Corrosion under insulation (CUI) is a global problem in the chemical industry. Much of the industrial process plants are now decades old, and thus the insulated equipment and piping pose a safety risk. Currently, for many plants, damage due to corrosion under insulation is not discovered until it is too late, with all the damage and risks involved. If it is up to Peter Janssen, Senior Mechanical Engineer Corrosion & Materials at Sitech Services, smart monitoring techniques will ensure that timely action can be taken: "We are constantly working on innovative ways to get corrosion under insulation under control."
Peter Janssen: "Actually, I have always been concerned with corrosion and materials. When I was working at DSM, it was mainly about cooling water and steam systems at Chemelot and the question of what to add to them to prevent possible deposits and corrosion." Meanwhile, Janssen and his colleagues at Sitech are considered the Dutch experts on combating corrosion in the chemical industry. He leads a team of six men who know everything about materials, wear and tear and failure mechanisms.
Invisible wear and tear
"At home, you can see whether the paintwork is still adequate or whether it's time for maintenance," Janssen begins. "Any damage can be seen with the naked eye. Here at Chemelot, pipes and installations are wrapped in insulation material, so it is not immediately visible what the condition of the material is. From a maintenance point of view, you would rather not wrap assets so that visual inspection is possible. But due to production disorder, energy loss and sustainability ambitions, that is not an option."
The problem is relatively easy to explain: a coating wears off after 10 to 15 years. If water is then added, the material starts to corrode. Janssen: "That doesn't have to be a problem right away, as long as we know where the moisture is. Because then you can take targeted action. Completely unpacking a column 40 meters high is very expensive. Just erecting scaffolding costs a couple of tons. And we know from experience that spot checks are no remedy. Then everything seems fine, but 1 meter further it can still be completely different." So the solution must lie in proper monitoring of the installation. There are two options for monitoring CUI online: under the insulation when the insulation has been removed or from the outside over the existing metal insulation sheeting.
Collaboration with CorrosionRADAR
In measuring temperature lies the key, Janssen explains. If you attach sensors to the outside of pipes, you can detect locations with moisture based on temperature differences. After all, moisture cancels out the insulating effect." This method has been put into practice by Sitech at Chemelot since 2019 as an addition to the existing inspection program and in cooperation with the English company CorrosionRADAR. Janssen: "A wire with an integrated sensor is placed under the insulation, after which a radar signal is sent through the wire that can accurately indicate where moisture is present. This allows us to detect problems with CUI in a timely manner. The data is read via a wireless network and can be continuously monitored."
Insight accurate to 1 meter
In 2019, the technology was applied to a column at AnQore during a Turn Around. This is already providing valuable insights, Janssen points out. "After 3 years, we already determined that there is water in the insulation. Apparently there is an aluminum cladding open somewhere. We can now draw up a targeted plan of action, because thanks to the measurements we know to 1 meter where the moisture is and where intervention is necessary. So we don't have to spend tons on erecting scaffolding, but can use 'rope access' to restore the location in a targeted way." It should therefore come as no surprise that Sitech and CorrosionRADAR announced on January 26 that the collaboration in the field of remote CUI monitoring is being extended.
Leveraging knowledge beyond Chemelot
Corrosion is an issue throughout the chemical industry, so innovations are followed by companies around the world. Sitech is therefore affiliated with the WCM project CUI (Corrosion Under Isolation) and is also taking part in the yet-to-be-started 'Joint Venture Project (JIP) Innovation CUI', which is being coordinated by the research institute Sirris in Belgium. An industrial consortium will compare coatings and monitoring techniques in a specially designed CUI installation. Janssen: "Sitech is going to help set up the test facility. We will also participate in the studies and advise on how best to evaluate the monitoring techniques and coatings." Companies such as Shell and DOW Chemical are also contributing to the two-year project. The results of the project will be incorporated by Sitech into CUI's plan of action. "Innovations to prevent failure due to CUI can potentially save millions of euros, so there is a lot of interest in the results of the JIP InnovationCUI project," Janssen concludes.
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