In many industrial communications, as well as in the construction of residential premises, asbestos or asbestos-cement pipes are used. The wide popularity of the use of products contributes to their high wear resistance to various adverse factors. In addition, asbestos pipes have a large assortment of sizes that differ in diameter and length.
Materials used in the manufacture
The main materials used in the manufacture are cement and asbestos fiber. To obtain asbestos fiber, asbestos is pre-crushed. The resulting powdery mass is divided into fibers and added to the cement mortar.
The amount of fibers in the solution does not exceed 15% of the total weight, but this results in a material with low weight and low thermal conductivity. Reinforcing the concrete solution with asbestos makes it possible to obtain a material with a strength of 40% more than that of conventional concrete products.
Types and application of asbestos-cement pipelines
Asbestos-cement products are divided into two types depending on the pressure of the conducted medium: pressure and non-pressure. In turn, the industry produces 4 types of pressure pipelines with the following designation:
- VT6 — designed for a pressure of 0.6 MPa;
- VT9 — withstands a pressure of 0.9 MPa;
- VT12 — design pressure of the conducted medium 1.2 MPa;
- VT15 — maximum pressure 1.5 MPa.
The scope of non-pressure pipes is as follows:
- in the manufacture of pipeline networks for water supply of residential buildings;
- for use as chimney pipes;
- in drainage collectors and when laying sewer systems;
- as foundation piles when installing prefabricated houses in flooded unstable soils with a diameter of the used asbestos pipe of more than 200 mm;
- electric and telephone cables are placed when laying inside the small diameters of the product, for protection against damage and insulation.
The use of asbestos pipes in the chimney should be done with caution, especially if the flue outlet has a high temperature. Such chimneys can crack from high temperatures, and the rubber seals that ensure the tightness of the connection will burn out.
In addition, a large accumulation of soot and condensate occurs on the walls, which also weaken its strength and reduce the draft of furnaces. If the source of fire is at a sufficiently large distance, then the use of asbestos products can be completely allowed.
The scope of application of pressure pipelines is no less extensive:
- transportation of gas, water and oil refinery products;
- installation of ventilation systems;
- use for systems with a hot conductive medium with a permissible temperature up to 115ºС;
- when laying sewer systems under pressure and for arranging water wells.
Pressure pipes differ from non-pressure pipes in wall thickness and the size of the inner diameter. For non-pressure pipelines, the wall thickness is carried out with dimensions of 7 … 18 mm, and for pressure pipelines 9 … 43.5 mm. The inner diameter in the first case is 50 … 500 mm, and in the second case up to 600 mm.
Important! Low thermal conductivity and the ability to maintain the temperature of the medium for a long time contributes to their widespread use in heating systems. And in accordance with SNiP, these products are allowed to be used even for drinking water supply systems.
Dimensions of asbestos-cement pipelines
Non-pressure pipelines are available in lengths of 4 or 5 meters. Other dimensions are shown in the table.
The pressure pipes are 5 meters long, the dimensions are shown in the table below.
Main advantages and disadvantages
Compared with metal pipelines, asbestos-cement products have a number of advantages, especially in terms of corrosion resistance and a service life of more than 40 years without repair and replacement. Other benefits include:
- Easy installation of pipelines when laying the route. They do not need to be welded or connected with threaded fittings.
- No need for additional insulation due to low coefficient of thermal expansion.
- Possibility of laying pipelines in any type of soil.
- High resistance to external load determines their use where the tracks pass under the roads with regular traffic.
- No maintenance is required during operation.
- There are no build-ups on the inner walls that narrow the inner diameter.
If water is supplied through the pipes, then over time the wall becomes stronger due to the compaction of the cement component. According to studies by scientists from a number of countries, the use of such products for drinking water is safe for humans. If asbestos particles enter the body, it is quickly eliminated from the body without any harm.
Well, the main disadvantage of asbestos-cement materials is their fragility. They can easily be damaged during transportation, careless unloading, or being hit by a heavy object. To prevent this from happening, care must be taken to maintain their integrity during transportation and installation.
Cutting of asbestos pipelines
When laying asbestos systems, there is often a need for a cut to size of the product. This operation is performed using a grinder with a diamond disc installed.
First, the required cut length is marked, and the risk is applied around the entire perimeter. To prevent the product from moving when cutting, it must be fixed, but not in a vice, as you can inadvertently squeeze the surface. If there is an assistant, then you can hold it with your hands, or install it for fixation between two bars.
When cutting, the smallest asbestos dust is formed, the inhalation of which is harmful to health. To protect yourself from dust, you must wear a respirator or protective mask, and goggles over your eyes. Cutting can be done with a diamond disc of any diameter, turning the product over in order to make the disc accessible.
Connection and installation methods
The laying of the pipeline can be done manually with small diameters up to 100 mm, and with large sizes it is necessary to use construction equipment. If a gravity sewer system is being installed, then the pipelines must be installed with a slope in accordance with the norms of SNiP, and completely lie on the base.
All the necessary technology requirements: how to connect asbestos pipes to each other, and how to adhere to certain rules, are set out below:
- The interconnection of pipelines is carried out using couplings. Grooves are made in the couplings for inserting sealing rubber rings. This type of connection provides a tight connection between the coupling and the pipe, which ensures tightness at design pressure.
- When installing pipes with a diameter of more than 150 mm, it is necessary to provide a gap between the connected elements. This is necessary to exclude the possibility of installing additional expansion joints along the length.
- Asbestos pipelines must have supports along the entire length, voids are not allowed, which can lead to deformation of the pipeline.
- When using products for hot heat supply, when the maximum temperature is more than 100ºС, an increase in the size of the walls occurs due to heating. In order not to damage the rubber seals, they are deformed by the end of the pipe by 0.2 mm.
To connect pipes with a diameter of up to 150 mm, plastic couplings are used. To install the coupling, it is heated with a building hair dryer, and then put on the junction. The coupling cools and tightly tightens both ends, providing the necessary tightness. Instead of a hair dryer, you can use hot water, where a PVC sleeve is lowered for 10 minutes.
Sometimes, when installing sewer drains for a house, it becomes necessary to connect an asbestos-cement pipe with a plastic one. Many do not know how to properly connect an asbestos pipe with a plastic one so that there are no leaks. For such a connection, a special MAGNAPLAST fitting is used, with its help non-pressure dissimilar pipes of 100 … 300 mm in diameter are joined. In industry, this connection is also used when laying communication cables inside products.
When arranging chimneys, in order to protect the asbestos product from contact with high temperatures, it is necessary to connect asbestos pipes with metal ones. If the products are of different diameters, then use a branch pipe with different diameters of the ends. One end should be equal to the diameter of the metal, and the other to the asbestos-cement pipe. It is welded onto the metal pipe, and the asbestos pipe is connected to the pipe with a conventional coupling. Another option is to cut the end of the metal to the size of the asbestos-cement diameter.
Estimated cost of products
The approximate cost of products depends on the type, diameter and purpose of the pipe. Some items are priced below:
- The cost of a non-pressure one with a nominal bore of 100 … 600 mm, a length of 3.95 m. Is 450 … 22$, when equipped with a coupling of the appropriate diameter, the price increases by 40–210 rubles.
- For a pressure product with a pressure of 0.9 MPa, a nominal bore of 250, a length of 5 m, the price will be 43$, and for the Du-400 already 71$.
- The price of a coupling equipped with rubber rings will be 260–9,5 dollars.
These prices are indicative, they may differ from the region of location and from the season, but for an approximate estimate of the estimate, you can use it.
Asbestos-cement products are used in many industries and among private households. They are especially in demand in the arrangement of sewer systems, which allows to increase the service life of such communications several times.