A new scanning technique that mimics the way that bats use differing wavelengths of ultrasound to detect objects could be used to detect corrosion in oil and gas pipelines, researchers claim.
Developed by a team from Lancaster University, the National Physical Laboratory, and technology firm Hybrid Instruments, the system produces a pencil-like beam of neutrons and gamma rays directed at the materials being inspected. It is then able to analyse this material by measuring the reflected signal or “backscatter”.
The group claims that the technology could play a role in addressing an issue that costs millions annually, endangers lives and causes significant environmental damage.
Corrosion in oil pipelines is typically measured with ultrasonic or electromagnetic techniques. However, these are not practical for underground pipelines, or for pipelines covered with insulating layers of concrete or plastic.
Neutrons and gamma rays have potential in this application because of their useful complementary characteristics: whilst neutrons interact mainly with low-density materials like plastics and have a high penetrating power gamma rays interact mainly with metals and not always are able to penetrate very thick materials of high density.
The new system, outlined in a paper in the journal Scientific Reports, simultaneously measures the signal produced by these two different radiation types using a novel detecting device called a ‘Mixed Field Analyser’.
During laboratory tests on different thicknesses of carbon steel the researchers were able to see differences in steel thickness. The sensors also worked when an insulating layer was replicated with concrete or plastic, indicating the likelihood that defects in steels, as well as corrosion and rust, would produce variations in the backscatter.
“The combined beams of neutrons and gamma rays in parallel bouncing back to an array of detectors yield a comprehensive and fast representation of the inner structure of steel,” said Mauro Licata, PhD researcher on the project from Lancaster University.
These results indicate that if used on real pipelines then potential issues could be more easily detected and resolved before oil and gas is able to escape.
“Isolating neutrons and gamma rays backscattered from a steel surface in real time, in a way analogous to the way bats’ brains isolate backscatter ultrasound and thus avoid confusion with their own chirps, could help us isolate flaws in pipe walls more quickly and effectively,” said Prof Malcolm Joyce of Lancaster University and Hybrid Instruments.