Multiple Data Inspection of Hard Spots and Cracking

Hard spots are serious threats to pipeline operations, especially in pre-1970s vintage pipe where they were unintentionally created in the manufacturing process. Steels with high hardness and tensile strength are susceptible to hydrogen induced cracking (HIC) and thus hard spots with hardnesses higher than that of the surrounding base material are areas in need of remediative action. One course of remediation has been sleeving, but if the sleeve is not properly sealed to the pipe, cracking can be accelerated due to the trapping of moisture. An inspection with multiple data sets (MDS) is capable of identifying hard spots through the use of high and low levels of magnetization and identifying cracking even in sleeved areas using helical field technology. This paper will show the initial tests that were done using an 18-inch MDS tool to measure different types of hardening and quenching. The results are compared to actual hard spots from a 30-inch diameter vintage pipe before and after notches were made, both with and without sleeves. The ability to assess hardness and the detectability of cracking is discussed.