Assembly and installation of sandwich pipes for chimneys

A sandwich pipe for a chimney is a composite structure assembled from 2 pipe blanks of various diameters, between which a layer of insulation made of polystyrene or mineral wool is placed. Its interior is made of steel and has a special anti-corrosion coating. The outer casing is made of stainless steel or galvanized sheet.

What are sandwich kits made of?

In various types of heating devices, sandwich chimney pipes are made of specially selected steel materials. The latter belong to the group of high-alloy and stainless steels, ideally suited for the assembly of chemically resistant and refractory sandwich chimneys. There are three types of materials most often used as a base:

• stainless steel with alloy additions;
• black metal;
• combined coating.

Each of these positions will need to be considered separately.

Stainless steel

The main brands of stainless steel used for the assembly of sandwich chimneys differ in the composition of their additives.

• Titanium-doped stainless steel. The metal is used in boilers and stoves fired with wood or pellets.
• Molybdenum stabilized stainless steel (AISI 316). Products made from such steel are used in installations fired with wood, gas or diesel fuel.
• Heat-resistant steel AISI 304 with a high content of chromium and nickel. Resistant to thermal influences and chemically acidic environments.

The latter type of material is used in the production of chimneys operated at high temperatures.

Black metal

The material quickly loses its shape, which is explained by its oxidation and gradual burning. For surface protection, inexpensive galvanizing or special enamel is used to increase resistance to acidic environments. The coating based on it will last a long time at operating temperatures of no more than 400 degrees. Ferrous metal pipes treated with enamel are used in heating columns, stove structures of various classes, as well as in fireplaces and boilers. Unlike other materials, its surface is easily painted in various colors, which allows it to be matched to the interiors of rooms, as well as the facades of houses and other buildings.

In order to reduce the cost of products, manufacturers have launched the production of special designs that combine expensive stainless steel and ferrous metals. At the same time, they try to make a pipe from the outside of high-quality stainless steel, and for the manufacture of the inside, relatively cheap galvanizing is used. Between them is placed a layer of thermal insulation, which is used as basalt or ceramic wool. Such structures can withstand temperatures from 600 to 1000 ° C.

Pros and cons

To assess the possibility of using sandwich pipes in a bath, you should familiarize yourself with their advantages and disadvantages. The disadvantages of chimneys assembled in the form of a sandwich structure include:

• the possibility of depressurization during long-term operation;
• high cost of structures in comparison with brick counterparts;
• short service life (no more than 15 years).

The last drawback is associated with the use of materials of low quality. Therefore, experts advise to take a responsible approach to the choice of a company that produces sandwich chimneys.

The following features are considered to be the advantage of these products:

• with reliable insulation, good draft is always maintained in the chimney;
• the multilayer structure of the structure does not allow the combustion products to cool down, excluding the possibility of condensation and soot formation;
• ease of installation, accessible even to a beginner;
• a wide range of modifications (angular, straight, etc.);
• minimum accumulation of soot.

The structures are lightweight and do not need a special base (foundation). They can be attached to floor elements and walls, as well as mounted directly on heating equipment.

The correct selection of pipes for a specific type of fuel is possible after reading the table of their correspondence to a particular type of heating equipment. Reference data is widely presented on the Internet and is available to anyone. When arranging sandwich pipes for a gas-fired boiler, they cost the cheapest option. For a Russian stove built in a bathhouse and fired with wood, it is recommended to choose products whose quality is beyond doubt.

Structural elements and their features

Chimneys for boiler rooms made of stainless steel of sandwich design, due to a wide choice of design solutions, allow you to equip chimneys of various configurations.

The main elements of the chimney duct:

• Straight pipe sections up to 1 meter long and 80-600 mm in diameter, used to assemble long sections (passages) of the chimney.
• Elbows and special tees used when it is necessary to lay the chimney through the walls or lead it outside the building.
• Pass-through pipes designed to insulate the pipe when it is guided through the interfloor partitions and are at the same time a fastener.
• Roofing cut, made in the form of a metal cone, attached to the roof at a certain angle.

The last element allows the sandwich pipe to pass through the roof, maintaining its tightness and guaranteeing the fire safety of the structure. Instead, a special silicone-based seal is often used, which reliably protects this area from leakage.

How to choose the required chimney diameter

The diameter of the chimney structure is selected based on the data on the power of the boiler or other heating equipment. For small installations with a capacity of less than 3.5 kW, pipes with a diameter of 8 cm are suitable.For equipment with this indicator of no more than 5.2 kW, workpieces with a diameter of 9.5 cm or more are required, and at high capacities, products with a typical size of about 110- 115 mm. At the same time, it is unacceptable to plan chimney narrowings; expansion, on the contrary, is encouraged.

Another important parameter that determines the choice of the diameter of the sandwich pipe for the stove is the thickness of the thermal insulation layer, on average 25-100 mm. With its increase, all the characteristics of the chimney improve, but at the same time the weight and cost increase. If it is necessary to replace or build up a small area, the user will have to select a section of a suitable structure produced by one or another manufacturer. As a rule, it is not possible to obtain reliable joints in this way. In some cases, due to a mismatch in typical dimensions, it is necessary to replace the entire structure as a whole.

System installation

Before assembling a pipe for a sandwich furnace, you need to familiarize yourself with the technical documentation and safety requirements. Compliance with the latter will eliminate the undesirable consequences of improper operation of the sandwich product. The instructions for carrying out these operations include several stages.

Assembly of chimney elements

The assembly of the structure is always carried out according to the "bottom-up" scheme. In this case, the chimneys are not directly connected to the sandwich heating unit. The general procedure for the operations performed:

1. A section of a transitional steel pipe about half a meter long or a special adapter is connected to the heating device.
2. If it is supposed to bring it out through the wall in this place, a horizontal bend is immediately mounted with a slope of about 2 degrees.
3. Structural elements and walls located close to it are covered with a special protective screen or casing.
4. It is necessary to install the chimney in the direction of the combustion waste movement - mount it on top of the pipe with protection of the resulting joint with a heat-resistant sealant.
5. All subsequent fragments are installed in the direction of the formation of condensate, which will exclude the possibility of its seepage inside and protect the heat-insulating layer from getting wet.

During the installation of sandwich pipes, it is necessary to ensure that they are securely fastened to each other with couplings, next to which a clamp is made to fix the structure on the wall (the fastening step is at least 5 meters). To prevent its lateral displacement, special wall brackets are installed after about two meters.

Organization of the passage of ceiling and wall ceilings

During the operation of the chimney sandwich, the outer surface of the pipes heats up strongly, which forces additional insulation at the places of their transition through building structures. At the same time, special attention is paid to ensure that the joints of the workpieces do not coincide with the zones of wiring through walls and ceilings. The size of the hole for them is made about 25 mm larger than the outer diameter of the pipe. The resulting gaps are filled with non-combustible basalt wool. From above, they are closed with heat-resistant material, which is later hidden under decorative trim.

These measures help to protect wooden structures from fire, while eliminating the possibility of deformation loads on the chimney during shrinkage of the building. For these purposes, special gangways or unloading platforms are also used. They are manufactured in the form of standard units that protect the walls and ceilings for heating and take on deformation loads.

Roof wiring

When sandwich pipes are removed through the roofing, its tightness is violated, which makes it necessary to take additional protective measures. For these purposes, special devices and sealants are used. These parts have standardized dimensions, fixed angles of inclination and are selected taking into account the parameters of a particular roof. The walls of the sandwich pipes should be located at a distance from flammable materials at least 250-370 mm. To protect against water leaks, a special apron is fitted around the outlet, the edges of which are wound under the cover.

Installation above the roof surface

The height of the chimney sandwich structure depends on the removal of its base to the ridge of the roof and must meet the following conditions:

• the pipe cannot rise more than 0.5 meters above the ridge;
• removal of the top from the surface of a flat roof no more than 120 cm;
• the same parameter for the option of the combined roof is no more than 200 cm;
• if there is another building nearby, the upper cut of the chimney is made one and a half meters higher than its roof.

In the latter case, the pipe of non-standard height has to be additionally strengthened by means of special braces.

Good draft in any chimney is obtained if the rules for its arrangement prescribed by the instructions are followed. The principle of its formation is based on the effect of ventilation or air movement due to the temperature difference in the middle of the smoke channel and outside.Due to this gradation, the density of the inner layers is less than the same indicator for the outer masses of cold air, which is the reason for the appearance of a pressure difference. Due to it, cold air is drawn into the inside of the furnace structure, and hot air rises through the chimney channel and is discharged outside.

Features of operation

Upon completion of the installation of the chimney sandwich, a trial commissioning is carried out, which allows you to check the tightness of the joints and make sure that there is no heating of the adjacent surfaces. During the first run of the system, slight smoke is sometimes observed and a characteristic smell of burnt oil, sealant and dust residues is felt.

Maintenance of a chimney sandwich put into operation consists, first of all, in the timely removal of soot accumulated in the pipes. When cleaning them, it is forbidden to use special detergents. It is best to entrust this operation to employees of an organization that has a license to carry out such work.