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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 were 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 a point where the bearing units become temporarily submerged, compromising the bearing seals and leading to premature bearing failure.
Costly crane hire
Replacement then presents its own set of problems. In order to change the solid bearings, each rotor must be lifted clear of the tank. 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 €3500 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 were 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 a point where the bearing units become temporarily submerged, compromising the bearing seals and leading to premature bearing failure. Costly crane hire Replacement then presents its own set of problems. In order to change the solid bearings, each rotor must be lifted clear of the tank. 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 €3500 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 with 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. Thanks to 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, because of the totally split design of these bearings. Should the future need arise to change a 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.
Successful trial
An initial trial of four SRB units was undertaken at United Utilities’ Hale Bank Works near Warrington. During the trial period, which took place 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.
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 with 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. Thanks to 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, because of the totally split design of these bearings. Should the future need arise to change a 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. Successful trial An initial trial of four SRB units was undertaken at United Utilities’ Hale Bank Works near Warrington. During the trial period, which took place 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.
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