Abstract: This invention refers to a device that has a direct applicability in the oil industry, detecting on a prevention basis, failures that may be externally visualized on the walls of the risers. Externally coupled to a pipe in free catenary, called riser, the device involves such a pipe in its entire perimeter and allows for the making of non-destructive inspections of several natures concurrently, while the device moves along all its extension. The device moves along the riser downwards and upwards by a combination of gravity, buoyancy, thrusters and action of expansion of gases.