Insulation has mostly been used for preventing heat loss of substance in metal pipeline and later introduces corrosion at the metal-insulation interface. An inspection system is designed to detect the corrosion under the insulation on the outside of pipe wall based on a nondestructive testing associated with the eddy current technique. This research was to design and develop prototype devices suitably used for testing. Detecting probes designed and manufactured were of two types. C iron core probe and pick up coil iron core probe. Flat specimen with localized uniform corrosions was machined and inspected. The signal frequency of 300 – 1000 Hz induced by a function generator was applied to detect the corrosion, and the results were demonstrated by an oscilloscope. The experimental results revealed that the pick up coil iron core probe can detect corrosion effectively more than C iron core probe and the diameter of uniform corrosion detected was equal or greater than 6 millimeters. Depth of uniform corrosion of 1 – 6 millimeters at 300 to 400 Hz frequency can be detected, and the method can also detect through the color coating and insulation with the total thickness of less than 3 millimeters.
Keywords
Eddy current, Insulation, Pick up coil, Nondestructive testing
THE JOURNAL OF INDUSTRIAL TECHNOLOGY
Published by : Research and Academic Supports Division College of Industrial Technology, King Mongkut’s University of Technology North Bangkok Contributions welcome at : http://j.cit.kmutnb.ac.th/en/
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