Patent ID: 6100684
Filing Date: 2000-08-08
Classification: G01N

Abstract:
A system for the detection of cracks and anomalies of thickness in a cylindrical pipeline that can be inserted into and moved within this pipeline, said system having at least one cylindrical measurement unit comprising:a plurality of magnetic means for producing and injecting a transversal magnetic flux into a portion of the pipeline,means to measure local magnetic fields, produced by the magnetic means, on the inner surface of the pipeline,means to drive this system by the movement of fluid flowing in this pipeline,the means for production and injection of flux and the measuring means being arranged within the substantially cylindrical measurement unit that further includes guidance means to make the measurement unit follow a substantially helical path inside the pipeline, wherein the magnetic means are circumferentially spaced evenly around the periphery of said measurement unit, each magnetic means comprising a yoke made of ferromagnetic material, the yoke comprising two poles directed towards the inner surface of the pipeline and each being provided with permanent magnets, these permanent magnets being arranged so that two adjacent poles belonging to two distinct magnetic means have one and the same polarity.