Performance enhancements of the spherical detector for pipeline spanning inspection through posture stabilization

Spherical detector (SD) is promising in the field of subsea pipeline defect detection because of low risk of blockage and quasi-real-time capacity. However, rolling stability has great influence on the detection performance of the SD. This paper proposes posture stabilization measures for enhancing performances of the SD in pipeline spanning inspections via analyzing the mathematical model of detection and experimental validations. Mass of the SD should be concentrated on a plane as much as possible, so that the SD can steadily roll around the unique normal axis with strong immunity to sudden disturbance and uncertainty of launch postures. Especially, when the rotation axis of the SD is one sensitive axis of the triaxial accelerometer equipped, the other two acceleration components can both achieve highest signal to noise ratio and are thus capable of sensitively and reliably detecting low-frequency vibration and downward bend of a spanning steel pipeline.