| 摘要 |
A magnetically detectable plastic pipe having magnetic particles distributed in the wall of the pipe so that it is easily detected from the surface when buried in the ground, in a wall in concrete or other distant or relatively inaccessible locations. The magnetic particles are preferably distributed in the wall of the pipe by extrusion with the plastic at the time the pipe is formed and the pipe is passed through a magnet to magnetize the pipe diametrically with one pole on one side of the pipe and the other pole diametrically opposite. The pipe magnetization polarity may be selectively reversed to encode a unique magnetic signature to the pipe. Changing the magnetization polarity may also be used to encode data on the pipe. The pipe may be rotated and passed linearly through the magnet, or the magnet may be rotated around the pipe to produce a spiralled diametrically oriented magnetic structure. Another magnetic material used is strontium ferrite.
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