Carbon-graphite stoker bushes are used in travel grate of boilers for high temperature applications because metal bushes needs oil/grease lubrication, Oil/grease lubricants can start to melt, volatilize or carbonize above this temperature above about 350ºF (177ºC).. When this occurs, oil/grease-lubricated metallic bearings start to experience high friction, high wear, galling, vibration and even seizing. Moreover Metallic bearings can start to have problems of thermal expansions at high temperatures.
At high temperatures, plastic and composite bearings are subject to other problems such as softening, melting, deformation and may extrude out of the bearing area all together.
Carbon graphite bearings are ideally suited for applications at elevated temperatures because they rely on graphite for their self-lubricating properties. These solid homogeneous bearing materials do not contain oil/grease lubricants and they do not rely on oil/grease for lubrication. Thus, bearings manufactured from these carbon graphite materials are not subject to the shortcomings associated with petroleum-based lubricants and metals at elevated temperatures.
Because the carbon graphite matrix is very strong, it is not subject to the deformation, melting, or even softening that can occur with plastic bearings at these elevated temperatures.
Carbon-graphite bearings are also used for dry running at room temperature or cold temperatures. This occurs in applications where oil/grease lubricated metal bearings can not be used because:
Carbon and graphite materials exhibit the following characteristic properties. Due to these properties, carbon and graphite bearings are used in many applications such as high and low temperature technology.