PURPOSE: To always keep constant the distance between inspected object and the flaw detecting sensor, by floating the sensor holder from the surface of inspected object through the use of a pair of magnets located mutually to be repulsive.
CONSTITUTION: On the surface of the steep pipe 1 to be inspected, the steel pipe 1 is turned while the roller 4 at both ends of the detection head fixed plate 2 is in contact, and the entire surface is scanned with the flaw detecting sensor 16. In this case, the holder 10 having the sensor 16 is floated by a distance and in noncontact state from the surface of steel pipe with the repulsive force by the permanent magnets 30, 32 and electromagnet 34. Next, if the distance between the steel pipe 1 and the holder 10 is shorter than the reference distance, the output of the distance sensor 18 is higher than the reference potential set to negative output of the differential amplifier 40, and the amplifier 40 produces positive output and magnetizes the magnet 34 via the amplifier 42 so that the repulsive force between the magnets 30 and 32 can be increased, and the distance is corrected to the reference interval. If the distance is longer, the opposite processing as the above is made. Accordingly, the distance between the inspected object and the flaw detecting sensor is always kept constant.
HIROTA TETSUYA
OOGAKI ICHIROU
| JPS51114188A | 1976-10-07 |