Bearings used within the food industry have to withstand processes that can result in corrosion, damage and failure. But with tests providing Molded-Oil bearings from NSK have a long service life in applications exposed to water, companies in a range of industries are also turning to the components.
At one food production company, the deep-groove ball bearings on a conveyor line were failing repeatedly due to regular pressure washdown, which was damaging the bearings’ seals and washing out the lubricant. This was consequently causing corrosion and damage to the rolling surfaces. To overcome this, NSK supplied its Molded-Oil bearings to the company.
With Molded-Oil bearings, the lubricant is incorporated into a carrier made from polyolefin resin which prevents it from being washed out and guarantees long-term lubrication because the carrier gradually releases the lubricant.
Following the introduction of the new bearings, downtime was dramatically reduced on the conveyor system. The bearings on the second line were then also changed. Since then, the user has been saving some €70,000 a year in costs associated with production downtime.
A confectionery manufacturer had a similar experience, with process water penetrating the bearings and forming sugar crystals inside. Under an initial trial with Molded-Oil bearings, there were no failures in 18 months. Following this, all the bearings in the conveyor machinery were replaced. The user now saves some €157,000 in bearing, maintenance and downtime costs every year.
The bearings, however, have another advantage, which is highly valued in food production and other applications where hygiene is crucial. As the lubricant is embedded in the carrier and is only released slowly, the risk of leakage and product contamination caused by bearings is minimised. The bearings also have low torque.
Preventing failure
According to the company, tests show that conventional grease-lubricated bearings in applications with water exposure – e.g. in cleaning machinery – achieve a service life of approximately 500 hours. By contrast, Molded-Oil bearings were found to have an average life of 1,400 hours. Comparative tests focusing on the extreme scenario of underwater use reached similar findings. Conventional bearings managed to run for approximately 500 hours before failing; Molded-Oil bearings lasted for some 1,200 hours.
NSK offers various types of bearings with Molded-Oil technology: deep-groove ball bearings, tapered roller bearings and spherical roller bearings. The range of deep-groove ball bearings also includes a series made from stainless steel. Corrosion-resistant Molded-Oil mounted units are also available. USDA H1-approved lubricants can be supplied for applications in the food industry. The company has also launched a separate product line for high-speed applications which uses a different type of polyolefin and lubricant to the conventional Molded-Oil bearings.
But, Molded-Oil bearings also offer benefits to applications outside the food industry. For example, the deep-groove ball bearings in a cutting and conveying machine in the paper processing industry had an average service life of just one week due to the environment allowing dust from both paper and non-woven fabrics to enter the bearings and mix with the lubricant. A year after switching to Molded-Oil bearings, the plant still had not experienced any downtime.
The bearings used for a conveyor system in material handling were different yet again. In this case, the bearings failed frequently and were difficult to replace because they were located 5m above the ground. Specialists from NSK analysed the operating conditions and identified that the downtime was caused by water penetrating the components in conjunction with abrasive particles. Since switching to Molded-Oil bearings, these have already lasted nine times as long as they used to.
In another application, a manufacturer of handbags frequently experienced downtime on some 40 machines used to dye the sides of shoulder straps. In some cases, the bearings in the conveyor and coating machines only lasted six weeks, with downtime generating costs of €624,000 a year. The failures were caused by dye penetrating the bearings virtually unhindered. The introduction of Molded Oil bearings enabled the manufacturer to make considerable savings.
According to the company, replacing conventional bearings with Molded-Oil technology is relatively inexpensive and often results in substantial savings.
NSK
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