Remote Field Examination of Heat Exchanger Tubes

摘要

The Remote Field Eddy Current (RFEC) Technique is currently recognized as the method of choice for the examination of ferromagnetic tubes such as those found in boilers and heat-exchangers. RFEC provides a fast, economical, and thorough heat exchanger tube assessment. RFEC examinations during turnarounds can reduce the risk of unexpected and costly forced shutdowns. With RFEC, a low-frequency A.C. field is used to penetrate the tube wall. Metal loss regions in mid-span, at bends, and at baffle plates are indicated by deviations in the phase and amplitude traces. The data is analyzed on the Strip Chart and Voltage Plane displays. Distinct signal shapes are used to characterize different types of metal loss such as erosion, overall wall loss, near-baffle fretting and erosion, and pitting.