
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.
Zurück zur ÜbersichtFeatures
- V-shaped rollers used for tube transport
- cylindrical twin rollers used to rotate the tube (adjustable rotational speed: 0.5 … 1.3 m/s)
- trolley driven along the tube’s axis by a DC-motor (adjustable axial speed: 0.5 … 1.3 m/s)
- adjustable vertical position of probe holder (depending on tube diameter)
- pneumatic lowering/lifting of the probe holder

- gapless scan of tube’s outer surface due to overlapping probe arrangement
- 48-coil array (24 dual probes)
- external multiplexer (32 kHz multiplex rate)
- reference notches used for calibration: hole 1.8 mm (60 mm tube diameter) / hole 3. 2 mm (180 mm tube diameter) / hole 3.7 mm (272 mm tube diameter) / axial flaws from 5 % of wall thickness on (depth 0.3 mm … 1.3 mm, length 50 mm)

- input of tube dimensions (diameter, length)
- input of test speed (helical scan)
- automatic calculation of rotational speed (tube) and axial speed (trolley) depending on tube dimensions
- operating mode control (automatic, transport, manual) as well as manual probe lowering/lifting
- menu navigation via graphic user interface incl. graphic output of test results and status information

System Data
- inspection mechanics (frame with main beam, trolley with probe holder, roller conveyor)
- 6-channel eddy current instrument PL500 with ProFiBus I/O module
- external multiplexer
- 24 dual probes (48-coil-array)
- control cabinet
- operator panel incl. display
- colour marking device
- light barrier (surveillance of danger zone)
