In-service detection of longitudinal cracks on drill pipes using induced circumferential current

Drill pipes are critical facilities in the oil & gas industry and suffer from the effects of an alternating stress and corrosion environment. Stress corrosion cracking (SCC) is one of the most common defects in drill pipes. The SCC usually begins axially and develops into a longitudinal crack that eventually leads to the failure of the drill pipe, which can cause massive property damage and casualties. In this paper, an in-service detection method is presented for the detection of longitudinal cracks on drill pipes using a circumferential current induced by a coaxial excitation coil fixed on the wellhead. The finite element method is proposed for analysing the characteristic signals of the longitudinal cracks. The in-service detection system is set up and a test experiment is carried out on a longitudinal crack. The results show that longitudinal cracks can be quantitatively detected using an induced circumferential current during the tripping operation. The induced circumferential current can be used for the in-service detection of longitudinal cracks on drill pipes.