METHOD OF DETERMINING MECHANICAL STRESS IN A STEEL PIPE Russian patent published in 2020 - IPC G01L1/12 G01N3/12 

FIELD: measurement.

SUBSTANCE: invention relates to assessment of technical condition of steel pipelines and can be used for determination of mechanical stress, for example, in steel pipelines of underground laying. Method comprises making a sample in the form of a hollow cylinder from a material similar to the material of the pipeline, step-by-step loading of sample by creation in it of excess internal pressure of liquid or gaseous medium and its bending, obtaining dependence of coercive force on value of mechanical stresses in sample. Two control points are set on the sample circumference: one is in the bending stretching zone and the second one is in the bending compression zone. Sample is loaded by simultaneous action of bending and internal pressure of medium. Coercive force is measured at control points by aligning the coercimeter sensor along the sample axis. Curves of dependence of coercive force H_f on bending stresses are plotted σ_bend, at different pressures medium P_ext. Pipeline section with potentially high bending stress is determined. Pipeline circle control points are marked in selected cross-section, coercive force is measured at selected points by aligning coercimeter sensor so that direction of magnetic flux in sensor is aligned with pipeline axis. Selecting maximum and minimum among measured values, note here that said values must refer to diametrically opposite points of pipeline cross-section. Note that point with minimum coercive force value is related to zone of maximum tension with maximum value of maximum compression zone. An angle of the bending plane passing through the points of maximum tension and compression is determined, pressure in the pipeline is measured and bending stresses in the pipeline are determined using the obtained relationship for the corresponding pressure.

EFFECT: possibility of determining mechanical stresses in the wall of a steel pipeline, taking into account simultaneous action of transverse bending and internal pressure of the transported medium, high reliability of the method and broader capabilities thereof.

1 cl, 3 dwg