Split Bearings Prevent Ship Layovers

The unique design of Revolvo’s split roller bearings can prevent unplanned layovers resulting from bearing failures on the shaft propulsion systems of marine vessels. Totally split to the shaft, SRB units allow simpler and quicker installation up to eight times faster than solid bearings. Easier replacement of bearing units used on the propeller shafts should be of particular interest to operators of ferries, work boats, offshore support craft and other commercial marine vessels.

Revolvo SRB is the bearing of choice in all arduous operating sectors: water treatment, oil and gas, mineral extraction, power generation, steel manufacture and marine. The reasons for this wide adoption are three-fold: easier bearing fitting – typically fitting a split roller bearing takes only about 1/8 of the time taken to fit an equivalent solid bearing; the ability to inspect the bearing in situ without any major disassembly; and the effectiveness if their sealing arrangements.

A further advantage is that the design of Revolvo SRB bearings 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 extremely valuable, generally, but especially in regard to 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 like Marine propulsion systems a lot of money in costly downtime.

SRB split roller bearings 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 in-line equipment, which might be involved in the installation, and they are designed to accept up to 3 degrees of shaft misalignment. In order to aid alignment during installation in marine propulsion applications, SRB offer a range of support pedestals that incorporate base jacking screws.

Complementing this facility, SRB split bearings use optimised profiled rolling elements to minimise damaging edge stresses that can occur under conditions of dynamic misalignment. These are able displace slightly, and so prevent potential damage to the bearing raceway & rolling elements. For the user this ability can mean all the difference between premature failure and reliable long-term operation.

In addition to the optimised roller profile, another key factor designed to extend the potential life of SRB split bearings is their unique precision machined brass cage. This has CNC bored pockets that are optimised to give very accurate roller guidance, 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 split bearings will operate up to 140oC, and high temperature S3 versions up to 300°C. Increased reliability at high operating speeds is another benefit of the SRB brass cage, compared to other manufacturer’s 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 offers a specialised vibration-resistant cage design to further enhance reliable bearing life.

The ability of SRB split roller bearings to perform reliably in aggressive environments is enhanced by the performance of their sealing systems protecting 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 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, SRB split roller bearings perform exceptionally well in harsh operating conditions even under conditions of shaft misalignment, whereas solid mounted roller bearings can suffer from non-concentric ineffective seals that will rapidly lead to expensive premature bearing failure.

The second major advantage provided by SRB in the area of sealing systems is the number of options available: eight standard designs are stocked & offered, including Viton high-temperature seals, aluminium triple labyrinth seals for high speeds with high contamination, and high- performance Kevlar packing seals for extremely aggressive environments encountered in quarries, mines and cement plants.

Also adding to the versatility of the SRB split bearing range is SRB’s ability to 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 maximum strength and durability of the product. 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 totally submerged under water when fitted with Revolvo’s specialised sealing arrangements, which are well proven in underwater applications as diverse as water treatment plants and amusement park rides.