TriStar’s engineering department was contacted by a large company that recycles cardboard which is de-inked and repulped to produce new brown stock. This material is then used to then produce corrugated product for box and tube production. They were looking for help in replacing the oil-lubricated bearings on the heated rollers used to press the pulp stock into the final material thickness.
100 Bearings Per Machine = A Lot of Maintenance and a Lot of Oil
Our customer wanted bearings that were self-lubricating to eliminate the risk of the oil contaminating the paper stock and to reduce maintenance intervals and equipment downtime. The machine in question is nearly two hundred feet long from the wet pulp delivery point to the take-up rolls at the end of the machine.
The calculated bearing loads on the 7” x 9” surface area is just under 310 psi. This was based on the load being spread over the two bearings supporting a 20 ft. long roller filled with hot oil. The machine has over 100 of these continuously lubricated bronze bushings. The speed on the rollers is 180 sfpm which means the PV is 56,000. A formidable challenge when this application is a 24-7 operation!
Ultraflon CFX was the Best Fit for the Specific Requirements of this Application
Our engineers looked at the material options on hand that could perform at the high PV, require no lubrication, operate 24/7 at 200-250°F, and last for at least 1 year. After looking at all the parameters, our goal was to source a high temperature material with the best thermal stability possible, long term dry wear, low friction, good heat dissipation and, finally, a cost that wasn’t prohibitive considering the number of bearings on the system.
Our team chose self-lubricating Ultraflon CFX, one of TriStar’s custom compounds developed specifically for high PV, low friction, and long performance life. The customer installed 4 prototype bearings on the machine, shut the lubricators off and let it run. Upon removal of the test bearings after 1 year, the average wear on the four bearings was only .007”, which fell well within their machine specifications.
TriStar Plastics Always Considers the Full Picture When Identifying Possible Material Solutions
Keeping in mind that not all problems TriStar receives have as many difficult bearing conditions as this one, our engineering experience and access to many material options helped save this customer over $150,000 in maintenance costs. Even more beneficial is the elimination of the lubrication system, which makes for a much cleaner environment in the plant, protecting the paper product from contamination.
If you have an application that you think would benefit from self-lubricating polymer bearings we encourage you to send us the details.
