Abstract: A device to give an indication of the passage of a pig through a pipeline and methods of performing various pipeline operations using the device are described. The device has a magnetic sensor based on a dip needle and the output of the sensor controls a flag actuating mechanism. Passage of a pig beneath a pig indicating device causes a flag to be raised giving a visual indication that the pig has passed that location. Methods are described in which one or more devices are used to find a lost pig, for accurately locating a defect in a pipeline, for determining if a pig has been correctly launched or received, and for determining and controlling the speed of a pig in a pipeline.

Abstract: A magnetometer is moved along the route of a pipeline and the output of the magnetometer is observed to identify pipeline characteristics. Used with a buried pipeline the magnetometer is moved over the surface of the overlay to identify and locate girth welds, pipeline fittings and accoutrements, changes in pipeline metallurgy such as occur with large hard spots and changes in wall thickness as occur in extensive and severe corrosion. Similar functions can be performed with underwater pipelines using a magnetometer which is located in an appropriate container and trolled along the route of the pipeline by a vessel. The pipeline is formed of pipe sections which are arranged in an identifiable pattern according to their magnetic characteristics to facilitate inspection and maintenance.