Method and apparatus for detecting defective portion on outer surface of pipe

摘要

A method and apparatus for detecting a defective portion on the outer surface not exposed of a pipe, which comprises: heating or cooling a pipe, the outer surface of which is not exposed, from the side of the inner surface thereof so that a difference in temperature is produced between a portion of the inner surface of the pipe corresponding to an accumulation of foreign matters or a thinner portion as a defective portion on the outer surface not exposed of the pipe and a portion of the inner surface of the pipe corresponding to a normal portion of the outer surface of the pipe; then shooting the inner surface of the pipe by means of a thermal imaging system while the difference in temperature still remains on the inner surface of the pipe to obtain a thermal image of the difference in temperature; and detecting the accumulation of foreign matters or the thinner portion as the defective portion on the outer surface of the pipe by means of the thus obtained thermal image.