Assessment of the Stress-Strain State of Pipelines Based on Measuring Magnetic Characteristics in Field Conditions

A series of measurements was conducted on four sections of a pipeline made of 17G1S steel using two measuring instruments: the magnetic multimeter MMT-3 and the KRM-Ts-K2M magnetic structural analyzer. Maps of the distribution of coercive force, residual magnetic induction, and maximum magnetic induction along the pipes were obtained. The load factor for various cross sections of the pipeline was calculated. Graphs of the dependences of the magnetic characteristics averaged over the cross section on the load factor were constructed. It was found that the cross sections most critical for failure, where the load factor exceeds the critical value of 1.2, corresponded to reduced values of coercive force and residual magnetic induction measured along the pipeline axis. It was shown that measurements along the axis at the upper part of the pipeline, i.e., at the 12 o’clock position, exhibit a similar dependence to the values averaged over the cross section, indicating that for pipeline aerial crossings, measurements at the 12 o’clock position alone may be sufficient.