Crack Detection of Hydrocracker Feed/Effluent Heat Exchanger Tubes

Abstract Non-ferromagnetic heat exchanger tubes are typically inspected using conventional eddy current bobbin probes to gather data on the integrity of the tubes. This technique provides operators with useful information on pitting and longitudinal cracks, but technical limitations of the conventional eddy current process leaves operators with limited ability to detect circumferential flaws and cracks. In this paper, extensive circumferential chloride stress corrosion cracks, originating from the tube outside diameter, were found by Eddy Current Array (ECA) in the front portion of SA 213 TP 321 SS tubes of a hydrocracker unit feed-effluent heat exchanger. The crevices between the tubes and the tube sheet trap chlorides in both normal operation, and in downtime. Deployment of ECA technology eliminates the limitations of conventional EC bobbin coil probes, effectively identifying circumferential cracking as well as pitting and axial cracking.