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 OPTIMISING BEARING MAINTENANCE COSTS START WITH DESIGN…says Adrian Menzies, Sales & Marketing Director of UK Split Roller bearing manufacturer, Revolvo Ltd.

High maintenance costs and poor reliability are often the result of improper selection and sizing of rolling bearings. When most engineering designers embark upon the task of specifying rolling bearings the chances are that they will not start with a clean piece of paper. In fact, in most cases, their selection will be based on what has gone before: the references provided by successful applications in pumps, transmissions, motors, and conveyors etc being too strong to ignore. Any variances from the established application norm will usually be of a peripheral nature, typically concerning sealing and lubricant selection.

However, what might be the best choice for the machine designer may not necessarily be the best for the end user. The requirement for the OEM is to achieve the lowest installed cost for new equipment, and that of the end user, improved reliability and longer operating life. The OEM is all too aware that a quoting a high price can cost him a contract; yet, as many bitter experiences reveal, things tend to go wrong sooner or later with equipment that is built down to a cost. Unfortunately, despite the many lessons, the cost down philosophy still appears to permeate all levels of industrial supply. In today’s highly competitive global economy, with Downtime a key production indicator (KPI) this is clearly not a strategy for ensuring optimum asset utilisation.

For rolling bearings, which are a key component in all rotating machines, the solution to avoid production interruptions and downtime is to ensure that the right bearings are specified at the design stage, even if this means that the bearings selected cost more initially. In fact, what is becoming increasingly obvious is that the decision to specify any critical bearing solution should always be taken after analysis of the total lifetime cost / benefit issues, and not merely on the basis of the initial purchase price.

This argument is particularly relevant in the debate between specifying solid or split bearings. Solid mounted roller bearings cost much less than equivalent sized split roller bearings, yet they can take up to 90% more time to install or replace. In addition, the SRB split roller bearing’s totally split to the shaft feature enables inspection of the bearing at any time, which is crucial to any planned maintenance schedule.    
                                                    
The question is: do the lifetime benefits of the split bearing outweigh the initial cost advantages of the solid bearing? Experience and many successful examples indicate that the answer to this question is a resounding “yes”. Examples in support of this are many, but one in particular recent example reveals the scale of savings that can be achieved by proper bearing selection at the design stage.

The purchase price of solid bearings used for a cement plant application were £500 each, while the SRB split bearing equivalent was £1500 per unit. However, this differential proved insignificant in view of the potential £10000 per hour cost of lost production when plant was stopped because of bearing failure. The solid bearings were taking ten hours to replace in each outage, and required three men to replace each bearing at a cost of £25 per man, per hour. In contrast, the SRB split bearing could be replaced in just two-hours with a single maintenance fitter. By multiplying the figures together for each respective bearing type and adding the initial bearing cost, the total cost for an unplanned outage in respect of the solid bearings was £101,250; consisting of £500 for the bearing, £750 for labour, and £100,000 in lost production. The corresponding figure for the SRB split bearing was £21,550; consisting of £1500 for the bearing, £50 labour and £20,000 lost production. Simply by subtracting the total figure for the split bearing from that of the solid bearing reveals overall savings in lost production amounting to £79,700, simply by switching to a SRB split roller bearing. 

What this real world example reveals that once the costs of lost production and the additional labour to replace failed bearings are considered, then the initial cost advantage in favour of solid bearings is reversed, with total overall costs of the SRB split bearing being only 20% of the solid bearing’s total costs.

In addition to being more cost effective over the longer term another reason to specify SRB split bearings at the design stage of a project is their whole life performance. In this area SRB split bearings have inherent advantages over traditional solid bearings due to the design of their sealing system. With SRB split bearings, the spherical location between the bearing housing and pedestal support ensures that whatever type of seal is used, under conditions of shaft misalignment the seal will always remain concentric to the shaft. 
                                                                                                            
As a result, SRB split roller bearings perform exceptionally well in harsh operating conditions even with shaft misalignment, whereas solid mounted roller bearings can suffer from non-concentric ineffective seals that will rapidly lead to expensive premature bearing failure.

Revolvo’s SRB split roller bearings can have a longer life span because they cannot be cross-located. Moreover, the design of the SRB split bearing allows the shaft to be supported by the lower section of the bearing, while the upper section can be removed without disturbing or lifting the shaft, making bearing inspection and servicing very simple. This intrinsic feature is extremely valuable, especially in regard to large machines, where sheer size & weight can be a barrier to fast and effective servicing. Bearing replacement is much faster, which can save continuous-type businesses a lot of money in costly downtime.

About Revolvo Ltd
A member of the ERIKS WYKO Group of companies, Revolvo manufactures solid and SRB split roller bearings in sizes from 25 mm bore to 1500 mm external diameter, plus imperial equivalents. In addition, the company also manufactures special custom designed and difficult to source sizes of inch and metric solid ball & roller bearings. All Revolvo bearings are produced to DIN PO/ABEC 1 standards, with up to P5 available on request.

                                                  ……….ENDS……….

For reader enquiries contact: Ravinder Singh, Revolvo Ltd, Unit 4 Yorks Park, Blowers Green Road, Dudley, West Midlands. DY2 8UL. Tel: 01384 245370 Fax: 01384 245371. Email: ravinder.singh@revolvo.com  Web. www.revolvo.com

For editorial enquiries contact:  Brett Davies, DMA Europa. 2nd Floor, Snuff Mill Warehouse, Park Lane, Bewdley, Worcestershire, DY12 2EL. Tel: 01299 405454.  Fax:  01299 403092.  Email:  Admin@dmaeuropa.com
 

 


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