Apparatus for monitoring the topography of the internal surface of a pipe.

摘要

A pig (1) for monitoring the internal surface profile (7) of a pipeline carries a plurality of sensors (5) to trace the surface as the pig (1) traverses the pipeline. Output signals from the sensors (5) are compared with an expected value and a reference signal generated when they differ by more than a predetermined amount. The sensor signals are recorded simultaneously with the reference signal.