Boiler Repairs St Paul's, Fleet Street, EC4, Boiler Breakdown Emergency Service

JamesNew
JamesNew

le 28/11/2017 à 06:13 Citer ce message

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 generally used if the reason is never to boil the liquid.) The heated or vaporized liquid exits the boiler for use in a variety of heating system or processes applications,[1 - [2 - including water heating, central heating, boiler-based power generation, 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 used in wetted parts of boilers thanks to stress and corrosion corrosion breaking.[3 - However, ferritic stainless is often used in superheater sections that will not be exposed to boiling drinking water, and electrically heated stainless shell boilers are allowed under the European "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 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 metal) are used instead.

For a lot of the Victorian "age group of steam", the only materials 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 transferred towards the use of steel instead, which is stronger and cheaper, with welded structure, 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 pitting and stress-corrosion. This makes the longevity of older wrought-iron boilers significantly superior to those of welded metal boilers.

Cast iron might be utilized for the heating system vessel of domestic water heaters. Although such heaters are usually termed "boilers" in some countries, their purpose is usually to produce hot water, not steam, and they also run at low pressure and stay away from boiling. The brittleness of cast iron makes it impractical for high-pressure vapor boilers.
Boiler Repairs St Paul's, Fleet Street, EC4, Boiler Breakdown Emergency Service http://boiler-repairs-st-pauls.co.uk - Show more...
Energy
The foundation of heating for a boiler is combustion of any of several fuels, such as wood, coal, oil, or natural 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 temperature exchangers called "steam generators" (PWR). Temperature 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 -direct method of boiler efficiency test is more functional or even more common

boiler efficiency =Q*((Hg-Hf)/q)*(GCV *100 ) Q =Total steam stream Hg= Enthalpy of saturated vapor in k cal/kg Hf =Enthalpy of feed 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 gauge the boiler efficiency in indirect method, we are in need of a subsequent parameter like

Ultimate analysis of energy (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 gas in kcal/kg
ash percentage in combustible fuel
GCV of ash in kcal/kg
Configurations
Boilers can be classified in to the following configurations:

Container boiler or Haycock boiler/Haystack boiler: a primitive "kettle" where a fireplace heats a partially filled water box from below. 18th century Haycock boilers generally produced and stored large volumes of very low-pressure vapor, hardly above that of the atmosphere often. These could burn wood or most often, coal. Efficiency was very 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, drinking water partially fills a boiler barrel with a little volume still left above to support the steam (vapor space). This is the type of boiler used in almost all steam locomotives. Heat source is in the furnace or firebox that needs to be kept completely 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 system surface which can be further increased by making the gases reverse direction through another parallel tube or a lot of money of multiple pipes (two-pass or return flue boiler); additionally the gases may be taken along the sides and then under the boiler through flues (3-move boiler). In case of a locomotive-type boiler, a boiler barrel stretches from the firebox and the hot gases go through a lot of money of fire tubes inside the barrel which greatly escalates the heating surface in comparison to a single tube and further improves heat transfer. Fire-tube boilers will often have a comparatively low rate of steam production, but high steam storage capacity. Fire-tube boilers burn solid fuels mostly, but are readily adaptable to the people of the gas or water variety.

Diagram of the water-tube boiler.
Water-tube boiler: In this kind, tubes filled up with drinking water are arranged inside a furnace in a true number of possible configurations. The water pipes connect large drums Often, the low ones comprising drinking water and the top ones steam and water; in other situations, such as a mono-tube boiler, drinking water is circulated by a pump through a succession of coils. This kind provides high steam production rates generally, but less storage capacity than the above. Water tube boilers can be made to exploit any heat source and are generally 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.
Flash boiler: A flash boiler is a specialized kind of water-tube boiler where pipes are close collectively and drinking water is pumped through them. A flash boiler differs from the type of mono-tube vapor generator where the pipe is permanently filled with water. In a flash boiler, the pipe is kept 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 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 set up of water tubes, 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 fulfilled with little success in other countries.
Sectional boiler. In a cast iron sectional boiler, sometimes called a "pork chop boiler" the water is included inside cast iron areas.[citation needed - These sections are assembled on site to create the finished boiler.
Safety
See also: Boiler explosion
To define and secure boilers safely, some professional specialized organizations like the American Society of Mechanical Technical engineers (ASME) develop criteria and regulation codes. 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 security, 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 metal shells can rupture, while welded or riveted seams could open up badly, leading to a violent eruption of the pressurized vapor. When water is changed into 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, vapor is a superb 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 flower will suffer from level corrosion and formation. At best, this increases energy costs and can result in poor quality steam, reduced efficiency, shorter plant life and unreliable procedure. At worst, it can result in catastrophic loss and failing of life. Collapsed or dislodged boiler tubes can also spray scalding-hot vapor and smoke out of the air intake and firing chute, injuring the firemen who insert the coal into the open fire chamber. Extremely large boilers providing a huge selection of horsepower to use factories can potentially demolish entire structures.[6 -

A boiler that has a loss of feed drinking water and it is permitted to boil dry out can be hugely dangerous. If nourish water is sent into the bare boiler then, the tiny cascade of inbound drinking water instantly boils on connection with the superheated metal shell and leads to a violent explosion that can't be controlled even by protection vapor valves. Draining of the boiler can also happen if a leak occurs in the vapor source lines that is bigger than the make-up water supply could replace. The Hartford Loop was invented in 1919 by the Hartford Steam Boiler and Insurance Company as a method to help prevent this problem from happening, and thereby reduce their insurance promises.[7 - [8 -

Superheated steam boiler

A superheated boiler on the steam locomotive.
Main article: Superheater
Most boilers produce vapor to be used at saturation temperatures; that is, saturated vapor. Superheated steam boilers vaporize water and then further high temperature the vapor in a superheater. This provides steam at much higher temperatures, but can reduce the overall thermal efficiency of the steam generating plant because the higher steam temp takes a higher flue gas exhaust heat.[citation needed - There are many ways to circumvent this problem, typically by giving an economizer that heats the feed drinking water, a combustion air heater in the hot flue gas exhaust route, or both. There are benefits to superheated steam that may, and will often, increase overall efficiency of both vapor generation and its utilization: benefits in input temperatures to a turbine should outweigh any cost in additional boiler problem and expense. There can also be useful limitations in using moist vapor, 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 high pressure and temperature can cause serious, instantaneous injury 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 obviously indicates its presence.

Superheater procedure 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 path in the boiler furnace. The temperature 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 temperature by radiation. Others are convection type, absorbing heat from a liquid. Some are a combination 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 steam in the superheater rises, the pressure of the vapor does not and the pressure remains exactly like 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 power plant.
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 higher pressure (over 3,200 psi or 22 MPa) that the physical turbulence that characterizes boiling ceases that occurs; the liquid is neither water nor gas but a super-critical liquid. There is absolutely no era of steam bubbles within water, because the pressure is above the critical pressure point of which vapor bubbles can develop. As the fluid expands through the turbine levels, its thermodynamic condition drops below the critical point as it does work turning the turbine which turns the power generator that power is ultimately extracted. The fluid at that time may be a mix of vapor and liquid droplets as it goes by in to the condenser. This leads to somewhat less fuel use and for that reason less greenhouse gas production. The term "boiler" should not be used for a supercritical pressure vapor generator, as no "boiling" occurs in this device.
Boiler Repairs St Paul's, Fleet Street, EC4, Boiler Breakdown Emergency Service http://boiler-repairs-st-pauls.co.uk - Click here!
Accessories
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 safety by setting top of the limit of steam pressure, the working pressuretrol, which controls when the boiler fires to keep pressure, and for boilers outfitted with a modulating burner, a modulating pressuretrol which settings the amount of fire.
Basic safety valve: It can be used to relieve pressure and prevent possible explosion of a boiler.
Water level signals: They show the operator the level of liquid in the boiler, known as a view glass also, water gauge or water column.
Bottom level blowdown valves: They provide a means for removing solid particulates that condense and lay on underneath of a boiler. As the name indicates, this valve is usually located on underneath of the boiler, and is occasionally opened to use the pressure in the boiler to push these particulates out.
Constant blowdown valve: This enables a small level of water to flee continuously. Its purpose is to avoid the 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 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 water level in a container. Most commonly found on a drinking water boiler.
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 while the ambient pressure blowdown flows 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 utmost amount of heat possible from the blowdown to the makeup water. No flash tank is normally needed as the blowdown discharged is close to the temperature of the make-up water.
Hand holes: They are steel plates installed in openings in "header" to permit for inspections & installation of tubes and inspection of inner surfaces.
Vapor drum internals, some screen, scrubber & cans (cyclone separators).
Low-water cutoff: It is a mechanical means (usually a float change) that can be used to turn off the burner or shut down energy to the boiler to prevent it from jogging once the water moves below a certain point. If a boiler is "dry-fired" (burnt without drinking water in it) it can cause rupture or catastrophic failure.
Surface blowdown range: It provides a way for removing foam or other lightweight non-condensible chemicals that have a tendency to float on top of water inside the boiler.
Circulating pump: It is made to circulate drinking water back again 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 line. This can be installed to the medial side of the boiler, just below the water level, or to the top of the boiler.[10 -
Top feed: With 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 a series of trays water is quickly heated which can reduce limescale.
Desuperheater tubes or bundles: Some tubes or bundles of pipes in the 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 vapor.
Chemical 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 dish:
Registration dish:

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