|A boiler is a closed vessel where water or other fluid is heated. The fluid will not boil. (In North America, the word "furnace" is normally used if the purpose is not to boil the fluid.) The heated or vaporized liquid exits the boiler for use in various heating system or processes applications,[1 - [2 - including drinking water heating, central heating, boiler-based power generation, food preparation, and sanitation. |
The pressure vessel of the boiler is usually manufactured from steel (or alloy steel), or of wrought iron historically. Stainless steel, especially of the austenitic types, is not used in wetted elements of boilers credited to corrosion and stress corrosion breaking.[3 - However, ferritic stainless steel is often used in superheater sections that won't come in contact with 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.[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 more fabricated in smaller size boilers easily. 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 a lot of the Victorian "age group of vapor", the only material used for boilermaking was the highest grade of wrought iron, with assembly by rivetting. This iron was 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 moved towards the utilization of steel instead, which is more powerful and cheaper, with welded building, which is quicker and requires less labour. It should be observed, however, that wrought iron boilers corrode significantly 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 much superior to those of welded steel boilers.
Cast iron might be used for the heating system vessel of local 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 foundation of heating for a boiler is combustion of any of several fuels, such as wood, coal, oil, or gas. Electric vapor 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, in most cases, in specialised high temperature exchangers called "vapor generators" (PWR). Heat recovery steam generators (HRSGs) use heat rejected from other processes such as gas turbine.
there are two solutions to measure the boiler efficiency 1) direct method 2) indirect method
Direct method -direct method of boiler efficiency test is more useful or more common
boiler efficiency =Q*((Hg-Hf)/q)*(GCV *100 ) Q =Total vapor circulation Hg= Enthalpy of saturated steam in k cal/kg Hf =Enthalpy of give food to 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 need 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" where a fire heats a partially filled water container from below. 18th century Haycock boilers generally produced and stored large amounts of very low-pressure steam, hardly above that of the atmosphere often. These could burn off wood or frequently, coal. Efficiency was very 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, drinking water partially fills a boiler barrel with a small volume still left above to accommodate the vapor (steam space). This is the kind of boiler used in nearly all steam locomotives. The heat source is in the furnace or firebox that needs to be held completely surrounded by the water in order to keep up the heat 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 invert direction through another parallel pipe or a lot of money of multiple tubes (two-pass or come back flue boiler); alternatively the gases may be studied along the sides and then beneath the boiler through flues (3-move boiler). In case there is 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 increases the heating surface in comparison to a single tube and further improves heat transfer. Fire-tube boilers have a comparatively low rate of vapor creation usually, but high vapor storage capacity. Fire-tube boilers mostly burn off solid fuels, but are readily flexible to people of the liquid or gas variety.
Diagram of the water-tube boiler.
Water-tube boiler: In this kind, pipes filled with drinking water are arranged inside a furnace in a number of possible configurations. Often the water pipes connect large drums, the lower ones filled with water and top of the ones steam and drinking water; in other situations, like a mono-tube boiler, water is circulated with a pump through a succession of coils. This type provides high vapor creation rates generally, but less storage capacity than the above. Water pipe boilers can be made to exploit any temperature source and are generally preferred in high-pressure applications because the high-pressure drinking 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 type of water-tube boiler where pipes are close together and drinking water is pumped through them. A flash boiler differs from the kind of mono-tube steam generator in which the pipe is permanently filled up with water. In a flash boiler, the pipe is held so hot that the water feed is quickly flashed into vapor and superheated. Flash boilers got some use in cars in the 19th century which 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 combined in the following manner: the firebox consists of an set up of water pipes, called thermic siphons. The gases then go through a conventional 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 cast iron sectional boiler, sometimes called a "pork chop boiler" the water is contained inside solid iron areas.[citation needed - These sections are assembled on site to create the finished boiler.
See also: Boiler explosion
To define and secure boilers safely, some professional specialized organizations like the American Society of Mechanical Technical engineers (ASME) develop requirements 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 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 metallic shells can rupture, while welded or riveted seams could open up badly, leading to a violent eruption of the pressurized steam. When drinking water is converted to steam it expands to over 1,000 times its original travels and volume down steam pipes at over 100 kilometres per hour. As a result of this, steam 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 feed water treatment, a steam-raising vegetable are affected from range corrosion and formation. At best, this increases energy costs and can result in poor quality vapor, reduced efficiency, shorter vegetation and unreliable operation. At worst, it can lead to catastrophic failure and lack of life. Collapsed or dislodged boiler tubes can also aerosol scalding-hot steam and smoke from the air intake and firing chute, injuring the firemen who fill the coal in to the open fire chamber. Extremely large boilers providing hundreds of horsepower to operate factories can potentially demolish entire structures.[6 -
A boiler which has a loss of feed water and is permitted to boil dry can be hugely dangerous. If supply water is sent in to the bare boiler then, the small cascade of incoming water instantly boils on connection with the superheated steel shell and leads to a violent explosion that cannot be managed even by basic safety 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 water source could replace. The Hartford Loop was created in 1919 by the Hartford Vapor Boiler and INSURANCE PROVIDER as a method to help prevent this problem from happening, and thus reduce their insurance claims.[7 - [8 -
Superheated steam boiler
A superheated boiler on the steam locomotive.
Main article: Superheater
Most boilers produce vapor to be utilized at saturation temperatures; that is, saturated steam. Superheated steam boilers vaporize the water and additional heating the steam in a superheater then. This provides steam at higher temp, but can reduce the overall thermal efficiency of the steam generating plant because the bigger vapor temperature takes a higher flue gas exhaust temperature.[citation needed - There are several 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 route, or both. You can find benefits to superheated steam that may, and often will, increase overall efficiency of both steam generation and its own utilization: benefits in input heat range to a turbine should outweigh any cost in additional boiler problem and expense. There may be practical 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 escape, the ruthless and temperature can cause serious, instantaneous harm to anyone in its path. Since the escaping steam will 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 air conditioning unit, although for a different purpose. The steam piping is directed through the flue gas route in the boiler furnace. The temp in this field is between 1 typically,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 temperature from a fluid. Some are a combination of both types. Through either method, the extreme warmth in the flue gas path will also high temperature the superheater steam piping and the steam within. While the temperature of the steam in the superheater goes up, the pressure of the vapor will 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 damage to the turbine blading and associated piping.
Supercritical steam generator
Boiler for a charged power vegetable.
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 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 no generation of steam bubbles within the water, because the pressure is above the critical pressure point of 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 converts the electrical generator from which power is ultimately extracted. The liquid at that time may be a mixture of steam and liquid droplets as it passes into the condenser. This leads to slightly less energy use and therefore less greenhouse gas creation. The word "boiler" should not be used for a supercritical pressure steam generator, as no "boiling" occurs in this device.
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Boiler accessories and fittings
Pressuretrols to regulate the vapor 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 working pressuretrol, which settings when the boiler fires to keep up pressure, and for boilers outfitted with a modulating burner, a modulating pressuretrol which handles the quantity of fire.
Basic safety valve: It is utilized to alleviate pressure and stop possible explosion of a boiler.
Water level indicators: They show the operator the amount of liquid in the boiler, also known as a sight glass, water measure or drinking water column.
Bottom blowdown valves: They provide a way for removing solid particulates that condense and rest on underneath of the boiler. As the name implies, this valve is located straight on the bottom of the boiler usually, and is sometimes opened up to use the pressure in the boiler to push these particulates out.
Continuous blowdown valve: This enables a small quantity of water to flee continuously. Its purpose is to prevent water in the boiler becoming saturated with dissolved salts. Saturation would lead to foaming and cause drinking 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 kind of valve that is often use to manually check a liquid level in a tank. Most commonly found on a drinking water boiler.
Flash tank: High-pressure blowdown enters this vessel where in fact the steam can 'flash' safely and become 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 system allows the boiler to blowdown only when make-up water is moving to the boiler, thereby transferring the maximum amount of heat possible from the blowdown to the make-up water. No flash tank is generally needed as the blowdown discharged is close to the temperatures of the make-up water.
Hand holes: They are metal plates installed in openings in "header" to permit for inspections & installing tubes and inspection of internal surfaces.
Vapor drum internals, a series of display, scrubber & cans (cyclone separators).
Low-water cutoff: It 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 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 failing.
Surface blowdown series: It offers a way for removing foam or other light-weight non-condensible chemicals that have a tendency to float together with water inside the boiler.
Circulating pump: It really is made to circulate water back 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 series. This can be fitted to the medial side of the boiler, just below water level, or to the very best of the boiler.[10 -
Top feed: With this design for feedwater injection, water is fed to the top of the boiler. This can reduce boiler exhaustion caused by thermal stress. By spraying the feedwater over some trays the water is quickly heated which can reduce limescale.
Desuperheater pipes or bundles: A series of pipes or bundles of pipes in water drum or the steam drum made to cool superheated steam, in order to provide auxiliary equipment that does 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 vapor stop/check valve: It can be used on multiple boiler installations.
Fuel oil system:gas oil heaters
Other essential items
Inspectors test pressure gauge attachment: