What causes corrosion under insulation?
What causes corrosion under insulation?
Corrosion under insulation (CUI) is the corrosion of piping and vessels that occurs beneath insulation as a result of water penetration. The water can come from rain water, leakage, deluge system water, wash water, or sweating from temperature cycling or low temperature operation such as refrigeration units.
How do you prevent corrosion under insulation from occurring?
Wrapping equipment with aluminum foil before applying insulation will reduce the risk of corrosion, since the foil provides a physical barrier that prevents the saturated chloride solution from reaching the metal surface.
What causes Cui?
CUI occurs through penetration of water or moisture and contamination via condensation or external sources (e.g., rain, sprinkler system). CUI can be very localized, with most of the equipment remaining in good condition.
What is CUI in oil and gas?
Corrosion under insulation (CUI) is one of the problems crippling the gas and oil industry. It can cost companies a lot of money every year in repair, inspections, and replacement costs. It refers to a form of corrosion that occurs between the material used for insulating gas lines and the outer surface of a pipeline.
Where does galvanic corrosion occur?
Galvanic corrosion occurs when two dissimilar metals are immersed in a conductive solution and are electrically connected. One metal (the cathode) is protected, whilst the other (the anode) is corroded. The rate of attack on the anode is accelerated, compared to the rate when the metal is uncoupled.
Why should stainless steel pipes be foiled?
The thermal insulation materials used for stainless steel pipes and vessels contain chlorides. If such insulation materials are exposed to moisture, chlorides may be released into a moisture layer on the pipe or vessel surface and pitting/stress corrosion cracking may result.
How do you know if insulation is under corrosion?
The most common and straightforward way to inspect for corrosion under insulation is to cut plugs in the insulation that can be removed to allow for ultrasonic testing. The other commonly used methods are radiography, and complete insulation removal. More advanced methods include pulsed eddy current.
How do you mitigate Cui?
Periodically and strategically organized, remove all insulation, prepare surfaces for coating and reinsulate. Maintenance of a conventional coating system (paint) is the only mitigation for CUI on carbon steel equipment with traditional metallic cladding.
What is Cui range?
According to API 570 there are also specific susceptible temperature ranges under which CUI may occur. For carbon steel piping systems, the range is between 25 and 250°F, particularly where operating temperatures cause frequent or continuous condensation and re-evaporation of atmospheric moisture.
How can you tell if there is corrosion under insulation?
How do you manage Cui?
Securing CUI
- Level 1 suggests performing basic cyber hygiene practices like installing anti-virus software and regularly changing passwords to safeguard Federal Contract Information (FCI).
- Level 2 describes an “intermediate level of cyber hygiene” that begins implementing NIST SP 800-171 requirements to secure CUI.
