METHOD AND DEVICE FOR FLAW DETECTION AND ITS EQUIVALENT RADIUS MEASUREMENTS IN SUBSURFACE STRUCTURES Russian patent published in 2000 - IPC

FIELD: corrosion protection of subsurface structures such as pipelines. SUBSTANCE: all measurements are made with cathodic protective gear turned on. Voltage across two comparison electrodes, subsurface structure-to-ground potential with resistive component, and subsurface structure-to-ground polarization potential are measured. Measured concurrently is also resistive component of subsurface structure-to-ground potential; result of this measurement is compared with difference between subsurface structure-to-ground potential incorporating resistive component and subsurface structure-to- ground polarization potential; resistive component of subsurface structure- to-ground potential having minimal deviation from values compared is chosen; then radius of equivalent flaw in insulating coating of subsurface structure is determined. EFFECT: improved measurement accuracy. 2 dwg