11 Dec Gaining higher grinding efficiencies through re-engineering
High pressure grinding rolls, also known as roller crushers, are used across mineral processing plants for a variety of applications, from cement processing to diamond liberation and iron ore pellet feed preparation. Other minerals and ores such as gold, copper and nickel are also often put through roller crushers for size reduction in the communication process.
With a design that centres around two large counter-rotating rolls, the efficient performance of roller crushers relies heavily on the performance of the spherical roller bearings that accommodate the radial and axial loads in the rollers.
So, when site engineers at a major gold production facility in Western Australia approached their long-term industrial partner, CBC, to help them reduce maintenance costs for their roller crushers, the conversation eventually led to replacing the machine’s existing bearings with the high performance but cost-effective FAG double row spherical roller bearings from Schaeffler.
Gary Payne, Principal Advisor at CBC Australia, says the FAG bearings delivered equivalent performance and service life as the spherical roller bearings incorporated in the original equipment design, but at lower upfront costs, resulting in significant savings for the mine.
“CBC has been supporting the gold mine with product supply and technical support for a number of years. Building on the back of this positive relationship, we proposed stocking the large size FAG double row spherical roller bearings at our warehouse and free-issuing them to the original equipment manufacturer as part of the maintenance cycles,” he says.
“Through this arrangement, our customer can save a substantial amount of in each maintenance cycle. This is in addition to the ease of supply and the product support that they receive from CBC.”
Steve Riley, Regional Manager, Schaeffler Australia, explains why the FAG spherical roller bearings are more cost-effective than their counterparts.
“The FAG double row spherical roller bearings contain improvements incorporated by Schaeffler both in the bearings’ design, as well as in their manufacturing process.
“The FAG spherical roller bearings have improved kinematics and optimised surfaces, are made from higher performance materials. All of these factors result in a bearing with higher load ratings so that under identical loading conditions, a smaller bearing arrangement can be designed to endure equivalent axial and radial forces.”
Compensation for angular misalignments is another factor contributing to the reliability of the FAG bearings, Steve says.
“The FAG spherical roller bearings are designed so that the symmetrical barrel rollers orient themselves freely on the concave outer ring raceway, as a result the shaft flexing and misalignment of the bearing seats are compensated. Depending on the bearing series used and the nature of the rotation, these bearings can compensate angular misalignments of 1.5 to 2 degrees.”
In addition to collaborating on the new bearing supply, Gary says the CBC technical team has also identified some issues related to water ingress into the bearings during the disassembly and re-assembly process, which they are currently working with the mine to address.
“The annual maintenance for roller crushers involves disassembling the equipment and shipping it to the manufacturer and then shipping it back to the site. This gives way to a higher risk of water ingress into the bearings, which we have identified to be the cause of some issues in the past. Through a program of full engineering support, we are currently working with the site engineers and maintenance personnel to help improve the sealing design for the bearings,” says Gary.
“Whereas the initial goal set out through our conversations with the customer was to achieve a service life of at least 12 months for the bearings, with the support from CBC’s engineering team to improve the sealing arrangement, we are now hoping we can extend the bearings’ service life to 15 months, which will align with the maintenance schedule for the rollers themselves. This would mean even higher efficiencies and cost savings than anticipated in the beginning,” he adds.