Key points
Properly functioning bearings are key to ensuring the efficient running of plant machinery. But without appropriate maintenance they can also be one of the main causes of equipment malfunction and unscheduled downtime.
Joshua Banks, of AESSEAL, explains how a proactive approach to bearing care can improve reliability and avoid unnecessary costs.
Bearings play a critical role in optimising the speed and efficiency of machinery, facilitating rotational or linear movement, minimising friction, and acting as a support for moving parts.
Therefore, it stands to reason that they can have an equally critical impact if they do not function properly. In fact, they have the potential to cause catastrophe if they fail.
At best, poorly functioning bearings require excessive maintenance time and regular replacement; at worst they can lead to unscheduled downtime and wasted product.
With bearing failure accounting for roughly 40% of all rotating equipment failures, it clearly pays to take care of these small but highly significant components.
Key causes of bearing failure
Around three quarters of all bearing failures are caused by inadequate lubrication, particle contamination, or misalignment. Yet all three of these issues can be dealt with simply and cost-efficiently if sealing solutions are considered with care and a proactive approach to condition based maintenance is taken.
Lubrication for bearing longevity
Poor lubrication is often at the root of bearing problems.
Typical errors include using the wrong type or amount of grease or oil, for example where ‘blue’ grease (regular load) is applied where ‘red’ grease (for higher operating temperatures) is required; using contaminated lubricant; applying it badly; storing it badly – or any combination of these.
Inadequate lubrication inevitably leads to the friction, overheating and wear which accounts for a significant proportion of bearing failures. Failing to address this most basic of maintenance procedures can incur high costs if a broken bearing brings the production process to a halt.
The condition of oil can be an important indication of the equipment being lubricated, therefore routine testing and analysis should be embedded in any condition based maintenance (CBM) programme.
Lip seals V bearing protectors
While many variations of lip seal are now available, all share a common weak link. They start to deteriorate almost immediately following installation due to contact with the rotating shaft, allowing contaminating particles of dust and moisture to leak into the bearings chamber, leading to bearing failure.
Research indicates that water contamination as low as 0.002% – equivalent to a single drop of water in a typical bearings chamber – can reduce bearing life in some oils by as much as 48%. Similarly, an oil-lubricated 45 mm radial bearing running at constant load and speed under ultra-clean conditions (nc = 1), has been calculated to complete 15,250 operating hours. Introduce contaminated conditions where nc = 0.02 and its operational life plummets to just 287 hours – a dramatic decrease in mean time between failure (MTBF).
One solution is to replace lip seals with non-contacting bearing protectors. This sealing solution uses the centrifugal force of the rotating equipment to open a temporary micro gap, which immediately closes when the equipment stops rotating, forming a perfect seal against potential contaminants.
The typical lifespan of most lip seals – under optimal operating conditions, which rarely occurs – is 1,000 to 3,000 hours, which equates to just two to five months of continuous operation. Increased maintenance time and reduced production time can be added to the cost of regular replacement of both seals and bearings.
By comparison, bearing protectors require minimal maintenance and will last until the bearings reach the end of their natural lifespan. Additionally, they can be retrofitted onto pump shafts and repaired in-situ.
Take these costs into consideration and the lower initial cost of a lip seal soon becomes irrelevant.
Technology for proactive maintenance
An advanced cloud based CM system safely collects and stores a wide range of data, including vibration readings and oil analysis, on one platform, which can be accessed by a standard web browser from any location. It not only provides 360° insight into an asset’s condition in real time, it also raises alerts about impending issues.
Where bearing care is concerned, this can help companies make the important shift from ‘run to failure’ to a truly proactive maintenance programme.
Conclusion
There is no reason why bearings should not last for their full predicted lifespan of more than 15,250 operational hours. And with wireless technology and sensors becoming more affordable even as the technology gets more advanced, it has never been timelier to consider a proactive, digital approach to a condition based maintenance programme.
