The splash zone—the part of the structure immediately above (+20 feet) and below (-50 feet) the waterline—presents challenges for offshore operators due to difficult access and constant exposure to atmospheric and marine conditions. This environment accelerates corrosion, fatigue, and the accumulation of marine growth, complicating inspection tasks.
ACFM, an electromagnetic technique for non-destructive testing (NDT), addresses several of these challenges:
- ACFM identifies surface cracks through layers of marine growth and corrosion, reducing the need for extensive cleaning.
- ACFM detects surface cracks without requiring bare metal exposure, preserving the integrity of protective coatings.
- ACFM systems can be operated via specialised robotic arms, allowing for safe, diverless inspections in hazardous areas.
- Built for resilience in challenging conditions, ACFM provides real-time, accurate data through a stable magnetic field that remains effective in harsh conditions.
ACFM applications for offshore inspections
OceanTech’s robotic solutions offer a stable platform for deploying sensors, cameras, probes, and other inspection tools—tasks that would be challenging or impossible using divers and ROVs. Our modular approach, along with our technology's adaptability to diverse materials, geometries, and surface conditions, enables our access robots and tools to connect to any offshore asset or structure.
We have recently developed an inspection robot capable of tracking and following 360-degree circular nodal welds. By using ACFM, the robot can detect surface cracks and measure their length and depth. It provides highly accurate measurements without stripping away coatings, preserving the protection against corrosion and enabling data-driven assessments of weld integrity.
Like our other access robots, it can operate with ease in the splash zone. However, it can also be carried by an ROV for deployment at greater depths, using the ROV as a mother vehicle.
Other applications of ACFM in the splash zone include inspecting:
- Risers
- Platform legs and jacket structures
- Hulls and external tanks
- Caissons and conductors
- Anodes and bracings
- Pipelines and flowlines
ACFM is particularly useful for inspecting platform legs and jacket structures–which are often subject to cyclic loading and vulnerable to cracking and corrosion–as well as caissons and conductors. But it can also be used on the outer surfaces of FPSO hulls or external tanks. These areas are constantly exposed to harsh conditions, and ACFM can detect and measure surface-breaking cracks through protective layers, helping operators assess hull integrity and prevent costly leaks or failures.
In addition to oil and gas installations, ACFM can also be used for inspecting offshore wind power installations. Applications include inspections of turbine towers, jackets, monopile foundations, transition pieces, and welded joints. Welded joints, often found at connection points between different structural elements, are particularly vulnerable to fatigue from cyclic loading. ACFM’s accurate crack sizing capabilities allow operators to assess the severity of any detected cracks and plan repairs accordingly.
OceanTech’s robotic solutions equipped with ACFM probes can inspect turbine structures, monopiles, and transition pieces remotely, eliminating the need for costly and risky dive operations. Due to the stability of our working platform, our solutions provide substantial advantages for both fixed and floating foundations.
ACFM certifications and competence requirements
Performing non-destructive testing such as ACFM requires a combination of formal certifications, technical competence, and safety training. In Norway, ACFM certifications are issued by recognised organisations like FORCE Technology Norway. FORCE Technology provides certification services for NDT operators in alignment with NS-EN ISO 9712 and Nordtest methods. They provide OceanTech and our subcontractors comprehensive training and certification programs to ensure that NDT operators meet industry standards.
Additionally, we undergo comprehensive training in ACFM technologies, systems, and inspection and sizing software. We are certified in the Lizard® NDE M8 System and Lizard® NDE inspection and sizing software. Driven by the realities faced by clients and from listening carefully to feedback from inspection personnel in the field, the LIZARD®technology continues to evolve into one of the most innovative and exciting NDE products on the market.
Practical experience in conducting NDT inspections, particularly in offshore and splash zone environments, is crucial. This experience ensures that NDT operators can effectively plan and execute inspections in challenging conditions. Our Subsea Test Centre in Trondheim, Norway, allows us to train in replica environments. By addressing all details upfront, we minimise the risk of downtime and accidents, and help operators and climbers become familiar with the operation. When we are offshore, it is important that everything works flawlessly.
By fulfilling all these requirements, we can competently and safely perform ACFM inspections in the splash zone, thereby contributing to the structural integrity and safety of offshore installations.