CASE-HISTORY - SEAWATER REFRIGERATING SYSTEM FAILURE

The cause of failures of copper-nickel pipes in the seawater refrigera ting systems of two ships was analyzed. Failure is attributed to poor design of the weldments aggravated by seawater contamination. Welds pl aced too close to each other promoted sensitization of the material. T he alloy had been heated to the precipitation range of an iron-rich se cond phase, and a pronounced root pass reinforcement created a very hi gh turbulence zone. Both factors, enhanced by the presence of sulfide- contaminated seawater, strongly increased the corrosion rate, leading to fast perforation of the tubes.