Sealing solution helps

SRB split roller bearings have been implemented into the latest water treatment process they have been specified by Rotating Biological Contactor (RBC) manufacturer Ovivo (formerly EIMCO) after other bearings were shown to fail under the harsh conditions, sometimes after a matter of months.

The latest Rotating Biological Contactors are being used to remove soluble, biodegradable, organic materials from sewage far more efficiently. Sealed units with much larger surface areas and optimum rotational speeds are achieving great results but were requiring lengthy and frequent bearing changes due to the harsh internal conditions. RBCs are used as a secondary treatment after grit and other solubles have been removed; the machines consist of a series of parallel discs mounted on a rotating shaft. Microorganisms grow on the surface of the discs where biological degradation of the wastewater pollutants takes place.

Each RBC has up to 6 modules of 4-6 discs which rotate at 1-2 rpm to assure proper growth of biological film on the disc. When water levels rise it is common that the shaft and bearings become fully submerged by the effluent. This can lead to bearings failing after just a number of months if they are not adequately sealed, as the consistency of the sludge makes ingress into the bearing's components possible.

Ovivo (formerly EIMCO) is a manufacturer of RBCs as well as other rotating water treatment machines such as Aerators and Sludge Mixing Systems. Having experiences premature bearing failure a number of times with traditional bearings, Ovivo was looking for an alternative solution and turned to Revolvo.

Revolvo bearings are well proven in many water treatment applications; the sealing solution that they have developed has allowed SRB split roller bearings to operate in fully submerged conditions for over 5 years with no more maintenance than standard regreasing required.

Adrian Menzies, Revolvo's Sales and Marketing Director, comments: "Revolvo has a very successful history of installing bearings in applications where they will be submerged in sludge or effluent. Thanks to a very effective sealing system our bearings are capable of surviving far longer than traditional bearings with no more than basic maintenance required. Another advantage of the SRB split roller bearings is that when they do reach the end of their life they are very easy to replace."

From the technical, economic and pure design point of views, SRB split roller bearings offer a host of advantages and cut downtime significantly. The SRB bearing is completely split to the shaft, which allows for complete bearing removal and replacement by simply supporting the shaft, without the need to lift it, or obtain access to the shaft ends. This intrinsic feature is extremely valuable, generally, but especially regarding large machines, where sheer weight and size can be a barrier to fast and effective servicing.

In addition to offering overall cost advantages, another major reason for replacing solid bearings with SRB split bearings is the effectiveness of the sealing systems available. Where solid mounted roller bearings can suffer from non-concentric, ineffective seals that will rapidly lead to expensive premature bearing failure, SRBs have a spherical location between the housing and pedestal support. This ensures that under conditions of shaft misalignment the bearing will always remain concentric to the shaft. As a result Revolvo is able to ensure that its seals won't fail; making SRB split roller bearings ideal for the harsh operating conditions found in RBCs.