Outsmarting corrosion

Detecting corrosion is a huge headache for the offshore industry. CMR is developing a tool to spot it before it takes hold.

Thomas Peter

Christian Michelsen Research (CMR) in Bergen has a long track record in developing innovative solutions together with clients.

Today is no different. The institute, whose primary area of expertise is in measurement and computer science, is tackling some of the most current issues in the industry, not least aging infrastructure and the drive towards lifetime extension.

Corrosion under insulation (CUI) is especially challenging, due to the difficulties to detect such degradation.

“CUI can lead to loss of containment, resulting in costly shutdowns, not to mention potentially far-reaching HSE consequences,” says Kari Marvik, Vice President CMR Science & Technology. “Furthermore, CUI inspection and maintenance jobs are notoriously time consuming and industry data shows that significant costs could be saved through smarter execution of maintenance programs.” Early in 2015, CMR was granted funding from the Research Council of Norway to develop two ideas, one of which was targeting CUI to help change how the industry operates and also result in significant cost savings.

Schematic representing the measuring principle and possible operation modes of the FKP.

Getting under the skin

The result has been the development of an Online Distributed Integrity Monitoring System (ODIMS), which will enable operators to perform targeted inspection and preventative maintenance – catching corrosion issues before they become a problem. “ODIMS uses distributed fiber optical sensing technology to detect humidity, water, salinity and temperature,” says Peter Thomas, a CMR scientist. The optical fiber is installed under the insulation, and a central electro-optical interrogation unit is measuring continuously to detect any exposure along the installed fiber. It is also possible to add point sensors along the fiber using the system as a communication infrastructure.

“The system is flexible and modular and can be installed on existing installations,” Thomas says. “The most cost efficient is to install the system during existing CUI maintenance campaigns. A central application for ODIMS is to serve as a facility-wide early warning system, identifying areas with high humidity and water ingress, which trigger CUI, reducing the risk of production shutdowns and accidents.”

However, the technology has the potential to be utilized in other applications too, both in the oil and gas industry and within civil engineering.

Norwegian operator Statoil and oil and gas service firm Beerenberg are participating in the steering committee of the project. They are also due to contribute with test facilities and piloting opportunities. Work done to date has demonstrated the feasibility of the ODIMS solutions with promising results so far.

Larger scale lab-testing started in 2015. Critical components and key features are due to be complete by the end of 2016.

Illustration of the ODIMS solution. Images from Christian Michelsen Research.

Kelvin comes to the rescue

However, it’s not just corrosion that can cause a problem. The oil and gas industry, as in many industries, depends to a high degree on the quality of the fabrication materials used and the ability to preserve the designed quality and functions of the assembled system or plant. This requires non-intrusive inspection (NII) technologies to ensure that desired quality and specifications are fulfilled during the lifetime of the component and or system.

A particular area of interest are NIIs that could detect hidden faults, from the fabrication process, especially if they could lead to delayed and sudden failures long after fabrication, i.e. fractures due to hydrogen-induced stress cracking (HISC).

For example, the presence of tiny amounts of freely diffusing hydrogen in steels can, some times, lead to dramatic consequences. “Unlike other detrimental substances, hydrogen can enter the steel right from the processing of the raw material and throughout fabrication, assembly and operation phases,” says Michael Rohwerder, Max Planck Institute for Iron Research (MPIE) Germany.

To help the industry mitigate the detrimental effect of the hydrogen, scientists at CMR are working with scientists from the MPIE to develop a hand-held, automated Field Kelvin Probe (FKP), a contactless technology to enable the detection of minute concentrations of diffusible hydrogen in steel components.

The FKP works by measuring Volta potential differences (i.e. differences of the electric potential resulting from an excess of electric charges) between the steel structure under examination and the Kelvin probe. There is a rather simple relation between this Volta potential and the absolute electrochemical potential of the steel. Moreover, there exists a mathematical relationship between the Volta potential difference and the level of diffusible hydrogen in steel, which could allow qualitative and quantitative detection of hydrogen without any direct contact to the steel. Referring to the working principle, one could say in simple words that the core of the FKP is not more than a variable capacitor.

Currently, CMR is running two projects on the FKP. The Research Council of Norway is funding a four-year project for basic research and development related to the FKP. Additionally, CMR receives industrial funding for more applied FKP applications.