PURPOSE: To detect the point and degree of a leakage or breaking of a cable by a method wherein gas flows into a void space between a line nearer to a center and a conductive shield, an outflow is monitored in a portion apart a little therefrom, and the relationship between an inflow and an outflow is observed.
CONSTITUTION: Ports 16, 26 of four-quarter valves 11, 21 of flow rate data capture units 50, 60 are coupled to needle valves 52, 62 of gas filter/drier 51, 61, and as the ports 16, 26 pass through flowmeters 54, 64 before returning to ports 17, 27, the four-quarter valve 11 directs a gas flow from pressurized gas supply sources 57, 67 to a cable segment 30 or a gas flow from the segment 30 to outflow ports 14, 24 through flowmeters 54, 64. Then, in pressure transducers 54, 64 connecting with a gas pipeline near an outlet of the flowmeters 54, 64, gas flow rate of a loop between the ports 16 and 17, and between the ports 26 and 27 is measured, and a signal in proportion thereto is A/D-converted 55, 65 and transmitted via radio modulators 56, 66, so that a leakage and a hindrance of a cable are detected from the relationship of the inflow and outflow of gas detected by units 50, 60.
MIGERU JIYOSE SHIYABU
DEIIN FURANKURIN KAWA
