Spiral magnetic field apparatus and method for pipeline inspection

A system comprising:

• a portion of pipe comprising a pipe wall forming a cylindrical tube defining a circumferential direction and an axial direction;
• and
• an in-line inspection tool positioned within the portion of pipe and comprising
• a frame extending in the axial direction,
• a plurality of armatures, each being independently suspended from the frame and comprising a first end and a second end, opposite the first end,
• a plurality of first magnets, each connected to the first end of a different armature of the plurality of armatures to form a first pole,
• a plurality of second magnets, each connected to the second end of a different armature of the plurality of armatures to form a second, opposite pole,
• the plurality of armatures, wherein a distance between the first and second poles corresponding to a first armature thereof is less than a distance between the first pole corresponding to the first armature and the second pole corresponding to an adjacent armature of the plurality of armatures, and
• the plurality of armatures, wherein the first and second magnets corresponding to each armature thereof generate a magnetic field orientated obliquely with respect to the circumferential and axial directions.

A system comprising:

• a portion of pipe comprising a pipe wall forming a cylindrical tube defining a circumferential direction and an axial direction;
• and
• an in-line inspection tool positioned within the portion of pipe and comprising
• a frame extending in the axial direction,
• the frame comprising a plurality of rigid sections connected together in series by one or more flexible couplers,
• a plurality of armatures connected to a rigid section of the plurality of rigid sections,
• the plurality of armatures, each armature thereof comprising two magnets spaced apart a first distance to form a magnetic dipole pair,
• the plurality of armatures connected to the frame with the first distance being the shortest distance between any poles of opposite polarity contained within the plurality of armatures, and
• the magnetic dipole pair of each armature of the plurality of armatures generating a magnetic field oriented obliquely with respect to the circumferential and axial directions.