Development of new methods for Non Destructive Testing of stranded ropes with a diameter larger than 100 mm

The magneto-inductive inspection method is a well-approved and verified technical state of art inspection method for locked coil ropes and stranded ropes up to a diameter of 100 mm. Up to now, it has not been systematically investigated and verified if the inspection method is also suitable for bigger stranded ropes of diameters beyond 100 mm to determine safely the discard point. For these reasons the IFT of University of Stuttgart has carried out a research project inspecting different designs of 109 mm diameter stranded rope within bending fatigue tests using the magneto-inductive method. Later on the results were verified by dismantling the worn rope components. Additionally, several crane ropes of diameters beyond 100 mm used in the offshore field have been inspected magnetically within the last 3 years in order to sustain the conclusions of the research project. The basic result of the research and practical experiences of the IFT is that the magneto-inductive method is capable of determining the discard point of such large scale rope diameters apart from the fact that single wire breaks inside the rope cannot be detected with certainty. After interpreting the measurement data the expected inner conditions of the ropes could be confirmed by dismantling the ropes which is an evidence of the inspection’s capability. This validates the reliability of defect determination of the magneto-inductive rope inspection method. It also turned out that it is not possible to determine the point of discard without NDT. So for these rope functions this leads to a necessary continuous supervision and based on this to specifically planned inspections.

Author(s): S. Winter, D. Moll and A. Steven