New interchangeable SRB split plummer block bearings cut maintenance downtime by half

Citation

(2004), "New interchangeable SRB split plummer block bearings cut maintenance downtime by half", Industrial Lubrication and Tribology, Vol. 56 No. 4. https://doi.org/10.1108/ilt.2004.01856dad.006

New interchangeable SRB split plummer block bearings cut maintenance downtime by half

New interchangeable SRB split plummer block bearings cut maintenance downtime by half

Keywords: SRB, Bearings, Plummer blocks

The new compact split plummer block bearing from SRB is the first split cylindrical roller bearing assembly to be dimensionally interchangeable with standard SN and SD series plummer blocks, bringing the benefits of a split design to a much wider audience. Split roller bearings offer dramatically reduced downtime in maintenance and replacement situations, but could not be used in many bearing applications because of their dimensional incompatibility with standard plummer block sizes.

Cast iron plummer blocks accommodating adapter sleeve mounted spherical roller bearings are amongst the most common types in use, supporting rotating shafts in everything from conveyors and fans to line shafts, yet their replacement is often time consuming and difficult. Replacing a typical bearing mounted in a cast iron plummer block can take 6-8 h, in contrast, it can take as little as 1-2 h to replace an SRB bearing unit (Plate 3).

Plate 3 New interchangeable SRB split plummer block bearings cut maintenance downtime by half

Nick Dent, Manager of SRB bearings comments, “despite its inherent advantages the split roller bearing design has remained a specialist product used predominantly in the mining and quarrying industries; largely due to its incompatibility with standard bearing and housing sizes. The base to centre line height, i.e. the distance between the centre of the rotating shaft and the base plate has been typically far larger in the split design due to the additional number and section of components.”

“SRB changed the market expectations for a split roller bearing in 1996 when we launched an improved design using better quality materials and an improved construction. This first generation SRB bearing is designed to be interchangeable with other split designs and has proved extremely popular. The physical improvements we introduced then have provided us with the scope to develop a new more compact second generation design that is now compatible with all popular SN and SD sizes and compliments the existing range. The new generation SRB plummer block bearings are the only split cylindrical roller bearing on the market to offer this interchangability.”

The main advantage to customers of the SRB design is that to inspect, maintain and replace a split bearing is much less complicated than it is with a standard plummer block with a solid bearing.

Removal of a solid bearing from a typical plummer block requires peripheral equipment such as belts, pulleys, gearboxes and couplings to be disconnected and removed. The shaft then has to be lifted above the lip of the lower half of the housing base (an action in itself that requires the opposite end of the shaft to be raised) the bearing has to be removed from its sleeve and then the sleeve is removed from the shaft. A replacement bearing can then be fitted. This process involves the measurement of reduction in radial clearance requiring the skilled use of feeler gauges and other equipment. This can be a lengthy process of many hours, or indeed days depending on the complexity of the installation.

The SRB units simply require the shaft to be supported: the top of the support and housing is then simply unbolted revealing the bearing. The remaining lower half of the housing, bearing races, cage and roller assembly then simply lift off or slide out.

The replacement process takes a fraction of the time required for solid equivalents and the overall result is a significant reduction in maintenance work and therefore, downtime.

Simple inspection is another key advantage of the SRB design. Unlike a solid bearing, where specialised vibration analysis maybe required to detect bearing wear. Many are replaced routinely rather than risk downtime due to failure; the top sections of an SRB unit however, can simply be unbolted and lifted off to provide a rapid visual inspection. Again, this feature can save time and reduce the risk of unplanned or pressurised downtime.

SRB split plummer block bearings also offer additional benefits when replacing adapter sleeve mounted floating ball or roller bearings, these bearings accommodate axial float by the movement of the outer ring within the housing. The resulting friction causes additional stresses within the bearing reducing reliability. The SRB design uses profiled cylindrical rollers retained in a machined brass cage as standard. This arrangement permits a high degree of unrestricted axial movement within the bearing envelope, allowing for heat expansion whilst avoiding additional stresses in the bearing. It also allows standard bearing operating temperatures up to 140°C without problems, and operating speeds comparable with other spherical roller bearings on the market.

Using an SRB bearing can also compensate for a high degree of shaft misalignment. Self-aligning ball and spherical roller bearings allow misalignment of the shaft relative to the seal, which results in inefficient sealing performance. The SRB bearing is enclosed by a housing that can swivel within the cast iron support allowing the bearing and seals to remain concentric to the shaft. This feature prevents the characteristic shaft wear and seal damage caused by standard bearings compensating for misalignment within the bearing.

SRB has a wealth of experience in specifying, supplying and supporting split bearings on a worldwide basis with 40 per cent of production exported. SRB plummer blocks are available from stock in common sizes and can be manufactured with very short lead times for extra large shaft diameters up to and over 900 mm.

For further information, contact: E-mail: marketing@wyko.co.uk; Web site: www.wyko.co.uk