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The continuous nature of water treatment processes, and the huge capacity of modern treatment plants, means that unplanned downtime is extremely expensive, and every effort has to be made to minimise it. This is against a background where planned maintenance windows are also becoming shorter and less frequent, and therefore more pressurised. Yet despite these operating conditions and pressures, one area that can bring real benefits in terms of reduced downtime – that of rolling bearings - is being largely ignored.
The major types of bearings used in water treatment applications today, are solid types. These are difficult to fit, impossible to inspect whilst in place - and even more difficult to replace when they fail. But because they are relatively cheap, no one questions that they may not provide the best solution in all applications. In an industry that is driven by cost - down pressures, this attitude is difficult to understand.
In other process industry sectors that live with similar cost-down pressures, companies are increasingly realising that to achieve performance gains and realise the full potential of their existing assets, they must achieve improved production efficiencies. However, to do this Downtime must be minimised, which in turn means a whole new approach of adopting components and equipment that might cost more initially, but are more cost effective over their lifetime.
This is particularly true of bearings, and is one of the major reasons why companies in all market sectors are increasingly turning to split roller bearings as a means of reducing downtime, even though these units can initially be substantially more expensive than their solid bearing equivalents. So why bear the additional cost?
The answer is threefold: easier bearing fitting – typically fitting a split roller bearing takes only 10% of the time taken to fit an equivalent solid bearing; the ability to inspect the bearing in situ without any major disassembly; and the ease and speed with which the bearing cartridges of split roller bearings can be replaced if there is a problem.                                                                      
From the technical, economic and pure design point of views, split roller bearings offer a host of advantages in addition to significantly cutting downtime. The simplicity of fitting a split roller bearing, compared to a solid bearing, is a major factor in its longevity. Unlike solid bearings, SRB split roller bearings are totally split to the shaft, a design that both simplifies and expedites installation and cuts installation downtime by up to 90%. There is no need to lift the shaft, or obtain access to the shaft ends, therefore expensive and awkward to handle lifting equipment is not required. This intrinsic feature is extremely valuable for all applications, and especially regarding large machines, where sheer size and weight can be a barrier to fast and effective servicing. It allows for much faster bearing replacement, which can save productivity focussed businesses a lot of money in costly downtime. Also, SRB split roller bearings can have a longer life span compared to conventional solid bearings, because they cannot be cross- located.
In addition to being easier to fit, inspect and maintain than solid bearings, Revolvo also provide superior sealing arrangements, which means longer bearing life with greatly reduced levels of maintenance, especially important for water treatment applications. SRB split bearings are available with seal designs that allows them to operate completely submerged, totally excluding water and contaminants from the bearing housing. This is achieved via an arrangement of two lip seals with garter springs, and centralised positive grease feed. The positive action of the grease purge between the two seals combined with the sealing efficiency offers consistent reliable long-term operation.
The example in Table 1 illustrates the savings in Downtime that can be accrued using SRB split bearings. The data is taken from an actual example, where solid bearings were replaced with SRB splits due to the costs that were being incurred as a result of extended times for bearing installation and replacement. As the table shows, the initial purchase cost for the SRB split far outweigh those of the solid bearing. However when the total replacement costs are considered, including labour and production losses, the position is reversed with the total overall cost for the SRB split bearing being 80% lower than that of the solid bearing.                                                                                                                              
The above example is supported by the recent installation of Revolvo SRB Bearings at United Utilities’ Hale Bank Works near Warrington. This water treatment plant is set to save many thousands of pounds in ongoing maintenance costs as a result of replacing solid bearings, which were failing prematurely due to becoming submerged, with SRB split bearings. These allow easy maintenance without having to remove the shafts of long horizontal rotors that agitate sewage and introduce oxygen to the treatment process. Previously a crane with an 80ft reach was required to completely remove the solid support bearings, at a cost in excess of £2500 per day. However,
should the future need arise to change a SRB split bearing, it will only be necessary to support the rotor shaft, eliminating the necessity and cost of crane hire. This in itself will easily recover the investment of using the SRB split bearing units.
A UK company, Revolvo designs and manufactures its own range of SRB split bearings, large sizes of solid ball & roller bearings, and bearings for specialised applications. With its many new design features, Revolvo’s range of SRB split roller bearings meets and surpasses all the demands of traditional users, and those of users in new industries. Manufactured in the West Midlands, in a plant that is benefiting from over £1.5 million of investment in new machinery, the SRB range is available in Light, Medium and Heavy series in sizes from 35mm to 600mm diameter, plus imperial equivalents, and larger non-catalogue sizes up to 1500 mm in outside diameter. It is fully interchangeable with competitive products on the market.
For reader enquiries contact: Adrian Menzies, Sales and Marketing Director, Revolvo Ltd, Queens Cross, Dudley, West Midlands. DY1 1QW. Tel: 01384 844000 Fax: 01384 – 844255. Web.
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:

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