Why bearings shouldn't cause paper mill downtime

Paper machines are one of the best examples of the need for optimised bearing solutions, based on the correct product for the given operating conditions.

All paper mills have a strong need for high efficiency levels.

After all, the machinery has extremely costly running rates and downtime is not a realistic option.

Efficiency directly relates to profitability, with quality and maintenance practices having a significant impact on both of these.

One of the most important elements of any rotating machinery is the bearings.

With the operating conditions that are found in most paper mills, these essential components are at the heart of machine efficiency.

SKF research shows that 36% of bearing failures are caused by inadequate lubrication.

Other reasons for failure include the 34% caused by fatigue (due to overload, excessive vibrations, use of the wrong bearing design and other factors such as out of balance, looseness and misalignment) and the 16% of bearings that fail due to poor installation and mounting.

Paper machines are one of the best examples of the need for optimised bearing solutions, based on the correct product for the given operating conditions.

Bearings are exposed to conditions that can punish poor product selection or installation.

However, correctly specified and installed bearings with an appropriate condition monitoring regime can provide valuable data on machine performance and allow predictive maintenance for the entire machine.

For new machinery and replacement parts, correct bearing selection is clearly critical.

However, this decision is not always that simple and expert knowledge can be required.

This is why SKF is happy to offer advice to its customers at an early stage of machine design or refurbishment.

Having selected the bearing, it must be installed correctly and this is another area where detailed advice and expertise from your bearing supplier is important.

The average operating speeds and productivity levels of many paper machines have increased considerably over recent years.

This has resulted in the need for more tightly toleranced roller bearings with higher running accuracy.

Accordingly, SKF has designed a high precision spherical roller bearing (indicated by the suffix VQ424) specifically for these operating demands.

Similarly, SKF has developed a special diamond like carbon coating called "NoWear" that is applied using physical vapour deposition to fully control the coating thickness and integrity.

The result is a much harder bearing surface that has a significantly lower coefficient of friction and which can significantly extend bearing life under zero and low load conditions.

Another development that can provide real benefits in paper machine applications is SKF's toroidal roller bearing CARB which can be used in the non-locating position on the self-aligning shafts found in drying cylinders and other applications.

This design accommodates axial expansion within the bearing itself at the same time as it allows misalignment.

In many cases, high vibration levels and elevated temperatures can be avoided leading to longer bearing service life.

Unplanned downtime is not acceptable to mill operators and needs to be minimised.

This can be achieved by good bearing selection and design as well as lubrication and thorough maintenance regimes.

SKF for example has developed a complete range of condition monitoring products and services to allow better prediction of service intervals and, experience has shown that, the bearings can sometimes reveal a lot about the performance of the entire machine.

The company also provides additional services such as lubricant analysis to help operators achieve the maximum life and performance form their bearings.

In conclusion, by bringing together the right combination of products, installation, condition monitoring and a good service concept, there is no reason why the bearings should be a cause of downtime in a paper mill.

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