Hydraulic method for the location of oil leaks from pressure-assisted 3-core and single-core cables

An investigation has been carried out into possible methods of oil-leak location in pressure-assisted cables. A hydraulic method of leak location, making use of the cable resistance to oil flow and involving measurements of pressure and flow at both ends of the cable is suggested as the most viable alternative to the present freezing technique on 3-core cables. The same principle can also be applied to single-core cables. The method was first tested in the laboratory using a long length of small-bore pipe to simulate a cable and the accuracy of location was repeatedly better than 1% of the total length. A small number of initial field trials on various types of cables provided useful information on the factors affecting the accuracy of locating actual leaks. Subsequent location tests on a wide variety of cables which developed leaks whilst in service, have proved highly successful. In most cases it was possible to correctly identify the leak position, without the need for freezing. The reasons for the variations in accuracy of test results together with practical problems are discussed.