Indoor natural gas pipelines are subject to certain pressures. Natural gas leaks can cause explosions, fires, personal injury and death, causing major economic losses. Therefore, the basic requirements for indoor natural gas pipes are: sufficient mechanical strength (tensile strength, elongation), good connectivity, and impermeability. To meet the basic requirements of pipes, the following five aspects should be selected:
1 Strength properties of materials The strength properties of pipe materials are analyzed from three parameters: tensile strength limit, yield limit and elongation. These three parameters vary greatly depending on the material. The tensile strength limit of steel pipes is generally 335-565 MPa, and the yield limit is generally 205-480 MPa. The higher the elongation of steel, the lower the yield limit and the higher the plasticity. Well, the easier it is to weld.
2 Fracture toughness of materials Pipe fractures can be divided into ductile fractures and brittle fractures. Excessive tensile stress and crack defect are the main causes of ductile fracture. The combination of low temperature, stress and crack defects is the main cause of brittle fracture. In order to prevent the pipe from breaking under working conditions, attention should be paid to eliminating pipe crack defects and reducing external stress during pipe making and construction.
3 The reliable connection performance of the material requires that the pipe can obtain reliable connection performance under certain conditions of connection (welding, screwing, etc.), process parameters and structural form.
4 Corrosion resistance of materials Natural gas used in cities is generally purified natural gas, regardless of the corrosion of the inner wall of the pipeline. The indoor natural gas pipeline is exposed to the atmosphere for a long time, and the corrosion resistance of the outer wall of the pipe should be considered.
5 Material temperature adaptability Under harsh environmental conditions, such as low temperature (0 ~ -20 °C), high temperature (40 ~ 70 °C), the pipe does not occur low temperature brittle fracture and high temperature deformation. The "Code for Design of Urban Gases" (GB 50028-2006) stipulates that steel pipes should be selected for indoor gas pipelines, and copper pipes, stainless steel pipes, aluminum-plastic composite pipes and connecting hoses are also available.
However, in the actual work, there are also a variety of pipes such as lining plastic (PE) aluminum alloy pipe, lining stainless steel aluminum alloy pipe, PE pipe, etc.