Hafei 310 model roll box large-end oil film bearing
172050XA
172050VA
Morgan 5th generation 8-inch large-end oil film bearing
172050LA
172050MB
Oil Film Bearing: The Power of Fluid Friction
An oil film bearing is a type of sliding bearing that operates on a thin layer of lubricating oil, which completely separates the moving shaft from the stationary housing. Unlike ball bearings that rely on rolling elements, oil film bearings use hydrodynamic pressure generated by the relative motion between surfaces to maintain a fluid wedge. This oil film prevents metal-to-metal contact, eliminating wear and enabling ultra-smooth, vibration-damped rotation.
The working principle is rooted in fluid dynamics. As the shaft rotates, it drags viscous oil into a converging wedge-shaped gap, creating sufficient pressure to lift the shaft off the bearing surface. This hydrodynamic regime occurs once a critical speed is reached; below that, the shaft may experience boundary lubrication or even momentary contact during start-up and shut-down. That's why many oil film bearings are equipped with auxiliary systems like jacking oil pumps to pre-lift the shaft before rotation begins.
Oil film bearings are broadly classified into two categories: hydrodynamic bearings, which generate pressure solely by motion, and hydrostatic bearings, which use an external pump to supply pressurized oil, allowing operation even at zero speed. Common designs include plain cylindrical, elliptical, and tilting-pad bearings, each offering different stability and load-carrying characteristics.
These bearings excel in heavy-duty, high-speed, and high-precision applications where ball bearings would fail—such as large turbines, compressors, ship propeller shafts, and industrial gearboxes. Their ability to absorb shock loads, dampen vibrations, and tolerate minor misalignments makes them indispensable in power generation and marine propulsion. However, they require continuous oil supply, careful temperature control, and regular maintenance. Though often overlooked, the oil film bearing is a masterpiece of tribological engineering—where a microns-thick layer of oil carries tonnes of load with near-infinite fatigue life.
