AN EXPERIMENTAL STUDY ON THE WEAR BEHAVIOR OF WATER-LUBRICATED ACM COMPOSITE BEARINGS AND PROPELLER SHAFT SYSTEMS UNDER SAND AND SEDIMENT IN LUBRICATING WATER

Tóm tắt

Water-lubricated composite bearings (WLCBs) are widely used in marine propulsion shaft systems because of their environmental compatibility, low maintenance requirements, and ease of replacement. Inland waterways often contain high concentrations of sand and sediment; therefore, dredging vessels, and vessels operating in shallow waters frequently experience abnormally rapid wear of propeller shaft bearings. This study presents field survey results on the wear behavior of ACM L2 Marine propeller shaft bearings and shaft journals. Ten vessels were inspected during dry-docking for bearing repair or replacement of propeller shaft bearings after 1.5–5 years of operation, in three operating environments: sea (clean water), estuary (water mixed with silt), and inland waterway/dredging vessels (water with a lot of sand and sediment). For each vessel, the authors assessed the overall wear condition, bearing surface and propeller shaft journal, and measured the lubrication clearance. After synthesizing the experimental data, two groups emerged: Group A, consisting of vessels operating in clean water, showed an increase in lubrication clearance of 0.13–0.16 mm/year, a value within the manufacturer's stated range; Groups B and C, consisting of vessels operating in water containing a lot of sand and sediment, showed an increase in lubrication clearance of 0.6–1.0 mm/year, which is up to six times higher than the manufacturer’s specified value. Therefore, the lifespan of propeller shaft bearings in groups B and C was only about 1.5-2 years. The mechanisms causing rapid wear of propeller shaft bearings and propeller shaft journals were identified by the authors as follows: three-body wear (predominant in water containing a lot of sand and sediment), bearing surface peeling, and poor cooling water flow due to clogged water channels. The main causes were the lack of separate cooling water filtration systems in the vessels, and installation and operation errors. In addition to analyzing the causes, the authors have put forward five recommendations to extend the lifespan of bearings and shafts for inland waterway vessels and dredging vessels.