RoCD² – the new high resolution in-line inspection tool incorporates EMAT technology
Pipeline deterioration by stress corrosion cracking (SCC) continues to be an increasing challenge for the pipeline industry. That’s why ROSEN targeted this problem as a priority in developing its new High Resolution In-Line Inspection tool.
RoCD² is a unique ultrasonic inspection tool, combining EMAT sensors, designed for gas pipelines. It embodies a high-resolution concept coupled with the rugged mechanical design and operational performance of the ROSEN in-line inspection tools.
EMAT Technology
The tool is based on a novel concept of an Electro-Magnetic Acoustic Transducer (EMAT) that allows the detection of both stress corrosion cracking and disbonded coating. Coating disbondment is understood to be a precursor to SCC by increasing the susceptibility of the pipeline to corrosion.
Mastery of the EMAT technique has been elusive in the past, due to the inefficient nature of the electromagnetic transduction and the practical application of guided-wave techniques. Improvements in magnetization capabilities and a more thorough understanding of guided-wave acoustics have changed this situation.
Disbondment detection
Due to the appropriate selection of wave mode, the SCC measurement sensor is only marginally sensitive to coating changes. Nevertheless, by changing the timing of the receiver units, coating disbondment information can be obtained. As outlined above, SCC tends to occur in areas where there is coating disbondment. If a pipeline has a large population of disbonded areas it becomes far more susceptible to SCC. An effective inspection tool must therefore be able to detect this failure.
