Remote thickness measurements by drone

GDI, an award-winning provider of applied technology solutions, has now added the use of the Skygauge drone to its range of marine sector capabilities.

GDI has now added the use of the Skygauge drone to its range of marine sector capabilities.

By adding airborne robotics, GDI can now take ultrasonic thickness measurements of large uncoated and painted surfaces, such as corrugated bulkheads and web frames. The technology has been proven, with certain limitations on the areas that can be reached, in demonstrations with four major classification societies.

“GDI has the equipment and the skills needed to take valuable measurements efficiently and safely in conjunction with approved Thickness Measurement (TM) suppliers,” commented David Knukkel, GDI’s CEO.  “Although GDI is not an approved TM-supplier, certain classification societies are open to innovative technology and partnerships between approved RIT (Remote Inspection Technology) and TM-suppliers.” 

During discussions with various class societies, GDI was provided with information regarding the working relationship between companies certified by TM and RIT.

• ABS approves the cooperation between RIT and TM-certified companies, provided both have procedures in place and the TM-certified companies are mentioned on the RIT certificate.
• ClassNK also allows cooperation between RIT and TM-certified suppliers, but they expect some form of agreement between both approved suppliers. While specific suppliers are not mentioned on the certificate, some form of agreement is expected.
• Bureau Veritas allows cooperation between RIT and TM-certified suppliers, but they do not mention this on the certificate. They encourage both suppliers to agree on the details of the cooperation.
• Lloyd’s Register only certifies the TM company for the use of drones, regardless of whether the drone company is RIT-certified.
• DNV has yet to indicate whether they have a drone programme for TM-certified companies.
• RINA has not provided any official feedback on this matter.

Working in conjunction with approved TM suppliers does not change the process of liability, validation of measurements, and reporting. GDI considers the drone to be a new additional tool which wirelessly supports the work of the TM engineer. The TM engineer remains responsible for validating measurements by executing a proper calibration and judging the accuracy by looking at the full A-scan. The TM engineer will report the values as usual within the different formats of each individual classification society.  

“We will continue to work closely with the classification societies to ensure that eventually the procedures and certification will be fully aligned,” said Knukkel.

Alignment not required

Among the salient characteristics of the Skygauge drone is the fact that 100% alignment with the contact surface is not required. The drone aligns itself by arranging an equal cup pressure of 20 Nm to the surface. Furthermore, artificial aids based on LIDAR assist the operator in estimating the alignment and movement to the next measurement position. The system’s software provides continuous measurements and delivers an indication of the accuracy of the readings as well as a final reading.

Challenging environments

GDI points out that there are certain limitations, with some environments posing a challenge to the onboard sensors. According to Knukkel, “It is a matter of time and effort to increase the operating areas of the drone. This technology is like a river; you need to control and steer the flow by learning how to live with and use the possibilities rather than trying to fight nature.”