Transitions steel: varieties and the scope of their application

During the design and construction of pipeline systems, special attention is paid to the detailing and junction of joints in pipes with different diameters. In the connection areas, an armature is used, which is called a steel transition and allows a free flow of the working medium in both directions. This material is in many cases very much in demand. Russian manufacturers produce standard steel transitions in accordance with GOST 17378-2001 and specialized transitions installed at joints that do not meet the standardization parameters. There are two types of fittings with which the pipelines are installed: eccentric and concentric.

In the first case, there is an offset at the inlet and outlet along the axis of the medium flow by a negligible amount, which can still affect the flow movement. Here the lower generator becomes the junction.

In the second case, the steel concentric transition promotes the jointing of the pipes in the joints without displacement along the axis of motion of the working flow.

The flow through the live section of the pipeline over a period of time may increase or decrease, and the operating pressure also changes. This process directly depends on the transition of steel.

The material for the manufacture of this armature is steel of different grades. For work under conditions of low pressure and non-aggressive environment, the steel transitions are made of carbon steel St3, St10, St20. These products, made of steel grades such as 12x18N10T, 15x5M, are used for transporting the flow with corrosive media, special compositions are added to the steel to improve corrosion resistance and service life. From steel with a low resistance to corrosion, steel junctions with zinc coating are produced in one layer.

A significant property of the armature is the maximum allowable working pressure, depending on the material and geometric parameters, allowing to withstand the operating pressure in the range from 4 to 160 MPa, corresponding to the maximum permissible.

Steel welded transitions are designed to operate at a pressure of 16 MPa and operate at an air temperature of -70 to + 450 ° C, and are also resistant to temperature and pressure differences.
The existing production technology makes it possible to produce reinforcement by stamping or casting an electroslag centrifugal, obtaining it without seams, which increases the reliability and service life.

Requirements for the valve material and installation:

- steel must have high plasticity, structure, weldability and toughness ;

- observance of the proportionality of the holes of the transition and the pipe, roundness and the plane of the ends.

When choosing steel transitions, one should adhere to the following criteria:

- inlet and outlet diameter of the pipe;

- the type of material and its strength characteristics;

- type of working medium and temperature difference;

- the limit of working pressures.