Question:
What is the best approach to detect and monitor CUI ? CL
Answer:
The most reliable method to detect and monitor CUI is a full strip of the insulation and visual inspection, although once CUI is detected with this method it is rarely monitored. The key disadvantage of this approach is the high cost and required resources associated with access, stripping, possible refurbishment of the coating, and reinstatement of the insulation. The need for a reliable screening technique to focus CUI inspection efforts has been recognised for many years. Various non-destructive techniques (NDT) are available to detect CUI directly without removing the insulation, such as real time radiography (RTR) and pulsed eddy current (PEC). However, the drawback of these techniques is the uncertainty around probability of detection (POD), despite significant technique improvements in recent years and development of technologies through joint industry projects such as those done by HOIS (Harwell Offshore Inspection Service). Possible presence of CUI can also be detected with indirect techniques which are based on detection of water or humidity in the insulation system. Techniques such as thermography, neutron & x-ray backscatter, and more recently various types of sensors are all capable of detecting water or humidity but similar to direct methods there is still uncertainty around the POD and questions about the reliability. Another drawback is that detecting water does not necessarily mean that CUI has occurred at the points where water is located. Much development work continues especially with sensors which may offer better monitoring capability including direct detection of corrosion. Improving CUI predictive capability through greater sharing of data and analysis can also help focus where to inspect, but the CUI still needs to be located and there are many instances of CUI “surprises” in the industry especially if 100% stripping of insulation is not done during service of the facility. It should also be recognised that it can take 15 to 20 years to fully validate CUI technology developments and therefore compromises will inevitably be sought. A complementary approach involving direct NDT, water detection, sensor monitoring and the application of better data analysis and CUI prediction is probably the optimal way forward to focus efforts with CUI inspection planning, but full strip and visual inspection remains the most reliable approach.
Steve Paterson, Arbeadie Consultants
