| 摘要 |
<p>PURPOSE:To enable non-contact detection of a damaged spot on the coating of a buried pipe by a method wherein the amplitude of a signal current flowing through the buried pipe and the depth of burying thereof are computed from the intensity of a magnetic field generated by the signal current flowing through the buried pipe which is detected by sensors. CONSTITUTION:First a truck 6 is moved to a point of measurement and a lower sensor 5 and an upper sensor 7 are provided. In this state, a signal current I of 440Hz, for instance, is made to flow from a signal current generating means 4 to a buried pipe 1 through a terminal lead wire 2. A magnetic field is generated by the signal current I flowing through this buried pipe 1. voltages are generated in the sensors 5 and 7 by the magnetic field thus generated. Signals of these voltages are inputted to a processing means 8 and the depth of burying of the buried pipe 1 is detected therefrom. While the signal current is made to flow through the buried pipe 1 from the signal current generating means 4 in this way, the point of measurement is shifted sequentially. Then, at a point P whereat the detection signal current changes from I1 to I2, it can be detected that the coating of the buried pipe 1 is damaged or that a gas pipe, for instance, is in contact with another buried pipe such as a water conduit, and thus a spot to be repaired and the depth of burying thereof can be made clear.</p> |
