Eliminating grease lines and fittings5 February 2010
Many bearings are located in difficult areas and greasing them can be a tough task. Over the years, new technologies have emerged to help reduce time spent on greasing bearings. Grease lines and fittings help to get to those difficult areas that are hard-to-reach but just a crucial as the rest. An automatic grease lubrication system can also free up a significant amount of time for maintenance that could be used to focus on other aspects of the plant. In either situation, it is still necessary to apply grease and spend time on cleaning; grease can leak, be messy and must be attended to in order to decrease polluting or corroding other materials. There are options for greaseless bearings that eliminate complex lubrication systems and undesired cleaning in a number of areas throughout a plant.
Columbia Industrial Products offers self-lubricating materials, CIP Composites, for bearing and wear applications. These composite materials eliminate the need for grease and reduce maintenance in high load and slow speed applications. As a laminated, polyester based composite, manufactured with solid lubricants, CIP Composites have low coefficients of friction in both wet and dry running applications. CIP Hydro Composite is a proprietary material blend of textiles and additives, designed specifically for inside the generating plant. CIP Hydro has been tested with excellent friction and wear results along with excellent performance when edge loaded at Power Tech Labs (Surrey, Canada), says the company. This 100% bearing material, which has no fiberglass or metallic shell, is stable where shock and misalignment may be present. Manufactured with no abrasive filler, such as calcium carbonate, CIP Hydro has been designed to be non-abrasive to mating surfaces, with a long wear life and easy to machine.
Where long wear life is a requirement in the high loaded bearings with limited rotation, such as wicket gates and their linking mechanisms, this is one of many applications where the lubrication system can be eliminated. For every wicket gate there are three possible bushings where CIP Hydro can be installed and the grease fittings removed. CIP Hydro can be installed by freeze or press fitting with the option to machine in place. With options of eccentric inner diameters, the composites are custom manufactured to customer specifications. One unit at the John Day Dam (Columbia River, US) has replaced all wicket gate bearings and link bushings, eliminated grease and applied a new coat of paint. CIP Hydro bushings, flange bearings and thrust washers were installed during refurbishment of this particular unit.
In other units and power plants, CIP Hydro has been utilized as operating ring wear pads, servo-motor connecting rod bushings, screen bushings/wear pads, pump bearings, lock and control gate bushings, and trunnion bearings. At Foster Dam (Oregon, US) the US Army Corps of Engineers (USACE) decided to use CIP Hydro as a replacement of the original bronze trunnion bushing and graphite plugged bronze thrust washer on the spillway gates. “We had three reasons for choosing self-lubricating materials,” said Ronald S Wridge, chief of mechanical design section of the USACE Portland District. “First trunnion friction will be reduced by upwards of 50 percent. Second they eliminate or significantly reduce maintenance requirements for the trunnion. And third, this eliminates the environmental issues associated with using grease near a waterway.” (Hydro Review, May 2009).