Boiler Repairs Brockley, Crofton Park, Honor Oak Park, SE4, Boiler Breakdown Emergency Service
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A boiler is a closed vessel in which water or other fluid is heated. The fluid does 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 a variety of processes or heating applications,[1][2] including water heating, central heating system, boiler-based power era, food preparation, and sanitation.
Materials
The pressure vessel of a boiler is usually made of steel (or alloy steel), or of wrought iron historically. Stainless steel, of the austenitic types especially, is not found in wetted parts of boilers due to stress and corrosion corrosion cracking.[3] However, ferritic stainless is often found in superheater sections that won't be exposed to boiling drinking water, and electrically heated stainless 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
In live steam models, copper or brass is often used since it is easier fabricated in smaller size boilers. 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 a lot of the Victorian "age of steam", the only materials used for boilermaking was the best grade 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 instead relocated towards the use of steel, which is stronger and cheaper, with welded building, which is quicker and requires less labour. It ought to be observed, however, that wrought iron boilers corrode much slower than their modern-day metal counterparts, and are less vunerable to localized stress-corrosion and pitting. This makes the durability of older wrought-iron boilers much more advanced than those of welded steel boilers.
Cast iron may be used for the heating vessel of local water heaters. Although such heaters are usually termed "boilers" in some countries, their purpose is to create warm water usually, 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 vapor boilers.
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Energy
The source of heating for a boiler is combustion of some of several fuels, such as wood, coal, oil, or natural gas. Electric steam boilers use resistance- or immersion-type heating system elements. Nuclear fission is used as a heat source for generating steam also, either straight (BWR) or, generally, in specialised high temperature exchangers called "vapor generators" (PWR). Temperature recovery steam generators (HRSGs) use the heat rejected from other processes 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 functional or more common
boiler efficiency =Q*((Hg-Hf)/q)*(GCV *100 ) Q =Total vapor flow Hg= Enthalpy of saturated steam 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 family 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 fuel 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 box from below. 18th century Haycock boilers produced and stored large quantities of very low-pressure vapor generally, barely 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 type or forerunner 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 type of boiler used in almost all steam locomotives. Heat source is inside a furnace or firebox that needs to be held completely surrounded by the water in order to maintain the temperatures 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 can be further increased by causing the gases invert direction through another parallel pipe or a lot of money of multiple tubes (two-pass or come back flue boiler); additionally the gases may be studied along the sides and then beneath the boiler through flues (3-pass boiler). In case of a locomotive-type boiler, a boiler barrel extends from the firebox and the hot gases go through a bundle of fire tubes inside the barrel which greatly increases the heating system surface in comparison to a single pipe and further improves heat transfer. Fire-tube boilers usually have a comparatively low rate of steam creation, but high vapor storage capacity. Fire-tube boilers burn solid fuels mostly, but are readily adaptable to those of the liquid or gas variety.
Diagram of a water-tube boiler.
Water-tube boiler: In this kind, tubes filled with drinking water are arranged inside a furnace in several possible configurations. The water pipes connect large drums Often, the low ones containing water and top of the ones water and steam; in other instances, such as a mono-tube boiler, drinking water is circulated with a pump through a succession of coils. This type generally provides high steam production rates, but less storage capacity than the above. Water pipe boilers can be designed to exploit any warmth source and tend to be preferred in high-pressure applications because the high-pressure water/steam 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 tubes are close collectively and water is pumped through them. A flash boiler differs from the type 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 steam 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 mixed in the following manner: the firebox contains 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 met with little success far away.
Sectional boiler. Within a ensemble iron sectional boiler, sometimes called a "pork chop boiler" the water is included inside solid iron sections.[citation needed] These sections 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 specifications and regulation rules. For instance, the ASME Boiler and Pressure Vessel Code is a typical providing an array of rules and directives to ensure compliance of the boilers and other pressure vessels with security, security and design standards.[5]
Historically, boilers were a way to obtain many serious injuries and property destruction as a consequence to badly understood engineering principles. Thin and brittle metal shells can rupture, while badly welded or riveted seams could start, resulting in 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. Because of this, steam is a superb way of moving energy and heat around a site from a central boiler house to where it is needed, but with no right boiler give food to water treatment, a steam-raising place are affected from scale corrosion and formation. At best, this increases energy costs and can lead to poor quality steam, reduced efficiency, shorter vegetation 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 vapor and smoke out of the air intake and firing chute, injuring the firemen who weight the coal in to the fire chamber. Extremely large boilers providing a huge selection of horsepower to operate factories can potentially demolish entire buildings.[6]
A boiler which has a loss of give food to water and it is permitted to boil dry can be extremely dangerous. If nourish water is then sent into the clear boiler, the tiny cascade of incoming water instantly boils on connection with the superheated steel 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 drinking water supply could replace. The Hartford Loop was created in 1919 by the Hartford Vapor Boiler and INSURANCE PROVIDER as a method to assist in preventing this problem from taking place, and thus reduce their insurance claims.[7][8]
Superheated steam boiler
A superheated boiler on the steam locomotive.
Main article: Superheater
Most boilers produce steam to be utilized at saturation heat; that is, saturated vapor. Superheated steam boilers vaporize the water and then further heat the steam in a superheater. This provides steam at higher temperature, but can reduce the overall thermal efficiency of the steam generating herb because the higher vapor temperatures requires a higher flue gas exhaust heat range.[citation needed] There are several ways to circumvent this issue, by providing an economizer that heats the give food to drinking water typically, a combustion air heating unit in the hot flue gas exhaust path, or both. You can find advantages to superheated steam that may, and will often, increase overall efficiency of both vapor generation and its own utilization: increases in input heat range to a turbine should outweigh any cost in additional boiler problem and expense. There could be practical limitations in using wet vapor 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 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 extreme heat and sound from such a leak indicates its existence clearly.
Superheater operation is similar to that of the coils on an fresh air conditioning unit, although for a different purpose. The steam piping is directed through the flue gas route in the boiler furnace. The temperature in this area is between 1 typically,300 and 1,600 °C (2,372 and 2,912 °F). Some superheaters are radiant type; that is, they absorb warmth by rays. Others are convection type, absorbing high temperature from a fluid. Some are a mixture of the two types. Through either method, the extreme high temperature in the flue gas route will also temperature the superheater steam piping and the vapor within. While the heat range of the steam in the superheater increases, 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 harm 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 electric power. They operate at supercritical pressure. In contrast to a "subcritical boiler", a supercritical steam 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 era of vapor bubbles within water, because the pressure is above the critical pressure point of which steam bubbles can develop. As the liquid expands through the turbine stages, 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 mixture of vapor and liquid droplets as it goes by in to the condenser. This results in slightly less gasoline use and for that reason less greenhouse gas production. The term "boiler" shouldn't be used for a supercritical pressure steam generator, as no "boiling" occurs in this product.
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Accessories
Boiler fittings and accessories
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 top of the limit of steam pressure, the operating pressuretrol, which settings when the boiler fires to maintain pressure, as well as for boilers equipped with a modulating burner, a modulating pressuretrol which settings the quantity of fire.
Safety valve: It is utilized to alleviate pressure and stop possible explosion of the boiler.
Water level indicators: They show the operator the amount of liquid in the boiler, known as a view cup also, water gauge or water column.
Bottom blowdown valves: They offer a way for removing solid particulates that condense and lay on underneath of a boiler. As the name indicates, this valve is usually located directly on the bottom of the boiler, and is occasionally opened up to use the pressure in the boiler to force these particulates out.
Constant blowdown valve: This enables a small level of water to flee continuously. Its purpose is to prevent water in the boiler becoming saturated with dissolved salts. Saturation would business lead to foaming and cause water droplets to be carried over with the steam - a disorder known as priming. Blowdown is also often used to monitor the chemistry of the boiler water.
Trycock: a kind 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 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 flows to drain.
Automatic blowdown/continuous heat recovery system: This system allows the boiler to blowdown only once makeup water is moving 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 heat of the make-up water.
Hand openings: They may be metal plates installed in openings in "header" to permit for inspections & installation of pipes and inspection of inner surfaces.
Vapor drum internals, some display, scrubber & cans (cyclone separators).
Low-water cutoff: It is a mechanical means (usually a float switch) that can be used to turn from the burner or shut down gas to the boiler to prevent it from working once the 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 range: It offers a means for removing foam or other lightweight non-condensible substances that have a tendency to float together with the water inside the boiler.
Circulating pump: It is made to circulate drinking 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 series. This may be fitted to the comparative part of the boiler, below the water level just, or to the top of the boiler.[10]
Top give food to: With this design for feedwater injection, the water is fed to the top of the boiler. This may reduce boiler exhaustion caused by thermal stress. By spraying the feedwater over some trays water is quickly heated which can reduce limescale.
Desuperheater tubes or bundles: Some 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.
Steam accessories
Main steam stop valve:
Steam traps:
Main vapor stop/check valve: It can be used on multiple boiler installations.
Combustion accessories
Energy oil system:energy 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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