Evident Ultrasonic Inspection Equipment
Rolling on to Better Tank Inspection Data and Decision Making
By: Eddyfi Technologies
Source: Eddyfi Technologies
Many owners of storage tanks understand the burden of inspecting tank shells and roofs for corrosion degradation. On one hand, the inspection quality needs to be met, while on the other hand personnel safety needs to be ensured. To make it even more complicated, downtime of the asset must be minimized. A traditional way of performing tank wall thickness degradation inspection is by ultrasonic wall thickness spot check measurements using a rope access approach or by building scaffolding. This approach leads to an intense inspection performance, while the gathered data on the asset is limited. In many cases, tank shutdown is also required.

For this reason, Eddyfi Technologies developed a dedicated tank inspection crawler, Scorpion 2. With its unique design features and high inspection speed, the examination of tank shells and roofs for corrosion is no longer a challenge. The remote access crawler enables fast inspections with high quality and high-density wall thickness data. The high-density data acquisition, due to a large number of points per distance, poses a new challenge in creating a proficient and condensed inspection report. This article offers the Beyond Current solution.

The prediction of how and where corrosion exists on tank shells and roofs is rather tricky to determine. It is influenced by many parameters such as tank contents, environment, weather conditions, loading and offloading rate, and much more. Therefore, it is vital to get excellent and representative data over large sections of the tank surface. With spot checks, this is not possible because it provides a limited number of data points on a measurement scanline. These scanlines are described in inspection guidelines such as EEMUA 159 or API 653.

Corrosion can be very localized and present itself in horizontal corrosion patterns

In this case, the corrosion pattern extends around the circumference of the tank on the bottom course 20 to 30 centimeters (8 to 12 inches) below the weld. When in-service spot checks are performed on the outside of the tank, the chances of missing defects would be significant. A B-scan scanline crawler such as Scorpion 2 likely would have detected and registered the small corrosion spots. If these spots can be seen on all scanlines taken around the tank surface, the corrosion pattern would also be detected. Once found, the decision could be made to increase the inspection with an even more dense inspection data system such as the RMS PA raster scanner.

Read the full article at Eddyfi.com.

Mistras Group