Revolvo Bearings For Commercial Marine Vessels
Typically, fitting an SRB takes about an eighth of time that it takes to fit an equivalent solid bearing. In addition, the bearing can be inspected in situ without any major disassembly. The SRBs are claimed to feature effective sealing arrangements. The design of Revolvo SRBs allows the shaft to be supported by the lower section of the bearing, while the upper sections of housing and outer raceway can be removed without any necessity to dismantle drives or remove the shaft itself.
This intrinsic feature is said to be especially useful for large-diameter bearings, 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 applications such as marine propulsion systems a lot of money in costly downtime. SRB units are designed to be statically self-aligning; this means that there is no need to accurately realign the bearing housing to the shaft or any other inline equipment that might be involved in the installation. In addition, they are designed to accept up to 3deg of shaft misalignment.
In order to aid alignment during installation in marine propulsion applications, SRBs come with support pedestals that incorporate base jacking screws. Complementing this facility, SRBs use optimised profiled rolling elements to minimise damaging edge stresses that can occur under conditions of dynamic misalignment. These are able to displace slightly and thus prevent potential damage to the bearing raceway and rolling elements. For the user, this ability can mean the difference between premature failure and reliable long-term operation, according to Revolvo.
In addition to the optimised roller profile, another feature designed to extend the potential life of SRBs is their precision-machined brass cage. The cage has CNC-bored pockets that are optimised to deliver accurate roller guidance, thus preventing roller skewing - a condition that also leads to roller edge loading and reduced bearing life. In addition to providing excellent roller guidance, the SRB brass cage also allows operation at higher temperatures - all standard SRB units will operate at up to 140C and high-temperature S3 versions will operate at up to 300C.
Increased reliability at high operating speeds is another benefit of the SRB brass cage, compared with other manufacturers' designs that utilise steel or aluminium cage materials. Overall, brass is one of the best cage materials for rolling element split bearings as it absorbs lubricant and performs well in aggressive environments where lubrication is marginal. For marine industry propulsion shaft applications, where high levels of vibration are often a problem, SRB units feature a specialised vibration-resistant cage design to further enhance bearing life. The ability of SRBs to perform reliably in aggressive environments is enhanced by the performance of the sealing systems that protect the bearing units.
In this area, the SRB product has inherent advantages over traditional solid bearing seal designs. With SRB split bearings, the spherical location between the housing and the pedestal support ensures that, irrespective of shaft misalignment and whatever type of seal is used, seals always remain concentric to the shaft. As a result, SRBs perform well in harsh conditions, even under conditions of shaft misalignment, whereas solid mounted roller bearings can suffer from non-concentric ineffective seals that will lead to expensive premature bearing failure.
The second advantage provided by SRBs in the area of sealing systems is the number of options available: eight standard designs are stocked and offered, including Viton high-temperature seals, aluminium triple labyrinth seals for high speeds with high contamination and high-performance Kevlar packing seals for the aggressive environments encountered in quarries, mines and cement plants. The company can engineer and manufacture bespoke seal designs in short manufacturing lead times if a standard catalogue solution is unsuitable.
Revolvo manufactures its SRB housings and pedestal supports in tough 250-grade grey cast iron to ensure strength and durability. In addition, as part of its specialised service for the SRB range, the company also offers housings and pedestal supports in ductile iron, cast steel and corrosion-resistant stainless steel that is suitable for long-term operation submerged under water when fitted with Revolvo's specialised sealing arrangements, which are ideal for underwater applications including water treatment plants and amusement park rides.
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