I learned something new while attending the Pipeline Pigging and Integrity Management Conference this month:  smart pigs that detect magnetic flux leakage.  A pig is typically used to push or bookmark a fluid in a pipeline – all that requires is just a plain pig made of some polyolefin material.  A smart pig, however is loaded with electronics.


A pig that detects magnetic flux leakage is a specific class of smart pig that detects corrosion, holes, and other defects in pipeline integrity.  The figure above is an example of a smart pig that detects magnetic flux leakage.  The sensor is in the middle of the pig, along  with a strong magnet that generates the flux though the pipe.

In this series, we are going to investigate the technology behind this class of pig and requires some physics; but fortunately, I am here to make the subject matter easy for you.  The concept is actually quite easy when you get past all the fancy jargon.

Gauss Law

To understand this technology, one must refer to Gauss’ Law, which essentially states that for any closed and defined volume of space, the magnetic flux in must equal the magnetic flux out (above Figure).  Magnetic flux, in simple terms, is the magnetic field B times the area.  Dont pay attention to that fancy equation up there, that is the formal definition of magnetic flux, so I just left it in for accuracy.

This type of smart pig uses a magnet.  As you can see from the figure, all the magnetic field that exits the north pole must reenter the south pole.  Thus, any closed surface in that field stream experiences a state where all the flux in equals all the flux out.  This is the key behind measuring magnetic flux leakage.

Stay tuned to this series as we explore how this type of smart pig technology is getting things done.









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