Influence of local bush wear on properties of water lubricated marine stern tube bearings

In recent years more and more frequently can be met ships in which propeller shaft water-lubricated polymer bearings have been applied. It results from their simplicity and associated relatively low initial and operational cost as compared with the complex classical sealed system based on oil-lubricated bearings. It is worth mentioning that the water-lubricated bearings are also environmentally friendly as no risk of pollution with lubricating oil used in classical systems, is involved. Design procedure of bearings in question based on materials available from their producers is relatively simple. However the calculating of such bearings creates many problems. For calculating the hydrodynamic lubricating theory is as a rule used and elastic bush flexibility taken into account. In the case of greater loads when lubricating film is very thin to achieve a proper solution is very difficult.

For this reason is proposed a novel method in which bush local wear effect can be accounted for. Such phenomenon has been observed during experimental tests of heavy-loaded water-lubricated slide bearings. With the use of the applied calculation algorithm bush local wear close to its edges can be taken into account, and - in consequence - a greater bearing capacity can be achieved.