SKF's Project Engineering department successfully reconditioned a housing arrangement on a hot gas kiln fan application at one of South Africa's leading cement manufacturing plants.
The plant approached SKF to submit a proposal for the reconditioning of the non-drive end, solid type housing on the customer's kiln fan. The solid housing assembly was delivered to SKF Witfield where it was cleaned and inspected. According to the company's project engineer Neil Maree, the bearing that was operating within this housing suffered a catastrophic failure and as a result, the housing fixing bolts were broken off and the housing lifted out of position by a bent fan shaft.
The bearing failure gave the cement plant an opportunity to perform a maintenance shut within a limited time period. "As a result of the time constraints that were involved with the shut, SKF was requested to perform the complete reconditioning within a very short time frame of five days," reports Maree. "Inspection of the housing assembly indicated that both cast iron through covers were damaged as they were fractured in localised areas."
He adds that from a visual inspection it was also found that housing bore damage was existent and that the measurements of the housing bore did not conform to the prescribed dimensional and geometric form tolerances and surface finish.
Maree recommended re-sleeving of the housing bore and replacement of the through-covers. The existing solid housing as well as the through covers are manufactured from cast iron and because the casting processes in the manufacturing of such components are time consuming, and time constraints meant that replacing the covers with similar ones was not an option, SKF replaced the covers with newly designed, fabricated through covers manufactured from mild steel.

The kiln fan bearings operate in a severely contaminated environment and in excessive heat. "It is therefore essential that contamination ingress be minimised as far as possible to provide improved bearing performance and reliability," explains Maree. Having conducted a complete design review of the through covers, Maree presented the customer with a long term, reliable solution which incorporated fabricated through covers with integral seals that were quick to manufacture in order to accommodate the tight delivery schedule.
"To improve the old gap seal mechanism on the existing through cover design, we integrated SKF's locally designed ‘taconite' type sealing arrangement with the new through cover design," he says. "This sealing arrangement is extremely successful in severely contaminated operating environments and provides superior contamination exclusion capacity, resulting in increased bearing life expectancy."
In addition, Maree performed a detailed and comprehensive bearing failure analysis on the failed bearing. The analysis showed the primary cause of bearing failure to be contamination ingress and lubrication break down for which the new incorporated sealing arrangements provided a solution.

SKF made a detailed design evaluation, constructed detailed manufacturing drawings of the new through covers and constructed a general arrangement drawing of the complete housing arrangement installed onto the fan shaft; the manufacturing process and quality assurance inspections were then completed. The completely reconditioned housing and new through covers with integrated, specially designed sealing arrangements were delivered to the cement plant with the general arrangement drawing five days from commencement of the project and Maree reports that the arrangement has to date been operating successfully.
Once the installation was completed, SKF performed a grease selection calculation and made a grease recommendation based on these results and SKF data base knowledge. The customer followed SKF's recommendations and changed to a more suitable grease for the application.