Engineers at Lancaster University (Lancashire, United Kingdom), the U.K.’s National Physical Laboratory (Teddington, United Kingdom), and technology company Hybrid Instruments Ltd. (Lancaster, United Kingdom) have collaborated to develop a new scanning technique to 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 say they developed a new system that combines two separate types of radiation—fast neutrons and gamma rays—to detect corrosion.
Typically, corrosion in oil pipelines is 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, according to the researchers. By contrast, their system exploits the reflected signals, known as ‘backscatter,’ of a combination of isolated fast-neutron and gamma radiation.
Neutrons and gamma rays have useful complementary characteristics, the researchers explain. Neutrons interact mainly with low-density materials, like plastics, and fast neutrons have a high penetrating power—which means they are suitable for probing thick materials. Gamma rays interact mainly with metals and are not always able to penetrate very thick materials of high density.
The two radiation types produce a different electronic signal, which means researchers can retain data on both radiation types simultaneously by using a novel detecting device called a mixed field analyzer. The system produces a pencil-like beam of probing radiation with neutrons and gamma rays, which are directed at the steel.
“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 Malcolm Joyce, a Lancaster professor.
In a laboratory, the team says it successfully tested the two imaging techniques in real time on carbon steel samples of different thicknesses. The sensors also worked when an insulating layer was replicated with concrete or plastic. This indicates the likelihood that defects in steels, as well as corrosion and rust, could produce variations in the backscatter.
According to the team, these results indicate that if used on real pipelines, potential issues could be more easily detected and resolved before oil and gas can escape. “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, a Lancaster researcher. “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.”
The goal of the research team is for the detector system to be further developed and used to detect faults by pointing it at sections of pipeline from the outside. However, the investigators say more research is needed in the field of neutron detectors to make the system faster. They suggest the technology could also be used in other applications, such as inspecting the integrity of bridges and other similar structures.
Source: Lancaster University, lancaster.ac.uk.