Magnetic Particle Inspection (MPI), a form of Non-Destructive Testing (NDT), is far more cost-effective and efficient as a maintenance method if it is carried out using rope access. This was proven recently at a large coal-fired power station in Limpopo, where Skyriders Access Specialists (Pty) Ltd. was called upon to examine three specific areas in a large boiler.
Installing scaffolding for such an operation is both costly and time-consuming, increasing the downtime of the power station itself. Instead, Skyriders simply had a two-person team of qualified rope access technicians abseil into the structure to carry out the inspection at the exact location where it was required.
MPI is mainly used to detect surface and shallow subsurface discontinuities in ferromagnetic materials such as iron, nickel, cobalt, and some alloys. The process involves direct or indirect magnetisation of the area in question.
The magnetic lines of force are perpendicular to the direction of the electric current, with the presence of a surface or subsurface discontinuity in the material allowing the magnetic flux to leak, since air cannot support as much magnetic field per unit volume as metals.
In order to identify a leak, ferrous particles are applied to the area, either dry or in a wet suspension. These are attracted to any area of flux leakage, forming what is known as an indication, which is evaluated to determine its nature, cause, and course of action if necessary.
The inspection process itself took a matter of hours, with no recordable indications of any problems, Skyriders Marketing Manager Mike Zinn reports. “In this instance, we were able to respond to the specific requirements of our client with the best possible solution that minimised disruption to normal operations.”
It is not the first time that Skyriders has carried out work at this particular power station. Previously it was called upon to deploy its Elios Sky Eye confined-space drone for an emergency inspection of a potential tube leak in a boiler.