JamesUtify
10.01.2018
00:31
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A boiler is a closed vessel in which water or other liquid is heated. The fluid will not boil. (In THE UNITED STATES, the word "furnace" is normally used if the reason is never to boil the liquid.) The warmed or vaporized fluid exits the boiler for use in various procedures or heating applications,[1 - [2 - including water heating, central heating, boiler-based power era, cooking, and sanitation.
Materials
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 elements of boilers due to corrosion and stress corrosion cracking.[3 - However, ferritic stainless steel is often found in superheater sections that will not be exposed to boiling drinking water, and electrically heated stainless steel shell boilers are allowed under the European "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 more fabricated in smaller size boilers easily. Historically, copper was often used for fireboxes (especially 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 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 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 use of steel instead, which is more powerful and cheaper, with welded construction, which is quicker and requires less labour. It ought to be noted, however, that wrought iron boilers corrode far slower than their modern-day steel counterparts, and are less vunerable to localized stress-corrosion and pitting. This makes the longevity of older wrought-iron boilers much superior to those of welded metal boilers.
Cast iron might be utilized for the heating vessel of local drinking water heaters. Although such heaters are usually termed "boilers" in some countries, their purpose is to produce warm water usually, not steam, and so they run at low pressure and stay away from boiling. The brittleness of cast iron makes it impractical for high-pressure steam boilers.
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Energy
The foundation 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 elements. Nuclear fission can be used as a heat source for generating steam also, either straight (BWR) or, generally, in specialised heat exchangers called "steam generators" (PWR). Warmth recovery vapor generators (HRSGs) use heat rejected from other processes such as gas turbine.
Boiler efficiency
there are two solutions to gauge the boiler efficiency 1) direct method 2) indirect method
Direct method -immediate method of 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 give food to drinking water in kcal/kg q= quantity of energy 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 gasoline in kcal/kg
ash percentage in combustible fuel
GCV of ash in kcal/kg
Configurations
Boilers can be classified in to the following configurations:
Pot boiler or Haycock boiler/Haystack boiler: a primitive "kettle" where a fire heats a partially filled drinking water box 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 wood or most often, coal. Efficiency was suprisingly low.
Flued boiler with one or two large flues-an early forerunner or kind of fire-tube boiler.
Diagram of a fire-tube boiler
Fire-tube boiler: Here, drinking water partially fills a boiler barrel with a small volume still left above to support the vapor (steam space). This is the type of boiler used in all steam locomotives nearly. Heat source is inside a furnace or firebox that has to be kept permanently surrounded by the water in order to keep the temp 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 system surface which may be further increased by making the gases invert direction through a second parallel tube or a bundle of multiple tubes (two-pass or come back flue boiler); on the other hand the gases may be studied along the edges and then under the boiler through flues (3-move boiler). In case of a locomotive-type boiler, a boiler barrel extends 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 compared to a single tube and further improves heat transfer. Fire-tube boilers will often have a comparatively low rate of vapor production, but high vapor storage capacity. Fire-tube boilers burn off solid fuels mainly, but are readily flexible to the people of the liquid or gas variety.
Diagram of a water-tube boiler.
Water-tube boiler: In this kind, pipes filled with drinking water are arranged in the furnace in a genuine quantity of possible configurations. Often the water pipes connect large drums, the lower ones containing water and top of the ones water and steam; in other cases, such as a mono-tube boiler, water is circulated by a pump through a succession of coils. This kind generally provides high vapor production rates, but less storage space capacity than the above. Water tube boilers can be designed to exploit any heat source and tend to be preferred in high-pressure applications because the high-pressure drinking water/vapor is included within small size pipes which can withstand the pressure with a thinner wall structure.
Flash boiler: A flash boiler is a specialized kind of water-tube boiler where tubes are close together and water is pumped through them. A flash boiler differs from the type of mono-tube steam generator where the tube is permanently filled with water. In a flash boiler, the pipe is held so hot that water give food to is quickly flashed into steam and superheated. Flash boilers experienced 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 combined in the next manner: the firebox includes an assembly of water pipes, called thermic siphons. The gases then pass through a conventional firetube boiler. Water-tube fireboxes were installed in many Hungarian locomotives,[citation needed - but have met with little success far away.
Sectional boiler. Within a solid iron sectional boiler, sometimes called a "pork chop boiler" the water is included inside cast iron areas.[citation needed - These areas are assembled on site to produce the finished boiler.
Safety
See also: Boiler explosion
To define and secure boilers safely, some professional specialized organizations such as the American Society of Mechanical Engineers (ASME) develop criteria and regulation rules. For example, the ASME Boiler and Pressure Vessel Code is a standard providing a wide range of rules and directives to ensure compliance of the boilers and other pressure vessels with protection, design and security standards.[5 -
Historically, boilers were a way to obtain many serious injuries and property destruction as a consequence to poorly understood engineering principles. Thin and brittle steel shells can rupture, while welded or riveted seams could start badly, leading to a violent eruption of the pressurized steam. When water is changed into 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 great way of moving energy and temperature around a niche site from a central boiler house to where it is needed, but without the right boiler feed water treatment, a steam-raising seed will suffer from range development and corrosion. At best, this increases energy costs and can result in poor quality steam, reduced efficiency, shorter plant life and unreliable operation. At worst, it can lead to catastrophic failing and loss of life. Collapsed or dislodged boiler tubes can also aerosol scalding-hot vapor and smoke from the air intake and firing chute, injuring the firemen who load the coal in to the open fire chamber. Extremely large boilers providing hundreds of horsepower to use factories could demolish entire buildings.[6 -
A boiler which has a loss of give food to drinking water and it is permitted to boil dry out can be hugely dangerous. If give food to water is sent in to the clear boiler then, the tiny cascade of inbound water instantly boils on contact with the superheated metal shell and leads to a violent explosion that cannot be managed even by safety vapor valves. Draining of the boiler can also happen if a leak occurs in the vapor source lines that is larger than the make-up drinking water source 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 condition from happening, and thus reduce their insurance claims.[7 - [8 -
Superheated steam boiler
A superheated boiler on a steam locomotive.
Main article: Superheater
Most boilers produce steam to be utilized at saturation temperature; that is, saturated steam. Superheated steam boilers vaporize the water and then further temperature the steam in a superheater. This provides vapor at much higher heat, but can decrease the overall thermal efficiency of the steam generating seed because the higher vapor heat takes a higher flue gas exhaust heat.[citation needed - There are many ways to circumvent this issue, typically by providing an economizer that heats the give food to drinking water, a combustion air heating unit in the hot flue gas exhaust path, or both. There are benefits to superheated vapor that may, and will often, increase overall efficiency of both steam generation and its own utilization: benefits in input heat to a turbine should outweigh any cost in additional boiler complication and expense. There could be practical restrictions in using damp 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 be completely superheated vapor, detection can be difficult, although the intense heat and sound from such a leak indicates its existence clearly.
Superheater procedure is similar to that of the coils on an fresh air conditioning unit, although for a different purpose. The vapor piping is directed through the flue gas path in the boiler furnace. The heat range in this area is between 1 typically,300 and 1,600 °C (2,372 and 2,912 °F). Some superheaters are glowing type; that is, they absorb warmth by rays. Others are convection type, absorbing heat from a fluid. Some are a mixture of the two 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 temp of the vapor in the superheater increases, the pressure of the steam 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 avoid harm to the turbine blading and associated piping.
Supercritical steam generator
Boiler for a charged power herb.
Main article: Supercritical steam generator
Supercritical steam generators are used for the production of electric power frequently. They operate at supercritical pressure. In contrast 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 fluid is neither water nor gas but a super-critical fluid. There is no generation of steam bubbles within water, because the pressure is above the critical pressure point of which vapor bubbles can form. As the fluid expands through the turbine stages, its thermodynamic state drops below the critical point as it does work turning the turbine which converts the power generator that power is ultimately extracted. The fluid at that point may be a mixture of steam and liquid droplets as it passes into the condenser. This leads to slightly less fuel use and therefore less greenhouse gas production. The term "boiler" should not be used for a supercritical pressure steam generator, as no "boiling" occurs in this product.
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Accessories
Boiler accessories and fittings
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 security by setting the top limit of vapor pressure, the working pressuretrol, which handles when the boiler fires to keep pressure, and for boilers outfitted with a modulating burner, a modulating pressuretrol which settings the quantity of fire.
Basic safety valve: It is utilized to relieve pressure and prevent possible explosion of the boiler.
Water level indications: They show the operator the level of fluid in the boiler, also known as a sight glass, water measure or water column.
Bottom level blowdown valves: They offer a means for removing solid particulates that condense and lie on underneath of a boiler. As the name suggests, this valve is usually located on underneath of the boiler, and is occasionally opened to use the pressure in the boiler to drive these particulates out.
Constant blowdown valve: This allows a small quantity of water to escape 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 vapor - an ailment known as priming. Blowdown is also often used to monitor the chemistry of the boiler drinking water.
Trycock: a kind of valve that is often use to manually check a liquid level in a tank. Most found on a water boiler commonly.
Flash container: High-pressure blowdown enters this vessel where the vapor can 'flash' safely and be found 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 make-up water is flowing to the boiler, thereby transferring the maximum amount of heat possible from the blowdown to the makeup water. No flash tank is generally needed as the blowdown discharged is near to the temp of the make-up water.
Hand openings: These are steel plates installed in openings in "header" to permit for inspections & installation of tubes and inspection of internal surfaces.
Steam drum internals, a series of display, scrubber & cans (cyclone separators).
Low-water cutoff: It really is a mechanical means (usually a float change) that is used to turn from the burner or shut down gasoline to the boiler to avoid it from working 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 failure.
Surface blowdown collection: It offers a way for removing foam or other lightweight non-condensible substances that tend to float together with water inside the boiler.
Circulating pump: It really is made to circulate water back again to the boiler after it has expelled a few 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, just below the water level, or to the top of the boiler.[10 -
Top feed: Within this design for feedwater injection, the water is fed to the top of the boiler. This can reduce boiler fatigue triggered by thermal stress. By spraying the feedwater over some trays the water is quickly heated and this can reduce limescale.
Desuperheater pipes or bundles: A series of tubes or bundles of tubes in water drum or the steam drum designed to cool superheated steam, in order to provide auxiliary equipment that does not need, or may be damaged by, dry steam.
Chemical injection line: A connection to add chemicals for controlling feedwater pH.
Steam accessories
Main vapor stop valve:
Steam traps:
Main steam stop/check valve: It is utilized on multiple boiler installations.
Combustion accessories
Fuel oil system:gas oil heaters
Gas system:
Coal system:
Soot blower
Other essential items
Pressure gauges:
Feed pumps:
Fusible plug:
Inspectors test pressure gauge attachment:
Name plate:
Registration plate: |
