DOI: 10.14489/td.2014.05.pp.060-066 

Guskov S.S., Aginey R.V., Musonov V.V., Spiridovich E.A.
FEATURES OF THE MAGNETIC FIELD OF UNDERGROUND PIPELINE FOR VARIATIONS IN INTERNAL PRESSURE
(pp. 60-66)

Abstract. The results of experiments on influence determination of change of mechanical stresses in the pipeline on a magnetic field, created by the pipeline on a ground surface, are presented. The remote magnetometric survey of an operating underground gas pipeline section of a large diameter was executed in the presence and in the absence of an excess internal gas pressure. There were estimated nature and value of change of the magnetic field, caused by known change of mechanical stresses. At analyzing a magnetic field behavior, the information of circumferential welds’ location was used, obtained in the course of diagnostic study of the concerned pipeline section. It is established that at change of mechanical stresses in pipeline the character of distribution of the pipeline magnetic field on a ground surface essentially changes. At 275 МPa change of circumferential stresses and 100 МPa of longitudinal stresses, changes of a magnetic field strength vertical component of ~ 13 А/m were observed in a number of points at a ground surface, remote at a distance of 1,9 m from the pipeline axis. Thus the average variation value of the vertical component at section with the length of 1700 m has made only ~ 1 А/m. The interaction between statistical characteristics of change of magnetic field strength components at change of mechanical stresses and pipes type is found out. The root-mean-square deviation of variation of a vertical strength component has made 1,46 А/m at the sections, consisted of  single-joint welded pipes, 2,59 А/m at the sections, consisted of  spiral-welded pipes, 3,41 А/m at the sections, consisted of double-seam pipes. It is shown that both in the presence, and in the absence of excess internal pressure the changes of strength component of magnetic field along pipeline axis are connected with differences of longitudinal magnetization of the neighboring pipes. Therefore some circumferential  welds can be defined by magnetograms. It is established that at change of underground pipeline’s deflected mode, the character of a magnetic field variation on a ground surface depends not only on mechanical stresses, arising at present moment, but also is substantially determined by magnetic background of pipes which for different pipes can essentially differ.

Keywords: remote magnetometric diagnostics, underground pipeline, internal pressure.

 

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