The constant cost-down pressures in the steel manufacturing process mean that failures in the continuous production operation are extremely costly. Bearings of course, are fundamental components in all steelmaking production machinery. Therefore, despite the many operational challenges, bearing manufacturers are constantly under pressure to provide ever increasing levels of reliability and operating life from their products.
Revolvo Ltd, a major supplier of specialist bearings to the worldwide steel industry, has studied the many operating challenges of bearings in this industry and through a development programme has produced a range of split roller bearings (SRB) that deliver both substantial reductions in downtime and enhanced operating life, compared to solid mounted bearings.
Revolvo's SRB split roller bearings take up to 90% less time to fit; compared to solid bearings in trapped applications. They also offer the user the ability to inspect the bearing in situ; and can provide higher levels of reliability and enhanced life compared to solid bearings in aggressive and heavily contaminated environments, such as continuous casting plants. In addition, Revolvo's SRB split bearings can operate at temperatures up to 300 degrees C when S3 heat treatment is specified, and the use of high quality cast iron housings (250 - grade material, to BSEN1561,1997), and the adoption of precision machined brass cages as standard make the product very durable & resistant to high levels of shock-loads & vibration.
The great advantage of Revolvo's SRB split bearing design is that it 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, and drives can remain in place. This intrinsic feature is extremely valuable for all applications, especially large machines, where sheer size and weight can be a barrier to fast and effective bearing replacement. This feature can save continuous-type industries such as steel making a lot of money in costly downtime.
In addition to their overall cost advantages, another important reason for using SRB split roller bearings in applications such as continuous casting machines, is their highly effective sealing systems, where they have inherent advantages compared to solid bearing sealing technology. Revolvo has developed special seals to exclude the contaminants of scale & water spray encountered in continuous casting operations. By keeping contamination out, and lubricant in this helps to increase bearing reliability and life, whilst also reducing grease consumption which contributes to lower operational costs.
The sealing advantages are intrinsic to the SRB split roller bearing design, where the spherical location between the housing and the pedestal support, ensures that under conditions of shaft misalignment, and irrespective of whatever type of seal is used, it will always remain concentric to the shaft. As a result, SRB split roller bearings can out-perform solid bearings in harsh operating conditions (in some cases operating completely submerged) even with shaft misalignment, where solid roller bearings can suffer from non-concentric ineffective seals that will rapidly lead to expensive premature bearing failure.
As a further aid to simple installation, Revolvo's SRB split bearings are designed to be statically self-aligning, accepting up to 3 degrees of shaft misalignment. This means that there is no need to accurately realign the bearing housing relative to the shaft, or to any other in-line equipment that might be involved in the bearing's installation.
In addition to offering easy installation, high reliability and long life, Revolvo's design also offers increased support rigidity. Their designers have optimised their support pedestal designs using structural analysis techniques to shape the housing and support castings. By incorporating stiffening ribs into the support pedestal cap, and increasing housing strength, it significantly increases the rigidity of the assembled unit. This is important, because operating conditions are tough in the type of industries where SRB split bearings are used, and the extra robustness designed into the product, helps to offset the effects of shocks and vibration, which in turn helps to increase long term reliability.
The many operational and extended life benefits of Revolvo's SRB split roller bearings have resulted in an order, worth in excess of £1.2m, for SRB split bearings from Jindal Steel & Power (JSPL) - the third largest steel producer in India. The SRB split bearings are destined for a new plate mill that JSPL is building in Angul, Orissa State.
More than 600 of Revolvo's SRB split bearings are involved in this JSPL order, all of which are being manufactured at Dudley in the West Midlands, in Revolvo's new state-of-the-art manufacturing facility. They include shaft sizes from 100mm to 360mm, for use in the cooling beds and transfer tables at the new JSPL plate mill.
The case for using SRB bearings in the new plate mill was strong. Conditions are extremely arduous: hot, humid with 24-hour operation 7-day's a week. However, despite the challenging conditions, the specification for these bearings calls for grease lubrication with the quantity of grease carefully controlled to optimise re-lubrication costs. Revolvo's SRB split roller bearings are able to satisfy this requirement, because unlike other designs of split roller bearings, SRB bearings have a precision machined high strength brass cage. Brass is acknowledged as being one of the best materials for rolling element bearing cages as it absorbs lubricant, and performs well in aggressive environments where lubrication is marginal.
"The proven durability and reliability of our SRB split roller bearings, especially compared to competitors designs that often use lower grade materials, were key factors in our winning this prestigious order, as was our long track record of success in supplying the steel industry in India and China," said Adrian Menzies, Sales and Marketing Director for Revolvo.