Keep Things Rolling with Flange Bushings
The wheel is perhaps one of the earliest innovations in human technology, and today’s wheels haven’t changed much in basic principle, but have been instilled with millennia of improvements and embellishments to improve performance in specific applications. One such addition is the bushing, which is a type of bearing used to enable smooth rotating motion between two parts. Bushings come in different shapes and sizes, but the most curiously-shaped of them all are the flanged variety.
The flange refers to one of the lips of the bushing extending outwards in a radial fashion, effectively extending the lip’s surface. This feature allows the bushing to be visible even when the parts it’s connected to are snugly joined. Having a flange also allows the bushing to be embedded into a part without sinking completely into the opening.
When embedded, flanged bushings are appropriately called thrust washers. These are usually seen in rotating machinery to ensure that the revolving components motion stay in place and can rotate unencumbered. They can be made from a variety of materials, but plastic seems to be one of the more popular choices due to its low weight, resistance to corrosion, and low maintenance. While these busing are usually built to last, they should still be monitored and routinely inspected by equipment operators to determine if they need replacement.
Source: http://www.ehow.com/info_12226316_engine-bushing.html
Advanced EMC Technologies 