Method and instrumentation for measuring and assessing AC corrosion risk of pipeline

摘要

A measuring and assessing method for the AC corrosion risk of a pipeline wherein the coupon is connected to a metallic pipeline buried in the earth and the AC corrosion risk of the pipeline is assessed on the basis of coupon DC current density and coupon AC current density that are acquired from a measured value of a coupon current, wherein the measuring and assessing method includes: a step of specifying frequency to specify a source of AC corrosion from a waveform of the measured value of the coupon current; and a step of calculating a coupon current density whereby a pair of coupon DC current density and coupon AC current density is acquired from the measured value of the coupon current in one time unit by defining one cycle of a specified frequency as one time unit.

主权项

1. A measuring and assessing method for an AC corrosion risk of a pipeline, wherein a coupon is connected to a metallic pipeline buried in earth, and the AC corrosion risk of the pipeline is assessed based on a coupon DC current density and a coupon AC current density that are acquired from a measured value of a coupon current, the measuring and assessing method comprising:
specifying a frequency of a source of AC corrosion from the measured value of the coupon current; and calculating a coupon current density by acquiring a pair of the coupon DC current density and the coupon AC current density from the measured value of the coupon current in one time unit by defining one cycle of the specified frequency as the one time unit, wherein the specifying of the frequency includes:
sequentially selecting a candidate frequency from among commercial frequencies of 16⅔ Hz, 50 Hz and 60 Hz;extracting a waveform of the measured value of the coupon current with one cycle of the selected candidate frequency;judging whether or not a difference in appearance time between a maximum value and a minimum value in the extracted waveform is equal to ½ of the one cycle of the selected candidate frequency; andspecifying the selected candidate frequency as the frequency of the source of AC corrosion when a result of the judging is equal.