Abstract
Over the last ten years a number of crankcase oils in low speed marine diesel engines have suffered massive microbial infections. Associated with these infections have been severe generalised corrosion in the lubricating oil systems, deep pitting of the journals, and white metal failure in the bearings. Various factors can be shown to have contributed to the appearance of this problem, such as an increasingly nutritious diet available (from new oils and new corrosion inhibitors) and less ‘oil care’. Short term anti-microbial chemicals have been successfully introduced and long term alleviation using heat pasteurisation is the subject of intensive investigation.
University College Cardiff has received samples of lubricating oils and coolants from 170 ships over the last 5 years. These samples were studied and tested for microbial contamination. The results of this study have been analysed and are presented in this paper. The results suggest that in most cases microbial infections start in the cooling systems and spread to the lubricating oil; modern coolant corrosion inhibitors are universally susceptible to microbial attack, and certain types of engine, and of oil, are more susceptible to attack than others.
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