DEVELOPMENT OF A NON-CONTACT HYDROGEN SENSOR FOR COATED PIPELINE STEEL WELDMENTS

Only a few parts per million of hydrogen are needed to produce detrimental results in higher strength pipeline steels. The cost of removal and subsequent replacement of a pipeline coating is high; thus a working hydrogen detector for field measurements must operate through the pipeline coating. An in-field sensor must utilize technology that provides rapid (or real-time) non-contact nondestructive measurements. Nondestructive low frequency impedance measurements can be used to determine hydrogen content in operating pipeline steel and weldments as well as through structural coatings. Low frequency impedance measurements have been correlated to hydrogen content in pipeline steel both in the laboratory and in the field. The use of real-time low frequency impedance measurements to monitor hydrogen content in coated steel weldments is presented.