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Publication of GB724533ApublicationCriticalpatent/GB724533A/en
724,533. Locating leakages in electric cables. JOHNSON & PHILLIPS, Ltd. Oct. 1, 1953 [Oct. 14, 1952], No. 25730/52. Class 99 (2). [Also in Group XXXVI] An electric cable system in which the cores 1, 2, 3 are enclosed in a sheath 4 filled with fluid under pressure, has the sheath divided by fluid barriers into a number of subsections a, b, c ... j, and is provided with a number of transfer tubes 5, 6, 7, extending along the system and connected in succession with successive sub-sections. The ends of the tubes are connected together and the common points at each end are connected to pressure gauges fitted with alarm contacts which operate a signal in the event of a leakage occurring in the system. To locate the leak the tubes 5, 6, 7 are isolated, and the tube connected to the leaky sub-section discovered by pressure gauge readings. The tubes are then re-connected at the left hand end and the right hand ends of the tube (e.g. 5) connected to the leaky sub-section and one other tube 7 are closed, fluid being fed at constant pressure to the third tube 6. Differential pressure gauges 10, 11 are connected between tube 7 and tubes 5 and 6. The distance #L from the feeding end to the communication point between tube 5 and the leaky sub-section is then calculated from the formula where L is the total length of the cable P 1 is the pressure difference between tubes 7 and 5 indicated by gauge 10. P 2 is the pressure difference between tubes 6 and 7 indicated by gauge 11. Location of the position of the leak in the leaky sub-section and repair thereof is then effected by known methods.