droplets to be transported over with the vapor - a condition known as priming. Blowdown is often used to monitor the chemistry of the boiler drinking water also.
Trycock: a kind of valve that is often use to manually check a liquid level in a tank. Mostly found on a water boiler.
Flash container: High-pressure blowdown enters this vessel where the vapor can 'flash' safely and become 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 when make-up water is flowing 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 heat range of the make-up water.
Hand openings: They may be metal plates installed in openings in "header" to allow for inspections & installing pipes and inspection of inner surfaces.
Steam drum internals, a series of screen, scrubber & cans (cyclone separators).
Low-water cutoff: It is a mechanical means (usually a float switch) that is used to turn from the burner or shut down fuel to the boiler to prevent it from jogging once the water moves below a certain point. If a boiler is "dry-fired" (burnt 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 substances that tend to float on top of water inside the boiler.
Circulating pump: It is made to circulate drinking 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 installed to the medial side of the boiler, just below water level, or to the very best of the boiler.
Top give food to: With 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 a series of trays water is quickly heated and this can reduce limescale.
Desuperheater tubes or bundles: Some tubes or bundles of tubes in the water drum or the steam drum made to cool superheated steam, in order to provide auxiliary equipment that will not need, or may be damaged by, dry out vapor.
Chemical injection line: A link with add chemicals for controlling feedwater pH.
Main vapor stop valve:
Main vapor stop/check valve: It is used on multiple boiler installations.
Gasoline oil system:fuel oil heaters
Other essential items
Inspectors test pressure measure attachment: