Conveyor belts are to the mining industry what veins are to our bodies. The pulleys that keep the conveyor belts rolling on track are often exposed to high levels of contamination, from both dirt and water.
The main challenge from a maintenance point of view is to keep contamination away from the bearing housing units that support the pulleys and the key to this, according to CBC’s Application Engineering Manager, Gary Payne, is having a good external seal.
CBC, in conjunction with bearing specialist company, NTN, provides a unique bearing-housing-sealing arrangement that works to ensure maximum protection for the bearing and lubrication.
The housing and the external seal are designed and manufactured by CBC’s engineering team, which work in conjunction with high performance spherical roller bearings by NTN to offer a complete solution.
CBC’s engineering team has extensive experience in designing external seals, with their in-house developed Scorpion seals being used by mining industry heavyweights.
“The Scorpion seal was developed based on our engineering team’s extensive research and hands-on experience from site trials. The idea was to improve sealing ability of external seals, while also simplifying the design,” Payne says.
The CBC Scorpion seal is designed as a unitised assembly that can be installed as a complete unit. This design means shorter assembly time on the site, as well as error-free assembly.
To demonstrate the time saving benefits, Payne compares the Scorpion seal with an open Taconite sealing arrangement.
“Taconite seals consist of many components, so installing them on the pulley can take the fitter anywhere between 10 to 15 minutes. By comparison, installing a Scorpion seal only takes 10 seconds,” he explains.
Apart from shorter assembly time, the Scorpion seal designed by CBC also limits labyrinth grease washout and reduces purging grease consumption significantly. Extensive tests by CBC have shown that the Scorpion seal enabled up to 40 to 60 per cent reduction in purging grease consumption compared to conventional open Taconite sealing arrangements.
For applications that need an added level of protection against water, the CBC team has also designed a universal shield that can be installed on both CBC seals and other conventional seals.
“In rugged environments such as in mining sites, mud builds up on the bearing housing. In some sites also water is sprayed on the conveyor to control the dust. This can be very detrimental to the seal assembly,” Payne explains.
Alignment control is another important aspect of designing external seals, according to Payne. CBC is currently developing a self-aligning seal that will help further reduce installation errors on site.
Complementing the CBC solution are the NTN Ultage series of sealed spherical roller bearings, which are designed to withstand the tough applications that are typical to mines and quarry sites.
NTN-CBC Product Manager for Bearings, Fabio Rebecchi says the Ultage series is the ultimate spherical roller bearing that NTN produce. NTN offers two series of the Ultage sealed spherical roller bearings in Australia: the 231-series and the 222-series.
“The 222-Ultage series are provided with pre-installed grease in the bearing. This feature allows us to use factory- specified grease that can carry high loads and operate efficiently in adverse operating conditions. Of course, operators can still re-lubricate the bearing through lubrication points on the CBC-designed housing,” he explains.
Another feature of the NTN Ultage spherical roller bearings, according to Rebecchi, is their performance under misalignment.
“These bearings have an allowable misalignment up to 0.5 degrees, they still maintain a constant contact pressure on the seal and do not lose their grip pressure. Therefore, there’s no decline in the seal performance. This is effective for keeping dust and moisture and other contaminants out of the bearing cavities,” he explains.
Importantly, the CBC and NTN teams’ collaboration extends beyond the bearing and housing design. The two teams work in conjunction to offer a complete solution to customers in the mining and quarrying industry.
“Field service engineers from CBC and NTN can assist the clients by either offering training to their maintenance teams or offering consultations on the best bearing for their applications. We have had a very successful partnership over the years, with our combined solutions used extensively by clients in the coal and iron ore mining sector,” says Rebecchi.
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