Magnetizers for pigging tools

A magnetizer module for a smart pig, comprising:

• a central shaft;
• and
• at least one magnet bar, coupled to the central shaft at one end by a collapsing system comprising a link and a torsion spring, coupled to the central shaft at an opposing end by a polyurethane ring disposed circumferentially around the central shaft, and configured to induce a persistent magnetic field coaxially with a longitudinal axis of the central shaft to a pipe wall, the at least one magnet bar comprising:
• a first magnet of a first polarity disposed on a front end of the magnet bar;
• a second magnet of a second polarity opposite the first polarity disposed on a rear end of the magnet bar;
• a front magnetic circuit pole coupled to the first magnet and extending radially outward from the magnet bar;
• a rear magnetic circuit pole coupled to the second magnet and extending radially outward from the magnet bar;
• and
• a sensor head comprising at least one sensor configured to measure magnetic flux, the at least one sensor disposed between the front magnetic circuit pole and rear magnetic circuit pole;
• wherein the front magnetic circuit pole and the rear magnetic circuit pole are configured to induce the magnetic field to the pipe wall;
• wherein the front magnetic circuit pole and the rear magnetic circuit pole include a plurality of wear pads configured to contact the inner diameter of a pipe.

A smart pig, comprising:

• two axial magnetizers, each axial magnetizer comprising:
• a central shaft;
• and
• six magnet bars, each magnet bar (a) coupled to the central shaft at one end by a collapsing system comprising a link and a torsion spring, (b) coupled to the central shaft at an opposing end by a polyurethane ring disposed circumferentially around the central shaft, and (c) configured to induce a persistent magnetic field coaxially with a longitudinal axis of the central shaft to a pipe wall, each magnet bar comprising:
• a first magnet of a first polarity disposed on a front end of the magnet bar;
• a second magnet of a second polarity opposite the first polarity disposed on a rear end of the magnet bar;
• a front magnetic circuit pole coupled to the first magnet and extending radially outward from the magnet bar;
• a rear magnetic circuit pole coupled to the second magnet and extending radially outward from the magnet bar;
• and
• a sensor head comprising at least one sensor configured to measure magnetic flux, the at least one sensor disposed between the front magnetic circuit pole and rear magnetic circuit pole;
• wherein the front magnetic circuit pole and the rear magnetic circuit pole are configured to induce the magnetic field to the pipe wall;
• wherein the front magnetic circuit pole and the rear magnetic circuit pole include a plurality of wear pads configured to contact the inner diameter of a pipe;
• and
• wherein the axial magnetizers are positioned relative to each other such that magnet bars cover the entire pipe wall.