Influence of Lubrication Water Contamination by Solid Particles of Mineral Origin on Marine Strut Propeller Shafts Bearings of Ships

Abstract The stern tube or strat bearings are key important component for safety of shipping. Modern global regulations required a low as possible negative impact on environment including lubricants leaking to the sea. The ship owners are looking for reliable and durable solutions. The costs of each ship components are carefully studied. The water lubricated bearings for ship propeller shafts are an environmentally friendly solution. That is the reason why water lubrication is an interesting option to consider. Because simplicity of the ship design is expected the open lubricating system with only one seal module, when sea water is a lubricant is often recommended by manufacturer. This research was inspired by a series of failures or premature excessive wear of the propeller shaft strut bearings of real ships. The experimental tests were conducted in the laboratory on custom designed and build test-rig. The large group of tested bearings was delivered by certified manufacturers. The results of long time wear tests clearly prove that the cause of this premature wear was abrasive wear resulting from water contamination with solid particles of mineral origin. The range of the wear strongly depends on bearing bush materials and bearing interspace geometry. The wear was low for bearings with elastic bushes especially when hydrodynamic phenomena takes place. The general conclusion is that water lubrication is an interesting option to consider when design of the ship is discussed. The simplicity resulting an attractive price, low maintenance costs and proven durability and reliability of some bearings materials cause that this technology is becoming popular and often applied.