Split bearings prevent ship layovers

The design of Revolvo’s split roller bearings (SRB) is claimed to allow simpler and quicker installation, up to eight times faster than with solid bearings. The company believes that easier replacement of bearing units used on propeller shafts should be of particular interest to operators of ferries, work boats, offshore support craft and other commercial vessels.

The bearings are said to be widely adopted in other industries, thanks to easier bearing fitting – typically fitting a split roller bearing takes only about one eighth 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 of the sealing arrangements.

A further advantage claimed for the Revolvo SRB bearings is that 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 necessity to dismantle drives or remove the shaft itself. This intrinsic feature is said to be particularly valuable for large diameter bearings, where weight and size can be a barrier to fast and effective servicing. It also allows for faster bearing replacement, which can save downtime.

SRB split roller bearings are designed to be statically self-aligning, avoiding the need to accurately realign the bearing housing to the shaft, as they are designed to accept up to 3° of shaft misalignment. To aid alignment during installation in marine propulsion applications, the company offers a range of support pedestals that incorporate base jacking screws.

The bearings use a machined brass cage with pockets to give accurate roller guidance, preventing skewing, allowing operation at temperatures up to 140 °C, with higher-temperature versions safe up to 300°C, and to increase reliability at high operating speeds. For marine propulsion applications, where high levels of vibration can occur, SRB offers a vibration-resistant cage.

Further advantages are claimed for the SRB seal design. The spherical location between the housing and pedestal support ensures that seals always remain concentric to the shaft. Eight standard designs are offered, including Viton high-temperature seals, aluminium triple labyrinth seals for high speeds with high contamination, and Kevlar packing seals for extremely aggressive environments. SRB can engineer bespoke seal designs in short lead-times, if a standard solution is unsuitable.

Housings and pedestal supports are manufactured in 250-grade grey cast iron to ensure maximum strength and durability, with alternatives available including ductile iron, cast steel and stainless steel.