De-nickelification of 70/30 Cupronickel Tubing in a Cooling Heat Exchanger.

A cupronickel heat exchanger failed after 10 years of service. The cooling heat exchanger was in service in a marine environment, with water flowing along shellside and natural gas along tubeside. Many tubes showed leakages during a regular maintenance test. A comprehensive failure analysis of the heat exchanger revealed the de-nickelification process on the external side of the damaged tubes (shellside). The de-nickelification originated from a large deposit of sea water scale, over tube lengths, which completely covered the area just outside the internal portion of the tubesheet, and occurred because of a failure of the regular cleaning operation. Stagnant water and possible hot spot formations on the tubes probably caused the phenomenon. [ABSTRACT FROM AUTHOR]