For insulated austenitic stainless steel vessels, what is the temperature range where CUI is a concern?

• A. 10-350°F
• B. 140-350°F
• C. 350-500°F
• D. 500-800°F

Answer: (B)

The correct answer highlights the specific temperature range of 140-350°F as critical for the concern of Corrosion Under Insulation (CUI) in insulated austenitic stainless steel vessels. This temperature range is significant because it represents conditions where moisture can accumulate and remain on the surface of the insulation, promoting an environment conducive to corrosion.

At temperatures below 140°F, moisture is less likely to remain liquid or condense, which reduces the risk of corrosion. However, as temperatures increase to around 140°F and above, combined with the presence of insulation and potentially water or corrosive agents, the risk of CUI dramatically increases. This is particularly true in industrial settings where stainless steel vessels operate within this temperature band, and moisture might be prevalent due to temperature fluctuations or leaks.

In contrast, temperatures that exceed 350°F typically result in the evaporation of moisture, thereby reducing the likelihood of CUI occurring. Understanding this temperature threshold is crucial for maintaining the integrity of stainless steel vessels and planning preventive measures against corrosion, such as regular inspections and the use of appropriate insulation materials.