By Ian Faass
Wheel bearings may seem like fairly basic components of a large piece of mining equipment, but they must be engineered diligently to accommodate various load and speed combinations during their service life in a vehicle. Every component must withstand the demands of the environment. Sometimes a standard offering will fit a customer’s need, but other times a specialty or custom product is a worthwhile investment—the key is finding the right level of performance for the components in the system. A knowledgeable supplier with technical experts who specialize in mining equipment can help. The more application information provided to these bearing specialists, the better, as not all bearings are created equal. The supplier has many different design “levers” to pull, depending on the situation.
To find the ideal solution, here are five application specifics to consider.
What sort of vehicle will use these bearings?
While haul trucks and wheel loaders are both large, heavy mining vehicles, the mechanical stress demands they place on bearings can be quite different. While a haul truck may move heavier loads over long distances and varying terrain, a wheel loader may move back and forth across relatively short distances as it scoops and deposits more frequent but lighter loads. We have found that haul trucks often require specialized bearings more often than wheel loaders due to their sustained heavy load and variable road condition operating environments.
In what type of mining environment are you operating?
Whether you’re operating in a downhill or open-pit mine can make a difference regarding what sort of wheel bearings a haul truck might need. Also, how much debris/grit that the bearing is exposed to in specific mine conditions can affect bearing choice. There are debris-resistant bearing options available that are designed specifically to improve the tolerance of bearings to debris ingress, so compare options carefully.
What conditions will the bearings operate under?
Applied load is an obvious factor that impacts bearing performance, but you should also consider other factors such as the speed at which a vehicle operates (low speed can actually be detrimental to lubrication film generation and affect bearing life), mating component temperatures, and how the vehicle is used—frequency of cornering, as well as the amount of time climbing or descending with load, for instance.
How well suited is the lubrication for the conditions at your mine?
Lubrication parameters and maintenance replacement intervals can be critical inputs into wheel bearing performance. In certain cases with marginal lubrication, it may be to your advantage to choose specialized wear-resistant bearings to prevent damage between internal contact surfaces within the bearing assemblies attributable to inadequate or poor lubrication. Engineered coatings can make roller body surfaces behave more like ceramics (hard, wear-resistant) and polymers (low friction, elastic for durability) in poorly lubricated bearing contacts. Coated bearing performance models are calibrated with laboratory data to allow application specialists to predict coated bearing life for your situation. Field experience with these premium wear-resistant solutions is 10 years and counting.
How durable are your other wheel end components?
Bearings are mounted and supported by surrounding components (such as shafts and housings) in the application, which also must be well designed and maintained to ensure optimum bearing performance.
Since every mining operation is different, bearing performance can vary substantially. To assist you in selecting the right parts for your application, work with a high-quality supplier with extensive industry experience.
By answering the questions above and defining your requirements before engaging an expert, you can identify the bearing solution that best delivers the level of performance for your needs.
Ian Faass is vice president, Off-Highway, The Timken Co.