LASER TUBE INSPECTION
Laser tube inspection is conducted using a class 2 Laser on a spinning head to achieve complete coverage of the tube bore. The probe is precisely centralized inside the tube using a laser table to provide 3 dimensional positioning and a motor drive rotates the sensor head and pulls it through the tube a constant speed. A distance encoder records the exact position of the sensor within the tube.
3D displays can either be in the form of a video image or a colour display highlighting low and high spots on the tube surface. Measurements of defect depth can be made to an accuracy of 20 microns.
The main limitation to laser tube inspection is that only the tube bore is inspected as no penetration of the material takes place. For this reason it tends to be used as a back up to other tube inspection techniques or where either from experience or process considerations it is known that damage will almost certainly be on the inside of the tube. Other applications include inspections within the tube sheets where eddy current data analysis is difficult and in the inspection of ferrous tubing where surface roughness gives rise to scattering of the ultrasonic beam in IRIS inspections.