Bearing failures on mine sites occur most often due to contaminants, such as aggregates, iron ore, coal or any mining material penetrating the seal of the housing. This is aggravated by poor maintenance of the equipment, insufficient or excessive lubrication, and incorrect installation.
On a mine site, water is often used to wash down equipment, leaking through the bearings, turning dust into mud, and hindering performance on production lines.
Sealed spherical roller bearings, as Tony Tormey, BSC’s Product Manager for Industrial Bearings explains, are the “last line of defence” where bearings are used in dust-prone applications in mining, such as in conveyor pulleys or conveyors in cement mills.
“Bearings in harsh conditions like mining generally have three barriers, which is the housing, the grease and the seal on the bearing. You can also fill the cavity in the housing with grease, which will act as another barrier,” says Tony. “But despite all that, water or dust can still penetrate the housing, and that’s where sealed spherical roller bearings provide an extra layer of protection to the bearing.”
For more than 70 years, the Schaeffler Group has been pioneering the roller bearing industry, setting things in motion across the mining, automotive and manufacturing sectors. BSC have been exclusive distributors for the company since 1983, stocking and supplying Schaeffler products all over Australia.
Schaeffler Australia Senior Service and Application Engineer Alan Burt reveals how Schaeffler designed and developed a superior sealed spherical roller bearing by researching what was already available on the market. What they discovered, he says, was a need for greater flexibility and clearance range than what their competitors were offering at the time.
“When we introduced the Schaeffler sealed spherical roller bearing to the market, we made some fundamental changes to the internal design and construction of the bearing. One common issue with sealed bearing designs is that when you add a seal component, you typically minimise the self-aligning capabilities within the bearings which can cause wear and tear internally. We added extra space in our design to minimise contact with the sealing arrangements during the life of the bearing. Thereby, improving the life expectancy of the bearing.”
Most of Schaeffler’s sealed spherical roller bearings are designed to match the sizes in the standard range of Schaeffler’s spherical roller bearings, enabling end-users to use these like-for-like in a wide range of applications.
Alan notes, however that some bearing sizes in the smaller end of the 222 series are an exception to the above rule.
“That’s because with the narrower width of these bearings, it would be difficult to put in the seal without increasing the width slightly. But the general rule is that you should be able to mix and match open bearings with sealed bearings without any modifications.”
A wider range of clearance sizes
is another first by Schaeffler.
“You can ask for C3 clearance bearing from Schaeffler, which isn’t normally available with other bearings. Normally clearances are based on temperature, but also you sometimes have other movements in the bearing based on their operational requirements. That is why we offer the C3 clearance in addition to our normal clearances.”
Being X-lifeTM certified is another differentiator of Schaeffler’s bearings. X-life is Schaeffler’s seal of quality, indicating the ultra-high performance for bearings in this series based on certified tests.
“All of our sealed bearing versions are X-life. In most cases we are using the 231 series, the standard bearing with the integration of a seal. This allows us to use the existing Schaeffler X-life bearings and that adds all of those additional benefits that come with the X-life range,” Alan enthuses.
Clearly the sealed bearings have the potential to optimise performance and operating life through lessening maintenance and monitoring requirements but it is important to note that they must be used correctly. The lubrication holes need to be covered properly so the seals can do their job.
“The original sealed bearings didn’t have any lubrication holes and most sealed bearings still don’t have re-lubrication holes. The idea is to lubricate the bearing so that the grease lasts for the life of the bearing,” says Alan. “The Schaeffler design has incorporated rubber seals to prevent entry of water through the re-lubrication holes, but care needs to be taken to cover these holes properly.”
BSC, and its sister company, CBC, continue to foster a successful ongoing partnership with Schaeffler. Afterall, they share a history together, says Alan, “I have worked for Schaeffler for 35 years and during this time have had a lot of involvement with the BSC and CBC team in projects and problem solving.”