Detection Optimization of Single-Axis Magnetic Anomaly Sensor for Pig Clog Locating

The oil and gas pipelines need to be cleaned regularly by the pigs during their long service. And the magnetic anomaly detection can be used for clog locating when a pig with magnetic marker is locked in the pipeline. In order to collect magnetic anomaly efficiently though single-axis magnetic sensor, a geometric detection model and calculation method for single-axis magnetic anomaly detection is established in this paper. The distribution of direction of magnetic anomaly is obtained based on magnetic inclination and declination of each measuring point. The results indicate that the magnetic inclination of all measuring point change in a small range. It is about 2° around the geomagnetic inclination. However, the magnetic declination at different positions on the detection surface is affected by the three elements of the geomagnetic field and the y-axis component of the magnetizing field and they are irregular in a wide range. Therefore, for high-efficiency detection with the single-axis sensor, in actual detection, the magnetic inclination of the installed probe is the same as the geomagnetic inclination. The magnetic declination of the installed probe can be obtained by the calculation formula of this paper. This article demonstrates the feasibility of pig clog locating based on the single-axis magnetic anomaly detection when a pig with magnetic marker is locked in the pipeline. And it will play a great practical significance for guiding the engineering detection.