Engineers in the United Kingdom have developed a new scanning technique inspired by the natural world that can detect corroding metals in oil and gas pipelines.
By mimicking how bats use differing wavelengths of ultrasound to detect objects, hunt, and avoid predators, the engineers have developed a new system that combines two separate types of radiation – fast neutrons and gamma rays – to detect corrosion, which is something the oil and gas industry is all too familiar with.
According to a study by NACE International, the annual cost of corrosion in the U.S. oil and gas production industry is estimated to be $1.3 billion, with $589 million dedicated to surface pipeline and facility costs alone.
Corrosion can also cause pipeline leaks which have the potential to cause serious accidents and injuries as well as significant environmental damage.
Corrosion in oil pipelines is commonly measured with ultrasonic or electromagnetic techniques. However, these techniques are not practical for underground pipelines, or for pipelines covered with insulating layers of concrete or plastic.
The new system, developed by engineers from Lancaster University, exploits the reflected signals, known as ‘backscatter’, with a combination of isolated fast-neutron and gamma radiation.
Neutrons and gamma rays have useful complementary characteristics. Neutrons interact mainly with low-density materials like plastics. In addition, fast neutrons have a high penetrating power, so they are suitable for probing thick materials. Gamma rays interact mainly with metals and cannot always penetrate very thick materials of high density.
The two radiation types produce a different electronic signal. This means researchers can retain data on both types of radiation simultaneously using a novel detecting device called a ‘Mixed Field Analyser’.
The system produces a pencil-like beam of probing radiation, of neutrons and gamma, which is directed at the steel section being inspected.
The team tested the two imaging techniques in real-time in a laboratory on samples of carbon-steel of different thicknesses.
The researchers were able to visualise 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 results indicate that if used on real pipelines, potential issues could be more easily detected and resolved before oil and gas can escape.
Mauro Licata, PhD researcher on the project, said the combined beams of neutrons and gammarays in parallel bouncing back to an array of detectors yield a comprehensive and fast representation of the inner structure of steel.
“This system works a bit like the chirps made by bats,” Licata shared. “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.”
Professor Malcolm Joyce of Lancaster University said: “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.”
The intention is that the detector system will be further developed and used to detect faults by pointing it at sections of pipeline from the outside. However, the investigators outline that more research is needed in the field of neutron detectors to make the system faster.
The researchers also suggest the technology could be used in other applications, such as inspecting the integrity of structures such as bridges.
The research has been outlined in the paper ‘Depicting corrosion-born defects in pipelines with combined neutron/γray backscatter: a biometric approach’, which has been published by the journal Scientific Reports.