Bearings - 2016-08-23
This confectionary plant was experiencing repeated failures on its dip tank conveyor nose roller. After inviting NSK to assess this increasingly costly issue, a thorough investigation was commenced. The AIP team concluded that a combination of NSK’s DDU seal arrangement on its deep groove ball bearings and a redesign of the bearing configuration would help reduce production downtime significantly, while also reducing labour costs as well as bearing costs.
NSK’s AIP programme is supported by experts who use tried and tested methodology to develop the ideal solution for the customer’s specific application, working closely with client engineering and maintenance teams to take every detail into account.
Indicating the extent of the problem at the confectionary plant, maintenance engineers were changing bearings approximately every seven weeks, a process that involved extended unplanned machine downtime.
The cost of manpower and lost production time, along with the cost of the replacement bearing sets, was proving to be very costly and unsustainable.
In the first instance, NSK suggested changing to its own series of deep groove ball bearings. These bearings are ‘sealed for life’ (a closure is positioned on each side of the bearing) and feature a high-performance contact seal design. To enhance operating life by protecting against the ingress of dust and moisture contamination, the NSK DDU seal offers three sealing lips; one forms a contact with the side face of the inner ring groove, while the other two form tight, non-contact constrictions at either side of the contact sealing lip. Importantly, the axial sealing lip also means that grease leakage is reduced in comparison with standard seals, particularly in outer ring rotating applications.
Bearing lifetime is a critical factor in materials handling equipment because it is directly related to production uptime, a factor noted immediately by the NSK team. Part of the AIP promise is greater efficiency through recognising potential gains in profitability, optimising operations and maintenance, minimising unplanned machine and plant downtime, and reducing the costs associated with continuous production processes.
On the confectionary gum manufacturer’s conveyor nose roller, a further issue recognised by NSK was that the bearing configuration comprised three bearing units assembled together flush, one set either side of the roller. However, the bearings were not designed to operate in this type of arrangement as they did not share the load equally and were also affected by axial preload.
As a consequence, NSK proposed placing a spacer shim between each bearing, an established industry practice which permits two or more bearings to be flush-mounted that were not originally intended for this type of use. The solution provides the separation required and avoids axial preloading. In addition, it facilitates improved load-sharing duties during operation.
Based on NSK’s proposal of new bearing sets and spacer shims, a trial was conducted that resulted in an immediate improvement in conveyor uptime. Furthermore, roller service intervals could be extended to one year, thus reducing maintenance requirements. Based on reduced downtime and labour costs, as well as fewer replacement bearings, the total annual savings amount to €80,493.
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