Inspection of Large Tubes Using Sensor Arrays

The eddy current inspection system was designed for detecting surface defects (e.g. cracks, pores) on hot-rolled tubes. The diameter range spans from 50 mm (2") up to 300 mm (12"), the tube length might vary between 3 m ( ~10 ft) and 15 m (~50 ft). During the inspection the tube is rotated by means of rotating rollers, while the trolley moves the 48-coil sensor array along the tube's axis. The external multiplexer switches with a rate of 32 kHz, so a maximum scan speed of 1.5 m/s can be achieved. A special analysis software provides not alone the GOOD/BAD classification, also the actual defect length is displayed on the operator panel. Using a colour marking device the actual defect position is labeled.