The mounting of bearings is a practice that requires the correct knowledge and skills. Historically, this task has seen maintenance personnel make a certain amount of mistakes, which consequently have reduced the lifespan of bearings.
Further factors compromising service life include a failure to keep the bearings clean, not respecting the recommended clearances between the bearing rings and the shaft, and failing to use professional mounting tools. According to global bearing manufacturer NSK, these errors can easily be avoided. Up to 20% of all bearing issues originate from faulty mounting, and this type of problem can lead to the stoppage of whole systems or production lines. This is reason enough to take extra care when mounting bearings.
For those concerned about this issue or simply keen to learn more, bearing users can get support from NSK. For example, NSK offers training that focuses specifically on the correct mounting and dismounting of bearings. Moreover, training can be held at the user's site or in cooperation with sales partners.
In addition to the training provision, as part of its AIP+ (Added Value Programme) service package, NSK offers tools for mounting bearings in a professional manner. These special tools are needed to apply the correct force necessary to press the bearing ring into place. In the case of cold mounting, it is important to ensure that mounting forces are never transferred through the rolling elements of the bearing, otherwise damage may occur, not just to the rolling elements, but also the raceways.
Even when performing hot mounting with hydraulic tools and induction heaters, damage can still occur to the bearings if the selected tools are not suitable for the application or used incorrectly. Such a scenario can lead to dents in the raceways, deformed seals, damage to adjacent components and even cracks in the bearing rings.
Another service offered by NSK is on-site failure analysis, to examine cases of bearing damage. These investigations conclude with recommendations on whether to use bearings from a different series or optimise the environmental conditions.
A case in point can be seen at a major car manufacturer that began witnessing a rise in bearing temperature on two exhaust ventilation rigs. With bearing failures occurring approximately every six months, NSK was invited to find a solution. A comprehensive application review performed by expert NSK engineers revealed that the temperature increase was caused by excessive preload applied to the bearings, as well as high external summer temperatures. Another probable reason was that the confined space made it difficult to mount the bearings correctly on the ventilation axle.
In the first instance, NSK recommended a change to the company’s Spherical Roller Bearings, which are not only the highest load-rating bearings of their type, but offer temperature stability up to 200°C. The bearings also compensate for misalignment and can tolerate mounting inaccuracies. Along with the change of bearing, NSK proposed training at the customer’s site on the professional mounting and dismounting of bearings for relevant maintenance staff.
After the new bearings had been correctly installed and adjusted under the supervision of NSK’s engineering team, the rise in temperature reduced. With no bearing failures reported for more than 12 months, annual savings in reduced downtime and bearing mounting/dismounting costs amount to €15,000.
This example illustrates the impact of correct mounting on a bearing's lifespan and how easy it can be for maintenance personnel to prolong service life.