PURPOSE: To improve detecting accuracy through elimination of induced noises from stray current and transmission line, by inserting a detecting electrode inside its buried area, permitting it to displace in an axial direction of pipe and conducting damage detection of coating film by detecting magnetic field inside the pipe.
CONSTITUTION: A DC power source 3 is connected by way of a switch 4 between a buried piping 1 provided with rust preventative coating film and supply electrode 2. Into this piping 1, a magnetic field detecting member 11A provided with sensors 21X, 21Y, 21Z detecting magnetic fields in directions XYZ mounted on a running bench 20 is fed with a thrusting force. A position of the member 11A is measured by a length of a wire 13, the position being indicated on a display unit 15. From this situation the wire 13 is wound around a drum 14 and the member 11A is drawn back and simultaneously, a switch 4 makes the switch on and off operations repeatedly to measure the magnetic field inside the pipe. In the neighborhood of a damage, a disturbance of an input current generates a magnetic field and thus, damage of coating is detected.
| JPH02178600 | IMPACT POSITION SENSOR |
| WO/2014/054529 | CAPACITIVE DISPLACEMENT SENSOR |
| JPH0658705 | DISTANCE DETECTOR OF METAL OBJECT |
HOUJIYOU HIROYUKI
NAGAMUNE AKIO
| JPS58168954A | 1983-10-05 |