Specialist NDT Testing Methods - Part 1

Magnetic Particle Inspection

Magnetic Particle Inspection (MPI) is used to detect cracks, stress fractures and other non-visual defects on ferromagnetic materials. This widely used method can be applied to various areas of a street lighting column or high mast but in particular around the corners of a column door or at welds such as the shaft or bracket assembly and where access is available on one surface only.

This test method begins with white paint being applied to the surface being inspected. A solution containing very fine iron particles is then applied and the area is magnetised using either a permanent or electro-magnetic current. If a defect is present the magnetic flux leaks through the defect attracting the iron particles and forms a visible line.

On completion, a detailed report is drawn together outlining the areas inspected and the general findings. If a defect has been noted then the report will give details of the exact location, nature of the defect and possible recommendations for remedial action.

Ultrasonic Thickness Testing

By testing two sections of a street lighting column – the column base (above ground) and the column shaft (swaged/welded section), using a multi-echo ultrasonic thickness gauge we are able to determine the remaining metal thickness and highlight dangerously corroded areas.

Flooded Member Detection

Flooded member detection is used to determine whether a defect within the column has allowed the ingress of water. The presence of water is a major contributor to corrosive activity. Using specialised ultrasonic equipment, which is first calibrated to the type of metal being inspected, a series of readings are taken at various points on the column base. By increasing and decreasing the height of the inspection, it is possible to determine the level to which water has risen.