SKF provided a custom mill pinion housing assembly solution for a new horizontal grinding mill to a key customer for a project in Africa.

Janus Bezuidenhout, SKF Application Engineering Manager, explains that as the current arrangement was non-standard, the customer, a leading Project House, subsequently requested SKF to provide an arrangement that will be suitable for the application as a standard. “The challenge we faced was to ensure that the solution we provide will comply with the current pinion shaft arrangement as it will be remanufactured and re-used. Additionally, since we had to use the existing base plates and structure, we also had to make sure that the solution can be modified to suit the current structure.” Bezuidenhout also adds that the project needed to be delivered within a specific time to avoid penalties.

SKF performed bearing life and housing strength calculations based on mill pinion requirements, design criteria, etc. that was provided by the customer. This approach was essential to ensure the suitability of the proposed components and that the proposed arrangement will be feasible for the existing pinion shaft. The solution also called for the downsizing of the existing bearing designation.

“It was imperative that our solution keeps the pinion shaft as close as possible to the original sizes to avoid any additional machining,” continues Bezuidenhout. “Based on the information gathered during the calculation phase, and also factoring in the customer’s cost and lead time requirements, we concluded that the SDAF 3296 housings assembly paired with 23296 CAK/C3W33 bearings and oil taconite seals would be the best solution for the design criteria for the mill.”

SKF has existing pattern designs of this particular SDAF housing which is locally manufactured in South Africa. In addition to meeting the customer’s turnaround time requirements, this particular housing provides additional strength to the cap that is usually paired with dual drive mills. “The fact that this specific housing has been used on other mill applications in the market with great results, gives us confidence in the product selection for this project,” elaborates Bezuidenhout.

The 23296 CAK/C3W33 bearing provided the best life calculations based on the design criteria given by the customer, making it a perfect fit for this project. The sealing arrangement, also locally designed and manufactured, has been implemented in the industry for many years and is custom for large size bearings operating with circulating oil lubrication. The arrangement consists of a static ring that is mounted on the housing and a flinger, clamping and spacer ring that is used to secure all the components on the shaft and matches the static ring. A V-ring, which is incorporated with a grease port in the static ring, prevents contaminants from entering the bearing; the grease port is used to purge contaminates out of the sealing arrangement. O-rings are also incorporated to seal the arrangement on the shaft and prevent bearing contamination.

In addition to supplying six complete mill pinion housing assemblies, SKF also successfully secured the tender for the assembly of two pinions at SKF South Africa prior to shipment to site. “SKF is always involved with the entire project, enabling us to add value throughout the supply chain, mitigate risks and communicate with the customer,” asserts Bezuidenhout.

The manufacturing of the project and the installation of the housing assemblies on the pinion shafts were completed at the end of June 2023. The pinion housing assemblies are being prepared for sea-freight delivery scheduled toward the end of July 2023.

The fact that the solution is based on a custom design offers two important advantages. It enables SKF to issue spare assemblies if needed and to provide similar solutions to the customer for some of their other projects.