An inspection robot for boiler tube using magnetic flux leakage and ultrasonic methods

Abstract

An inspection robot system has been developed to test boiler tube effectively based on the magnetic flux leakage (MFL) technique and ultrasonic method. Using the magnetic flux leakage technique, the corrosion and erosion on the outer diameter (OD) surface can be inspected. The wall loss can be tested with the magnetic bridge principle firstly, and inspected by ultrasonic probe quantitatively. A magnetic sensor was designed by the above-mentioned principle and developed with Hall element arrays. Experiments demonstrate that the NDT robot, which includes furnace wall cleaning apparatus, adhesion and crawling and safety mechanisms, the inspection device, the control system and the signal processing software, can be driven up and down the tube automatically, and the apparatus was able to identify a through hole (bigger than 1.6 mm diameter) defect and wall loss.