For HXR backup trains or essential service water systems, tubes must be resistant to attack under what condition?

For HXR backup trains or essential service water systems, tubes must be resistant to attack under what condition?

• A. Stagnant water conditions
• B. High-velocity flow
• C. Elevated temperature
• D. Vacuum conditions

Answer: (A)

The important idea is that tubes in essential service water systems must withstand attack when water isn’t circulating. Stagnant water creates unique corrosive conditions: oxygen and other aggressive species can become concentrated at or near the metal surface, protective films may dissolve or fail, and biofilms or deposits can form, all of which accelerate corrosion and promote pitting or crevice attack. Because there’s no flow to remove corrosion products or supply fresh inhibitors, the material must be resistant specifically to this stagnant-conditions attack. While high-velocity flow, higher temperatures, or vacuum are less representative of the standby condition these systems face, stagnation poses the greatest risk and dictates the needed material robustness.

The important idea is that tubes in essential service water systems must withstand attack when water isn’t circulating. Stagnant water creates unique corrosive conditions: oxygen and other aggressive species can become concentrated at or near the metal surface, protective films may dissolve or fail, and biofilms or deposits can form, all of which accelerate corrosion and promote pitting or crevice attack. Because there’s no flow to remove corrosion products or supply fresh inhibitors, the material must be resistant specifically to this stagnant-conditions attack. While high-velocity flow, higher temperatures, or vacuum are less representative of the standby condition these systems face, stagnation poses the greatest risk and dictates the needed material robustness.