July 17, 2012
Keeping a belt conveyor running for long, predictable periods of time is essential to high productivity when processing sand, gravel, crushed stone, or other minerals. Here are some insights on how to keep them running efficiently to maximize uptime.
The primary points of failure in belt conveyors are often the idler, tension, drive, and head pulleys. When one of them has a bearing problem, the belt stops moving — even though the bearings are often not the root cause of the failure. Proper diagnosis of the problem can help increase bearing life and extend overall uptime.
Load sources and types
The main loads on a pulley bearing come from the belt pull, the weight of the pulley, the belt, and the payload. Payloads have been increasing in recent years due to improvements in belt design and the use of stronger materials. There may also be a small thrust load originating from the belt, riding against the lateral belt guide rollers. In the case of a belt track problem, the common solution is to mount fixed bearings on both ends of the tail pulley. This results in additional thrust loads on both bearings. Thermal expansion of the shaft further increases the thrust loads.
Extending bearing life
The harsh, contaminated environments in quarries, mines, and construction sites once meant shortened bearing life was difficult to prevent. Products on the market now have reversed that trend. For example, some new steel bearings resist spalling caused by damage-inducing contaminants, increasing the bearing’s life several times and reducing catastrophic failures, as well as overall maintenance costs.
High-performance spherical roller bearings are designed to reduce slip and minimize flaking between the bearing raceway and rolling element. Molded oil bearings can reduce the number of lubrication failures and eliminate the need to re-lubricate bearings.
Split housings — available in cast iron, ductile iron, and cast steel with a variety of seal options for contaminated environments — can also help resist wear and improve bearing performance. Small housings have two mounting-bolt slots or four bolt slots as an option. The slotted-hole design allows for easier alignment of the pulley. Additional features include an easy-to-read temperature strip mounted to the pillow blocks to alert users of potential failure due to overheating. Blocks also contain strategically located predrilled and tapped holes to allow for remote monitoring.
Tips for mounting bearings
Information for this article courtesy of NSK Corp. For more information, visit www.nskamericas.com.