METHOD AND APPARATUS FOR INSPECTING MULTIPLE PIPING

PROBLEM TO BE SOLVED: To inspect a piping to be inspected even when the piping includes a rib by nondestructively inspecting an outer piping from the side of an innermost piping where the rib does not exist when a corrosion or the like of a multiple piping supported by ribs is to be inspected. SOLUTION: A multiple piping, namely, an oil pipeline 1 is fixedly supported by a rib between an outer pipe 1A and a main pipe 18 and by a rib between the main pipe 1B and an innermost piping (inner pipe) 1C in a fixing structure part. The inner pipe 1C is utilized as a guide pipe for a pig 11 and no rib to be an obstacle is present thereinside. The pig 11 with ultrasonic probes 13 is inserted into the inner pipe 1C, and a water 12 is filled in the main pipe 1B to be inspected. The interior of the main pipe 1B outside the inner pipe 1C is subjected to ultrasonic flaw detection from the side of the inner pipe 1C by each ultrasonic probe 13. A degree of wear in thickness of an inner face of the main pipe 1B because of corrosion or the like is judged on the basis of a distance between each ultrasonic probe 13 and the inner face of the main pipe 1B. Even when the rib is present in the main pipe 1B, the degree of wear can be correctly measured in this manner.