Automated Non-Destructive Weld Inspection in Splash/Subsea Zone

Abstract

Jacket structures all over the world are now reaching the limit of their estimated service life, but new discoveries and improved production methods require lifetime extension of the assets. In this paper, an automated underwater robot and a Non-Destructive Testing (NDT) eddy current probe for Alternating Current Field Measurement analysis of jackets main welds, is presented. This robot makes integrity testing possible, which often is required for lifetime extensions. Once the robot is attached to any welded brace, it has the potential to move around the pipes and at the same time control the position of the eddy current probe. The robot is guided by a 3D vision system that includes two lasers and two cameras. The camera system also supplies visual information useful for the pilot. The quality of the measured data is improved by using an eddy current probe that tolerates challenging conditions. The robot collects the measured results and stores them together with positioning information. Eddy current surveys in the splash zone is challenging, time consuming and exhaustive for the pilots. Prototypes of the robot and eddy current probe has been tested in lab. The results confirm that this robot will ease the pilot's job and help the operator to make more accurate detections of the jacket integrity. The robot control system can operate in either a First Person View (FPV) mode where the pilot has full and easy control, or the robot can operate in closed loop mode where the robot places the eddy current probe in optimal alignment against the weld. The eddy current probe includes multiple Alternating Current Field Measurement sensors that tolerates some miss alignment, lift-off, and even variations in permeability. The robot presented has already been used offshore, but the newly added 3D vision and control system will reduce measurement time and increase quality of the data. In addition, the eddy current probe presented will make it easier for NDT technicians to stay focused and to make correct decisions.