Ensuring oil and gas pipelines do not fail is an issue of utmost importance to the energy industry. The spilling of oil or gas can result in huge environmental disasters, loss of human life and financial damage, therefore regular inspection of the condition of oil and gas pipelines is a necessity.

The most common way of assessing the structural health of pipelines is by internal inspection with a device known as a “smart pig”. In order to use a pig, there must be access; launches and traps for the device; suitable in-line valves; a lack of sharp bends; and no contaminants or defects that significantly reduce the pipe bore. These restrictions result in thousands of kilometres of pipeline that cannot be tested internally and require alternate inspection methods. This project concerns the development of one such method which measures the external magnetic field from the pipe that is induced as a result of an injected electric current. As the current flows around defects such as cracks or corrosion patches, the induced field profile is altered. Measurement of changes in the magnetic field can therefore facilitate the detection of defects or monitoring of defect growth.

There exist other ways to inspect unpiggable pipes, yet there are numerous problems associated with these such as lack of sensitivity or reliance on complex physical phenomena that are very difficult to model. A significant advantage of exploiting the magnetic field as a means to locate or monitor defects is that the signal intensity is not as significantly affected by the distance between the pipe and the sensor (stand-off) as other techniques such as ultrasound or eddy current inspection. This allows the technique to be applied outside of insulation coating, which greatly reduces the amount of preparatory work needed on the pipeline.

This research project will allow the development of a prototype system that can test industrial pipes. This will be achieved by the creation of an experimental rig with a moving magnetic sensor array that can complete a scan of the magnetic field around a defective pipe. A computer simulation of the experiment will be also be created that is capable of predicting the defect signals from various geometries and testing parameters.


Radial magnetic flux 75mm above a 6-inch steel pipe carrying a 2A current. A bowl shaped defect of 3 wall thickness diameter and 1/3 wall thickness depth is centred on the outer surface at (0,0) (outlined in red).