The chimney system plays an important role in the house, responsible for the stable removal of combustion products. The device of this design and manufacturing materials determine the safety of the entire system. For many years now, the construction of sandwich pipes for the chimney has been practiced . This solution has several fundamental differences from coaxial and single-layer systems.
Design advantages
Despite the complex technical device, such pipes are easier to install. An optimized structure with a wide range of additional elements allows you to install the system on a wide variety of roofs without requiring significant changes in the roof itself. This also implies the compactness of the structure. Thin-layer shells regularly perform the basic functions of protection against thermal influences, but do not take up much space, especially when compared with brick chimneys.
In terms of durability, the most attractive is a stainless steel sandwich pipe that does not undergo destructive processes from precipitation and soot. The multilayer structure prevents condensation due to efficient ventilation of the circuits. It is worth emphasizing the main operational quality of the chimney - stable support of the draft for the output of combustion products. Due to its smooth surface and circular cross-section, the metal pipe minimizes resistance, eliminating the delay of exhaust gases.
Pipe design features
The main technical and operational advantages stem from the multilayer structure of the chimney. The structure is formed of two pipes of different diameters, one of which is embedded in the other. The main material used is high-strength steel with a corrosion-resistant coating, which largely determines the durability of the system. The gap between the two cylinders is filled with a heat insulator, which takes on the main thermal loads from internal surfaces. Due to this technical solution, the pipes do not overheat and maintain optimal fire safety indicators. Therefore, the design can be safely installed in wooden houses.
Of course, not only pipes form the structure. The configurations may vary, depending on the purpose and operating conditions of the system. For example, a sandwich pipe for ventilation includes splitters, condensate collectors and swivel bends. Furnace modular structures, as a rule, are directly interfaced with heating units, without requiring complex installation wiring.
Pipe dimensions
Manufacturers strive to cover the entire size range, relevant to modern requirements for the installation of the chimney. The standard dimensions of the sandwich pipe can be represented as follows:
- The height of the structure is at least 50 cm above the roofing.
- The diameter of the inner cylinder is 30 cm.
- The diameter of the outer cylinder is 40 cm.
- The thickness of the pipes is 1 mm.
- The thickness of the layer of heat insulator (basalt) is from 3 to 5 cm.
- Knee angle - 90 degrees.
Design calculation
More precisely determine the parameters for an individual project will allow the assessment of the technical conditions of operation of the pipe. Of fundamental importance will be the power of the heating unit. For a kiln sandwich pipe, the diameter of the inner pipe will be calculated based on this indicator. For example, if the power does not exceed 3.5 kW, then a thickness of 8 cm will be optimal. If the power potential of the boiler varies from 3.5 to 5 kW, then the internal diameter of the chimney should be 9-10 cm.
No less significant is the thickness of the insulating layer. It has already been noted that in the standard configuration it varies from 3 to 5 cm, but there are also special basalt enclosures of 10 cm, as well as ultra-thin insulation with a thickness of 2 cm. It is not recommended to take a design with dimensions “in reserve”, since an increase in throughput negatively affects on the energy-saving function of the house. The selection of characteristics should be optimally suited to specific requests.
Pipe assembly
The system takes its origin from the source of exhaust gases - a fireplace, a furnace structure or a boiler. The first link is connected in a pipe extending from the target unit. At the time of installation it is necessary to cover the already assembled circuits with plugs so that they are not contaminated with garbage and construction waste. Next, one cylinder is installed in another. At this stage, it is important to observe the orientation of the joints along the segments so that the overlap is directed towards the exit and does not delay the combustion products.
Specialists recommend assembling the inner circuit first and then reinforcing the structure with insulation and external protective layers. How to assemble a sandwich pipe with high tightness? Much will depend on the bonding system chosen. For this task, it is better to use steel clamps that envelop the structure along the entire diameter. Next, you can adjust the tightening with nuts, but you should not overdo it, otherwise overvoltage deforms the insulation layer and the pipes themselves. The joints are treated with a sealant, which includes heat-resistant additives.
Organization of the conclusion to the roof
The most important stage of installation is the direct arrangement of the chimney behind the rafter system. In order for the pipe to go outside, it is necessary to provide an appropriate opening in the roofing “pie” in advance. For this, there are special roof cuts. Some chimney manufacturers complete the pipes with them, but you can purchase this design in a separate order for your requirements. It is advisable to use metal cutting, which allows installation in a specific corner of the ramp. The range of slopes varies from 15 to 55 degrees. A win-win option would be a universal or adjustable splitter spanning several tens of degrees.
Next, you can proceed to the installation of the structure. After marking for installation, a hole should be made in the roofing. A bearing roof sheet is fixed from the inside, and a roof cut is mounted outside. Installation of a sandwich pipe should be done so that it is not affected by the “cold bridges”. To do this, you need to make cutting sheets for the roofing. This solution will increase the tightness at the joints and improve the fastening of the entire structure.
Condensation protection
Dew on the outer surfaces of a metal chimney in the under-roof space is a common occurrence in conditions of convergence of heat, moisture and cold. But to ensure long-term operation, this effect should be minimized. Condensation can be prevented with the help of special drives - a kind of bypass channels that eliminate the harmful mixture of water and soot. On the horizontal section of the sandwich pipe, these devices are mounted using brackets and clamps. The main thing in this task is to initially correctly arrange the joints so that the water flows down freely and does not go under the sheet of the lower segment of the pipe.
Chimney insulation
The assembled and installed structure must be sealed and covered with insulation from the outside. Work should begin with the processing of joints, gaps and crevices that give air leaks. To maintain traction, maximum insulation with sealant must be ensured. But on external surfaces not only a heat-resistant composition is used, but also protected from external influences in the form of precipitation and wind. Sandwich pipe manufacturers recommend the use of silicone high-temperature sealants, as well as fused polymer mixtures. As for thermal insulation, it is arranged in part of the lower pipes. The best option is a foil basalt mat in combination with fireproof mastic. Outlets can be insulated with mineral wool insulation.
System operation
Support for the optimal technical condition of the chimney does not stop after installation and finishing measures. In the process of removing combustion products, soot is formed on the inner surfaces of the pipe, adversely affecting the metal structure and preventing the passage of gases. It is recommended to clean the chimney twice during the heating season . This problem is solved by special brushes for the chimney from a sandwich pipe with a set of flexible mating rods. It is advisable to choose carbon fiber constructions as the most practical and universal. It will also be useful to periodically remove the plugs and audit pipe edges with segment connections.
User feedback on the design
The complexity of their device turns away from the choice of chimneys on the sandwich components. There are also complaints about the need for preliminary assembly, but there is a downside to this - the positive side. The multi-layer system is justified in the sense that it allows the user to design different systems without making adjustments to existing structures. As a result, already in the practice of operation, the owners note a high degree of reliability and security of the sandwich pipe. Feedback on traction power is also generally favorable. The advantages of steel sheets from which the inner and outer segments of the cylinders are made are also noted. However, it is a large number of joints that over time leads to a loss of tightness, forcing the owner to take a closer look at assessing the state of the structure to identify problem areas.
Price issue
Cost is also put among the disadvantages of such systems, and it is worth preparing for the costs even after installation. In the domestic market, the minimum price level for a complete set is 1000-2000 rubles. Of the main factors affecting this amount, one can distinguish the thickness of the pipes, the material of the insulation, the size, type of protective coating, etc. The increase in cost can be associated with the expansion of the kit. The presence of tees, elbows, condensate collectors also increases purchase costs. For example, a modular sandwich pipe with a 90-degree elbow and a basalt heat insulator can cost 4000-5000 rubles. But, saving on additional elements and high-quality insulating coatings is not recommended, since the consequences of lowering the technical and operational qualities will appear in the near future and will entail new costs for the maintenance of the chimney.
Conclusion
A sandwich construction is far from the only option for a modern design of a system that exhausts combustion products. Direct competition is made by monolithic structures, the characteristics of which also in recent years have become more attractive due to the use of new, more technologically advanced materials. In what cases is a sandwich pipe for a chimney justified? It is recommended to turn to this configuration for owners of private houses who plan to implement a compact system with complex contours, branches and transition sections. This also applies to the lower tier with connection to ventilation and heating equipment, and the under-roof space, in which it is also not always possible to implement a traditional chimney.