Once every 15 years, a Turn Around takes place at the Integrated Wastewater Purification Installation (IAZI). In 2022, the first of the three wastewater treatment plants began this cycle. In both the preparation and execution of the project, the Turn Around team deployed drones, for visual inspections both internally and externally. The conclusion? The use of drones is an excellent inspection method.
Determining the condition of circulation and aeration pipes
Peter Janssen, Senior Mechanical Engineer Corrosion & Materials, explains: "To determine the scope of the Turn Around, we first wanted to assess the condition of the circulation and aeration pipes after 15 years. This required internal visual inspections. To get a representative picture, we sampled the two pipes that were least and most in use. I manually undertook the first inspection myself, followed by an inspection by a specialised company using a drone with a camera."
“After comparing both inspections, the drone camera proved to give an accurate picture of the local damage.” Peter Janssen, Senior Mechanical Engineer Corrosion & Materials
Accurate drone inspection
By comparing the results of both inspections, the findings could be confirmed. Peter explains, "Observations with the human eye are three-dimensional, while drone images are only two-dimensional. Moreover, humans can also sense. Nevertheless, after comparing the two inspections, the drone camera showed an accurate picture of the local damage to the coating and the rusting of the pipes underneath." These repairs were completed during the Turn Around. Eric Timmermans, Senior Reliability Engineer, is satisfied: "We now have drone images of the inside of 2 aeration pipes. We plan to take drone images of the remaining 10 pipes in phases, so that we will have a complete overview in the future."
External inspections by fire brigade drone team
External inspections were also conducted on the pipes prior to the Turn Around. Eric explains: "We wanted to know whether the outlets of the aeration pipes were still intact. These external inspections were taken by our company fire team. After cleaning the pipes, the drone team flew past the outflow openings to check for any damage. There were some minimal damages, but they are so minor that we can easily continue for another 15 years."
“The great thing is that we now have a baseline measurement, so that in a few years' time we can determine the degradation rate.” Eric Timmermans, Senior Reliability Engineer
Drones deployed instead of human inspection
During the implementation of the Turn Around, drones were again used for inspections. Eric explains: "At four wells, we had to check the integrity of the walls, coating and seams. Initially, I had planned to do this inspection myself, but when I was on site, I decided it was not safe enough. The access to the well is 1 by 1 metre and the well is 7 metres deep. Therefore, we still called in a drone team for a visual inspection. Fortunately, this went quickly, as the Mechanical Engineer Civil immediately watched the images being taken. Within two hours, everything had been inspected, without the need for people to enter the well, extra safety measures or rope access." This inspection showed that the wells were also in good condition and could last for another 15 years.
Optimism about future use of drones
Peter is positive about this inspection method: "Inspecting using drones offers several advantages. Firstly, it is safer because there is no need to send people into confined spaces. Moreover, in this case it is also faster. Instead of dismantling an entire pump, only a flange needed to be loosened." Eric and Peter therefore see a lot of potential for the future use of drone inspections. They reveal, "The technology is getting better and better. Drones are being developed that can take three-dimensional images and use ultrasonic measurements to determine wall thickness. In this way, we can use our technically trained staff for tasks that add more value. In addition, this saves both man-hours and costs!"