For insulated duplex stainless steel vessels, what temperature range indicates CUI is a concern?

For insulated duplex stainless steel vessels, what temperature range indicates CUI is a concern?

• A. 10 to 350°F
• B. 40 to 125°F
• C. 140 to 350°F
• D. 280 to 350°F

Answer: (D)

The correct range for indicating that Corrosion Under Insulation (CUI) is a concern for insulated duplex stainless steel vessels is 280 to 350°F. This temperature range is critical because it represents the conditions under which the passive layer of the stainless steel can become unstable due to the presence of moisture trapped under the insulation. In this temperature zone, the risk of localized corrosion increases especially if there are contaminants present, such as chlorides. Duplex stainless steels, while generally more resistant to stress corrosion cracking than austenitic stainless steels, are not immune to corrosion and can suffer under high-temperature and moisture conditions. Maintaining awareness of this temperature range is critical for inspectors to ensure that appropriate measures are taken to prevent CUI, such as regular inspections, correct insulation materials and methods, and proper maintenance programs. This awareness helps in mitigating failures and extending the lifespan of the vessel.

The correct range for indicating that Corrosion Under Insulation (CUI) is a concern for insulated duplex stainless steel vessels is 280 to 350°F. This temperature range is critical because it represents the conditions under which the passive layer of the stainless steel can become unstable due to the presence of moisture trapped under the insulation.

In this temperature zone, the risk of localized corrosion increases especially if there are contaminants present, such as chlorides. Duplex stainless steels, while generally more resistant to stress corrosion cracking than austenitic stainless steels, are not immune to corrosion and can suffer under high-temperature and moisture conditions.

Maintaining awareness of this temperature range is critical for inspectors to ensure that appropriate measures are taken to prevent CUI, such as regular inspections, correct insulation materials and methods, and proper maintenance programs. This awareness helps in mitigating failures and extending the lifespan of the vessel.