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Boiler Repairs Seven Sisters, N15, Boiler Breakdown Emergency Service

# 28/11/2017 à 05:53 JamesTef (site web)
A boiler is a closed vessel where drinking water or other fluid is heated. The fluid will not always boil. (In THE UNITED STATES, the term "furnace" is normally used if the purpose is not to boil the fluid.) The warmed or vaporized liquid exits the boiler for use in various heating or procedures applications,[1][2] including water heating, central heating, boiler-based power generation, cooking food, and sanitation.

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 used in wetted elements of boilers due to corrosion and stress corrosion breaking.[3] However, ferritic stainless steel is often found in superheater sections that won't come in contact with boiling drinking water, and electrically heated stainless shell boilers are allowed under the Western european "Pressure Equipment Directive" for creation of steam for sterilizers and disinfectors.[4]
In live steam models, copper or brass is often used since it is more easily fabricated in smaller size boilers. Historically, copper was often used for fireboxes (especially for steam locomotives), because of its better formability and higher thermal conductivity; however, in more recent 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 steam", the only material used for boilermaking was the highest grade of wrought iron, with set up by rivetting. This iron was 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 shifted towards the utilization of metal, which is more powerful and cheaper, with welded construction, which is quicker and requires less labour. It should be mentioned, however, that wrought iron boilers corrode much slower than their modern-day steel counterparts, and are less susceptible to localized stress-corrosion and pitting. This makes the durability of old wrought-iron boilers considerably superior to those of welded steel boilers.

Cast iron may be used for the heating system vessel of local drinking water heaters. Although such heaters are usually termed "boilers" in some countries, their purpose will be to produce warm water, not steam, and so they 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 any of several fuels, such as wood, coal, oil, or gas. Electric vapor boilers use level of resistance- or immersion-type heating elements. Nuclear fission is also used as a heat source for producing steam, either directly (BWR) or, generally, in specialised warmth exchangers called "vapor generators" (PWR). Temperature recovery steam generators (HRSGs) use 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

Direct method -direct approach to boiler efficiency test is more useful 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 are in need of 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
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 produced and stored large volumes of very low-pressure vapor generally, hardly above that of the atmosphere often. These could burn wood or most often, coal. Efficiency was very low.
Flued boiler with a couple of 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 little volume left above to accommodate 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 held permanently surrounded by water in order to keep the temperature of the heating 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 surface which can be further increased by causing the gases invert direction through another parallel tube or a bundle of multiple pipes (two-pass or come back flue boiler); alternatively the gases may be studied along the edges and then beneath the boiler through flues (3-pass 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 tubes inside the barrel which greatly escalates the heating system surface in comparison to a single tube and further improves heat transfer. Fire-tube boilers have a comparatively low rate of steam production usually, but high vapor storage capacity. Fire-tube boilers mostly burn solid fuels, but are readily adaptable to those of the gas or liquid variety.

Diagram of the water-tube boiler.
Water-tube boiler: In this type, tubes filled with drinking water are arranged inside a furnace in a number of possible configurations. Often the water pipes connect large drums, the low ones formulated with drinking water and top of the ones steam and water; in other situations, like a mono-tube boiler, drinking water is circulated with a pump through a succession of coils. This type generally gives high vapor production rates, but less storage space capacity than the above. Water pipe boilers can be designed to exploit any warmth source and are generally preferred in high-pressure applications since the high-pressure drinking water/steam 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 jointly and water is pumped through them. A flash boiler differs from the type of mono-tube steam generator where the pipe is permanently filled up with water. Super fast boiler, the tube is held so hot that water give food to is quickly flashed into steam and superheated. Flash boilers experienced some use in automobiles 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 both above types have been mixed in the next manner: the firebox includes an assembly of water pipes, called thermic siphons. The gases then go through a typical firetube boiler. Water-tube fireboxes were installed in many Hungarian locomotives,[citation needed] but have fulfilled with little success far away.
Sectional boiler. Within a cast iron sectional boiler, sometimes called a "pork chop boiler" water is included inside ensemble iron areas.[citation needed] These sections are assembled on site to make the finished boiler.
See also: Boiler explosion
To define and secure boilers safely, some professional specialized organizations such as the American Culture of Mechanical Technicians (ASME) develop requirements and regulation rules. For instance, the ASME Boiler and Pressure Vessel Code is a typical providing a wide range of guidelines and directives to ensure compliance of the boilers and other pressure vessels with basic safety, security and design standards.[5]

Historically, boilers were a source of many serious injuries and property destruction as a consequence to badly 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 vapor. When water is converted to steam it expands to over 1,000 times its original travels and volume down steam pipes at over 100 kilometres each hour. Because of this, steam is a superb way of moving energy and high temperature around a site from a central boiler house to where it is necessary, but with no right boiler feed water treatment, a steam-raising plant are affected from range formation and corrosion. At best, this increases energy costs and can result in poor quality steam, reduced efficiency, shorter vegetation and unreliable operation. At worst, it can result in catastrophic reduction and failure of life. Collapsed or dislodged boiler tubes can also aerosol scalding-hot steam and smoke out of the air intake and firing chute, injuring the firemen who fill the coal into the open fire chamber. Extremely large boilers providing hundreds of horsepower to operate factories could demolish entire buildings.[6]

A boiler which has a loss of feed drinking water and it is permitted to boil dry can be hugely dangerous. If nourish water is then sent into the bare boiler, the tiny cascade of inbound water instantly boils on contact with the superheated steel shell and leads to a violent explosion that cannot be managed even by security steam valves. Draining of the boiler can also happen if a leak occurs in the steam source lines that is larger 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 condition from happening, and therefore 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 heat range; that is, saturated steam. Superheated vapor boilers vaporize water and then further warmth the vapor in a superheater. This provides vapor at much higher temperatures, but can decrease the overall thermal efficiency of the vapor generating vegetable because the bigger vapor temp requires a higher flue gas exhaust temperatures.[citation needed] There are several ways to circumvent this issue, typically by providing an economizer that heats the feed drinking 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 vapor generation and its utilization: benefits in input heat range to a turbine should outweigh any cost in additional boiler problem and expense. There may also be useful restrictions in using wet steam, as entrained condensation droplets will harm turbine blades.

Superheated steam presents unique safety concerns because, if any system component fails and allows steam to flee, the high 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 extreme heat and sound from such a leak indicates its existence clearly.

Superheater procedure is similar to that of the coils on an air conditioning unit, although for a different purpose. The vapor 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 radiant type; that is, they absorb heat by rays. Others are convection type, absorbing heat from a liquid. Some are a combination of both types. Through either method, the extreme heat in the flue gas path will also warmth the superheater steam piping and the vapor within. While the heat range of the vapor in the superheater goes up, the pressure of the steam does not and the pressure remains the same as that of the boiler.[9] Virtually 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 seed.
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 steam generator operates at such a high 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 the water, because the pressure is above the critical pressure point at which vapor bubbles can develop. As the fluid expands through the turbine levels, its thermodynamic condition drops below the critical point as it can work turning the turbine which turns the electrical generator that power is ultimately extracted. The liquid at that point may be considered a mix of steam and liquid droplets as it goes by in to the condenser. This leads to slightly less gas use and for that reason less greenhouse gas creation. The term "boiler" should not be used for a supercritical pressure vapor generator, as no "boiling" occurs in this device.
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Boiler accessories and fittings
Pressuretrols to control the vapor pressure in the boiler. Boilers generally have 2 or 3 3 pressuretrols: a manual-reset pressuretrol, which functions as a basic safety by setting top of the limit of vapor pressure, the operating pressuretrol, which controls when the boiler fires to maintain pressure, as well as for boilers equipped with a modulating burner, a modulating pressuretrol which controls the quantity of fire.
Security valve: It is utilized to alleviate pressure and stop possible explosion of the boiler.
Water level indications: They show the operator the amount of liquid in the boiler, known as a sight cup also, water measure or drinking water column.
Bottom level blowdown valves: They offer a means for removing solid particulates that condense and lie on the bottom of the boiler. As the name implies, this valve is situated straight on the bottom of the boiler usually, and is sometimes opened to use the pressure in the boiler to force these particulates out.
Constant blowdown valve: This allows a small level of water to flee continuously. Its purpose is to avoid water in the boiler becoming saturated with dissolved salts. Saturation would business lead to foaming and cause drinking 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 drinking water.
Trycock: a kind of valve that is often use to manually check a liquid level in a container. Most entirely on a water boiler commonly.
Flash tank: High-pressure blowdown enters this vessel where the vapor can 'flash' safely and be used 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 make-up water is moving to the boiler, thereby transferring the utmost 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 makeup water.
Hand openings: These are steel plates installed in openings in "header" to permit for inspections & installing pipes and inspection of inner surfaces.
Vapor drum internals, some display screen, scrubber & cans (cyclone separators).
Low-water cutoff: It really is a mechanical means (usually a float change) that is used to turn off the burner or shut down energy to the boiler to prevent it from jogging once the drinking water moves below a certain point. If a boiler is "dry-fired" (burnt without drinking water in it) it can cause rupture or catastrophic failing.
Surface blowdown series: It provides a means for removing foam or other lightweight non-condensible chemicals that have a tendency to float together with the water inside the boiler.
Circulating pump: It is designed to circulate 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 line. This can be suited to the comparative aspect of the boiler, below water level just, or to the very best of the boiler.[10]
Top give food to: With this design for feedwater injection, the water is fed to the very best of the boiler. This may reduce boiler fatigue 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 pipes or bundles of tubes in the water drum or the vapor drum made to cool superheated steam, in order to supply auxiliary equipment that does not need, or may be damaged by, dry out vapor.
Chemical injection line: A link with add chemicals for controlling feedwater pH.
Steam accessories
Main vapor stop valve:
Steam traps:
Main vapor stop/check valve: It is used on multiple boiler installations.
Combustion accessories
Gasoline 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 dish:
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