What are asbestos cement pipes and what are they made of?
Asbestos cement pipes are products made from asbestos cement, which is widely used in various fields of human activity. Asbestos cement is a material obtained by pressing a water-cement mixture with the addition of asbestos fibers. The fibers are based on the mineral chrysolite and have an average length of about 5 mm. The proportion of asbestos fibers is about 10-15% of the total product, and it is thanks to its presence that a solid and durable material is formed. Strong asbestos fibers behave similarly to steel rods used in reinforcing concrete. Initially, asbestos cement was used as an insulating and fire-resistant protection – it is weather-resistant and does not allow water to pass through. In modern industry, it is used for the manufacture of corrugated roofs, downpipes, water tanks, gutters, chimneys, street trash cans, oil pipelines, water tanks, etc. In addition to the main products, enterprises producing asbestos-cement products produce fastening couplings, the main feature of which is the inner diameter slightly exceeding the outer diameter of pipes, which provides a more reliable connection.
Types of asbestos cement pipes and their sizes
Pipes made of asbestos cement are divided into two types: non-pressure and pressure pipes. The latter can be used for both internal and external water supply systems designed to transport liquids under pressure. Pipes are produced in accordance with the requirements of GOST 539-80 and TU 5786-013-00281708-03, have a special recess for couplings, and are supplied with them and rubber O-rings. Seals made of heat-resistant rubber reliably seal pipe connections from the inside. Pressure pipes can withstand different pressures, so they are divided into four types::
- VT6 pipe-can withstand a pressure of 0.6 MPa;
- VT9-pressure 0.9 MPa;
- VT12-1.2 MPa;
- VT15 – 1.5 MPa.
Pressure pipes can have an internal diameter of 50 to 500 millimeters. Non-pressure pipes are most often used for laying underground utilities and other structures associated with a gravity drainage system. They are manufactured in accordance with GOST 1839-80 and can have a diameter of 100 to 500 millimeters, a length of 3.95 to 5 meters. Non-pressure pipes do not have special recesses for couplings. When making pipes from asbestos cement, each product is marked with a special label indicating the type of product, its internal diameter and compliance with the established standards. So, for example, the designation BNT-200 GOST 1839-80 stands for a pressure-free pipe with an internal diameter of 200 millimeters, manufactured in accordance with the specified GOST. Before going on sale, all products made of asbestos cement must be checked for straightness and detection of defects, and tested for the ability to withstand the loads declared by the manufacturer.
Scope of application of asbestos cement pipes
Pressure and non-pressure pipes have different fields of application, so non-pressure pipes made of asbestos cement are used for:
- laying of water supply networks;
- production of chimneys;
- arrangement of drainage collectors;
- installation of in-house garbage chutes;
- manufacture of pressure-free sewage systems;
- construction of observation wells;
- construction of columnar foundations for prefabricated panel houses. Most often, pipe foundations are installed on flooded soils. For the foundation, use a diameter of 200 mm;
- thin-walled asbestos-cement products with an internal diameter of 100-150 millimeters are often used to protect telephone, Internet and electrical cables.
Pressure pipes are used for such purposes:
- manufacture of domestic pipelines, as well as pipelines that can carry gas, water and petroleum products;
- arrangement of ventilation systems;
- laying of heating mains;
- structure of the pressure sewer system;
- in the manufacture of chimneys;
- for laying foundations in wetlands;
- when arranging drains;
- when drilling wells.
In the modern world, non-metallic pipes made of asbestos cement are widely used in heat supply, as they have low thermal conductivity and perfectly resist corrosion. In the heat supply system, pipes can be operated for more than thirty years, and their initial characteristics will not deteriorate. The SNIP specifies the parameters of heat carriers that these pipes fully correspond to:
- coolant temperature up to 115 degrees;
- pressure not exceeding 1.6 MPa.
Item 10.4 allows the use of asbestos-cement pipes in domestic and potable water supply.
Advantages of pipes
Asbestos-cement pipes began to be used more than 70 years ago, and they are still very popular in various fields of activity. Thanks to the pressing of cement with asbestos, pipes acquire tremendous strength. The main advantages of asbestos cement pipes include:
- resistance to aggressive environments;
- operation in any type of ground;
- reliability-asbestos-cement pipes can withstand up to 15 times more water pressure than concrete pipes of the same thickness;
- long service life, for example, a steel water pipe needs to be changed every 5-7 years, nothing will happen to an asbestos-cement pipe in 50 years;
- resistance to chemical and electrolytic corrosion;
- minimum hydraulic resistance;
- resistance to abrasive wear;
- withstand transverse stress caused by internal pressure, including water pressure surges;
- high crushing strength, therefore safe to use under heavy external loads and heavy traffic.;
- low coefficient of thermal expansion, which counteracts internal destruction caused by water temperature fluctuations;
- low thermal conductivity and excellent insulation characteristics that minimize water heat loss;
- relative ease of connection;
- asbestos cement pipes are virtually maintenance-free;
- heat resistance and fire resistance;
- can be used in hot regions;
- relatively low price.
Asbestos-cement pipes are widely used in Europe and the USA, in particular for creating water heating systems.
Installation Recommendations
When laying the main line, it is necessary to observe a slope of 2 to 3 millimeters per linear meter of pipe, the slope should be made in the direction of the well. If there is a natural slope of the terrain, you don’t need to create an additional slope. When connecting asbestos-cement pipes, it is important to use only certified cylindrical couplings