Investigation of the failure of a high-pressure pump motor bearing oil cooler

This article describes an investigation of a cupronickel cooling coil tube failure in the main bearing oil cooler of a pump in a reverse osmosis plant. The cooling medium is aerated seawater. The failure was a wide pit at the outlet of the cooling coil tube. Detailed physical inspection and energy dispersive x-ray analysis of the tube and corrosion products attributed the failure to localized pitting from the synergic action of low water velocity, welding heat-affected zone, and the presence of high chloride content and sulfur in the water. Various measures to minimize such failures are recommended.