BEARINGS, SEALS & GASKETS FEATURE
Fear of failure: How to overcome bearing mounting problems
There are multiple factors behind the correct mounting of bearings, as SKF explains
M
any engineers fear bearing failure, and there is both good and bad
news here. The good news is that only 0.5% of bearings fail in service; but the bad news is that this equates to around 50 million bearings per year worldwide. One-sixth of these failures – more than eight million – are caused by poor mounting procedures such as installation and remounting. Part of the problem is that there are
so many different types and sizes of bearing. Each must be fitted correctly, which may require specialist tools and techniques. Helping staff to improve their mounting skills can extend bearing lifespan and lengthen service intervals on critical machinery. This, in turn, can raise both productivity and efficiency.
CORRECT BEHAVIOUR Correctly mounting and replacing a bearing requires a technician to identify the exact bearing needed for an application and understand its mounting specification requirements. Failure to do this means the bearing will not function correctly, leading to damage and premature failure. Technicians must assess multiple factors, including bearing type and size, and mounting technique. There are many different bearing
types, including multiple variants of roller bearing. The most appropriate installation method depends on a variety of factors, such as whether the bearing has a cylindrical or tapered seating. Different bearing types also benefit from different mounting techniques. Bearings can be heated – expanding to fit into place more easily – or are installed ‘cold’. They can also be installed using techniques such as oil injection. In each case, the method must be matched to the bearing. Dismounting can also lead to bearing
failure. This is why a good bearing should not be dismounted unless absolutely necessary. If it must be done – and a bearing is to be re-mounted – a few procedures should be followed. The main rule is to remove gently. Do not hit bearing rings or any other part directly.
Also, do not allow the dismounting force to be transmitted through the rolling elements. In addition, it is critical not to heat the bearing with an open flame, and to use a heating ring instead.
BEARING PROBLEMS Bearings typically start showing problems by running with too much noise or vibration, or at high temperature. This can be caused by a range of factors, including incorrect mounting. If problems are not addressed, they can cause long-term damage. A common cause of early fatigue failure
is impact damage – which can happen during handling, mounting, storage or operation. Because the impact is higher than the material strength, this leads to plastic deformation – which results in premature bearing failure. For instance, applying the mounting
force to the wrong ring can cause the force to be passed through the rolling elements. This can also happen if the bearing is put under an abnormal loading when not running. Because the impact load is axial, dents will be seen in the rings – axially displaced from the centre. The distance between dents is equal to the rolling element spacing. Cylindrical roller bearings can easily be
damaged during assembly. If the shaft is askew during assembly, and not rotated, rollers can scratch the raceway of the inner ring. This can be overcome by correctly lubricating all components and the inner ring when mounting. Also, contaminants in the bearing or
housing can cause early fatigue. These can be introduced during mounting or may be left over from a previous bearing failure.
HELP IS AT HAND With so many factors affecting correct mounting, a tool such as SKF’s Bearing Assist app is particularly useful. Bearing Assist is a phone app that simplifies the task of mounting and replacing bearings. This was developed with feedback
from customers and provides detailed instructions for mounting many different
/ DESIGNSOLUTIONS
Correctly mounting and replacing a bearing requires a technician to identify the exact bearing needed for an application and understand its mounting specification requirement
SKF bearings. It is suitable for use by all levels of technician. Technicians can record the work they have carried out to improve the way that bearing knowledge is shared across an organisation. Bearing Assist contains detailed product
information, including bearing designation and type (including a photograph) and suffix descriptions, as well as dimensions and an illustration. It also has mounting instructions, covering bearings with basic design that are included in the standard assortment. Information such as clearance reduction and drive-up method calculations – and lubrication recommendations – can save time and effort when fitting new bearings. Once a bearing has been mounted, this
can be recorded on the app, with details including date, specific asset, location and work order. Results can be exported as a PDF, which cuts the time needed to produce a mounting report. Recording details so efficiently helps to improve maintenance collaboration – which in turn improves maintenance planning and ultimately raises asset reliability. There are multiple factors behind the
correct selection and mounting of a bearing. An app like Bearing Assist helps technicians to perform this vital task as quickly and accurately as possible.
SKF (UK)
www.skf.co.uk
DESIGN SOLUTIONS | DECEMBER/JANUARY 2021 31
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