ABSTRACT
Recently, the number of the accidents caused by Corrosion Under Insulation (CUI) leaks has been increasing in many countries. CUI is the most expensive problem in refineries and petrochemical plants due to the highly corrosive conditions and the lack of visual access. In general, CUI is caused by water under, or within, the insulation in contact with pipe. Visual inspection of steel piping, vessels and equipment by removing the insulation is the most reliable way to find CUI locations at present. However the cost of the inspection is significantly high, so that only limited areas are selected for the visual inspection. In cyclic and low temperature operating pipes and equipment, the main source of water is condensation, so that the entire piping and vessel surfaces are subject to CUI regardless of whether there may be ingress of water from the outside environment.
Often, thermal sprayed aluminum (TSA) coatings are used to control CUI at present. Some CUI monitoring methods and non-destructive testing are also used to detect CUI. However, because these methods are limited and lack accuracy, the risks of CUIstill exist. Based on the shortcomings of the existing methods, a cost-effective three-layer CUI protection system was developed by combining galvanic, cathodic and barrier protection.
This paper discusses how to protect pipes from CUI using this three-layer system including cathodic protection and barrier protections and a new method to detect CUIlocations remotely.
