During the design and construction of pipeline systems, special attention is paid to the detailing and joint of joints in pipes with different diameters. At the connection sites, reinforcement is used, which is called a steel transition and allows the working medium to flow freely in both directions. This material in many cases is very popular.
Russian manufacturers produce standard steel transitions in accordance with GOST 17378-2001 and specialized transitions installed at joints that do not meet standardization parameters.
There are two types of fittings with which pipelines are installed: eccentric and concentric.
In the first case, there is a displacement at the inlet and outlet along the axis of the medium flow by a small amount, which can still affect the flow movement. Here, the lower generatrix becomes the junction.
In the second case, the steel concentric transition contributes to the joint of pipes in the joints without displacement along the axis of movement of the working stream.
The flow rate passing through the living section of the pipeline over a period of time can increase or decrease, and the working pressure also changes. This process directly depends on the transition of steel.
The material for the manufacture of this reinforcement is steel of various grades. To work in low pressure and non-aggressive environments, steel transitions are made of
carbon steel St3, St10, St20. These products, made of steel of grades such as 12x18H10T, 15x5M, are used when transporting a stream with aggressive media, special compounds are added to steel to increase corrosion resistance and service life. Steel transitions with zinc coating in one layer are produced from steel with low corrosion resistance.
A significant property of the reinforcement is the maximum allowable working pressure, which depends on the material and geometric parameters, allowing to withstand the working pressure in the range from 4 to 160 MPa, corresponding to the maximum allowable.
Welded steel transitions are designed for operation at a pressure of 16 MPa and operation at air temperatures from –70 to + 450 ° C, and are also resistant to temperature and pressure differences.
The existing production technology allows you to produce valves by stamping or casting electroslag centrifugal, getting it without seams, which increases the reliability and durability.
Requirements for reinforcement material and installation:
- steel should have high ductility, structure, weldability and impact strength ;
- compliance with the proportionality of the transition holes and pipes, the roundness and plane of the ends.
When choosing steel transitions, the following criteria should be followed:
- diameter of the inlet and outlet of the pipe;
- type of material and its strength characteristics;
- type of working medium and temperature difference;
- limit of working pressures.