Split roller bearings survive three years at 100degC

Installed more than three years ago, and operating in ambient temperatures constantly exceeding 100degC, Revolvo SRB split roller bearings have now been deemed to have 'successfully' replaced the original bronze-bush bearings on the drying cylinders at a paper mill operated by Lothlorien Pty Ltd – a leading South African manufacturer of tissue paper from recycled fibres.

Adrian Menzies, Revolvo's Sales & Marketing Director, puts the success down to the bearings being fundamentally fit-for-purpose in their ability to cope with demanding applications: "Part of the reason why SRB split roller bearings are operating successfully after three years in such a harsh operating environment is the fact that they are specifically designed to be extremely tolerant of adverse working conditions, while having the capability to support very high loads - unlike a conventional solid bearing design that may have to be adapted to meet demanding applications."

SRB split-roller bearings accommodate thermal growth of the shaft by the movement of the inner race and rollers relative to the outer race of the bearing. This permits a high degree of unrestricted axial movement within the bearing envelope, allowing for thermal expansion of the shaft while avoiding additional stresses within the bearing. It also allows standard bearings to operate at temperatures up to 140degC without problems, and at operating speeds comparable with solid spherical roller bearings on the market, making them well suited to the application in the drying cylinders running consistently at over 100degC at Lothlorien paper.

Simple to swap

The principle of the SRB Split Roller Bearing design allows for complete bearing removal and replacement by simply supporting the shaft. There is no need to lift the shaft or obtain access to the shaft ends, therefore expensive and awkward-to-handle lifting equipment is not required. 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. It allows for much faster bearing replacement, which was a key reason why Lothlorien opted for SRB Split Roller Bearings. The Plant Manager comments: "To replace a typical solid roller bearing can take six to eight hours, whereas with split bearings it takes one or two hours - which saves us a lot of money in costly downtime."

Revolvo SRB split roller bearings were designed from the outset as a premium product to accommodate high loads and offer long life. This quality is reflected in the use of optimised profiled cylindrical rollers with bored pocket machined brass cages as standard, where other designs rely on parallel rollers and weaker aluminium cages. The SRB split bearing design is also superior to that of spherical-roller bearings where the entire bearing has to float within the plummer block to accommodate shaft thermal expansion. The high friction between the bearing outer race and the bearing housing causes additional stresses within the bearing, which reduces reliability and life.

Split-roller bearings can also accommodate a high degree of shaft misalignment making them, which is useful for heavy applications such as those within paper mills. The bearings are enclosed by a cartridge housing that swivels within the cast-iron support pedestal; this feature ensures that the seals always remain concentric to the shaft, which further extends the potential life of the bearing because contaminants are effectively excluded.

Adrian Menzies adds: "About 70 per cent of the bearings supplied are for conversion applications where solid conventional roller bearings are being removed and the application converted to SRB Split Roller Bearings to save bearing fitting time and improve machine up-time and maintenance efficiency."