Carbon Bearings have been developed by Assam Carbon Products Limited over the last 30 years. The generic term “Carbon Bearings” includes all possible variations of the basic material “Carbon”. Therefore it covers “carbon-graphite”, “metal-graphite” and “electro graphite”. Carbon is self-lubricating and has a low coefficient of friction at high and low temperatures. Its use as a bearing material is extensive when a conventional lubricant is not possible and also where the performance of other lubrication is poor. There are other properties which give it unique and distinctive advantages for bearings.
Chain Grate Stoker :
Formerly, grease lubricated cast iron bearings were employed. Cast iron bearings needed replacement at approximately 18-month interval, after 9,5mm radial wear. Shafts also badly worn and scored needed “building-up” and re-grinding. Considerable consumption of grease and frequent maintenance.
In one case after several years, carbon bearings have worn only 0,08mm and shafts are highly polished with negligible wear. No maintenance required and use of grease obviate. In another stoker, carbon bearings have run for 17 years, without replacement.
Flue Gas Damper : Formerly, unlubricated cast iron bearings employed. Excessive and rapid bearing and shaft wear, with frequent seizures with cast iron bearings. Wear of carbon bearings negligible over long operating periods. No shaft wear and no seizures experienced.
Ten-ton Furnace Charging Machine : Carbon bearings proven highly satisfactory. No conven-tional type of bearings possible because of high operating temperature. Carbon bearings have been in service for seven years to date.
Veneer Drying Oven : A total of 850 carbon bearings are fitted to this oven, each pair of bearing supporting a 400mm long hollow steel roller. Each bearing is mounted in a self-aligning housing. Carbon bearings have been in service for eight years to date without the need of any maintenance. Before the employment of carbon bearings, machines were fitted with grease lubricated ball bearings which required frequent attention.
Rust Proofing Conveyor : Sever hundred carbon bearings are fitted to a 4,6m long double roller suspension conveyor. Conveyor passes through various stages of bonderising cycle, i.e., caustic solution 90°C, water at 80°C, Phosphate solution at 90°C, Chromic acid rinse at 80°C, and, finally, drying oven at 230°C. Carbon bearings originally fitted in 1937 and are still giving satisfactory performance with very few replacements being necessary. Original oil-retaining sintered bronze bearings gave constant trouble – exces-sive wear, high friction and frequent seizures due to high temperature.
Submersible Pump Motor : Carbon bearings employed as 260kW motor main bearing operating completely immersed in circulating distilled water. Bearings, therefore, copiously water-lubricated. Highly satisfactory results obtained with negligible bearing or shaft wear after several years continuous service. Original bearings employed were lignum vitae which gave trouble due to swelling. Frequent seizures and excessive wear were experienced.
Vertical Centrifugal Pump : Carbon bearings employed as steady bearings, running completely immersed in circulating 10% caustic solution. Negligible bearing or shaft wear after several month continuous service. Previous pumps employed Bakelised Fabric composition bearings, which gave trouble due to swelling.
Aircraft Fuel Pump “Swash Plate” Type : Carbon bearings employed as main rotor bearings oper-ating completely immersed in circulating fuel, i.e., petrol, paraffin, kerosene, etc. Highly successful application. Carbon bearings found to be the most suitable type of bearings for these pumps.