Defect Detection for Drill Pipe Thread Based on Eddy Current Testing

Drill pipe threads are critical components in oil and gas drilling operations, but are susceptible to surface and subsurface defects that can lead to failures and significant economic losses. Eddy current testing (ECT) has emerged as a viable non-destructive testing (NDT) technique for detecting defects, offering advantages in terms of sensitivity and efficiency. This study investigates the application of differential ECT transmitter-receiver (T-R) probes for their performance of reducing the common sources of noise. A finite-element (FE) model was developed to optimize the probe's configuration and sensing parameters. Subsequently, a detection system was constructed, comprising a customized ECT instrument and a designed thread inspection probe with specialized protective layer. A signal processing algorithm, utilizing morphological and energy features of the defect signal, was designed to distinguish defect signal from noise such as tilt variations. Experimental results validated the efficacy of the system and the proposed algorithm, demonstrating their ability to reliably detect defects in drill pipe threads.