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United Utilities’ Water Treatment Plant at Widnes is set to save many thousands of pounds in ongoing maintenance costs as a result of replacing solid bearings with SRB split roller bearings from Revolvo. The SRB split bearings 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.
United Utilities operates electricity, wastewater and water networks throughout North West England. Several of the company’s wastewater sites incorporate orbital aeration tanks as part of the sewage treatment process. Each of these tanks has a number of horizontal rotors which agitate the sewage and introduce oxygen, thereby accelerating the treatment process. In the past, the rotors have always been supported by two solid bearings with internal seals. However, this arrangement has not proved ideal over the long term. During periods of heavy rain it is possible for the sludge level in the aerator tanks to rise to the point where the bearing units become temporarily submerged, compromising the bearing seals and leading to premature bearing failure.
Replacement then presents its own set of problems. In order to change out the solid bearings, each rotor must be lifted clear of the tank. Furthermore, depending on the level of corrosion, the rotor may then have to be completely removed for workshop based remedial work. In either case, the most substantial part of the cost is crane hire, which can be in excess of £2500 per day.
In an effort to eliminate these costs, Revolvo was called in. The company undertook a full evaluation of the existing application conditions and proposed a solution based upon its SRB range of split roller bearings. The split bearing units were specified with housings and supports designed to be interchangeable with the existing bearing units wherever possible, or incorporate adaptor plates if necessary.
In addition, the housings were equipped with high performance split rubber lip seals with garter springs and retaining plates, to guard against water ingress during intermittent submersion. As a result of the SRB split bearing units self aligning properties, these seals are always concentric with the shaft, maximising seal efficiency.
The use of SRB units also represents large future cost savings for United Utilities, as a result of SRB’s totally split design. 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.
An initial trial of four SRB units was undertaken at United Utilities’ Hale Bank Works near Warrington. During the trial period, which was undertaken throughout the winter months, and contained several periods of heavy rainfall, the units were subjected to a number of high water level situations. Despite this, the bearings have performed to expectations and continue to run smoothly.
Following the successful outcome of the Hale Bank trial, United Utilities is now in the process of evaluating the logistics and cost savings involved in replacing other existing solid bearing units on this type of application with the Revolvo design of SRB split roller bearings.
About SRB Bearings
Unlike solid bearings, SRB split bearings are totally split to the shaft, a design that both simplifies and expedites installation and cuts downtime to approximately 10% of that required to replace solid bearings of a similar size. In addition, Revolvo SRB bearings can have a longer life span because they cannot be cross- located. They also provide superior sealing arrangements, which means longer bearing life with greatly reduced levels of maintenance.                
A further advantage is that the design of Revolvo’s SRB split bearing allows the upper half of the cartridge housing and outer bearing raceway to be removed, whilst the shaft is still supported by the lower section of the housing and bearing; this feature enables inspection of the raceways, cage and rollers to be undertaken with the bearing and shaft in situ, which would be impossible with a conventional solid roller bearing.
This feature is extremely valuable, generally, but especially regarding large machines, where sheer weight and size can be a barrier to fast and effective servicing. It also allows for faster bearing replacement, which can save continuous-type businesses a lot of money in costly downtime.
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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