CUI is a common problem for petroleum refineries, petrochemical facilities, power plants and chemical and fertilizer plants. One’s predisposition could be to consider CUI as a problem that is isolated only to sites in close proximity to a marine environment, but this is not always the case. CUI can happen in dry industrial sites as far away from the sea as the Canadian prairies (Figure 1). Once equipment is insulated, the proximity to cooling towers, leaking heat tracing, rain, mist from melting snow that saturates insulation and other leaks or steam can have an impact on CUI.

CUI can remain undetected until a leak develops or until the insulation and cladding or jacketing are removed or damaged, making CUI exceedingly challenging to find (Figure 2). Earlier reports stated that one single non-destructive examination (NDE) could not be used to identify CUI [ 2]. This remains the case today as engineers combine several NDE techniques to perform CUI assessments. In such assessments, corrosion rates are usually presented in mils per year (mpy), where one mil is equal to 1/1,000 of an inch. The techniques and strategies now used are summarized throughout this article, and several images are provided to illustrate CUI in piping and tanks and the detection methods applied in industry today to improve overall reliability.

Read the full article at Chemical Engineering Online.