Start Date

2016 12:00 AM

Description

Accurate characterization of pipeline corrosion defects is required in order to identify the criticality of the defect, and calculate the remaining lifespan of the pipe. In radiography, accurate characterization of a defect generally requires an additional object – such as a step wedge – to be included in the exposure setup. This is used to calibrate the resulting radiograph, allowing for accurate measurements. In the case of the step wedge, calibration means calculating the relationship between intensity and wall thickness, allowing wall thickness loss to be found from the change in intensity caused by the defect. However, in situations where pipe access is limited, for example in a subsea environment, it may be difficult to include additional objects in the inspection setup. Therefore there is a need to develop methods of defect characterization that would not require additional calibration objects.


This work presents a method of pipeline defect characterization based on knowledge of the setup geometry and the use of images taken at different angles around the pipe. The method uses background subtraction to identify a defect, with a ray tracing algorithm used to calculate the range of possible locations of the defect in 3D space. Constraints are applied on the pipe wall location and the effective attenuation coefficient to further refine the defect range. This presentation addresses the methodology, its limitations and assumptions, and illustrates its use on example inspections, both simulated and experimental. Results from a range of different defect sizes and shapes are compared and the reliability of the method is discussed.

Language

en

File Format

application/pdf

Share

COinS
 
Jan 1st, 12:00 AM

Defect Characterization from Limited View Pipeline Radiography

Accurate characterization of pipeline corrosion defects is required in order to identify the criticality of the defect, and calculate the remaining lifespan of the pipe. In radiography, accurate characterization of a defect generally requires an additional object – such as a step wedge – to be included in the exposure setup. This is used to calibrate the resulting radiograph, allowing for accurate measurements. In the case of the step wedge, calibration means calculating the relationship between intensity and wall thickness, allowing wall thickness loss to be found from the change in intensity caused by the defect. However, in situations where pipe access is limited, for example in a subsea environment, it may be difficult to include additional objects in the inspection setup. Therefore there is a need to develop methods of defect characterization that would not require additional calibration objects.


This work presents a method of pipeline defect characterization based on knowledge of the setup geometry and the use of images taken at different angles around the pipe. The method uses background subtraction to identify a defect, with a ray tracing algorithm used to calculate the range of possible locations of the defect in 3D space. Constraints are applied on the pipe wall location and the effective attenuation coefficient to further refine the defect range. This presentation addresses the methodology, its limitations and assumptions, and illustrates its use on example inspections, both simulated and experimental. Results from a range of different defect sizes and shapes are compared and the reliability of the method is discussed.