In simplest terms, CUI (corrosion under insulation) is any type of corrosion that occurs due to a moisture buildup on the external surface of insulated equipment. It can be caused by multiple factors and can occur in equipment operating at ambient, low, and high temperatures, depending upon conditions. Moreover, CUI can occur in equipment that is in service, out of service, or in cyclic service.
Damaged insulation (as well as many other factors) provide a very easy route for water ingress into insulation. Once inside it can cause very serious damage to pipework and other susceptible steel elements.
Below are a couple of examples of damaged insulation that we recently identified during routine CUI Risk inspections for one of our clients.
Example 1: Insulation damage, visible water/moisture intrusion.
Visible insulation damage and moisture spread.
Example 2: Insulation damage caught early.
Damaged insulation caught early.
Example 3: Not so obvious, no visible sign of insulation damage.
Not so obvious, no visible signs of damage to insulation.
Inspection programs should ensure comprehensive coverage of all plant (vessels and pipework) including ‘running’ plant (pumps, valves etc) which may be subject to CUI. It is essential to consider items exposed to localized cooling/heating effects, as well as the effects of outage periods for components operating at high temperature. This promotes CUI in plant or pipework which would otherwise be excluded from the survey.
To discover more out more about this inspection service click here.
There are a number of techniques available for detecting corrosion under insulation (CUI) in the Oil & Gas industry, however most are very slow and require direct contact with the equipment being inspected.
These techniques are time consuming and expensive. Scaffolding is often required to reach pipework, which can take time to organize and be labor intensive.
A thermography program is an effective method for identifying existing CUI, as well as areas that may be at risk. It is also useful for quickly assessing insulation integrity.
Thermography allows the user to detect areas of water/moisture ingress within insulation, where CUI may be occurring and where there is potential for it to occur in the future.
When water or moisture gets into insulation, it changes the thermal capacity of the insulation. After a number of cycles that “change in insulation capacity” becomes permanent. This allows users to inspect surface temperature profile and identify anomalies.
Applied correctly, thermography is a very effective method for finding existing CUI and early stage water ingress.
Intec Analysis thermal image – CUI risk identification image.
An active CUI risk monitoring program has many benefits. Companies can target areas of interest and prioritise maintenance.
Many insulated lines and components in a facility can be scanned quickly, saving excessive scaffolding and labour costs.
Thermal imaging inspections are very efficient. It is possible to maintain a high level of safety on an asset or facility. This helps to prevent unexpected downtime and maximize production.
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Part 2 of this topic covers the application from a technical aspect.
Thanks for reading.