Feasibility Study of Biodegradable Sterntube Lubricant on Field Test Vessel

Medium and large merchant vessels use oil-lubricated shafting and bearings in the sterntube. Oil leakage from the sterntube is a serious environmental issue and the biodegradable oil beings an interest measure for its solution. Biodegradable oil is environmentally friendly due to its characteristic of quick decomposition into carbon dioxide and water in the marine environment. Existing biodegradable oils, however, do not satisfy all the properties required for sterntube lubricants. The authors newly developed a soluble, biodegradable lubricant based on polyethylene glycol, and a sterntube seal material compatible with the lubricant. The lubricant and the seal material were practically applied to a vessel on January 2006. Until now, they are running normally and the vessel experiences no trouble. In this paper, the field test of the lubricant and seal material is presented. The results for the lubricant sample analysis and the lubricant consumption measurement, which were derived until January 2007, are described. In addition, the sterntube seal performance of the field test vessel is discussed as compared with seal bench test results.