MATHEMATICAL MODELING OF X-PROBE EDDY CURRENT ARRAY COILS USED IN TUBE INSPECTION

摘要

This paper presents a mathematical model that calculates eddy current signals from laterally spaced transmit-receive pancake coils. This model was validated by comparing calculations with: laboratory: measurements and; it has been applied to evaluating design variations in X-Probe eddy current array coils. This model was used to quantify detection capabilities of probe designs with different numbers of coils. The current standard X-Probe design for 13 mm (0.5 inch) diameter steam generator tubes uses 3: rows of coils with 8 coils per row. This design is commonly referred: ta>as the "8 coil X-Probe". A significant improvement in detection capability was predicted for an X-Probe with 12 coils per row (called the "12 coil X-Probe") detecting short circumferential crack-like flaws. Based on these calculations, a prototype 12 coil X-Probe was constructed and used in laboratory measurements in comparison with a standard 8 coil X-Probe design. The laboratory measurements confirmed the predictions from the mathematical model demonstrating that a new prototype 12 coil X-Probe has much better detection capability for: short circumferential crack-like flaws than the standard 8 coil probe in 13 mm (0.5 inch) diameter steam generator tubes.!