November 25, 2020
DPM-EduSeries Post 3: Full-Length EMI and UT
For the third post of our DPM-EduSeries, we will be looking at Full-length EMI (Electromagnetic Inspection) / UT (Ultrasonic Inspection)!
Full-length EMI / UT is performed on each tube for the detection of imperfections (longitudinal and transverse) on the outside and inside surfaces. In EMI, the tube is magnetised and when there is an imperfection, causes a leak in the magnetic field and the equipment would be able to pick this up and shown on the charts. The UT involves the use of ultrasonic waves transmitted into the tube with a probe creating a peak from the initial pulse and a second peak due to the back-wall echo. An imperfection would create an additional pulse and also reduce the amplitude of the back-wall echo. If the imperfections exceed the limits of the threshold set, the tube would be rejected. These non-destructive tests are performed after final heat treatment. Tubes that passed the full-length inspection is then moved to the Special End Area inspection as the end areas were not inspected by the automated equipment due to the upset ends.
Stay tuned to our next post in our DPM-EduSeries as we discuss more about Special End Area inspection!