Crack detection technology

2018-04-07: From CIUS Annual Report 2017.

Halfwave and InPhase Solutions

The companies Halfwave and InPhase Solutions, both industry partners in the Centre for Innovative Ultrasound Solutions (CIUS), have a long-standing relationship. First collaboration dates back to more than five years ago, where InPhase Solutions contributed to relevant research and development tasks to improve Halfwave's successful Acoustic Resonance Technology (ART) as pipeline inspection technology. Since consultants from InPhase Solutions have specific competence in the fields of ultrasound and signal processing, they can temporary support related technology development in times where more resources are needed.

The solution to pipe wall crack?

Currently, InPhase is involved in Halfwave's pursue to develop a Crack Detection technology for in-line inspection of gas pipes, based on Halfwave's ART scan tool. This intriguing project was initiated based on observations of propagating acoustic modes that were detected with ART hardware and that can be dependent on defects in the gas pipe wall. One of the more relevant defects is stress corrosion cracking (SCC), which poses a serious risk to pipeline integrity. Cracks in the pipe wall can change the signature of propagating acoustic waves. These acoustic signal changes can be detected and subsequently be used to potentially size and locate the cracks. However, due to the small size of typical stress corrosion cracks, they appear to be very difficult to detect with existing in-line inspection technologies.

Promising results

Results from the first development phases in the past two years at Halfwave, have all been successful. In controlled experiments in water, both artificially machined notches in steel plates, and real cracks in real pipe samples, could be clearly discriminated with undamaged areas. Dedicated signal processing results even showed ways to discriminate cracks from other defect types. These very promising results, led to the current development phase, where water is replaced by pressurized gas as the propagation medium; like in a real gas pipeline. The complicated test set-up contains of many transducers with programmable transmit and receive channels, that can record on all transducers simultaneously. Initial processed results show many different aspects of the acoustic waves, and are extremely promising in the pursue to detect SCC based on Halfwave's ART tool.

Continued research in CIUS

HalfWave will continue research on the crack detection challenge within CIUS, and plan to start a PhD project in 2018. Dr. Petter Norli, R&D Director of HalfWave states: "We are looking forward to continuing this exciting project in CIUS with more in-depth research in the years to come, and we are currently building a strong team within CIUS on understanding the basis of ultrasound propagation in steel layers among all the oil & gas partners."

The picture illustrates a high-pressure test set-up consisting of a test scanner head with many transducers inside a pipe sample with real cracks. The test scanner head can mechanically translate and rotate to make circumferential scans of part of the pipe sample. The set-up is placed inside a pressure vessel at NUI (Bergen) that allows pressures up to 65 bar.