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Proof positive: improving bearing life in bakeries

19 July 2021

The high humidity in proving ovens can play havoc with bearings. Food Processing finds out how the use of solid oil lubrication can lead to longer bearing lifetimes in such arduous applications. 

Most bread is now produced in large-scale bakeries which, according to the Federation of Bakers, account for about 85% of volume.

These large plant bakeries are under pressure to deliver but there are some process challenges. The proving oven, for example, is critical to industrial baking. This is where dough is kept – at 40-45°C and high humidity. It helps the dough to rise before it is baked. However, moisture in the proving oven is so high that it can create a rain-like atmosphere – with water droplets covering almost every moving part.

The moisture can work its way into bearings, such as those used to rotate the conveyor chains in the proving oven.

The bearing grease absorbs the moisture and slowly emulsifies, which changes its consistency. The emulsified grease can then wash out of the bearing, which could lead to early failure through accelerated wear and corrosion.

This results in maintenance teams scrambling to solve the problem to prevent a shutdown. Unless bearings are changed regularly, this remains a risk.

Solid improvement
One way of keeping bearings operational without swapping them out – which is costly and time consuming – is to use an oil-saturated polymer, rather than traditional grease. This fills most of the free space within the bearing – while still allowing it to rotate freely. It creates a strong barrier against the high moisture levels in proving ovens.

The polymer material of SKF’s Solid Oil lubrication technology, for example, has millions of micro-pores, so can hold the lubricating oil in place using surface tension. During operation, the oil seeps through the pores into the gaps between bearing components, to provide sufficient lubrication. Because there is no traditional grease in the bearing, there is nothing to emulsify – or leak out – during prolonged use or routine washdowns.

This enables high-humidity applications, such as proving ovens, to be run with a lower risk of unplanned production shutdowns. This helps to reduce the need for maintenance, while raising productivity and efficiency.

At the same time, Solid Oil helps to improve safety for both production staff and customers. Leaking grease could fall onto the factory floor and become a slipping hazard to workers – but could also contaminate the product, with far-reaching consequences.

Better bread
SKF recently used this approach to help a bakery overcome failures in its proving oven conveyor.

Previously, the baker’s conveyor chain had been prone to bearing failure. This became so severe that the bakery had to stop production for a 35-hour stretch every year, to replace its 800-plus bearings. This was very expensive – and inconvenient – for a line that typically runs seven days a week. If an unexpected failure could not be fixed within five minutes, the production process had to be stopped – and all dough and loaves in the prover scrapped.

By installing SKF bearings with Solid Oil lubrication, the bakery has been able to avoid unplanned stoppages which has saved over 300 hours of maintenance activity and £3,750 in yearly bearing costs. It has also eliminated the cost of scrapping dough.

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