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Corrosion Under Insulation
Corrosion Under Insulation – No Problem?
MB Inspection has an exclusive agreement with RTD bv to provide the RTD-Incotest system in the United Kingdom and Ireland.
INCOTEST (an acronym for INsulated COmponent TEST) formerly known as ARCO-TEMP, is a unique corrosion survey method that allows ferrous pipes and vessels to be surveyed without the time and expense of removing insulation, asbestos, fireproofing concrete or similar coatings. The system will operate under the following challenging conditions, without disturbing the insulation or coating:
- When insulation is Aluminium, Stainless Steel or Low Alloy Steel clad.
- While the plant is in operation.
- When test item is hot (500ºC) or cold (-100ºC).
- When the insulation is wet.
- When the surface is rough or encrusted.
- When insulation is irregular or inhomogeneous.
- When the insulation is wire mesh reinforced.
Principle
A special eddy current probe is placed on top of the thermal insulation. This generates a low frequency (pulsed) magnetic field which produces eddy currents in the material. Material thickness is calculated from the eddy current (pulse) duration. This thickness calculation gives the average thickness of the material within the enclosed magnetic field (probe footprint).
The diameter of the footprint varies between 25 and 150mm and is dependent on wall thickness and thickness of the insulation.
Applications
Although originally developed for the detection of Corrosion Under Insulation (CUI) Incotest is well suited to detect internal wall loss such as Flow Accelerated Corrosion, again without removal of the insulation.
The detection of corrosion through coatings, concrete and marine growths were also quickly identified as good applications. Surveying heavily corroded pipes on which grinding, needed for an ultrasonic survey, would not be safe has also proved a successful application.
New applications are constantly emerging, as people realise the big benefits from this technology. One of the attractive features of Incotest is its tolerance with regard to coupling the signal to the object. Holding the probe at the right location is sufficient; as a result measurements can be taken in demanding circumstances. For example, on offshore risers and caissons using rope access or by divers or ROV underwater to a depth of 10m.
Fast and Affordable
The RTD-Incotest is a fast survey tool; an experienced two-man team can survey and store up to 1000 points per day depending on accessibility. The system is well suited to carrying out baseline surveys and has demonstrated excellent repeatability.
