METHOD OF TESTING MECHANICAL STRESSES IN PIPELINES Russian patent published in 2004 - IPC

FIELD: nondestructive testing.

SUBSTANCE: invention refers to magnetometric methods of nondestructive testing of ferromagnetic materials. It can be used for urgent remote testing of mechanical stresses in underground oil- and gas pipelines. Magnetizer, magnetometer-gradiometer and ferroprobe of magnetometer-gradiometer are placed about pipeline and the other ferroprobe is placed at specific distance from pipe-line. Total signal of ferroprobes reduce to zero before magnetizing by magnetometer-gradiometer. Preset magnetic field intensity in pipeline, being sufficient for magnetizing material, is generated by means of magnetization pulse. Pulse magnetization process repeats until stable value of magnetic induction is achieved which is measured above magnetometer-gradiometer. Value of mechanical stress efficient onto surface of pipeline is found from experimental curve for stabilized value of magnetic induction depending on mechanical stress. External magnetic field is compensated by means of magnetometer-gradiometer. Intensity of filed in magnetizing device is found from relation: H₀=H_z·Z³/K, Where H₀ is magnetic field intensity in magnetizing device, A/m; Z is distance to pipe-line,m; H_z is magnetic field intensity onto pipe-line, A/m; K is factor relating to sizes of magnetizing device, m³.

EFFECT: remote magnetization of surface of ferromagnetic without preliminary de-magnetization.