The in-service inspection of coated steel welds using Eddy-Current Techniques

Abstract

Traditionally surface crack detection in coated Ferritic Steel Welds with Eddy-Current Techniques has been difficult due to the change in material properties in the Heat Affected Zone. These typically produce signals larger than crack signals. Sophisticated probe design and construction, combined with modern electronic equipment, have largely overcome the traditional problems and now enable the advantages of Eddy-Current Techniques to be applied to In-Service Inspection of Coated Ferritic Steel Structures in the as-we!ded conditions. Specifically, the advantage of the technique is that under quantifiable conditions an inspection may now be carried out through corrosion protection systems. It is the intention of this paper to review the current information available, establish the limiting parameters of the technique and detail the practical experiments conducted to determine the extent of the limiting parameters. The results of these experiments are detailed. Having determined the limiting factors, outline testing procedures have been established together with relative sensitivity settings.