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may fail catastrophically – causing expensive downtime. Bearing failure also increases the need for maintenance and requires the bearings to be replaced – adding yet more cost to the operation.
However, by far the most serious problem is that of a product recall. This might occur if, for instance, the wrong lubricant is used in a particular machine – and then contaminates the product. (One way is for emulsified grease to leak out of bearings onto a surface such as a conveyor belt.) A product recall is potentially more costly than any other lubricant- related problem.
Food solutions
Despite the many challenges of maintaining the performance of rotating equipment in food production, there are two main solutions. One is to choose the correct bearings; the other is to select the right lubricant.
As previously explained, lubricants should be food-grade – known as H1 lubricants. A wide variety of these are tailored for different types of food processing machinery. SKF LGFQ 2 grease, for instance, is suitable for applications under high loads, wet environments and fluctuating temperature – such as pellet presses or mixers. SKF LGED 2 is suitable for high temperatures such as baking ovens, while SKF LFFM 1000 is formulated for use in applications such as conveyor chains.
Overcoming problems However, there are other solutions – such as by careful selection of a particular bearing, which might be pre-lubricated, sealed or rely on ‘dry’ lubrication. Some industries – such as poultry production – require a washdown every shift, which can force water, detergents and other contaminants into seals, causing early failure. This led to one poultry processer replacing hundreds of nickel-plated cast iron bearings every few months.
To overcome this, it fitted Food-Line Y-bearings with composite housings, stainless steel bearing inserts and a special multi-lip seal that prevented grease displacement and water ingress. The result was a fourfold increase in bearing service life – and a huge reduction in the cost of re-lubrication.
Bearings can also be run without traditional lubricant. 18 LUBE MAGAZINE NO.167 FEBRUARY 2022
Using graphite cages creates a thin layer on metal surfaces – which lubricates bearings without the need for grease. This has been put into action in a number of applications, including baked goods. Here, the bearings in ovens typically need to be re-lubricated every 16 weeks. However, using ‘dry’ lubricant overcomes this – which helps to reduce the amount of maintenance needed – and downtime.
Solid answer
Another baking industry application – the proving oven – has also benefited from ‘grease free’ bearings. Proving ovens are held at 40-45°C when yeasting bread – which is done in high humidity. This can create a ‘rain-like’ atmosphere, causing moisture to find its way into bearings that rotate conveyor chains – and corrode them. This can be resolved using specified bearings with Solid Oil Lubrication Technology. Here, an oil-saturated polymer virtually fills all the free space within the bearing while still allowing it to rotate freely.
This design creates a strong barrier against the moisture. Because the polymer material has millions of micro-pores, it holds the lubricating oil in place using surface tension. In operation, the oil seeps through the pores and into the gaps between the bearing components. With no traditional grease, there is nothing to emulsify and leak out into the oven. This helps bakers and other manufacturers operating high-humidity applications to increase uptime and eliminate unplanned production stops.
In this example, the conveyor chain was originally prone to constant bearing failures – at one point requiring a 35-hour stoppage to replace around 800-plus bearings. In the case of an unexpected failure, a delay of more than five minutes meant that all dough and loaves in the prover had to be scrapped. Since
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