Problem-free prediction

Crushing and grinding, blending, drying and heating, cooling and more grinding… The motors, drives, and gearboxes in crushers, kilns, mills, and other machines in cement production are critical equipment that keep cement plants running even in the harshest conditions. They have to withstand heavy loads, some operate within extreme heat, and conditions are always dusty. Maintenance is indispensable for ensuring smooth and efficient production and preventing machine failures which can lead to very costly unplanned shutdowns. When motors fail the stress level rises, especially when the failure comes unexpectedly.

With more than 2000 motors in a cement plant, the number of failures occurring within a year is not to be underestimated. More than 50% of the time bearing failures are the cause – and up to 80% of premature bearing failures are caused by improper lubrication.

The good news is that this means up to 80% of premature bearing failures can be prevented.

With over 2000 motors, the number of lubrication points in a cement plant quickly exceeds 5000. With this high number of lubrication points, traditional lubrication approaches can present a significant challenge and that figure of up to 80% of premature bearing failures being due to lubrication issues is no longer very surprising.

Selecting the right lubricant

It all starts with selecting the right lubricant. Correct lubricant selection not only has a crucial impact on the life of the bearing and its energy consumption, but also on the correct functioning of the machine or system into which it is integrated. The most important task of a lubricant is to reduce friction and wear in the bearing through the formation of a lubricant film that separates the surfaces – ideally with no metal-to-metal contact occurring between the rolling element and raceway surfaces. This effect is comparable with the dreaded ‘hydroplaning’ that can occur when a film of water causes a car’s tyres to lose their grip on the road above a certain speed. Although highly undesirable when driving, this effect is an ideal scenario in lubrication, as it reliably minimises friction and prevents wear. The separating lubricating film is ensured by the right lubricant, or respectively, by the right combination of base oil, thickener, and additives.

But there are various other requirements a lubricant might have to meet. If elevated temperatures occur in a machine or system, for instance, oil lubrication can act as a coolant. In many cases, this can have a critical impact on how the machine or system functions. Oil lubrication also has the ability to remove contamination from the system by means of filtration. With standard grease lubrication, grease practically being an ‘immobilised oil’, the lubricant cannot provide any cooling function. The grease must be capable of tolerating the resulting temperatures over longer operating periods. Temperature suitability is, therefore, a key selection criterion for greases. Despite not providing any cooling benefits, grease lubrication does have its advantages in that it requires no or very little special design work. Grease acts as an ‘onsite’ oil reservoir and it provides additional protection against the ingress of contaminants from outside.

Choosing the right lubricant is always a compromise for which the expected operating conditions, such as speed or operating and ambient temperature range and load, should be known. The bearing type matters, too. Ball bearings, for example, tend to be less demanding in terms of wear protection than bearings with line contact, such as tapered or spherical rolling bearings, and require different combinations of oil, thickener, and additives. In truth, a ‘one-size-fits-all’ grease does not exist. With all these specifications governing the selection of a lubricant, expert advice should be obtained from the bearing manufacturer to ensure the right lubricant for the application.

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