Patent ID: 7268541
Filing Date: 2007-09-11
Classification: G01N

Abstract:
1. A method for monitoring a flexible elongate structure with a generally cylindrical surface, the structure comprising at least one layer of steel wires near the cylindrical surface, the steel wires extending at least partly along the length of the structure, the method comprising inducing an alternating magnetic field in the steel wires using at least one electromagnetic probe adjacent to the cylindrical surface of the structure, the or each probe incorporating an electromagnetic coil to induce the said alternating magnetic field, and monitoring the alternating magnetic flux density near the cylindrical surface of the structure in the vicinity of the said probe, determining from the monitored flux density a corresponding parameter indicative of stress in the steel wires, detecting a position at which the stress in the wires is significantly less than at other positions, and hence detecting if any wires have broken.