To do correct device chimney, you must have a detailed diagram of this structure. Improper laying can provoke the accumulation of harmful toxic substances indoors. Such work should be carried out by a highly qualified specialist who knows everything about such a structure.

The correct level of flue draft ensures that carbon monoxide is quickly removed from the living space. Such a structure is a kind of pencil case that removes caustic combustion products.

Several models of chimneys are presented in specialized departments. They differ in their structure and the material from which they are made. Our guide provides detailed instructions how to make a chimney for a stove with your own hands. Recommendations from experienced professionals greatly facilitate the task.

Types of chimneys

Drainage shafts through which the withdrawal is carried out harmful gases, saturated with combustion products, are required not only for standard stoves, but also for fireplaces and gas boilers. To date, several types of chimneys are known. These include:

Direct streaming. This variety is considered a popular building, which is most often used for arranging living space. The only drawback of such a chimney is the rapid heat loss. In addition to toxic substances, most of the thermal energy escapes here.

Straight flow pipes with lintels. They retain most of the heat in the combustion process of materials. This design is quite often used in baths. Such a long-burning chimney for a stove requires constant cleaning. Ash quickly settles on the surface of the jumpers, thereby preventing the rapid removal of toxic substances.

Straight flow chimney with labyrinth. This variety has a high heat dissipation. Carbon monoxide gases pass through numerous bridges. They quickly heat the walls of the chimney, thereby contributing to the maximum heating of the room.

Kolpakovy. It is used for the Russian stove. Hot smoke quickly rises up, where it gradually begins to cool. After that, it descends along the arch of the chimney masonry. The only drawback of such a structure is its uneven heating.

Modular. They are made from metal alloy. They are designed for gas-fired heating systems. Metal chimneys for furnaces are able to cope with the acidic compounds of methane combustion products. Brickwork in this case will quickly collapse.

Chimney device

The effective operation of the chimney shaft directly depends on several criteria. For example, sections, heights and the material from which it is made.

What should be considered in the process of a device of this design:

Outlet size heating device should be slightly smaller than the cross section of the chimney channel. If the diameter is slightly larger, then you will need an additional adapter that will regulate the process of smoke removal.

Particular attention must be paid to the horizontal part of the structure. Warm air moves up quickly. Soot and combustion products quickly begin to settle here.

Thrust control will help shorten this process by reducing the length of these segments. They must be less than one meter. In addition, it is necessary to provide a condensate collector and doors for cleaning the chimney.

For sauna stove, it is best to use a vertical chimney. In some cases, a metal pipe can be laid. During the fixing process, it is recommended to observe correct angle tilt. It should be no more than 2 meters.

Stages of creating a vertical chimney

To create a chimney shaft, you need to prepare the following tools and materials. For this you will need:

• brick of the first grade;
• building composition;
• level;
• rope for guide;
• stairs;
• construction diagram.

Creating a chimney includes the following steps:

The first layer is laid out of five bricks. The laying should be neat and even. The subsequent rows are made in the same way.

When the required height is obtained, you can proceed to the construction of the edge. Each subsequent row lays down 35 ml more. The result is a stepped structure in the area of ​​\u200b\u200bthe ceiling.

After the pipe has reached the level of the attic, it begins to be laid according to the initial stage. The hole diameter should gradually decrease.

The final stage will be the removal of the brick shaft beyond the roof. The photo of the chimney for the furnace shows the entire workflow.

Photo of chimneys for the furnace

For the manufacture of chimneys are used various materials, some of which have been in use for several centuries, while others have been actively used only a few years ago. Any type of smoke outlet has its own characteristics, so it is important to have an idea about each of them.

Chimney materials

Structural element in question heating system can be built from traditional building materials, but wealthy owners can afford materials created according to the latest technologies. The choice of a solution for a particular house primarily depends on economic feasibility, requirements fire safety and aesthetic views of the homeowner. We advise you to study more information about in addition to this article.

Metal chimneys

As mentioned above, metal pipes for smoke removal are divided into single-layer and double-layer. Single-layer are a cylinder, which, as a rule, is installed inside a brick or ceramic chimney. Two-layer ones consist of two cylinders of different radii, between which a layer of heat-insulating material is placed, which is most often basalt mineral wool.

Advice! If the exterior design of your home is antique, then to maintain stylistic uniformity, the metal chimney can be covered with a copper casing.

Black metal

High-quality chimneys made of this material are covered with a layer of enamel on top, which reduces their susceptibility to burnout and corrosion. As a result, such a product may for a long time to serve at temperatures up to 500 ° C, while short-term drops up to 700 ° C are acceptable.

The key advantage of ferrous metal smoke exhaust pipes is the most low price, but performance characteristics don't let them be effective solution for furnace heating working in intensive mode.

Stainless steel

This material is ideal for all types of chimneys. Alloyed stainless steel tolerates temperatures well up to 850°C and also withstands peaks up to 1200°C. Earlier we already wrote about and recommended to bookmark the article.

AISI 321 is considered the best brand for structures of this type (they contain molybdenum impurities), but AISI 316 and AISI 304 are also widely used. It is worth noting that many unscrupulous manufacturers produce products from less heat-resistant grades, as a result of which they can burn out already after 10-15 years of light use.

Advice! When choosing a stainless steel chimney, be sure to ask about the quality of the steel. You can independently evaluate this parameter using a magnet: good steel has a large amount of alloying additives, as a result of which it does not magnetize.

Do-it-yourself sandwich chimney for a stove

The best option for installing a do-it-yourself stove chimney is a stainless steel sandwich system. It looks good and meets all modern fire safety standards. An important advantage is the fact that it is as simple as possible to assemble it alone, without having experience and special knowledge. It is enough to adhere to the following recommendations:

• The installation process should start from the bottom elements.
• In places where the pipe comes into contact with wood and other flammable materials (in the area of ​​​​the attic or roof), insulation, such as stone wool, must be used.
• In order to protect the surface of the ceiling, a steel platform must be installed in the area of ​​the chimney passage.
• In case of creation outer pipe it is necessary to include in the system tees designed to drain condensate.
• The above elements are inserted into the ones below.
• It is advisable to protect the top outlet of the chimney with a fungus, weather vane, deflector or spark arrester.

Homeowners, as a rule, take the organization of heating in their home with all seriousness, choose the safest models of boilers, turn to experienced stove-makers. However, it is sometimes overlooked that incorrect chimney installation is often even more dangerous.

flue pipe - essential element heating system in a private house, the assembly of which is carried out in accordance with building codes and fire safety requirements. Installing a chimney without following these rules is fraught with irreversible consequences - a fire or carbon monoxide poisoning in the house. Today's article will tell about the types of chimneys, the device and installation methods.

The chimney is used to transfer smoke and combustion products into the atmosphere, it starts from the inlet heater in the house and ends above the roof ridge with a protective umbrella. In private construction, the following types are mainly used:

The material from which the chimney is made can be correctly selected based on three factors: compliance with the material of the heater, low thermal conductivity and tightness of the joints.

Chimney outlet methods

The main task of the chimney is to remove smoke outside the house, which can be organized in several ways. The choice of pipe insertion point depends on the location of the heater, the free area and the type of chimney. use the following options pipe placement:

External placement is well suited for the bulky construction of a brick chimney, and if you bring a metal pipe through the wall, you will have to take care of additional insulation or use special sandwich pipes.

Chimney Requirements

The selection of elements is carried out taking into account the requirements specifications heating device. In order for the system to work smoothly, the basic principles of chimney design must be observed:

1. A round shape is preferred, as combustion products and dust accumulate in the corners of the pipe. Round chimneys require cleaning less often than rectangular and square.
2. The cross section of the pipe must not be less than the diameter of the heater nozzle. It is calculated that for every kilowatt of power, 8 sq. see section. Usually information about required amount chimney is contained in the instructions for the heater.
3. Each heater requires its own chimney. In some cases, you can deviate from this rule, but then the devices should be located at the same height, the distance between the connection points is 1 m or more. And the size of the pipe section should take into account the total power of the heat generators.
4. The total length of the horizontal sections of the chimney cannot exceed 1 m; violation of this rule reduces the draft force.
5. The chimney ends 0.5-1.5 m above the ridge, on a flat roof - 0.5 m above the surface.

The main criterion for selecting pipes is fire safety requirements and compliance with a heat generating device, appearance, aesthetics and saving space inside the house are secondary.

Mounting sequence

Installation of an internal chimney begins with drawing up a diagram and calculation required amount pipe segments. To assemble correctly, the device is performed in the following order:

Scheme of the chimney outlet through the corrugated roof

After the installation is completed, it is necessary to start the heating system, check the draft and the tightness of the connections - even a slight slight smoke indicates serious problems, the solution of which is unsafe to postpone.

Installing a chimney in a house is a responsible event, the quality of which depends on the comfort and safety of the heating system, so follow the recommendations of the manufacturers, the installation technology.

Video instruction

The technology of laying a brick chimney in itself is quite simple and understandable, since, unlike the brick oven itself, the pipe usually does not have internal channels that are complex in configuration. However, despite the relative simplicity of the design, one cannot but take into account the enormous importance of this department of the furnace, since the quality of the heating of the house and the safety of both the building itself and the people living in it directly depend on it. Therefore, in order for all the work to be crowned with success, it is necessary to approach it with the utmost care, based on the recommendations experienced craftsmen and on developed and tested design schemes.

When erecting a chimney, it should be remembered that the evenness of the inner walls of the channel is no less important than the aesthetics of the outer masonry. Not only the stability of the required draft in the furnace depends on this circumstance, but also the duration of operation of the chimney without cleaning, since the smoke rising through the pipe leaves on smooth walls, without protruding mortar and deep seams, a much smaller amount of fuel combustion waste, and the channel overgrows much slower.

What are brick chimneys?

Chimneys of brick ovens can have different types, depending on the place of their installation, the design of the furnace, and also on how many heaters will be connected to the pipe. So, there are three main types of chimney brick pipes: these are mounted, root and wall.

• Wall-mounted chimneys . The most widely used constructions are packed pipes. They are good because they are compact and do not take up any additional space in the room at all, but are simply a vertical continuation of the furnace.

They are erected on top of the last row of bricks covering the furnace, around the left hole. The pipe is then passed through attic floor, attic, truss system and rise above the roof.

• Indigenous chimneys . This type of pipe is installed in cases where it is planned to connect a metal stove to it, or several heating appliances located on one or even several floors.

In addition to metal, such a pipe can be connected and brick ovens. This type of chimney is especially convenient if it is necessary to build two stoves in the house in neighboring rooms. For example, a kitchen needs an oven with hob, and for the next room - only heating. In order not to lay out a separate pipe for each of them, a root chimney is built between the rooms, to which both heaters are connected. Not only two, but also three or four stoves located on different floors of the house can be connected to a pipe of this type. In any case, it is necessary to calculate the size of the internal chimney channel very accurately, otherwise normal draft may not be ensured when several devices are operating simultaneously. The answer to the question why may be different.

• Wall chimneys line up near the main (external or internal) walls or are built into them. They can be used, just like the main ones, to connect several furnaces located on different floors of the building.

The convenience of this design lies in the fact that it is, as it were, outside the living quarters, without occupying their area. For example, on the first floor of the house a fireplace can be built and connected to the wall chimney (there the pipe will be more like a wall chimney according to the principle of structure), and on the second floor a chimney pipe is embedded metal furnace(in the same way as in the version with the root requirement).

The disadvantages of this version of the chimney are the considerable cost of the project and the complexity of the work. Firstly, the construction of this structure will require much more building material. Secondly, the chimney, if it is partially on the street, requires serious insulation measures, otherwise winter period, with temperature changes, condensate will form in the internal channels, which will significantly reduce the efficiency of the heater. Therefore, if this chimney option is chosen, then it would be more prudent to sacrifice the area inside the premises and bring the pipe along inner wall Houses.

Parameters of brick chimneys

The main sections of the brick chimney

A brick chimney is divided into departments that have an owl purpose and are named differently. These features must be immediately clarified so that in the future it will be easier to understand the description of the work on the construction of the pipe.

1 - Pipe head. Laying out this part of the chimney, the bricks are shifted into outside to get a kind of "visor", as if hanging over the lower sections, partially protecting the pipe walls from atmospheric precipitation.

2 - The neck of the pipe is located immediately below the head and has the same perimeter over its entire height, without protrusions, extensions or narrowing.

3 - "Otter" has more complex scheme masonry, as it has a protective function. Firstly, the laying of the "otter" hanging over the gap formed at the junction roofing material and the walls of the pipe, closes it from the penetration of precipitation, and forms a space for the installation of a waterproofing material. Secondly, its expanded walls become a guarantee of safety - at the point of passage through roofing due to the increased thickness, the necessary level of thermal insulation is created.

4 - A metal or other sheet (apron), mounted in the lower part of the otter, forms a kind of ebb, which closes the junction of the brick wall of the pipe and the roofing material.

5 - "Fluffing" - this expanded part of the pipe, located in the area of ​​\u200b\u200bits passage through the attic floor. The walls of the "fluff", like the "otter", are thicker than other flat sections of the chimney - this is necessary for fire safety, since the attic floor very often consists of flammable materials, and they cannot be allowed to overheat.

6 - Roofing structure.

7 - A riser is a straight section of a pipe that has an even masonry along its entire height and is located in the attic space from the “fluff” to the “otter”.

8 - Attic floor.

9 - An umbrella cap is often fixed on top of the head, which will protect the internal chimney channel from water and debris entering it.

You may be interested in information about what is

The main function of the chimney is to effectively remove combustion products from the combustion chamber into the atmosphere. To do this, the chimney is connected to numerous channels located in the furnace structure, with which it must interact harmoniously. If the stove and chimney are built correctly, in accordance with the developed parameters, then during the operation of the heater inside the channels, good traction, which will contribute to the timely removal of smoke to the street. However, at the same time, this should not lead to the fact that the heat generated by it will fly out of the furnace literally “into the pipe”. In a word, everything needs a “golden mean”.

Cross section of the chimney channel

To select the correct parameters for the section of the chimney channel, it is necessary to take into account the power of the furnace, as well as the size of the combustion chamber. The flue ducts will remain clean longer if their inner walls are made smooth, without protrusions and sagging of the solution.

For this reason, during the laying of bricks, the excess masonry mortar it is necessary to clean not only from the outer, but also from the inner walls. Some owners of houses equipped with fireplaces or stoves also use another way to achieve the smoothness of the walls of the channel - they install a ceramic pipe called an inlay inside the brick chimney.

The advantage of this design is not only that the inlay has absolutely smooth inner walls. It is round in cross section, that is, it has no corners, which means that the smoke flows will not encounter obstacles in their path and, at the same time, unnecessary turbulences and the “back draft” effect will not be created.

On the right of the illustration, the “ideal” movement of the flow of hot gases is shown, which are twisted into a regular spiral in a round pipe and do not meet resistance.

In addition, one must take into account the fact that chimneys with a large width, which are still installed in old houses, often have poor draft. This is due to the fact that the air heated in the furnace in large space inside the pipe, cools down quickly, which leads to the formation of condensate, which contributes to a decrease in traction, as well as smoke in the premises, and the channel quickly overgrows with soot. To heat a stove with such a chimney design, you will need to use too much fuel. Therefore, it would be most rational to fix them by dismantling the wide upper part of the chimney, then narrowing the shaft and installing a round or square with rounded corners, ceramic, metal or asbestos insert into it.

Now from the form - to linear parameters. The size of the internal section of the chimney channel is one of the most important characteristics, since the efficiency of the furnace directly depends on it. The correct ratio of the power of the heater and the dimensions of the pipe section must be observed. Another guideline for determining the correct size of the channel can be the opening of the blower door - in any case, the cross section of the pipe should not be less than the blower hole.

The cross section of the chimney shaft, relative to the size of the combustion chamber window, can be determined as follows. For fireplaces with an open firebox, the size of the chimney opening is on average 1:10. However, depending on the shape of the section and the height of the pipe, this indicator may vary in one direction or another. Approximate values ​​of the cross-sectional area of ​​the channel (in percent) are shown in the table below.

Ratiof/F in % (f is the cross-sectional area of ​​the chimney channel;F is the area of ​​the combustion chamber window)

Pipe height, m	Sectional shape of the inner channel of the chimney pipe
	ROUND	SQUARE	RECTANGULAR
5	11.2	12.4	13.2
6	10.5	11.6	12.3
7	10	11	11.7
8	9.5	10.5	11.2
9	9.1	10.1	10.6
10	8.7	9.7	10.2
11	8.9	9.4	9.8

It is clear that in addition to the size of the furnace window, it is also necessary to build on the reasonable height of the pipe - it will look absolutely ridiculous, for example, a huge 10-meter pipe on the roof of a small squat country house.

The calculation itself is easy. According to the table, based on the height of the pipe and the shape of its internal channel, the optimal f / F ratio is determined. Then, based on the area of ​​​​the furnace window, it will not be difficult to determine the area of ​​\u200b\u200bthe chimney channel. Well, then, using geometric formulas, it remains only to bring the resulting value to linear dimensions - the diameter for round pipe or the length of the sides for a rectangle.

This calculation algorithm is implemented in the calculator below.

Despite the wide range of modern and modern systems heating, solid fuel stoves are not going to give up their positions of popularity at all. This is quite understandable - the presence of such heating facility gives a certain sense of autonomy - even under the most adverse circumstances caused by interruptions in the supply of other energy sources, a stove with a supply of fuel will help both heat the house and cook food for the family.

But the stove will only work efficiently and safely if it is designed, built or built to the right specifications. And one of the key conditions for the functioning of the furnace is thoughtful and reliable system removal of combustion products - . There are several options for the equipment of this system - from laying out a classic brick pipe "the old fashioned way" to the use of completely new, sometimes even unexpected technological solutions using modern composite materials. And at the peak of popularity in this matter in our time, probably, are sandwich pipes for furnaces.

What are sandwich pipes for furnaces, how they differ, what you need to know about their choice and the basic rules for designing a system - all this in this publication.

What are sandwich pipes and their main advantages

The developers of sandwich chimneys set themselves the task of minimizing the disadvantages that are characteristic of almost all chimneys, regardless of the material they are made of.

Any chimney is subject to negative destructive influence both from the inside and from the outside. The combustion products have a high temperature and are highly corrosive. chemical composition, resulting in erosion or corrosion of the internal channel materials. In addition, over time, the chimney channel becomes overgrown with soot, which reduces the patency of the pipe, and as a result, the efficiency and safety of the furnace.

outside on open areas pipes are affected external factors- high humidity, precipitation, fluctuations in air temperature outside. In addition, the temperature difference between the outside and inside the chimney leads to the active formation of condensate - and this, in turn, increases the likelihood of soot deposits.

"Classic" brick chimneys, although considered time-tested, have a whole "bouquet" of shortcomings.

• Firstly, rectangular section channel is by no means optimal - unnecessary turbulence of the gas flow inevitably occurs in it. Reduce overall traction.
• Secondly, it is impossible to achieve ideal smoothness of the channel walls - the porous structure of the brick will still contribute to soot deposits.
• Thirdly, on its own brick chimney represents a very massive structure, quite difficult to erect and requiring a reliable foundation.

How to lay out a brick chimney

If this option is chosen, then it is necessary to strictly observe whole line important rules. How to fold a brick chimney on your own - in a special publication of our portal.

• And fourthly, even a high-quality brick is subject to erosion under the influence of a whole range of negative influences, and the picture of crumbling chimneys is by no means uncommon.

This means that in order for the chimney to be optimal, it must be made with a round cross section, smooth inner walls, from heat-resistant, erosion-resistant and corrosion-resistant material. and light enough not to weigh down the entire furnace structure. It would seem that all these requirements are met modern views stainless steels. However, such a simplified scheme is impossible for a number of reasons:

• Any metal has a high thermal conductivity, and a high temperature difference inside the chimney channel and outside can have a destructive effect on thin walls, and most importantly, leads to abundant condensed water vapor, which is always contained in the combustion products.
• The rapid cooling of gases in open areas of the chimney will inevitably lead to a decrease in the draft of the furnace.
• The sections of the metal pipe located inside the building are heated to very high temperatures, and this is unsafe both from a fire point of view and from the standpoint of a high probability of accidental injury - a burn.

This complex of problems would be completely or to the maximum extent possible resolved by creating a sandwich chimney structure. The inner channel and the outer surface of this design are two separate metal cylinders separated by a layer of heat-resistant thermal insulating material with a markedly low thermal conductivity.

The inner duct must always be made of a special type of stainless steel, with a reliable welding of the seam - usually argon welding is used.

The outer casing is also metal, but options are already possible here. Certainly the most resistant external influences will be a stainless steel casing. However, sometimes, in order to save money, they also purchase cheaper options in which the outer pipe is made of galvanized steel.

Most often used as a thermal insulation layer mineral wool from basalt fiber, as the most resistant to high temperatures. The high density of basalt wool (from 120 to 200 kg/m³) provides the necessary structural strength. The thickness of this layer can vary - from 25 and even up to 100 mm. It depends on the parameters heating equipment and, to a certain extent, on the climatic conditions of the region.

The great convenience of such a design is that it carefully considers the issues of mounting individual parts into a single system. For this, there are connecting nodes in the form of sockets and narrowed sections, special clamps, stoppers, sometimes flanges, etc.

Such a chimney system for the furnace immediately acquires a number of important virtues :

• The mass of the entire chimney system assembly is not so large, that is, it is not necessary to strengthen the foundation of the furnace and its structure, as is the case with a brick pipe.
• The chimney can be positioned on brackets vertically along outer wall building. And this is a simplification of assembly, especially when passing through floors, and significant savings usable space indoors.
• The system is very "flexible" in terms of the possibilities of its placement. Manufacturers provide a wide range additional nodes and accessories that allow you to quickly and reliably assemble the chimney of the required configuration. It becomes possible to bypass possible obstacles without resorting to large-scale alterations in the design of the house.

• The temperature difference between outside and inside is compensated by a thermal insulation layer. This stability guarantees normal stable traction, and condensation and soot deposits are minimized.
• The outer surface of the sandwich pipe at correct assembly does not heat up to critical temperatures, that is, the safety of the chimney operation is significantly increased.
• The assembly of such a chimney, subject to all technological recommendations, is an accessible and intuitive event that does not require any special training.

Such chimneys also have certain limitations :

• A quality set will be quite expensive.
• Over time, under the influence of high and low temperatures, signs of depressurization may appear at the junctions of individual nodes - this requires special attention: regular inspections and, if necessary, preventive maintenance.
• Limited overall service life. Despite the fact that high-quality stainless steel is highly resistant, aging processes also do not bypass it. As a rule, manufacturers guarantee up to 15 years of trouble-free operation of their products. However, any other chimney for such a period will most likely require some kind of repair and restoration work.

How to choose a metal sandwich chimney

As already mentioned, the cost of such a chimney system is quite high, and replacing low-quality pipe sections can result in considerable costs. Therefore, it is very important to be able to correctly evaluate products when choosing, so that disappointment does not come after one or two years of operation.

Selection criteria can be roughly divided into several categories. So, first of all, the quality of the materials used in the production of sandwich pipes is evaluated. The necessary linear parameters- that is, the diameter of the chimney channel, the height of the future pipe, the thickness of the insulation layer. It is important to immediately think over the features of the structure being created in order to assess whether all the components are commercially available for its installation.

Assessment of the quality of manufacturing materials

To the untrained eye, all stainless steels look the same. The new pipe shines - but this is not at all a criterion for the quality of the metal.

The same “beautiful and shiny” pipe after a short period of time can be deformed and even simply burn through - alas, there is a lot of evidence of this on the Internet. And such a situation is a direct road to a fire or carbon monoxide poisoning.

Unfortunately, we have to state that the increased demand for such chimneys has also given rise to the "shadow sector" of their production, where materials are used that are of little use for such purposes. There is another situation when a perfectly high-quality sandwich was used in conditions for which it was simply not designed. For example, a pipe that is quite suitable for a gas boiler is unsuitable for use with a solid fuel stove.

Stainless steel grade

When choosing sandwich pipes, it is necessary to focus on the steel grade, which is used primarily for the internal channel. This parameter should be indicated in the passport documentation of the product, unless, of course, it is produced by a bona fide manufacturer. If the steel grade is not indicated, then it is better to look for another option.

So, the following grades of stainless steel can be found:

— AISI 430. Such steel belongs to the category of the most inexpensive. It is quite suitable for outer cladding sandwich, as its weather resistance is quite enough. But for inner pipe it doesn't fit perfectly. Its composition predetermines unimportant weldability, that is, it is very problematic to obtain a sealed seam. Such steel does not meet the requirements of increased heat resistance.

— AISI 439. This alloy is enriched with titanium additives, which significantly increases its resistance to corrosion and mechanical strength. Pipes made of such steel are quite suitable for any gas installations, as well as for solid fuel boilers and furnaces, but only a small heat output.

— AISI 316. This steel has a pronounced corrosion resistance to almost all aggressive substances. Thermal stability is average, so the pipe is only suitable for gas-powered equipment.

— AISI 304. Steel does not have the highest heat resistance, therefore it is usually not used by serious manufacturers from being used as an internal channel. Perfect for outer shells.

— AISI 321 and AISI 316i. They have excellent heat resistance and good ductility, easily amenable to high-quality welding. Such pipes are quite suitable for most types of boiler and furnace equipment, as they can withstand heating up to 850 ° C without deformation.

— AISI 310S. Fully versatile steel that can withstand temperatures up to 1000°C. It is quite suitable even for powerful solid fuel furnaces and boilers operating on the principle of afterburning pyrolysis gases. The only conditional drawback is the high price.

Knowing the parameters of your furnace, you can choose the optimal grade of stainless steel.

Do not forget about another way to check stainless steel. Of course, it will not give an accurate picture, but it will help you immediately avoid buying a low-quality fake:

It is necessary to take an ordinary magnet and try to “glue” it to the inner wall of a vertically standing sandwich pipe. The magnet should not be held - ideally it will just slide down. If it stays in place or goes down with visible braking, the “black” component of such steel is too high, and the pipe is unsuitable for a chimney.

Type of insulation material

As already noted, as insulation material for the thermal insulation layer, only basalt mineral wool should be used. In no case, no matter how attractive the price may seem, you should not purchase a sandwich pipe filled with glass wool. The thermal conductivity coefficient of glass wool is no worse, the heat resistance is completely different. At temperatures of about 300 ° C, its sintering begins, subsidence in size, and all its advantages are reduced to zero. In addition, fiberglass is very brittle, and insulation layer does not differ in volumetric stability, is prone to shrinkage.

In really high-quality sandwich pipes, manufacturers use heaters from leading brands - ROCKWOOL, PAROC and the like.

The diameter of the chimney channel and the thickness of the insulation

Manufacturers provide a fairly wide range of diameters. So, models are produced with an inner pipe from 110 to 300 mm, with different thicknesses of the insulation layer, that is, different external diameters of the structure.

The main parameters of a sandwich pipe are the diameter of the inner channel, the thickness of the insulation and, accordingly, the size of the outer casing

If new equipment, a boiler or a furnace is purchased, then the required diameter of the chimney pipe must be indicated in the passport data - this value should be followed. It is more difficult if the chimney is planned to be installed on a brick or home-made one - here it is important not to make a mistake with this parameter.

In this case, you can do it in several ways. The first, simple one, is to navigate according to the table showing the dependence of the thermal power of the equipment and the diameter of the chimney.

Thermal power of solid fuel furnace		Minimum section of a rectangular chimney	Square cross section pipes	Minimum diameter of the inner pipe of a sandwich chimney
kW	kcal/hour
up to 3.5	up to 3000	140×140 mm	19600 mm²	158 mm
3.6 ÷ 5.2	3000 ÷ 4500	140×200 mm	28000 mm²	189 mm
5.3 ÷ 7.0	4500 ÷ 6000	140×270 mm	37800 mm²	220 mm

You can also focus on the approximate consumption of an existing furnace of one or another fuel. In this case, the following formula is used to calculate:

S=Vg/wg

S- cross-sectional area of ​​the chimney channel.

Vg is the volume of combustion products.

wg- the speed of movement of gases through the chimney (optimum is 2 m / s).

Thus, to calculate the diameter, it is necessary to apply the formula for the area of ​​a circle:

d = √4 ×S/π = √(4 ×Vg /wg) /π = √2 ×Vg /π

The value remains unclear. Vg. It is calculated as follows:

Vg = M × Vy × (1 +T / 273) / 3600

M- the total approximate mass of fuel burned in one hour.

Vy– specific volume of combustion products from combustion of 1 kg of fuel.

T- temperature at the outlet of the chimney

273 - the difference between the value of temperature zero in degrees Celsius and Kelvin.

3600 - the number of seconds in an hour, to bring the value to a single value.

So the formula looks like this:

d = √(2 × M ×Vу × (1 + T / 273) / (3600 × π))

Values Vy and T you can accept tabular ones using the table below.

Fuel type	Average calorific value of fuel, kcal/kg	Specific volume of combustion products from combustion 1 kg, m³/kg	Chimney outlet temperature, °С
Firewood, average humidity level 25%	3300	10	150
Peat lump or loose, air dried, humidity up to 30%	3000	10	130
Peat in briquettes	4000	11	130
Brown coal	4700	12	120
Coal	6500	17	110
Anthracite	7000	17	110

Surely, the formula will seem “heavyweight” to many, not conducive to independent calculations. To simplify the task, a calculator is placed below, in which the necessary arithmetic ratios are already laid down.