Is it possible to do the lining of the furnace with your own hands. Lining or why furnaces do not crumble from high temperatures

Ph.D. V.P. Frolov, chief technologist, A.S. Sebyakin, shop manager, Vermolit LLC, Podolsk

During the operation of boiler equipment, both domestic and European production, the lining of the boiler cover can be destroyed in the place where the burner is located, as well as the lining of the manhole covers, which is typical for domestic boilers.

Due to the fact that it is not always possible to promptly deliver a new boiler cover (especially made in Europe) to the equipment operation site in Russia, many organizations themselves, using "improvised" means, are trying to repair the lining. As practice shows, this operation brings a short-term effect, which ultimately comes down to frequent shutdowns of the boiler and subsequent inefficient alterations of the lining using all kinds of refractory materials (often of dubious quality), which can be found in great abundance on the Internet.

These experiments can eventually lead to sad consequences: the metal wall of the boiler lid can be deformed or burn out, moreover, the high temperature of the lid surface is a violation of the requirements safe operation equipment. Taking into account the fact that many European models of boilers operated in Russia are no longer produced, then, accordingly, the most optimal solution- Contact specialists who will help solve the problem associated with the repair of worn insulation.

Experience in performing work related to the replacement of thermal insulation of boiler covers has shown that it is better to perform these works in industrial (production) conditions, because. using household tools at hand (such as a bucket, a drill with a nozzle, etc., instead of specialized and technically sophisticated equipment), it is impossible to achieve uniformity in pouring the prepared solution (charge), which, in turn, is fraught with a heterogeneous distribution of material densities, and its further rapid destruction.

The raw material base and production capacities of Vermolit allow:

Select a refractory high-temperature mixture;

In special installations, prepare a mixture of the desired fractional composition;

Fill the material in one step, which will allow you to evenly distribute the charge density over the entire occupied volume of the lid;

With the help of furnaces, make a smooth distillation of water from the flooded thermal insulation material, which will give the material the necessary thermal insulation and strength properties, as well as avoid possible errors when drying the lid in place (as part of the boiler), because it is not the correct drying mode that can lead to the destruction of the lining of the cover.

Below are two examples: 1 - non-industrial lining of the cover of a European boiler, 2 - an example of manufacturing the cover of the inspection hole of the KVGM-30/150 boiler, poured in an industrial way.

1. In 2011, we were approached by a company from Tula - food production. In view of the non-standard - sectoral design of the boiler cover, the customer asked to carry out work to replace the insulation at the place of operation of the equipment. It should be noted that the implementation of such work is not often possible due to a number of design and other features.

There are three Italian-made boilers of the same type in the workshop, two of which run on gas and one on fuel oil. Steel fire-tube steam boilers, horizontal design, manufactured in 1995, with a capacity of 3.5 MW, with a maximum operating pressure of up to 16 bar, a maximum steam temperature of up to +210 ° C. The boiler lining is partially worn out and has local destruction(Fig. 1).

Rice. 1. Old boiler lining.

The boiler has three prefabricated parts, which at the same time are the formwork, into which, just, the filling of the refractory heat-insulating mixture (charge) was made (Fig. 2).

The mixture ready for pouring was prepared using a drill with a nozzle, with the possibility of switching the rotation speed when using warm water(more than 25 °C) in a warm shop. This ensures relatively good foamability of the material, but at the same time, the volume of the mixture obtained must be carefully controlled so as not to overfoam the material. The prepared mixture was thoroughly mixed and distributed according to the shape with a trowel (Fig. 2). After initial curing, the molds were covered plastic wrap and left in this state for more than 30 days.

After repair, the covers continue to be used for more than 3 years.

Rice. 2. Preparation and application of the mixture.

I would like to note that in the vast majority of cases, such a design of the boiler cover, which is given above, is rare. Today, thermal insulation is mounted directly into the cover, the inner diameter of which can reach 3 m or more, and the volume of thermal insulation mixture required for lining can exceed 200 liters. Such a volume of the mixture cannot be prepared, poured and dried with the help of an improvised tool.

Mixers are used to prepare the mixture in our production. different types, allowing to obtain a homogeneous mixture in the quantity and quality required for pouring. Empirically, the time was selected (from 7 to 10 days), during which the lid with the charge poured into it is dried, with intrashop temperature conditions(20-25 °C). After natural in-shop drying, the lid is placed in an oven, where stepwise heating to a temperature of 120-140 ° C takes place - this allows you to remove most of the free water from the poured lining material. Since a certain amount of water still remains in the filled material, the first start-up of the boiler with new thermal insulation should be as soft and not long as possible. After the first start-up, a small surface cracking may appear, which is not deep and critical for the operation of the cover.

2. Repair of covers of inspection hatches of boilers installed on boilers KVGM-30/150, operated by JSC "Podilsk Heat and Power Company".

A fairly common problem in KVGM type boilers is the destruction of the lining of the side inspection hatch cover. Since the destruction of the lining causes deformation of the cast-iron mold in which the lining material was placed, further operation of this mold is not possible. This, in turn, entails an appeal to the manufacturer (who does not sell the molds separately, but only the entire hatch assembly) and a series of experiments with improvised, inefficient refractory materials.

Rice. 3. Iron mold manhole cover. View from above. Rice. 4. The same mold filled with lining.

Together with the company's employees, an effective and optimal solution was developed to replace the cast-iron factory mold: a round billet was made from the pipe with three guides, which was reinforced with steel bars (Fig. 3). Next, the mold was filled with an allowance to completely isolate the edges metal surface, as well as on side surfaces was pasted, using high temperature adhesive, special mineral wool(Fig. 4). After pouring, the mold was subjected to stepwise temporary heating to remove moisture from the lining refractory mixture. The finished form was mounted on the manhole cover.

Ecology of consumption. Homestead: Only refractory materials are used for the construction of furnaces. But even they are not able to withstand high temperatures for a long time. To protect the outer walls near the firebox from radiation, thermal or chemical influences, a lining is arranged inside.

In order for the lining made with fireclay products to be strong, durable and efficient, a special solution is required. The best option- ready-made dry mixes adapted for chamotte and laboratory-tested for the mode of operation. Heat-resistant and refractory compounds for masonry are presented on the market in an assortment, and the prices are quite affordable, and experiments with lining are more expensive, since the repair and restoration work of heating structures is a laborious and long process.

Lining with fireclay bricks

Ready-made dry mixes for lining have manufacturer's instructions on the packaging and information on the exact purpose of the composition. The lining of the furnace sections of furnaces requires refractory mixtures, and for other departments, heat-resistant solutions can also be used. Refractory compositions are much more expensive, but only they should be used for lining furnaces, especially since a little mortar is required - you can take it at the rate of 70 kg of dry matter per 100 pieces. bricks.

When lining with fireclay bricks, it should not always be soaked before laying, but in certain cases:

• Dry brick quickly absorbs water from the mortar, as a result, the mortar joint sets faster and loses its plasticity. Correcting something is very difficult, so a good masonry skill is required. If the brick is soaked before work, then it is possible to obtain an additional resource for correcting errors in the masonry by extending the mobility of the mortar mixture.
• When reusing bricks from the disassembly of old stoves, soaking opens the capillaries and pore structures of the brick, into which dust and solutions have entered during the service. Moisture and solutions as a result of moisture penetrate the brick more easily, the adhesion and strength of the masonry increases.
• During summer masonry work, when air temperatures are high, it is recommended to soak the brick for a short time before laying. In autumn and winter, this procedure becomes superfluous and harmful, since the overmoistened brick in the masonry must be dried, and it is unacceptable to heat the stove before the mortar dries naturally and sets in the masonry joints - this can cause deformations in the masonry joints and reduce its strength. Sometimes drying is carried out using heat from a powerful electric lamp incandescence with the full opening of all the doors of the stove.

Dry fireclay brick it is preferable for masonry, therefore, instead of soaking the brick, you can make the mortar mixture a little less thick in order to have a little time to correct possible flaws in masonry work.

Linings with refractory adhesives and pastes

Alternatively, the use of refractory aluminosilicate adhesive for linings, rather than fireclay solutions, has invaluable advantages. These compositions are used not only for linings domestic ovens as masonry and coating mortars, but also in metallurgy. high-temperature adhesives are used for mounting products made of basalt and kaolin fiber, ceramic fiber, fireclay products, with excellent adhesion as a result.

Aluminosilicate glue is sold ready for use, in sealed plastic containers of various packaging, at least 2 kg.

Refractory adhesive lining includes the following steps:

• Before work, the glue is thoroughly mixed until completely homogeneous.
• Apply glue to pre-moistened surfaces with steel spatulas. Glue is applied to the walls of the furnace section and / or other elements of the lining thin layer- no more than 3 mm. In the case when the lining is carried out only with an adhesive layer, without sticking cardboard or other materials, the adhesive is applied 3-4 times, with each layer holding for about 15 minutes.
• When fixing basalt cardboard on horizontal surfaces the adhesive mass can be diluted with water up to 15%. The consumption of the adhesive composition is affected by the quality of the treated surfaces and the thickness of the applied layers, the adhesive can go per square meter. Meter within 2-4 kg.
• The adhesive layer dries completely in a day, if the temperature is not lower than 25⁰С and the application thickness is not more than 3 mm. At high temperatures (more than 85⁰С), complete drying occurs in 5-7 hours.

Furnace linings for brick ovens and fireplaces

When lining the walls of the furnace departments, it is imperative to take into account the inevitable thermal expansion of materials under temperature effects when stoves, fireplaces or boilers are in operation. Internal protection from a layer of fireclay and an outer masonry layer of ordinary red brick should have a compensation gap of 0.7-1.0 cm and / or a gasket layer of asbestos cardboard, basalt or kaolin sheet, or rolled material. Direct contact of the outer wall of the furnace section with the lining of the furnace is unacceptable; there must be either free clearance or filling with heat-resistant material, otherwise the difference in the thermal expansion of materials will cause deformations and the structure will gradually collapse.

Before starting masonry, the need for materials is calculated. Fireclay bricks are more common standard sizes 250*150*65 mm. Chamotte products are produced in large assortment, this makes it possible to select fireclay for a configuration of any complexity - for combustion chambers, a fireplace vault, arches, etc. It is possible to lay out inclined surfaces along the frames of grates and form the back walls of fireplaces, the so-called "tooth" - a reflector of heat flows. In fireplaces, the inner walls are made with a slope so that the heat goes into the room, and the combustion products are directed into a precisely calculated hole. In the same way as in furnaces, fireplaces are required expansion gaps between fireclay lining and external brick walls.

The thickness and materials for lining are selected based on the operating mode of the furnace or boiler unit. In order to strengthen the fireclay masonry, reinforcement is also used. Reinforce seams steel wire with a diameter of 3 - 5 mm in every second row. When furnaces are built according to ordering schemes, the linings are made in parallel, and all dimensions are already calculated and painted in order, as well as the shapes and sizes of fireclay products.

But if you need to carry out the lining of the furnace of an already built furnace, the process steps are as follows:

• The first row of fireclay bricks is laid around the grates, and a brick with a sloped edge is preferred to provide a slope towards the grates.
• AT finished fireboxes laying out the back wall with a slope is extremely difficult, so you have to make them even. The rear and side walls of the lining are lifted simultaneously.
• With small sizes of furnaces and the need for their lining, not fireclay bricks are used, but thin-walled fireclay panels or coatings with a paste-like refractory composition. When performing coatings, it is necessary that the entire surface has been treated. Before work, they arrange an upper illumination by removing cast-iron rings from the burners.

When lining furnaces of any size, as well as when laying, it is unacceptable to combine ceramic heat-resistant bricks and refractory fireclay bricks. These materials vary greatly in density and linear expansion, and in addition, they have different coefficient thermal conductivity. The combination of fireclay and red brick will give masonry that is subject to deformation when heated, unstable and unreliable, with the main red brick cracking and breaking first. To compensate thermal expansion, between fireclay and ceramics, gaps are always necessary with a gasket of a refractory sheet made of asbestos board, basalt or kaolin. In small furnaces, when lining, it is also difficult to arrange gaps, but this is necessary, at least minimum size half a centimetre.

Metal furnace furnace lining

The linear expansion of metal and fireclay is incomparable with similar parameters of bricks different kind, therefore, when lining steel furnaces, the issue of gaps does not even arise. The thermal gaps between the steel sheet of the furnace and fireclay are filled with asbestos, but kaolin or basalt wool or mats.

Metal lining heating stoves inevitably reduces the heating efficiency, since part of the heat from the combustion of the fuel will go not to heat the walls, but to the chimney. Therefore, in the presence of an internal lining of furnaces, the outer lining of a steel furnace ceramic brick it is completely unnecessary to do this - the high heat capacity and low thermal conductivity of ceramics will greatly reduce heat transfer from the furnace.

They begin to line a metal firebox from the bottom to the top, just like a brick one - they lay out the bottom, along the flooring of, for example, basalt cardboard, not thinner than 1 cm. Cardboard or sheets of other heat-resistant material are fixed with refractory glue.

Differences in the lining of heating solid fuel boilers

Features of the lining of boilers consist in taking into account the specifics of work - the boiler unit must generate thermal energy and continuously transfer it to the heat exchange circuit to the circulating coolant, and heat dissipation through outer case design of boilers is reduced to a minimum, since in the context of boilers, heat transfer to the outside is heat loss. All this determines the differences in the lining of various boilers, depending on their shielding.

The main three methods of boiler lining

1. Rarely used for domestic boilers - heavy linings. If the boiler has weak shielding and heats up during operation above 1200⁰С, then there are risks that the walls of sheet steel will quickly burn out. In addition, servicing such a unit is no longer safe, and fires are possible. When making heavy linings, fireclay bricks are laid with a spoon in two or even three layers. As a result, the temperature of the outer surfaces of the boiler drops to 80⁰С.
2. A single-layer fireclay lining is considered lightweight. At the same time, from the outside, the surface of the boilers is additionally lined with non-combustible material based on the specific temperatures to which the unit is heated, and from above, sheathing with sheet steel is also possible.
3. External lining of refractory compounds - glue, viscous coatings or pastes in order to thermally insulate the pipes from above. This simple lining method is used in areas where it is difficult or impossible to use other heaters due to high heat. Coating lining is applied with brushes for two, less often three or four times, laying a reinforcing fiberglass mesh. Steel meshes are not used, because when heated, they give too much linear expansion. The mesh provides protection against possible through mechanical damage to the lining layer. Such a thickened multi-layer lining prevents heat loss through the pipes.

Features of the lining of fireboxes of stucco clay stoves

Stucco adobe oven now in big fashion, and the variety of such furnaces in terms of designs, constructions and dimensions is growing, despite the huge range of cast-iron and steel furnaces and all the necessary building materials for the construction of brick stoves. Stucco stoves are special - they are very ancient, time-tested and highly functional, and heat, and "treat", and create an exclusive chic. A bizarre stucco stove with stove benches is now an unconditional powerful trend. Stucco firebox adobe oven also needs protection - lining.

For stucco furnaces, experts recommend using fireclay as linings. A small exception is if the stove is made of mortar with stone reinforcement (quite sophisticated technology on the verge of art), it is possible to confine oneself to coating lining with refractory glue or pastes. The same compositions are used as for furnace furnaces and boiler pipes - mullite or corundum mixture, special expanding alumina cements, fireclay mortar mixtures or marls, as well as adhesive aluminosilicate compositions.

Lining with pastes and viscous adhesive compositions It is simple and does not require high qualification, but only accuracy and attention. When the refractory coating hardens, it forms a monolithic protective shell and will not allow cracking of the main clay walls of the furnace during strong heating.

Lining, repair and restoration of furnace chambers

All furnaces before starting a new season of operation after the summer months are subject to revision checks. During the period summer downtime impacts are possible, the results of which are not immediately noticeable, but will lead to cracks and chips at the beginning of the furnace. These phenomena not only reduce the efficiency of heat transfer from the stove, but can also become very dangerous - these are the risks of carbon monoxide in the residential area. Carbon monoxide, or carbon monoxide, a gas without taste, color and smell, extremely dangerous to health and life - this information is trivial and familiar to everyone. Revisions of the furnace after downtime are carried out along the outer brick (lined, plastered, tiled, etc.) layers, as well as in without fail and on the internal surfaces of the existing lining. All cracks and damage are carefully sealed.

The lining is repaired with refractory coatings - mastic, glue, mortar. It is enough to restore the outer surfaces with a heat-resistant material. Fire up the stove after repair work should not be earlier than the refractory and heat-resistant material is completely dry and seized, and only by natural drying. Deformations in the areas of embedding occur if the furnace is started to be fired immediately after repair.

Independent lining of the furnace and boiler is possible, but it requires knowledge and some experience, therefore, professionals are often turned to these issues. After all, it is not enough just to carry out the work, you also need to calculate the required thickness of the lining and choose the right material from a considerable range of materials. published

If you have any questions on this topic, ask them to specialists and readers of our project.

What is a lining, and is it always necessary? Let's try to understand this issue.

Lining - this is a way to protect the walls of the furnace or fireplace from overheating when very high temperatures Oh. The walls of the firebox can crack, and the metal can get too hot and break down over time if the temperatures in the firebox exceed 700-800 degrees Celsius. This occurs, as a rule, when burning coal, although pellets can be very hot.

Overheating is not the only effect that negatively affects the walls of a metal or brick firebox. The lining can also have the following functions:

• Protection against temperature extremes (thermal insulation properties).
• Protection against aggressive reagents (acid-resistant lining).
• Lining as a facing material.

In general, the lining can create a tight environment inside the firebox and can extend the life of the furnace firebox and the stove / fireplace as a whole.

Negative moments of lining:

• The inner lining of the furnace absorbs or reflects part of the radiant heat fluxes (heat goes into chimney), and, accordingly, the fireplace heats less.
• Actually, the labor costs and the cost of lining.

In what cases is it necessary to do without a furnace lining?

The lining is necessary if you have a metal firebox (cast iron, steel), and the firebox is powerful enough to generate a temperature of 700-800 degrees Celsius. Large fireplaces with a large amount of firewood on one tab, almost all, even without coal, are able to reach this temperature, and the lining will significantly extend the life of the fireplace.

For a medium-sized potbelly stove made of cast iron, whose task is to smolder firewood, lining is not necessary.

A fireclay firebox also does not need a lining: fireclay is a lining in its essence.

Lining inner surface chimney , in addition to protection against high temperatures, it helps to smooth the inner surface of the chimney (as a result, combustion products accumulate in it less, and the chimney does not need to be cleaned so often) and its sealing.

What materials are used for lining the stove/fireplace?

Furnace lining materials, depending on the degree of protection, are divided into 3 classes:

• Class A materials - based on silica. This is artificial materials(bricks made of pressed rocks) and natural (rocks) materials. Such materials are suitable for facing the fireplace portal (these are well-known granite, sandstone, quartz), but for lining the furnace from the inside, thermal protection is weak, since the materials have low thermal conductivity and are prone to cracking.
• Class B materials - based on clay and alumina. This is the usual, familiar to us fireclay refractory brick and bauxite brick (fired alumina brick with an admixture of iron oxide and bauxite). Suitable for lining inside the furnace, withstand high temperatures.
• Class C materials are mixed materials that cannot be attributed to the first two classes. These are refractory mortars, coal bricks and basic heels based on hammer scale, ore and slag.

Lining errors

Many craftsmen, making brick lining, butt it to the firebox, leaving no gap. The fact is that under the influence of high temperatures, brick and metal expand in different ways, and such laying can lead to cracking of the lining.

In addition, conventional brick used for lining has low thermal conductivity. The metal furnace lined with it back to back will be shielded with a brick from environment(the room that needs to be heated), and all the heat will go into the chimney instead of the room.

How are the lining bricks attached inside the firebox?

There are two popular ways of fixing bricks inside the firebox:

• With the help of clay.
• Bricks are stacked on top of each other with an intersection, and fastened with metal bolts to each other, for which holes are made in the bricks.

The focus is on structural performance, work individual components constructions and provision of smoke removal function. Initially, materials for the manufacture of the structure are also calculated, since the specifics of its operation determines stringent requirements for the characteristics of the unit. At the same time, the base material is far from always able to cope with the thermal effects that a particular furnace is designed for. Lining like technological operation additional processing, allows and minimizes thermal negative factors and prevent mechanical damage to the structure.

In what cases is lining performed?

The initial choice of building material for the technical implementation of the structure is made taking into account its ability to cope with operational loads. As noted above, basic characteristics is not enough. It is necessary to use additional thermal insulation materials in some cases associated with an increase in temperature loads on the surface of the structure. In particular, this applies to furnaces designed to operate in long-term combustion modes. Also elevated temperatures gives high-calorie fuel, although such units are rarely used and mainly in enterprises.

As for household furnace structures, they, as a rule, do not require additional protective coatings, but only when it comes to structures of small and medium sizes. The situation is different if a massive Russian stove is considered. The lining in this case allows you to provide protection for functional areas that can also be used for cooking.

Basic lining materials

Brick is considered a classic material for lining stoves. With its help, an external shielded protection is formed. This option is suitable for sauna stoves, which require some kind of complete thermal insulation. In the usual version, the refractory lining with fireclay is a lining of the furnace part in order to protect against elevated temperatures.

With the development of technology, other means of ensuring the protection of furnace structures have appeared. So, if earlier concrete mortars were prepared, from which ordinary plaster was later laid, then in its modern form the same method looks somewhat different. The main difference is that the mixture is applied to a hot surface using shotcrete technology. That is, the refractory concrete is applied to the target surface in layers using pneumatic means based on compressed air.

Roll lining

The fundamental difference from classical coatings and masonry with a heat-insulating function is roll coatings. First, they are easy to apply. Secondly, the coating takes up a minimum of space, increasing the thickness of the structure by no more than 1 cm. For comparison, heat-resistant concrete in the form of plaster increases the thickness of the walls of the furnace structure by 1-2 cm, and a brick can reach 10 cm in this indicator. roll material presented in several forms, as a rule, on a paper fire-resistant basis.

The most widespread in this segment is mullite-silica, which is obtained by melting silicon and oxide in an electric furnace. In practice, it is noted that this material has low thermal conductivity and at the same time increased thermal stability. Also, kaolin thermal insulation materials are not destroyed by chemicals, for which they are valued in industrial production.

Induction Furnace Protection Features

To begin with, it should be noted that the need for lining induction furnaces arises not because of the weakness of the structure before thermal shocks, but because of the specifics of their application. Such units are used for melting metals at high temperatures, therefore, to protect them, special means in the form of dry mixes. In essence, this is a classic coating, but the composition for the mass is radically different from concrete solutions. Thus, the lining of induction furnaces, which melt low-alloy and carbon steel, involves the use of spinel-forming masses. The latter, by the way, are resistant to the formation of slag. Units for melting cast iron are treated with quartzite compositions, and if non-ferrous grades with steel are added to this metal, then technologists add mullite-forming components to the lining recipe.

Execution technology

Exist different techniques and lining approaches that differ in surface coverage and insulating material application. Protective lining can be external and internal. The outer lining is usually applied over the entire height - from the bottom to the crowning edges. Interior decoration may provide for the protection of working surfaces in contact with both direct flame and smoke in the form of high-temperature exhaust gases. The greatest effect is given by protection circuits that comprehensively isolate the furnace. Lining is carried out only on cleaned surfaces. Preparation of the material, as a rule, involves the dilution of active substances in solvents. In this way, a mixture for coating is formed, which is applied to the surfaces of the structure using traditional facing tools. Brick, in turn, is laid on typical schemes in accordance with the requirements for the protection of structures.

Conclusion

External coatings of furnaces should not only provide resistance to thermal effects, but also provide protection from other factors. For example, in the conditions industrial premises increases the risk of mechanical stress to which the furnace may be subjected. The lining in this case also involves the fulfillment of the tasks of physical protection of the structure. Therefore, special plasticizers can be added to the mixture, modifying the strength properties of the composition. But this applies only to the means of creating external thermal insulation, and internal coatings completely focused on the formation of effective temperature screens.

The operation of a steam boiler is accompanied by significant heat release, which affects not only the heating surfaces, but also other structural elements steam boiler. To protect the metal elements of the inner casing from high temperatures, all structures that are not covered by heating surfaces are covered with a layer of thermal insulation.

as insulation in steam boilers use; asbestos, fireclay bricks, refractory ceramic products, refractory silicon carbide products, covelite boards.

Brickwork (lining) covers all the walls of the furnace and gas ducts (Fig. 26, 27) up to the area where the temperature of the gases does not exceed 600 0C (usually the economizer area). Bricks are usually square shape, and are attached to the inner casing through a layer of asbestos cardboard. More heat-stressed bricks located in the area of ​​​​the furnace are attached to the elements of the inner casing of the boiler using individual bolts. The heads of the bolts are sunk into bricks, and the recesses are filled with a mortar - a mixture of fireclay powder, refractory clay and sand. Less heat-stressed bricks are attached to the inner casing of the boiler with T-bars, into which they enter with their grooves.

1 - a layer of asbestos cardboard; 2 - fireclay bricks; 3 - silicon carbide product;

4 - mortar; 5 - insulation of the outer casing.

The bricks from which the lances of the furnace devices and viewing devices are laid out (Fig. 27) have complex shapes with bevelled edges.

Brickwork is carried out in such a way that the surface from the flue side is even, without ledges (Fig. 26). In the area of ​​​​transitions from one brick thickness to another, the inner casing of the boiler is made stepped. Near maximum temperatures in high-stress furnaces, brickwork can be done in two layers; the bottom layer is fireclay bricks; upper layer- refractory silicon carbide products.

The lining is one of the most expensive parts of steam boilers. The weight brickwork in some steam boilers it can reach 10 tons or more.

To insulate the outer casing of the boiler and collectors, covelite plates are used, which are laid on a covelite base grease and tightened from the outside. metal mesh. The grid is coated on top with covelite plaster, covered with fabric (percale or twill) and painted with silver.

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