High pressure boiler room. What is a high pressure steam boiler? Rules for operating a steam boiler. Gas and water pipe

This is a type of unit for transferring thermal energy, the steam pressure in which exceeds 22 atmospheres. The creation and use of such devices is associated with operation in factories power units significant power, with increased requirements, as well as with the need to optimize fuel consumption.

A high pressure level allows you to obtain a larger useful volume of steam than in standard models industrial boilers.

Increasing the specific power of steam became possible in the 20s of the twentieth century. New technologies, the development of mechanical engineering and metallurgy have made it possible to realize the full potential of steam systems in increasing power, productivity and rationalizing fuel consumption.

Areas of application:

• metallurgical plants;
• mining industry enterprises;
• production of various reinforced concrete products and other building materials;
• plants involved in processing petroleum products (heating petroleum products, ensuring pipeline transportation, etc.);
• woodworking (wood drying);
• production of compound feed and feed additives.

Benefits of using high pressure steam

The use of water vapor under significant pressure is associated with some features:

• the higher the liquid temperature, the higher the vapor pressure;
• the vapor pressure level is inversely proportional to the evaporation temperature;
• the direct relationship between the pressure of saturated dry steam and its temperature works up to 40 atmospheres, after which the temperature begins to decrease;
• The temperature of superheated steam constantly increases with increasing pressure.

All this together means that at pressures up to 40 atmospheres and when using saturated dry steam, it is possible to reduce fuel consumption (per unit of steam). When working with superheated steam, a continuous increase in pressure makes it possible to continuously reduce fuel consumption, but the level of savings is insignificant.

The greatest productivity of couples high pressure shows the operation of steam turbines and machines in various factories.

Intermediate (secondary) superheating of high pressure steam

Based on the totality of parameters, it is the exhaust (superheated) steam that is best choice for heating and heating tasks. At a pressure of 80 atmospheres the coefficient beneficial use the heat produced can reach 70%. That is why waste steam is widely used in units high blood pressure.

Secondary overheating makes it possible to level out the significant moisture content of the steam, which appears on last stages development process. Thus, it is possible to achieve practically full application total heat expended.

Average fuel savings when using intermediate superheating is 1-3%. If implemented additional settings regenerative processes responsible for heating the feed water using steam can achieve 8 percent savings.

Designs and diagrams of industrial high-pressure steam boilers

Steam boilers that use steam under significant pressure are represented by two main categories:

1. Relatively old models of industrial boilers (sectional, vertical water tube), redesigned taking into account the operational requirements for systems with significant pressure; as a rule, they are used in the absence of a more modern alternative and are not very effective.
2. Variants of high pressure boilers, originally designed to operate in such conditions.

The most common systems belonging to the second category:

• Atmos - several pipes (rotors) located horizontally in the combustion chamber and rotating at a speed of about 300 revolutions per minute; steam production depends on the speed of the rotors. The upper limit of steam production of Atmos systems is 300--350 kg/m 2. The main advantages are a simple water circulation scheme, the absence of expensive parts (drums); disadvantages - high complexity of the rotor rotation device, the need for constant maintenance of the installation.
• Lefler - such a boiler allows you to produce steam under pressure by admitting superheated steam into the evaporator (drum) simultaneously with boiling water. The main advantages are a significant volume of liquid in the evaporators, there is no need for water softening, and the absence of boiling pipes. Disadvantages are the complexity of the pump responsible for removing steam, the risk of burning pipes when the pump suddenly stops, as well as the uneconomical nature of the entire installation at a pressure of less than 100 atmospheres.
• Benson - the unit uses an original scheme in which water turns into steam without additional heat. The advantages of such a high-pressure steam boiler are low water volume, high safety and relative low cost of construction.
• Schmidt-Hartmann - a boiler using a drum with an integrated coil system. Advantages - safety, good heat transfer coefficient, hot gases do not directly affect the drum. Disadvantages - relatively high price, some design features (the need to provide a higher level of pressure for the coils than for the working steam).

Common features of any designs designed for high-pressure steam are increased strength of components, especially gate valves and valves, as well as use as main construction materials alloy steel, open-hearth casting, electric steel.

A steam boiler is a device that is used in everyday life and industry. It is designed to convert water into steam. The resulting steam is subsequently used to heat housing or rotate turbomachines. What types of steam engines are there and where are they most in demand?

A steam boiler is a unit for producing steam. In this case, the device can produce 2 types of steam: saturated and superheated. Saturated steam has a temperature of 100ºC and a pressure of 100 kPa. Superheated steam is distinguished by high temperature (up to 500ºC) and high pressure (more than 26 MPa).

Note: Saturated steam is used in heating private houses, and superheated steam is used in industry and energy. It tolerates heat better, so the use of superheated steam increases the efficiency of the installation.

Where are steam boilers used:

1. IN heating system— steam is an energy carrier.
2. In the energy sector, industrial steam engines (steam generators) are used to generate electricity.
3. In industry, superheated steam can be used to convert into mechanical motion and move vehicles.

Steam boilers: scope of application

Household steam devices are used as a heat source to heat a home. They heat a container of water and drive the resulting steam into the heating pipes. Often such a system is installed together with a stationary coal stove or boiler. Usually, Appliances For heating with steam, only saturated, non-superheated steam is created.

For industrial applications, the steam is superheated. It is continued to be heated after evaporation to raise the temperature even further. Such installations require high-quality execution to prevent the steam tank from exploding.

Superheated steam from the boiler can be used to generate electricity or mechanical movement. How does this happen? After evaporation, the steam enters the steam turbine. Here the steam flow rotates the shaft. This rotation is further converted into electricity. This is how electrical energy is obtained in the turbines of power plants - when the shaft of the turbomachines rotates, an electric current is generated.

In addition to the generation of electric current, shaft rotation can be transmitted directly to the engine and wheels. As a result, steam transport begins to move. Famous example steam engine - steam locomotive. In it, when coal was burned, water was heated, saturated steam was formed, which rotated the engine shaft and wheels.

Operating principle of a steam boiler

The heat source for heating water in a steam boiler can be any type of energy: solar, geothermal, electric, heat from the combustion of solid fuel or gas. The resulting steam is a coolant; it transfers the heat of combustion of the fuel to the place of its use.

In various designs of steam boilers it is used general scheme heating water and turning it into steam:

• The water is purified and supplied to the tank using an electric pump. Typically, the reservoir is located at the top of the boiler.
• From the reservoir, water flows down through pipes into the collector.
• From the collector, water rises again through the heating zone (fuel combustion).
• Steam is formed inside the water pipe, which rises upward under the influence of the pressure difference between the liquid and gas.
• At the top, the steam passes through a separator. Here it is separated from the water, the remainder of which is returned to the tank. Then the steam enters the steam line.
• If this is not a simple steam boiler, but a steam generator, then its pipes pass through the combustion and heating zone a second time.

Steam boiler design

A steam boiler is a container in which heated water evaporates and forms steam. As a rule, this is a pipe of various sizes.

In addition to the water pipe, the boilers have a combustion chamber (fuel is burned in it). The design of the firebox is determined by the type of fuel for which the boiler is designed. If it is hard coal or firewood, then at the bottom of the combustion chamber there is a grate. Coal and firewood are placed on it. Air passes from below through the grate into the combustion chamber. For effective draft (air movement and fuel combustion), a firebox is installed at the top of the firebox.

If the energy carrier is liquid or gaseous (fuel oil, gas), then a burner is inserted into the combustion chamber. For air movement, an inlet and outlet are also made (grid and chimney).

Hot gas from fuel combustion rises to a container of water. It heats the water and exits through the chimney. Water heated to boiling temperature begins to evaporate. The steam rises up and enters the pipes. This is how natural steam circulation occurs in the system.

Classification of steam boilers

Steam boilers are classified according to several criteria. According to the type of fuel they operate on:

• gas;
• coal;
• fuel oil;
• electric.

By purpose:

• household;
• industrial;
• energy;
• recycling.

By design features:

• gas pipes;
• water tube

Let's look at how the design of gas-pipe and water-pipe machines differs.

Gas and water tube boilers: differences

The container for generating steam is often a pipe or several pipes. The water in the pipes is heated by hot gases generated during fuel combustion. Devices in which gases rise to water pipes are called gas-tube boilers. The diagram of the gas-pipe unit is shown in the figure.

Diagram of a gas-tube boiler: 1 - fuel and water supply, 2 - combustion chamber, 3 and 4 - smoke pipes with hot gas that exits further through the chimney (positions 13 and 14 - chimney), 5 - grate between the pipes, 6 - water inlet , the output is indicated by the number 11 - its output, in addition, at the outlet there is a device for measuring the amount of water (indicated by the number 12), 7 - steam output, the zone of its formation is indicated by the number 10, 8 - steam separator, 9 - the outer surface of the container in which water circulates.

There are other designs in which gas moves through a pipe inside a container of water. In such devices, water tanks are called drums, and the devices themselves are called water-tube steam boilers. Depending on the location of the water drums, water tube boilers are classified into horizontal, vertical, radial, and combinations of different pipe directions. The diagram of water movement through a water-tube boiler is shown in the figure.

Diagram of a water tube boiler: 1 - fuel supply, 2 - firebox, 3 - pipes for water movement; the direction of its movement is indicated by numbers 5,6 and 7, the place of water entry - 13, the place of water exit - 11 and the place of discharge - 12, 4 - the zone where water begins to turn into steam, 19 - the zone where there is both steam and water , 18 - steam zone, 8 - partitions that direct the movement of water, 9 - chimney and 10 - chimney, 14 - steam exit through the separator 15, 16 - outer surface of the water tank (drum).

Gas and water tube boilers: comparison

To compare gas and water tube boilers, here are some facts:

1. Size of pipes for water and steam: gas-tube boilers have larger pipes, water-tube boilers have smaller pipes.
2. The power of a gas-tube boiler is limited to a pressure of 1 MPa and a heat-generating capacity of up to 360 kW. This is due to the large size of the pipes. They can generate significant amounts of steam and high pressure. An increase in pressure and the amount of heat generated requires significant thickening of the walls. The price of such a boiler with thick walls will be unreasonably high and not economically profitable.
3. The power of a water-tube boiler is higher than that of a gas-tube boiler. Small diameter pipes are used here. Therefore, the pressure and temperature of the steam can be higher than in gas-pipe units.

Note: Water tube boilers are safer, more powerful, produce high temperatures and can handle significant overloads. This gives them an advantage over gas-pipe units.

Additional elements of the unit

The design of a steam boiler may include not only a combustion chamber and pipes (drums) for circulating water and steam. Additionally, devices are used that increase the efficiency of the system (raise the steam temperature, its pressure, quantity):

1. Superheater - increases the steam temperature above +100ºC. This in turn increases the efficiency and efficiency of the machine. The temperature of superheated steam can reach 500 ºC (this is how steam boilers work in nuclear power plants). The steam is additionally heated in the pipes into which it enters after evaporation. Moreover, it can have its own combustion chamber or be built into a common steam boiler. Structurally, convection and radiation superheaters are distinguished. Radiation structures heat steam 2-3 times more than convection structures.
2. Steam separator - removes moisture from steam and makes it dry. This increases the efficiency of the device and its efficiency.
3. A steam accumulator is a device that takes steam from the system when there is a lot of it, and adds it to the system when there is not enough or little of it.
4. A device for water preparation - reduces the amount of oxygen dissolved in water (which prevents corrosion), removes minerals dissolved in water (using chemical reagents). These measures prevent pipes from becoming clogged with scale, which impairs heat transfer and creates conditions for pipes to burn out.

In addition, there are valves for draining condensate, air heaters, and, of course, a monitoring and control system. It includes a combustion switch and switch, automatic regulators of water and fuel flow.

Steam generator: powerful steam engine

A steam generator is a steam boiler that is equipped with several additional devices. Its design includes one or more intermediate superheaters, which increase its operating power tens of times. Where are powerful steam engines used?

The main application of steam generators is in nuclear power plants. Here, with the help of steam, the energy of the decay of an atom is converted into electricity. Let us describe two methods of heating water and generating steam in a reactor:

1. Water washes the reactor vessel from the outside, while it heats itself and cools the reactor. Thus, steam formation occurs in a separate circuit (water is heated against the walls of the reactor and transfers heat to the evaporation circuit). This design uses a steam generator - it acts as a heat exchanger.
2. Pipes for heating water run inside the reactor. When pipes are fed into the reactor, it becomes a combustion chamber, and the steam is transferred directly to the electric generator. This design is called a boiling reactor. A steam generator is not needed here.

Industrial steam units are powerful machines that provide people with electricity. Household units also work in the service of humans. Steam boilers allow you to heat your home and perform various jobs, and also provide the lion's share of electrical energy for metallurgical plants. Steam boilers are the basis of industry.

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A steam boiler is designed to produce working (or strong) steam capable of performing mechanical work or releasing an equivalent amount of heat. Devices that generate steam, from which a certain amount of force is not required, are called steam generators. They are widely used in industry (for example, for steaming concrete), in food technologies (steam digesters), medicine (inhalers, sterilizers) and in everyday life (for steaming and cleaning, in a bathhouse, etc.), but a steam generator is far from steam boiler

Why do you need strong steam?

In an age when quantum computers and communication devices, self-thinking artificial intelligence and spacecraft for interstellar flights are on the way, the need for a working pair remains high. In industry, primarily for the transmission of large quantities of ready-to-use heat and drive over distances technological equipment: presses, hammers, pile drivers, etc. In water transport and in the energy sector, this is the production of working fluid for steam turbines and other high-power mechanical engines: starting from about 5-10 MW per unit cost mechanical work steam turns out to be lower than any other working fluid.

Note: The steam cylinder-piston pair has a remarkable property: the greatest force on the rod develops at zero piston speed. In other words, the external characteristics of a steam engine are ideal, and its efficiency almost does not depend on the operating mode; A steam engine does not need a gearbox.

Steam boilers are also used in everyday life; most of all in steam and dual circuit systems heating (CO). Steam CO requires more thorough sealing than with a liquid coolant, but at the height of the heating season, it allows you to disconnect and reconnect individual branches to the system without the risk of breaking down the entire heating system. This, in turn, makes it possible to heat well-insulated utility rooms impulses, which in places with harsh climates saves up to 30% or more of heating costs per season.

Double-circuit COs, on the contrary, turn out to be more economical in areas with a long off-season and mild, unstable winters. The return temperature of the single-circuit CO must not fall below approx. +45 degrees Celsius, otherwise acidic condensation will form in the heating boiler, which may cause the entire system to fail. Heat losses in main pipes are considerable, so in houses and/or distribution heating points they install so-called. elevator units, in which part of the coolant from the supply is sucked into the return, heating it. However, at the same time, the hot water boiler circulates a good part of the coolant in a circle, consuming excess fuel, for which subscribers have to pay. The higher the outside temperature and the less heating required, the larger part of the heat generated by the boiler is spent not on heating users, but on maintaining itself in mode. Which is still not optimal.

In a 2-circuit CO system, the steam boiler produces steam, which heats the CO coolant through a heat exchanger. The supply temperature can now be lowered, which will reduce losses in the lines: the hotter the coolant, the greater they are. The return temperature can be as low as desired, as long as the system does not defrost: nothing burns in the heat exchanger and no acid radicals are formed that can form acid rain. The steam boiler is also not in danger: there are no main losses, because heat exchanger nearby; the supply of steam into it is regulated by an automatic valve according to the temperature of the 2nd circuit, and the return steam to the boiler remains very hot.

What's bad about it?

The main disadvantage of steam boilers is their long readiness time. The best modern ones reach operating mode in 3-5 minutes, and in a regular boiler the couples are separated for about an hour. Therefore, there is practically no land-based steam transport, although the efficiency of modern ceramic steam engines is no worse than that of internal combustion engines. But you can turn off the internal combustion engine, but you cannot stop the boiler.

No less significant is the risk of explosion. If the energy reserve in a car fuel tank is measured in tens of kg of TNT equivalent, then in a steam boiler it is measured in centners and tons. Gasoline and diesel fuel can simply burn out, and the boiler explodes in an accident. Modern ones are extremely rare, but their explosiveness is still not zero.

Another drawback follows from the 2nd drawback: the steam boiler needs to be fed with very high-quality, well-prepared water. Scale is a boiler’s terrible enemy; it sharply reduces its thermal efficiency and increases the risk of explosion.

As a consequence of the 2nd and 3rd - 4th serious drawback: steam boilers require regular qualified inspection and maintenance with boiler shutdown. Imagine that you definitely need to take your car to a service station every six months and order an engine overhaul, otherwise it will stop listening to the steering wheel and crash into a pole itself.

A little history

Thoughts on using steam power for practical purposes have been around for millennia. It is believed that the first steam boiler, which was also a jet steam turbine, invented by Heron of Alexandria. There is information that in the 16th century. The captain of the Spanish fleet, Blasco de Garay, built and demonstrated to the king... a steamboat that sailed. But if this is true, then it is a single accidental find - thermodynamics as a science did not yet exist, and without it it is impossible to calculate a steam engine and a boiler for it. Edison, one of the practical practitioners, once said: “There is nothing more practical than a good theory.”

The patent for a mine water lift powered by a boiler with steam was first received by the Englishman T. Severy in 1698. In practice, his idea was also implemented by the Englishman T. Newcomen at the same time. late XVII V. But Newcomen’s boiler, in principle, was no different from a household kettle and produced very weak steam, so Newcomen’s machines were not widely used and did not revolutionize technology.

They were the first to understand how a boiler should operate, producing strong steam (power steam) in the second half of the 18th century. independently of each other, also the English designer J. Watt (the unit of power Watt is named after him) and the Russian self-taught mechanic I. I. Polzunov. He was unable to finish his steam engine - he died of illness, but he completed the boiler in 1765. The designs of Watt's and Polzunov's steam boilers (shown on the right) are almost identical, and there could not have been any other technical solution at that time.

The thermal efficiency and steam production (see below) of the Watt and Polzunov boilers made it possible to run machines that performed cost-effective useful work, but were far from what was possible with the technology of that time. The inventors of the first steam locomotives, R. Trevithick and J. Stephenson, improved the technical performance of steam boilers and made them more compact. Subsequently, a great contribution to the development of boiler building was made by the English engineers J. Thornycroft and E. Yarrow, and then by the Russian scientist V. G. Shukhov, the same one who built the television tower on Shabolovka.

Note: on Stephenson's first steam locomotive "Blücher" (in the center in the figure) No. 2 is listed, but this is because its experienced predecessor turned out to be unsuitable for long-term operation.

A little theory

This section will not contain formulas from school and university textbooks. You are expected to remember them. And if you forgot, you know where to look. Here we will talk about the essence of the processes occurring in a steam boiler and their practical details and conclusions from them. And mathematics is a profitable business. Without understanding the essence, the calculations are still of no use.

The main operating principle of a steam boiler, which Watt and Polzunov guessed, is that the water in it does not boil. Boiling is a process that is not smoothly controlled from the outside: the water has reached boiling temperature and received latent heat of evaporation - it boils; no no. At normal pressure, boiling water is relatively safe, but the efficiency of the exhaust steam is negligible; he is said to be low potential. And its condensation instantly begins, causing the steam to completely lose its strength.

Steam works by its pressure. Let's say its excess over atmospheric is only 1 MPa. Then for a piston with an area of ​​500 sq. cm steam will press with a force of approx. half tons. Not a bad start.

The pressure of saturated water vapor increases with increasing temperature according to a power law, i.e. very quickly, on the left in Fig. At the same time, the boiling point of water and the steam output per unit area of ​​the vaporization mirror (VP) also increase. But the latent heat of evaporation remains unchanged, and the part of the fuel consumption that does not impart force to the steam decreases and decreases. So, in all respects it is beneficial to increase the pressure in the boiler, but this increases its risk of explosion (see below). And up to a certain limit, above which non-thermodynamic forces begin to interfere with the process.

The table of parameters of superheated saturated water vapor is given on the right in Fig. Pay attention to the green highlighted columns (partially or completely). They show that the maximum steam performance occurs in the temperature range of 200-260 degrees. The steam pressure in it, on which the force created by the actuator depends, triples. The total heat capacity (including latent heat) continuously increases in this range. This is beneficial for vapor-liquid COs with partial or complete condensation of the coolant.

The bad news begins in the yellow lines: the steam becomes chemically very active - it corrodes steam lines and mechanisms made of ordinary steel, and part of its strength is spent on “chemistry” despite the increase in pressure. Red lines - the news is even worse: thermal dissociation of water becomes noticeable in the steam, and the boiler becomes extremely dangerous.

About notation

In the era of steam engines, the units of pressure used were atmosphere (at) and excess atmosphere (ati). 1 at = 1 kgf*sq. see p(at) = p(at) –1, because air pressure 1 at. Nowadays pressure is measured in pascals (Pa). 1 at = 1.05 MPa. This is correct, because The boiler operating mode significantly depends on the ambient air pressure. But there are no excess pascals, so to determine the steam force you need to subtract 1 MPa from the pressure in the boiler. For example, at 240 degrees the pressure in the boiler is 3.348 MPa. For work, you can use no more than 2.298 MPa, but for each sq. cm surfaces of parts inside the boiler will press more than 30 kg*sq. cm. To calculate the boiler power, you must also use its steam production in kg*s or kg*h. Another value you need to know is the thermal efficiency of the boiler, equal to the ratio thermal energy stored in a unit mass of steam to the heat of combustion of the fuel required for its production. Thermal efficiency is often called boiler efficiency, but it must be borne in mind that the efficiency of power and heating boilers of the same design is different: in the latter case, the latent heat of vaporization can be returned in the form of latent heat of condensation, but in the former it is not.

Note: sometimes excess steam pressure above atmospheric is expressed in bars (bar). For example, in the specification for the boiler they write - pressure 1.5 bar, which is equal to approx. 1.5 ati. But the bar is also a non-systemic unit, its use is not regulated. Therefore, in the same specification you need to find the temperature of the water in the boiler and compare it.

Steam potential

Along with the temperature in the boiler, its explosiveness also increases rapidly. At temperatures above approx. 200 degrees, even a decrease in pressure due to excess steam extraction can lead to boiling of the entire mass of water in the boiler and its explosion. In Novikov-Priboy’s story “Otrada Bay” with everyone technical details it is described how a fireman who sympathized with the Reds blew up a boiler on a White military steamship, in whose crew he was forcibly enlisted. Based on these considerations, steam is divided into:

• Low potential - temperature up to 113 degrees Celsius, pressure up to 1.7 MPa. A boiler explosion is practically impossible due to the small energy reserve in it.
• Low potential - temperature 113-132 degrees, pressure 1.7-3 MPa. A boiler explosion is possible if its body suddenly collapses.
• Average potential - temperature 132-280 degrees, pressure 3-6.42 MPa. An explosion is possible if the boiler body is destroyed or the automation fails.
• High potential - temperature 280-340 degrees, pressure 6.42-14.61 MPa. An explosion is possible, in addition to the reasons mentioned above, due to violations of the boiler operating rules (see below) and depressurization of steam lines.
• Ultra-high potential - temperature above 340 degrees, pressure more than 14.61 MPa. An explosion, in addition to the reasons described, is possible due to a random combination of circumstances.

Subtleties of vaporization

For practical purposes, it is convenient to use the value of steam output per unit area of ​​the boiler, but in fact, steam formation in the boiler occurs in the volume of water: it is saturated with steam microbubbles. An idea of ​​this is given by white boiling water, which, according to the rules of oriental cooking, is supposed to be used to brew tea. But in white boiling water, air dissolved in the water is released, and in a normally operating boiler the water appears transparent. If the water gauge glass becomes cloudy, the boiler is on the verge of explosion. The red stoker mentioned above was an extra-class specialist: he determined by the type of water how soon the boiler would explode and managed to escape. The steamer was old with a medium-potential boiler; In it, several minutes pass from the whitening of the water meter to the explosion. The high-potential boiler explodes immediately and the water meter becomes cloudy.

The second important point is that with the salary the so-called wet steam, which also contains invisible microdrops of water. Wet steam is a boiler’s enemy no less terrible than scale: microdrops of moisture are natural centers of steam condensation. If in some place in the steam circuit the temperature begins to fall faster than the pressure, an avalanche-like condensation of steam may begin. The pressure in the entire system will drop sharply, and then even a low-potential boiler can boil and explode. As for the mechanisms driven by steam from the boiler, condensation also sharply worsens their technical parameters (the pressure in the working parts drops significantly) and causes increased wear: microdroplets of superheated water are chemically aggressive. The only place where condensation of working steam is useful is in vapor-liquid CO (see above), because At the same time, latent heat of condensation is released for heating.

Ideal boiler

Knowing these features, one can imagine from the standpoint of today how a certain ideal steam boiler should be constructed. In fact, it will turn out to be very expensive and difficult to maintain, and in the “golden age” of steam, such a boiler was technically impossible. The entire evolution of boiler construction has followed the path of simplifying the equipment (piping) of the boiler and combining the functions of its systems. But this diagram will help you figure out what the boiler needs for normal operation.

A general diagram of the structure of a steam boiler is shown in Fig.:

The steam generator is a channel (tubular) gas-water heat exchanger. An increase in the contact area of ​​the coolant with the heater enhances the formation of microbubbles of steam in its mass and the separation of steam from a unit area of ​​the heater at the same temperature. In the steam tank, pure steam and water micro-suspension are separated by gravity or absorption without releasing the latent heat of condensation. The hot condensate flows back into the steam generator or, in circulation boilers (see below), is pumped into it by a circulation pump.

The role of the superheater is very important. Without a pressure drop along the length of the steam line, there will be no steam flow through it, but at the same time the strength of the steam decreases and the likelihood of its violent condensation increases. The superheater “pumps up” the exhaust steam with energy for free - due to the residual heat of the flue gases.

The economizer further increases the thermal efficiency of the boiler. This is also a channel heat exchanger, in which also flue gases heated feed water. At the lowest boiler speed, the economizer can become overcooled and become overgrown with soot, and when the boiler is boosted, it can overheat and even boil. Therefore, sometimes a separate water circulation circuit with a water elevator, similar to those used in single-circuit CO systems (see above), is introduced into the economizer. During normal operation of the boiler, the economizer's own circulation is cut off by a shut-off valve.

The last thing that allows you to “extend” the thermal efficiency of the boiler to the theoretical limit is heating the air entering the firebox. In high-power thermal devices this is very effective measure. At one time, heating the air in cowpers made it possible to reduce fuel consumption for blast furnaces by almost three times. As for the control unit (or device) for all this equipment, now it is a box or cabinet with a microprocessor and its electromechanical wiring, and in the old days it was a team of a driver and a fireman.

Steam boiler designs

Depending on the purpose, operating conditions and requirements for steam parameters, the design of a steam boiler may be different. Structurally, steam boilers differ in:

1. Method of steam separation – direct-flow (flow-through) and circulating;
2. According to the design of the steam separator - drum and others (bell-shaped, coil, etc.);
3. Heat transfer method - gas-tube (formerly fire-tube; old fire-tube) and water-tube;
4. According to the orientation and configuration of the steam generator channels - horizontal, vertical, combined (flue gas inlet is horizontal, outlet is vertical; curved channels), inclined, multi-collector, coil, jacket vortex combustion, etc.;
5. Along the flow of flue gases - direct flow and reverse flow;
6. According to hydrodynamics - with an open or closed steam-water circuit, see below;
7. By heating method - flame (fuel), electric, indirect heating, solar boilers, etc.

As for the heating method, electric steam boilers produce only low- and low-potential steam - the heating element does not withstand more severe operating conditions in the boiler. Indirect heating boilers are used primarily. at a nuclear power plant. When they write that the temperature of the coolant in them reaches 500 degrees and above, this refers to the primary circuit, which, through a heat exchanger, heats an ordinary high-potential boiler that supplies steam to the turbine. Solar boilers (solar boilers), etc. exoticism is a subject for separate consideration. We will touch on them briefly at the end, and will mainly deal with flame steam boilers - the unit of steam efficiency from them is the cheapest and most accessible.

Note: submarine sailors sometimes play tricks on land-based “dummies” with tales of how they, supposedly having left their watch, slept on the primary circuit of a nuclear submarine reactor. This clean water It's funny - on the primary circuit, not only the temperature is above 400 degrees, but also deadly radiation, and leaving the watch without permission is a serious crime. First circuit nuclear reactors it is designed so that there is no release of steam from the coolant.

Direct flow or circulation

In direct flow steam boilers(pos. A in the figure) wet steam enters the coil, tubular collector or under the hood, where a water suspension falls out of it, flowing by gravity into the steam generator.

Once-through boilers are simpler in design, and from automation they generally only need an experienced fireman. Once-through boilers can be energy-independent - they can do without a feed pump, receiving water by gravity from the feed tank. But they are much more explosive than circulation ones, and their thermal efficiency and steam production are low. The most intense steam is released from the uppermost layers of water in the boiler. Freed from steam microbubbles, the water sinks down and rises again as it becomes saturated with steam. In a once-through boiler, water renewal occurs through gravitational convection (the water that has released steam is heavier), which consumes fuel. You need a lot of it, because... convective currents are chaotic, with vortices, and dissipate the received energy more than transporting water upward. The thermal efficiency of a once-through boiler is approx. 35-40% Multiplying this value by the efficiency of a steam engine 25-30% (for modern ones up to 45%), we get the notorious “locomotive” efficiency of 8-16%

In a circulation boiler, the total water flow is directed upward by a separate circulation pump, which pumps out condensate from the steam tank; losses due to internal friction in water are minimal and the power of the circulation pump is required to be small. An elementary volume of water, before completely evaporating, makes from 5 to 30 or more revolutions, which further increases the thermal efficiency and steam output of the boiler. Let’s say that during one revolution of a portion of water, only 10% of it evaporates. At the next revolution, 90% will remain, of which 10% will evaporate, i.e. another 9% of the original volume and water will remain 81% Calculating In a similar way further (mathematicians call such calculations recurrent relations), we get 63% boiler efficiency for 5 revolutions, and 92.6% for 30 revolutions. In this case, the effective area of ​​the zone increases against the geometric one by approx. 1.5 and 2 times.

Drum boilers

The circulation boiler must be equipped with not only pumps, but also a condensate level regulator in the steam separator. If there is too much of it, the technical parameters of the boiler will deteriorate sharply. If it is not enough, it threatens disaster: the wet steam will quickly condense, the pressure in the boiler will also drop sharply - boiling - explosion. Drum-type boilers allow you to avoid this situation. In them, a steam separator is a section of a wide pipe (drum), into which steam-saturated water flows from a boiler (heater), which in this case is not a steam generator; thus, the heating of water and the release of steam from it are separated. In principle, the heater is not capable of boiling, and boiling the drum is not so dangerous, because Most of the energy released is spent on squeezing water back into the heater and supply tank.

Wet steam from the steam separator enters a “free” small-volume condenser, also round in cross-section. The supply pipe rises above the bottom of the condenser, ensuring a constant level of condensate in it. For normal operation of a drum boiler, it is necessary that the pressures of the water columns in the drum and the condenser be equal to each other. To provide last condition The capacitor is not placed close to the drum, but raised above it. As a result, the drum boiler mode is clearly maintained by non-volatile automation (see figure above): there is a lot of water in the drum, the outlet pressure is higher than normal - the differential steam generation regulator cuts off the power; on the contrary, it turns it on. At the same time, the standard water level in the drum is maintained within acceptable limits. A drum steam boiler can also operate on natural circulation, see video below:

Video: about the structure of a drum boiler

A word about water for the drum

Since the water in drum boilers is circulated many times, it must be pure; practically a distillate. Powering drum boilers from water supply sources, as hydrodynamically open boilers, is unacceptable. Drum boilers are built only hydrodynamically closed: the feed water in them is circulated according to the scheme: feed tank - boiler - steam-water condenser (on ships it is washed with sea water) - back to the feed tank, etc.

Gas and water pipe

Gas-tube and water-tube boilers are, one might say, one inverted from the other. In a gas-tube steam generator, a container of water penetrates a bundle of pipes through which hot gases flow from the furnace. In a water-tube, on the contrary, a bundle of pipes with a coolant is washed by a current of flue gases. The difference is very, very significant.

To transfer the energy of flue gases to water, a large temperature gradient (difference) is required. The thermal conductivity of the metal of the steam generator pipes is hundreds of times greater than that of the flue gases. Therefore, the temperature inside the flame tubes can be over 1000 degrees, and their outer surface is cooled with water no higher than 350-400 degrees. Huge thermal stresses arise in the walls of the pipes, and around there is a large volume of superheated water, boiling throughout the mass as the pressure decreases. A rupture of just one pipe of a gas-tube boiler inevitably leads to its explosion. Therefore, the regulations for checking and preventive replacement of gas pipes must be strictly observed, and this work is complex, quite long and expensive.

For these reasons, the temperature of the outer surface of the steam generator pipes of a water-tube boiler is almost equal to the temperature of the water in them. Thermal stresses in the material of water pipes are orders of magnitude lower than in gas pipes. The reliability of the boiler is much higher, the time between shutdowns for maintenance is longer. A rupture of one pipe does not lead to an explosion of the boiler: before boiling spreads to the entire mass of water (which in a water-tube boiler is several times less than in a gas-tube boiler), a powerful flow of steam-water mixture extinguishes the furnace and cools the remaining pipes. The disadvantage of water-tube boilers is that the thermal efficiency and steam production are theoretically lower than those of gas-tube boilers. But structural improvements in water-tube boilers have allowed them to occupy a dominant position in the industry - today gas-tube boilers are not being built, and the remaining units of the classical design are completing their service life.

Note: Drum steam boilers can only be made of water tube type.

Evolution of designs

It is convenient to consider the design of the most archaic (and turned out to be very durable) horizontal gas-tube steam boiler using the example of a locomotive boiler, see figure:

Sukhaparnik is the simplest bell-shaped one. Automation is just one safety valve. There is no feed pump; water comes from the tank by gravity. Thermal efficiency approx. 40%., but the “oakiness” of the centuries-old design is exceptional. Some locomotive boilers are still in use today. They no longer drive trains, they provide steam for production.

There are also water tube boilers with over 100 years of operating experience. But in general, this type of steam boiler is far from retired. In the navy, water-tube boilers are still widely used in power plants today. On ships, the problem of boiler compactness is quite acute. Civilian ships need space for cargo holds and passenger accommodations. On warships, it is necessary to protect the vital and most vulnerable units more reliably from enemy ammunition.

The natural solution here seems to be the use of a vertical boiler, but “verticals” with bundles of pipes are theoretically ineffective: too many flue gases are wasted by the steam generator and the area of ​​the boiler is small. Therefore, preem. are used in ship power plants. drum steam boilers with inclined pipes (see figure; B – drum, P – superheater):

1. With natural circulation, low and partly medium power;
2. With forced circulation – up to and including high power;
3. Multi-collector symmetrical (with 2-3 water collectors and heat exchangers operating on one drum) - from medium to ultra-high power;
4. The same, asymmetrical - at power from high to unique.

On land, compact boilers are also required - maintaining production space is not cheap. But in civilian life, cost, design simplicity and ease of maintenance of equipment often prevail over technical excellence. Therefore, compact land boilers are often made according to the principle: not only turn them inside out, but also bend them in half. Specifically: turn off the flow of flue gases. This slightly deteriorates the quality indicators of the boiler, but the space required for it is almost half as much as for the same power of a locomotive, and it is much more convenient to maintain the boiler, because the chimney root, the firebox throat and the ash pan (if the boiler is solid fuel) are located in the same room.

It is easier to make a gas-tube boiler reversible. The horizontal full-size (on the left in the figure) in this design turns out to be almost as effective, durable and safe as the water-tube one: almost all the heat released in the firebox goes to heating the water, and the gas pipes heat up less from the inside, because the flue gases enter them already quite cooled. A boiler with a shortened steam generator (in the center; such boilers are sometimes incorrectly called vertical) is extremely compact, but uneconomical. Shields in the heat chamber, which well reflect thermal (infrared, IR) radiation, make it possible to bring its performance to acceptable levels.

Modern achievements

Equipping a steam boiler with IR reflectors is generally a fruitful idea. Modern water-tube boilers, in addition to external thermal insulation, are lined from the inside with reflective IR material. This allows the bundles of channels of their steam generators to be made from identical straight pipes, see Fig.. Which, in turn, makes it possible to abandon the drum and feed the boiler from the outside. It’s not hard to imagine how much cheaper it and its operation become from this.

Note: Steam boilers with built-in IR reflectors are called radiation boilers in specialized literature. Of course, there is no radioactivity in them. Meaning thermal radiation(IR radiation).

One of latest achievements large boiler industry - gas-fuel boilers made of heat-resistant special steels with a double-action firebox on counter-flames, see fig. on right. The efficiency of a boiler, like any heat engine, is theoretically determined by the ratio of temperatures at the beginning and end of the operating cycle to the initial temperature (Carnot’s formula, remember?) In boilers with counter-flames, the temperature in the furnace reaches 1800-1900 degrees versus 1100-1200 and others, and the temperature of the flue gases remains the same, 140-200 degrees. In total, the efficiency of the boiler on the counter can exceed 90% without complex additional measures, and with them to be more than 95%.

Note: how modern steam boilers for mass use are structured and operate, see next. video clip:

Video: how a steam boiler works

And in everyday life too

The progress of heating technology has also affected household steam boilers. They must produce low-grade steam for heating systems and cooking equipment, but the safety requirements for domestic steam steamers are stringent, and they must allow routine maintenance by unqualified personnel. Additional requirement– a household steam boiler should be as compact as possible, lighter (not require a foundation) and cheaper. Another thing is the extremely short startup time. Spend up to an hour or more work shift to separate couples is an unacceptable waste even in a society of developed socialism.

The classic solution of this kind is a coil boiler. It is extremely safe for this class of devices: the probability of superheated steam being released outside the outer casing during an accident (this case is considered a boiler explosion) is the same number of times less than there would be pipes in a bundle of a water-tube boiler of the same power. The reason is that there is only one pipe, long, coiled. The steam production and steam efficiency of coil boilers are small, but the first is insignificant in this case, and the second is increased by computer design of a spatial coil and installation of an IR reflector, see figure. But the coil boiler holds a record for start-up time: it produces working steam within 3 minutes after turning on the burner . Automation for a coil boiler is sufficient: thermomechanical, non-volatile, which switches the burner to minimum mode.

The latest achievement in the design of low-potential low-power steam boilers is the vortex jacket boiler. It was, figuratively speaking, turned inside out along with all its entrails. And technically, they swirled the burner flame and instead of a not very technologically advanced bundle of pipes or a coil, they installed a regular boiler jacket, but not a water-heating one, but a steam-water one.

The device and switching diagram of a steam boiler with a vortex burner are shown in the figure:

Symbols on the diagram:

1. feed pump;
2. chimney;
3. economizer (required for boilers of this type, otherwise the flame vortex below may get lost);
4. air duct;
5. blower;
6. vortex burner;
7. steam zone of the jacket;
8. jacket water zone;
9. valve and emergency steam release valve;
10. steam separator (usually absorption);
11. steam output;
12. water level meter (water meter glass);
13. drain valve.

Vortex combustion steam boilers are extremely compact, because fundamentally vertical. Their thermal efficiency is no worse than that of drum ones. Steam can be produced up to and including medium potential. Start-up time – approx. 5 minutes. Disadvantages - complexity, high cost and complete dependence on energy: without pressurizing air into the burner, the boiler does not work at all.

Operation of steam boilers

Not articles are written about the rules for using steam boilers, but volumes of regulatory documents. And neglecting any of their points can lead to an accident. And burns from overheated steam are much more dangerous than ordinary thermal burns: a large latent heat of condensation is released on the body and objects doused with steam and the degree of damage is much greater. In practice, if a steam burn of the body is more than 10-15% of its area, medicine is often powerless. Therefore, we simply inform readers that The old code of safety regulations for boilers and pressure vessels is no longer valid. It is necessary to be guided by the federal set of documents, which have the force of law, “Rules for industrial safety of hazardous production facilities that use equipment operating under excess pressure,” adopted in 2003, published in open, widely available sources in 2013, put into effect at the end of 2014 and fully updated (i.e. excluding the application of the previous Rules) in 2017. You can study the new Rules for the operation of steam boilers and download them in .pdf format for free use.

Note: You can view a course of video lessons on the operation of common DVKR steam boilers below:

Video: series of lessons on DVKR steam boilers

Note to DIYers

Actually, boiler building is not a matter for a workshop in a garage. But the conscience of an engineer does not allow him to indiscriminately dissuade readers from engaging in it: there is too much uncultivated field of activity in this industry. For example, the use of power steam boilers in everyday life. The scheme, let's say, is as follows: a solar concentrator heats a hydrodynamically closed boiler, the steam from which drives a mini-turbine that rotates an electric generator. Insolation is more stable than wind, and in the southern regions it reaches significant values. The service life of steam mechanisms of more than 100 years is not a wonder, but solar battery degrades after 3-10 years. Experts have been working on installations of this type for a long time, but so far there is no sense. And the same Edison also said: “Everyone knows that this cannot be done. There is a fool who doesn't know this. He is the one who makes the invention.”

However, do not rush into cutting, bending, and welding. First, remember: you are dealing with an explosive device. There are no steam boilers with zero explosion hazard and, in principle, there cannot be. Therefore, add additional popular materials to what you read, for example. from here: ( ru.teplowiki.org/wiki/Steam_boiler). Together with the contents of this publication, they will help you understand the specialized literature. Then carefully study the above Safety Rules.

Next, remember that you cannot achieve the same efficiency of a small boiler as a large one by design. The reason is the square-cube law, well known in technology. As the size of the boiler decreases, the volume of the coolant and the heat reserve in it fall along the cube of linear dimensions, and the surface area giving heat loss falls along the square, i.e. slower.

Finally, be fully aware of what you want to achieve. After this, carefully think through the design in your mind (or model it on the computer, if you know how). And only now can you start experimenting, see for example. video

Video: experiments with a homemade steam boiler

To meet technical needs industrial enterprises, electricity generation, as well as for the possibility of functioning of centralized or autonomous systems High pressure steam boilers are used for heating and ventilation. The function of the equipment is to generate saturated steam during the combustion of one or another type of fuel. There are quite a few models of units on the market, differing in size, power and design features. DKVR steam boilers (or double-drum boilers, vertical-water-tube, reconstructed) belong to the high-performance heating equipment, working for different types fuel.

DKVR design

The design of high-pressure boilers is quite complex, which is reflected in the price of the equipment. The units consist of two drums:

• lower – short;
• the top one is longer.

The equipment has a shielded combustion compartment, an afterburning chamber (not everywhere), shield and convective tube bundles. To allow for periodic or emergency cleaning, the bottom of the housing is equipped with manholes, which are also used when inspecting the drums. Platforms intended for maintenance and stairs are installed outside for easy access to the top. The boiler design also includes supply pipelines and partitions, blowers and smoke exhausters. Each basic and additional element performs its own function. They all have a specific installation location.

Natural circulation in a closed circuit of a high-pressure fuel water-tube unit occurs due to the different densities of the moving steam-water mixture in the risers and water in the downpipes, bent in a certain way. The pressure is created due to unequal heating of areas with hot gases. Boilers are called vertical because the pipes in the structure are placed at an angle of 25 degrees or more relative to the horizon. Such units have a larger number of bundles and the number of pipes in them, which is reflected in the increase total area heating This design solution allows for the production of high-pressure boilers without expanding the volume of the drums.

An important component of a number of high-pressure steam generators (with a capacity of up to 10 t/h) is the combustion chamber, divided into two segments by means of brickwork:

• firebox;
• an afterburner chamber that increases efficiency.

Depending on the model, boilers are equipped with additional elements:

• various valves - safety, drain, selection, supply, etc.;
• shut-off valves;
• purge fittings;
• fittings;
• water level indicators;
• pressure gauges and other measuring instruments;
• steam superheaters.

Steam boilers of the DKVR series have the ability to operate in hot water mode. Their design features and technical characteristics make it possible to increase the pressure three times – from 1.3 to 3.9 MPa. As a result, the temperature of superheated steam can increase from 195 to 440 degrees Celsius. The optimal power of the manufactured equipment is in the range of 2.5…20 t/h. The price of DKVR depends on this indicator and the model of the unit.

The operation of steam gas boilers of the modification in question can be carried out in different climatic zones, even in the Far North.

More details about some components

Steam boilers are equipped with:

• protective automation - cuts off fuel in emergency and emergency situations (lack of voltage, flame extinction, sharp deviation from the standard pressure in any of the structural units);
• emergency or warning alarms - light and sound;
• automatic water level adjustment;
• safe ignition system – checks the valve tightness indicator;
• control automation – monitors steam and fuel pressure;
• automatic adjustment of the fuel-air ratio in the firebox.

Screen and convective seamless pipes are made of steel with a diameter of 51 mm. They are connected to the boiler using rolled joints.

Special gas-oil burners are used in cases of separate use of fuel - either gas or fuel oil. They are produced in five standard sizes, differing in power and type of swirler - direct-flow or axial. Each burner is equipped with two nozzles - the main one and the replaceable one. The additional element is activated only when cleaning or installing a new nozzle.

High-pressure solid fuel units are equipped with ash collectors:

• mechanical cyclone type - block or battery;
• working on the basis of ionization - electrostatic precipitators attract charged particles;
• wet – removal is carried out using water.

The centrifugal smoke exhauster is intended for solid fuel boilers. It is installed both indoors and under outdoor canopies. The equipment sucks out of the furnace in one direction carbon monoxide. The function of another element - the fan - is to provide the opposite effect - it forces air into the firebox, which promotes more productive combustion of fuel.

The firebox for solid fuel boilers with a capacity of up to 10 t/h is equipped with belt pneumo-mechanical fuel feeders, thanks to which coal can be continuously loaded onto an already burning layer. It is also equipped with fixed grates with rotating grates. To control them, the boiler design provides special drives, as well as for air dampers.

Principle of operation

After water enters the upper drum through the inlet collectors, it is mixed with the boiler water inside, part of which, in turn, partially enters the lower drum through the circulation pipes. As the water warms up, it rises, again ending up in the upper drum, but with a steam component. The process occurs cyclically.

The resulting steam penetrates the separation mechanisms of the boiler, where moisture is “selected”. The result is dry steam, ready for use. It is either sent directly to the process network or brought to higher temperatures in a superheater.

The process of natural circulation obeys the laws of physics. The fact is that water has a higher density compared to the steam-water mixture. Due to this, the first fluid will always go down, and the second connection will always go up. At a certain moment, the steam separates and rushes upward, while the water, thanks to gravity, returns to its original technological position. It should be noted that in different models the number of circulation circuits varies.

Until recently, DKVR were manufactured for almost any type of fuel - gas and fuel oil, coal, sawdust and peat. But today some of them have been replaced by new, more modern models:

• KE - intended for solid fuel;
• DE – runs on gas-oil fuel.

But many enterprises still use DKVR steam units that have been proven over the years. On secondary market you can buy used boilers in good condition and by affordable price, which will probably last for quite a long period.

Reasons for failure

Correct operation of high-pressure boilers of the DKVR series is a guarantee of its safe work. The heating surface must be cooled in a timely manner, since it receives the maximum impact of flue gases. For this reason, the process provides for constant and intensively uniform circulation of the coolant inside the circuit through the lowering and rising pipes. Otherwise, fistulas will appear on the metal walls over time, and with increasing pressure, ruptures in the pipeline.

In addition, failures can result from:

• incorrect distribution of coolant through the pipes, which is caused by the accumulation of sludge on the internal walls;
• uneven heating of the evaporating walls, resulting from contamination of individual areas;
• improper adjustment of the combustion torch, leading to technologically incorrect filling of the combustion chamber space.

Advantages of DKVR

Design features and technical capabilities heating units DKVR series allows us to highlight:

• significant range of adjustable steam output of equipment;
• delivery in disassembled form - allows installation of high-pressure boilers without dismantling the enclosing structures;
• the ability to select equipment for a specific type of fuel;
• high efficiency rate;
• affordable service price;
• maintainability.

Boiler selection

When purchasing a particular model of high-pressure steam generator, you need to pay attention to the following indicators:

• productivity – uninterrupted technological process and absence of downtime will ensure optimal quantity generated steam per unit of time. In this case – t/hour;
• rated power (steam pressure) – for DKVR it is 1.3 MPa;
• dimensions - determined by the volume of the boiler room;
• price - depends on the three above factors and additional equipment;
• type of fuel used.

The weight of a steam gas or solid fuel boiler should also be taken into account, as it can reach up to 44 tons.

approximate price

The cost of steam boilers depends on their technical characteristics and a set of additional components. Basic price of units Russian production operating on gas-oil fuel is approximately - with productivity:

• 2.5t/h – 1400-1500 thousand rubles;
• 4t/h – 1700-1800 thousand rubles;
• 6.5 t/h – 2300-2500 thousand rubles;
• 10t/h – 3300-3800 thousand rubles;
• 20t/h – 5500-6000 thousand rubles.

The price of high-pressure steam boilers using solid fuel is in the range of 1500-7200 thousand rubles. It should be noted that the basic cost of equipment does not include fans, smoke exhausters and economizers.

To prevent accidents in steam boilers due to excess pressure, the Boiler Rules provide for the installation safety valves.

: The purpose of safety valves is to prevent pressure increases in steam boilers and pipelines above established limits.

Exceeding the operating pressure in the boiler can lead to rupture of the boiler screen and economizer pipes and drum walls.

The reasons for increased pressure in the boiler are a sudden decrease or cessation of steam flow (switching off consumers) and excessive boost of the furnace,

Table 2.3. Malfunctions of water indicating devices, their causes and solutions Nature of the malfunction Causes of malfunction Remedy The glass is completely filled with water Steam tap clogged. Due to the condensation of steam above the water level, a vacuum is formed in the upper part of the glass and the water rises, filling the entire glass Blow glass Covering the upper end of the tube (the upper fitting of the flat water-indicating glass column) with an oil seal packing. The rubber ring of the oil seal was squeezed out through the edge of the glass and closed its clearance Water level is slightly higher than normal Reduced passage of the steam valve as a result of blockage or scale formation in it. The pressure of steam passing through the narrowed hole decreases. Due to the fact that the water pressure in this case will become slightly greater than the pressure. steam, the water level will rise Blow glass Calm level Water tap clogged. The lower end of the glass tube (the lower fitting of the flat water-indicating glass column) was blocked by the oil seal packing Blow out the steam fitting The water level in the glass gradually rises due to the condensation of steam above the water Install longer glass

Continuation of the table. 2.3 Nature of the malfunction Causes of malfunction Remedy Slight fluctuation in water level Partial blockage of the water tap or partial obstruction of the lower end of the glass tube by the stuffing box Blow the glass, clean the lower end of the tube The hole in the faucet plug is not opposite the hole in the body as a result of improper grinding. When moving through offset holes, water encounters hydraulic resistance If there is a large discrepancy between the holes, the plug should be replaced Passage of steam or water in the oil seal of the water indicator glass and, as a result, an incorrect reading Leaky seals, poor lapping of valves, worn plugs Change the stuffing box, grind the taps, change the plugs of the taps Ruptures of water indicator glasses Warping of glass, presence of cracks, entry of hot water into unheated glass Eliminate misalignment. Install glass that does not have cracks, warm up the glass before turning it on

Especially when working with heavy oil or gaseous fuels.

Therefore, to prevent the pressure in the boiler from rising above the permissible limit, the operation of boilers with faulty or unregulated valves is strictly prohibited.

Measures to prevent an increase in pressure in a steam boiler are: regular checks of serviceability of safety valves and pressure gauges, alarm systems from steam consumers to obtain information about upcoming steam consumption, trained personnel and good knowledge and compliance with production instructions and emergency circulars. -

To check the serviceability of the safety valves of the boiler, superheater and economizer, they are purged by forcefully opening them manually:

At operating pressure in the boiler up to 2.4 MPa inclusive, each valve must be used at least once a day;

At an operating pressure from 2.4 to 3.9 MPa inclusive, one valve at a time for each boiler, superheater and economizer at least once a day, as well as at each boiler start-up, and at a pressure above 3.9 MPa, within a period of time established by the instructions.

In the practice of operating boilers, accidents still occur when the pressure in the boiler exceeds the permissible limit. The main cause of these accidents is the operation of boilers with faulty or unregulated safety valves and faulty pressure gauges. IN in some cases accidents occur due to the fact that boilers are put into operation with safety valves turned off using plugs or jammed, or they allow arbitrary changes in valve adjustment, placing additional load on the valve levers in the event of a malfunction or absence of automation and safety equipment.

In the boiler room, an accident occurred with the E-1/9-1T steam boiler due to excess pressure, as a result of which the boiler room was partially destroyed. The E-1/9-IT boiler was manufactured by the Taganrog House-Building Plant to operate on solid fuel. In agreement with the manufacturer, the boiler was converted to liquid fuel, an AR-90 burner device was installed and automatic devices were installed to shut off the fuel supply to the boiler in two cases - when the water level drops below the permissible level and the pressure rises above the set one. Before putting the boiler into operation, the ND-1600/10 feed pump with a flow rate of 1.6 m3/h and a discharge pressure of 0.98 MPa, which turned out to be faulty, was replaced with a centrifugal vortex pump with a flow rate of 14.4 m3/h and a discharge pressure 0.82 MPa. The high power of the engine of this pump did not allow it to be included in the electrical circuit for automatically regulating the water supply to the boiler, so it was carried out manually. The automatic protection against low water level was disabled, and the automatic protection against overpressure did not work due to a sensor malfunction. The operator, having detected a loss of water, turned on the feed pump. The hatch cover of the upper drum was immediately torn out and the lower left manifold was destroyed at the place where the grate beam was welded to it. The accident occurred due to a sharp increase in pressure in the boiler due to a deep release of water and its subsequent replenishment. Calculations showed that the pressure in the boiler in this case could increase to 2.94 MPa.

The thickness of the hatch cover in a number of places was less than 8 mm, and the cover was deformed.

In connection with this accident, the USSR Gosgortekhnadzor suggested that owners operating steam boilers: do not allow the operation of boilers in the absence or malfunction of automatic safety equipment and instrumentation; ensure maintenance, adjustment and repair of security automation equipment by qualified specialists.

In accordance with the letter of the USSR State Mining and Technical Supervision No. 06-1-40/98 dated May 14, 1987 “On ensuring reliable operation of steam boilers E-1.0-9”, owners of boilers of this type are required to reduce the pressure allowed for operation for boilers that have a cover thickness 8 mm hatch with fastening the hatch cover with studs up to 0.6 MPa, since the plants of the Ministry of Energy of Mash produced E-1.0-9 boiler drums with a steam capacity of 1 t/h with hatch covers 8 mm thick and the thickness of the hatch cover was increased to 10 mm.

An accident occurred in the boiler room with the E-1/9T boiler due to excess pressure.

As a result of the bottom of the lower drum being torn off, the boiler was thrown from the installation site towards another boiler and, upon impact, tore off the casing, destroyed the lining, deformed 9 pipes of the side screen. Safety valves were torn out of their seats upon impact. When tested on a pressure bench 1 .1 MPa valves did not work. When disassembling the valves, it was established that its moving parts of the valve were stuck.

The investigation established that the bottom of the boiler 0 600X8 mm was made in a handicraft manner from steel that did not have a certificate.

After welding the bottom, the boiler room workers carried out hydraulic test pressure of 0.6 MPa, while the bottom was deformed. After a few days of boiler operation weld cracks appeared that were welded.

Due to changes in the design of the lower drum hatch cover (without the approval of the manufacturer) and unsatisfactory repairs, an accident with serious consequences became possible.

Safety valve malfunctions

To prevent accidents of steam and hot water boilers due to excess pressure in them, the State Rules

Table 2.4. Malfunctions of safety valves, their causes and solutions Nature of the malfunction Cause of malfunction Remedy Safety valve does not open Too much weight attached Valve plate stuck to seat Remove excess weight Blow out the valve, and if it does not open, turn it with a key Presence of wedges in forks Remove wedges from valve forks Safety valve opens too late The weight is located very close to the edge of the lever Move the weight closer to the valve Extra weight, spring valves have too tight a spring Remove excess weight, loosen the spring at the spring safety valves The lever is rusty at the hinge Remove rust from the hinge and lubricate it The valve plate began to stick to the seat Blow out the valve Lever jamming in skewed guide fork Eliminate misalignment of the guide fork The safety valve opens too early (before the arrow reaches the red line of the pressure gauge) The weight is very close to the valve, the spring of the spring valve is loosely tightened Move the weight to the edge of the lever, tighten the spring at the spring valve Reduced weight on the lever Worn valve plate or seat Add weight Replace plate or saddle (or both) Presence of shells in the seat or plate Sand and scale ingress between the plate and the “valve seat” Distortion of the disc in the valve seat Grind the seat or plate and grind it in. Blow out the valve. Correct skew Lever or spindle misalignment Correct lever or spindle misalignment

The USSR Gortechnadzor provides for the installation of at least two safety valves for each boiler with a steam capacity of more than 100 kg/h.

On steam boilers with pressures above 3.9 MPa, only pulse safety valves are installed.

Due to improper operation of safety valves or their defects, accidents occurred in boiler rooms of industrial enterprises and power plants. Thus, at one power plant, during a sharp load shed due to a malfunction of the safety valves, the steam pressure in the boiler increased from 11.0 to 16.0 MPa. This disrupted the circulation and the screen pipe ruptured.

At another power plant, under the same operating conditions, the pressure increased from 11.0 to 14.0 MPa, as a result of which two screen pipes ruptured.

The investigation found that some safety valves did not work because the impulse lines were blocked by the valves, and the remaining valves did not provide the necessary steam release due to the use of uncalibrated springs in the impulse safety valves and, as a result, some of them broke.

The destruction of springs was observed in pulse valves after each opening. This occurred as a result of large dynamic forces from the jet of escaping steam at the moment of opening of the valve, which has a seat cross-sectional diameter of 70 mm.

The main malfunctions in the operation of lever-load and spring safety valves are given in table. 2.4.

Safety valves must protect boilers and superheaters from exceeding their pressure by more than 10% of the design pressure. An excess of pressure when the safety valves are fully opened by more than 10% of the calculated value can only be allowed if this possible increase in pressure is taken into account when calculating the strength of the boiler and superheater.