Abstract: 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.

Abstract: A method for detecting a thinned out portion on the inner surface or the outer surface of a pipe, comprising heating or cooling a pipe to be tested from the outer surface or the inner surface thereof so that a difference in temperature is produced between two portions of the outer surface or the inner surface of the pipe corresponding to a thinned out portion and a normal portion of the inner surface or the outer surface of the pipe; shooting the outer surface or the inner surface of the pipe by means of a thermal imaging system to obtain a thermal image of the difference in temperature; and then calculating a differential value of a temperature distribution of the thermal image of the difference in temperature on a line passing the highest temperature point or the lowest temperature point in the thermal image of the difference in temperature.

Abstract: A method for detecting a state of a substance existing in a pipe, the outer surface of which is exposed, which comprises: heating or cooling a pipe, the outer surface of which is exposed, from the side of the outer surface thereof so that a difference in temperature is produced between a portion of the outer surface of the pipe corresponding to a portion of the inner surface thereof, which is in contact with a solid or liquid substance existing in the pipe, and a portion of the outer surface of the pipe corresponding to a portion of the inner surface thereof, which is not in contact with the substance; then shooting the outer surface of the pipe by means of a thermal imaging system while the above-mentioned difference in temperature still remains on the outer surface of the pipe to obtain a thermal image of the difference in temperature; and detecting a state of the substance existing in the pipe by means of the thus obtained thermal image.

Abstract: A method and an apparatus for detecting a defective portion on the inner surface of a pipe, the outer surface of which is exposed, includes: heating or cooling a pipe, the outer surface of which is exposed, from the side of the outer surface thereof so that a difference in temperature is produced between a portion of the outer surface of the pipe corresponding to an accumulation of foreign matters or a thinner portion as a defective portion on the inner surface thereof, and a portion of the outer surface of the pipe corresponding to a normal portion of the inner surface thereof; then shooting the outer surface of the pipe by means of a thermal imaging system while the above-mentioned difference in temperature still remains on the outer 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 of the inner surface of the pipe by means of the thus obtained thermal image.