Condition monitoring of carbon steel piping using Barkhausen noise measurement

Various industrial process plants, including nuclear reactors, use carbon steel piping in their fluid and heat transport circuit. Fatigue-related changes in the material characteristics which appear in a period before and during the crack initiation and stress-related changes due to loading can be non-destructively quantified with the micromagnetic testing method known as Magnetic Barkhausen Noise (MBN) measurement. Investigations were carried out for studying: (i) the fatigue crack growth on a cyclically loaded notched piping; and (ii) the stress distribution pattern under in-plane bending test on a carbon steel seamless pipe butt welding elbow specimen of a 90degrees long radius. The progressive changes in MBN were observed during fatigue test both before crack initiation and during crack growth. Elbows underwent geometric distortion during in-plane bending and Barkhausen noise was found to change in the extrados-intrados as well as flank-flank zone. It is therefore suggested that the technique can be used in monitoring fatigue damage under service and stress distribution on ferromagnetic piping components.