Engineers are turning to bats to learn more about how to protect the thousands of miles of pipelines that cross the Earth. A team from Lancaster University, the National Physical Laboratory, and the technology company Hybrid Instruments aren't sending the little squeakers down the pipes. Instead, they're working on how to use nuclear radiation to mimic the sonic hunting system used by bats to locate their prey.
Bats and pipelines may not seem to have much in common, but when it comes to inspecting already installed pipes for potentially damaging corrosion, the engineers are in the same boat as a bat looking for its supper. Both are hunting for something in the dark and at a distance.
Most people who have sat through a few nature documentaries know that bats navigate using ultrasonic chirps, but these are much more complex than simple peeps at frequencies outside the range of human hearing. They are a complex mix of sounds that interact with their target and send back to the bat a wealth of information, such as whether the object in question is a tree branch or a nice juicy mosquito on the wing.
The new pipeline inspection technique imitates that of the bat but with fast neutrons and gamma rays taking the place of sound waves. The idea is to be able to inspect pipes that are underground or clad in heavy insulation, making them impractical to inspect using ultrasonic or electromagnetic techniques.
It's basically a large-scale version of a common laboratory technique called backscatter, where a beam of radiation is aimed at an object and the returning rays reflected back from the thing in question reveal its properties. According to the team, the mixture of neutrons and gamma rays complement one another because neutrons interact with plastics and other low-density materials and fast neutrons have strong penetrating powers. Meanwhile, gamma rays interact more with metals, but can't penetrate materials that have a high density very well.
The new backscatter technique works using a new device called a Mixed Field Analyzer developed by Lancaster University and Hybrid Instruments that records the electronic signal returned by the pencil-like beam of neutrons and gamma rays aimed at the section of steel under inspection.
"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," says Mauro Licata of Lancaster University. "This system works a bit like the chirps made by bats. These chirps are a superposition of different ultrasound wavelengths, which bounce back to the bats’ ears. As well as highlighting the benefits of combining multiple reflection sensing techniques to detect for problems such as corrosion, our work further illustrates the significant potential that can be had from taking inspiration from, and mimicking, systems that have evolved in the natural world."
According to the team, laboratory tests were conducted on carbon steel samples of different thicknesses in real-time and the technique was able to measure the thicknesses even under an insulating layer of plastic or concrete. This would make it possible to find defects in the steel as well as more general corrosion before they become major problems.
"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," says Professor Malcolm Joyce of Lancaster University and Hybrid Instruments.
The team says that the next step will be to test the technique on sections of a pipeline as well as producing a faster neutron detector.
The research was published in Scientific Reports.
Source: Lancaster University
