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Page : < 1 2 3 ... 4895 [4896] 4897 ... 15653 15654 15655 >
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| Jameswaw |  Posted : 01/08/18 20:51
A boiler is a closed vessel where water or other fluid is heated. The fluid does not 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 procedures or heating system applications,[1][2] including drinking 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 breaking.[3] However, ferritic stainless is often used in superheater sections that will not come in contact with boiling drinking water, and electrically heated stainless 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
In live steam models, copper or brass is often used since it is more fabricated in smaller size boilers easily. Historically, copper was often used for fireboxes (particularly 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 a lot of the Victorian "age group of vapor", the only material used for boilermaking was the best grade of wrought iron, with set up by rivetting. This iron was 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 relocated towards the use of steel instead, which is stronger 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 pitting and stress-corrosion. This makes the durability of older wrought-iron boilers considerably more advanced than those of welded steel boilers.
Cast iron can be utilized for the heating vessel of local water heaters. Although such heaters are usually termed "boilers" in a few countries, their purpose will be to produce warm water, not steam, and so they 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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Energy
The foundation of heating for a boiler is combustion of some of several fuels, such as wood, coal, oil, or gas. Electric steam boilers use level of resistance- or immersion-type heating system elements. Nuclear fission can be used as a heat source for generating steam also, either straight (BWR) or, in most cases, in specialised warmth exchangers called "steam generators" (PWR). Heat recovery vapor generators (HRSGs) use heat rejected from other procedures such as gas turbine.
Boiler efficiency
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 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 feed 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 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
Configurations
Boilers can be classified in to the following configurations:
Pot boiler or Haycock boiler/Haystack boiler: a primitive "kettle" where a open fire heats a partially filled water container from below. 18th century Haycock boilers generally produced and stored large quantities of very low-pressure vapor, barely above that of the atmosphere often. These could burn off wood or most often, coal. Efficiency was suprisingly 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 small volume left above to support the vapor (vapor space). This is the type of boiler used in almost all steam locomotives. Heat source is in the furnace or firebox that has to be held permanently surrounded by the water in order to keep up the heat range of the heating surface below the boiling point. The furnace can be situated at one end of the fire-tube which lengthens the path of the hot gases, thus augmenting the heating surface which may be further increased by causing the gases reverse direction through a second parallel pipe or a lot of money of multiple tubes (two-pass or come back flue boiler); additionally the gases may be taken along the edges and then under the boiler through flues (3-pass boiler). In case there is a locomotive-type boiler, a boiler barrel expands from the firebox and the hot gases go through a bundle of fire tubes inside the barrel which greatly escalates the heating surface in comparison to a single tube and further enhances heat transfer. Fire-tube boilers will often have a comparatively low rate of steam production, but high steam 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 type, pipes filled up with water are arranged inside a furnace in several possible configurations. Often the drinking water tubes connect large drums, the low ones containing water and the top ones steam and water; in other cases, such as 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 space capacity than the above. Water tube boilers can be made to exploit any warmth source and tend to be preferred in high-pressure applications because the high-pressure water/steam is contained 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 drinking water is pumped through them. A flash boiler differs from the type of mono-tube vapor generator in which the pipe is permanently filled with water. In a flash boiler, the tube is held so hot that the water give food to is quickly flashed into vapor and superheated. Flash boilers experienced some use in cars in the 19th century and this use continued into the early 20th century. .
1950s design steam locomotive boiler, from a Victorian Railways J class
Fire-tube boiler with Water-tube firebox. Sometimes the two above types have been combined in the next manner: the firebox consists of an assembly of water pipes, called thermic siphons. The gases go through a typical firetube boiler then. Water-tube fireboxes were installed in many Hungarian locomotives,[citation needed] but have met 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 ensemble iron areas.[citation needed] These areas are assembled on site to generate the finished boiler.
Safety
See also: Boiler explosion
To define and secure boilers safely, some professional specialized organizations like the American Society of Mechanical Designers (ASME) develop requirements and regulation rules. For instance, 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 safety, security and design 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 metallic shells can rupture, while welded or riveted seams could start poorly, leading to a violent eruption of the pressurized vapor. When 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 temperature around a site from a central boiler house to where it is needed, but with no right boiler feed water treatment, a steam-raising plant will suffer from level corrosion and formation. At best, this increases energy costs and can result in poor quality steam, reduced efficiency, shorter vegetation and unreliable operation. At worst, it can lead to catastrophic loss and failure 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.[6]
A boiler that has a loss of feed drinking water and it is permitted to boil dry can be extremely dangerous. If nourish drinking water is sent into the empty boiler then, the small cascade of inbound drinking water instantly boils on connection with the superheated metal shell and leads to a violent explosion that can't be managed even by basic safety 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 water supply could replace. The Hartford Loop was developed in 1919 by the Hartford Vapor Boiler and INSURANCE PROVIDER as a strategy to assist in preventing this condition from occurring, and thus reduce their insurance statements.[7][8]
Superheated steam boiler
A superheated boiler on a steam locomotive.
Main article: Superheater
Most boilers produce vapor to be used at saturation heat range; that is, saturated vapor. Superheated vapor boilers vaporize the water and then further temperature the steam in a superheater. This provides steam at much higher temperature, but can decrease the overall thermal efficiency of the steam generating herb because the bigger steam heat range requires a higher flue gas exhaust heat range.[citation needed] There are many ways to circumvent this issue, by providing an economizer that heats the feed water typically, a combustion air heating unit in the hot flue gas exhaust path, or both. There are benefits to superheated steam that may, and will often, increase overall efficiency of both vapor 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 moist vapor also, as entrained condensation droplets will harm turbine blades.
Superheated steam presents unique safety concerns because, if any system component fails and allows steam to escape, the high temperature and pressure can cause serious, instantaneous injury to anyone in its path. Since the escaping steam will at first be completely superheated vapor, detection can be difficult, although the intense 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 temperatures in this field is normally between 1,300 and 1,600 °C (2,372 and 2,912 °F). Some superheaters are glowing type; that is, they absorb temperature by rays. 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 heat the superheater steam piping and the steam within also. While the temperatures of the vapor in the superheater increases, the pressure of the vapor will 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 vegetable.
Main article: Supercritical steam generator
Supercritical steam generators are used for the production of electric power frequently. They operate at supercritical pressure. As opposed to a "subcritical boiler", a supercritical vapor 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 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 at which steam bubbles can form. As the fluid expands through the turbine levels, its thermodynamic state drops below the critical point as it does work turning the turbine which turns the electrical generator that power is eventually extracted. The fluid at that time may be considered a mix of vapor and liquid droplets as it passes in to the condenser. This results in less fuel use and therefore less greenhouse gas production slightly. The word "boiler" should not be used for a supercritical pressure vapor generator, as no "boiling" occurs in this device.
Boiler Repairs Bethnal Green, Shoreditch, E2, Boiler Breakdown Emergency Service Show more...
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 protection by setting the top limit of vapor pressure, the working pressuretrol, which settings when the boiler fires to maintain pressure, and for boilers outfitted with a modulating burner, a modulating pressuretrol which controls the amount of fire.
Basic safety valve: It is utilized to alleviate pressure and stop 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 gauge or water column.
Bottom blowdown valves: They provide a means for removing solid particulates that condense and rest on underneath of a boiler. As the name suggests, this valve is situated directly on the bottom of the boiler usually, and is sometimes opened to use the pressure in the boiler to drive these particulates out.
Constant blowdown valve: This enables a small level of water to escape continuously. Its purpose is to avoid the 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 vapor - an ailment known as priming. Blowdown is often used to monitor the chemistry of the boiler water also.
Trycock: a kind of valve that is often use to manually check a water level in a container. Most commonly found on a water boiler.
Flash container: High-pressure blowdown enters this vessel where in fact the steam 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/continuous heat recovery system: This technique allows the boiler to blowdown only once makeup water is flowing to the boiler, thereby transferring the maximum amount of heat possible from the blowdown to the makeup water. No flash container is normally needed as the blowdown discharged is close to the temperature of the makeup water.
Hand holes: They are steel plates installed in openings in "header" to allow for inspections & installing 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 utilized to turn from the burner or shut off fuel to the boiler to avoid it from working once the drinking water moves below a certain point. If a boiler is "dry-fired" (burned without water in it) it can cause rupture or catastrophic failure.
Surface blowdown line: It offers 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 designed to circulate water back 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 collection. This can be fitted to the side of the boiler, below water level just, or to the very best of the boiler.[10]
Top give food to: Within this design for feedwater injection, water is fed to the top of the boiler. This may reduce boiler fatigue caused by thermal stress. By spraying the feedwater over some trays the water is quickly heated which can reduce limescale.
Desuperheater tubes or bundles: Some pipes or bundles of pipes in the water drum or the vapor drum designed to cool superheated steam, in order to provide auxiliary equipment that does not need, or may be damaged by, dry vapor.
Chemical substance injection line: A link with add chemicals for controlling feedwater pH.
Steam accessories
Main steam stop valve:
Steam traps:
Main steam stop/check valve: It is utilized on multiple boiler installations.
Combustion accessories
Gas oil system:gasoline 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:
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