Marine Thruster Lip Seals: A Comparative Study of Frictional Behavior and a Condition-Based Monitoring Approach

Abstract The present work studies the behavior of a polyurethane (PU) seal and a hybrid seal design with a PU body with a polytetrafluoroethylene (PTFE) insert, and compares it to a conventional nitrile butadiene rubber (NBR) seal used in marine thrusters. The seals had a 300 mm diameter. Three samples of each seal were tested under 27 operating condition combinations, and were characterized by the frictional torque and subsurface temperature. The PU seal had the highest frictional torque and subsurface temperature, followed by the NBR seal, then the PTFE seal. The contact temperature was estimated with a simplified conjugate heat transfer model, and a condition-based monitoring approach was proposed based on the results of the model and online measurement of near-lip temperature.