The problem became apparent shortly after the sorting system was installed: after just three months of operation, five bearing failures had already occurred. As these failures led to costly repairs and unplanned downtime, the operator was looking for a solution and asked NSK for an analysis.

As part of the AIP program ("Added Value Programme"), an NSK application engineer inspected the system on site and determined that vibrations and a lack of lubrication were causing the premature bearing failures. The vibrations were causing the grub screws to loosen. This caused the bearing inner ring to rotate on the shaft. The expert also found that the bearing did not provide an outlet for excess grease. This led to increased grease accumulation and excessive heat generation in the bearing.

Based on these findings, NSK recommended replacing the bearings with NSKHPS ("High Performance Standard") spherical roller bearings, which are mounted with adapter sleeves in SNN bearing housings. The adapter sleeves secure the bearing so that it cannot come loose from the shaft even in the event of vibrations. The SNN bearing housings are also equipped with a grease outlet hole as standard. This prevents excess grease from accumulating in the bearing.

With the SNN series, NSK has bearing housings in its range that have been specially developed for use in unfavorable environmental conditions - for example in conveyor systems for the steel, recycling and mining industries. The well thought-out design of the housings includes solid corners in the lower part of the housing, which provide support for locating pins, and a center marking for easy alignment. The split housing makes it easy to replace bearings. Two lubrication holes are provided for relubrication.

The SNN bearing housings from NSK have been developed for use in harsh environmental conditions. © NSK

According to the manufacturer, further advantages of the SNN bearing housings made of precision casting include high rigidity, which prevents deformation of the seal, very good heat distribution and the choice of numerous seal variants. The housings can be used with either double-row self-aligning ball bearings or double-row spherical roller bearings - with shaft diameters from 20 to 140 millimetres.

The NSKHPS spherical roller bearings used in the sorting system are suitable for operation under high loads and at high speeds. They are available with steel and brass cages. The design features include an optimized running surface contour, special surface treatment and temperature stability up to 200 degrees Celsius. Due to these design features, NSKHPS bearings have a 25 percent higher dynamic load rating compared to conventional bearings. The limiting speed is increased by 20 percent and the service life is doubled.

By using these NSKHPS spherical roller bearings in combination with the SNN bearing housings, the user of the sorting system was able to reduce the number of unplanned downtimes from ten per year to zero. as