Marine Propeller Shaft Bearings under Low-Speed Conditions: Water vs. Oil Lubrication

The bearings used in shipbuilding, hydropower, and water pumps have undergone a metamorphosis in recent decades. Due to environmental regulations, lubrication with grease or mineral oil is prohibited. Thus, the standard solutions include water-lubricated bearings with polymer bushings or sealed systems lubricated with oil. When properly designed, assembled, and operated, bearings can operate reliably for years. However, specific operating conditions, such as a low rotational speed of the shaft, may result in intensive wear and premature failure. In this study, four sliding bearings approved for use in shipbuilding were experimentally tested. The test results showed that the choice of the bearing type has a key effect on friction during low-speed operation. Some of the tested bearings had significant static friction with intense slip–stick phenomena; they should not be used in applications requiring low-speed operation.