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A leading global technology and service supplier to the process industry recently requested SKF to evaluate the bearing arrangements on a pair of bearings and housings selected for the main drive shaft assembly of an apron coal feeder.
"The customer required verification of the suitability of the bearings, bearing arrangement design, cap bolts and holding down bolts for the applied loading in the application as well as an expected bearing life in order to be able to better plan routine maintenance and bearing replacement," says SKF Applications Engineer, Devlin Moodley.
SKF application engineering services performed detailed calculations and simulations, based on the loading conditions of the entire conveyor system. "The information provided was used to calculate the resultant loads acting on the bearings and in turn the basic rating lives (L10h) of the bearings. Factors that were considered for calculation purposes included loads due to shaft, hubs, sprockets, belt and conveyed material masses; belt tension forces acting on the sprockets; strength of housing, attachment bolts and cap bolts; bearing; adapter sleeve; and housing," explains Moodley.
Based on the results of the simulations, SKF Application Engineers made the following recommendations:
SNL plumber blocks are replaced with spherical graphite SNLD plumber blocks.
Cap bolts and holding down bolts be changed from grade 8.8 to grade 12.9.
The calculated ISO basic rating life of the recommended spherical roller bearings for the apron feeder main drive shaft assembly far exceeds the normal design life requirement of 100 000 hours for this type of equipment.
"This confirms the suitability of the bearings for this particular application," continues Moodley.
According to Darren Chetty, SKF Application Engineering Manager, the customer has confidence in the apron feeder design "because SKF reviewed the design of the main drive shaft assembly. Our customer can also be confident of a longer bearing arrangement life due to the necessary design calculations being done upfront as well as stronger, more durable products being chosen for the final design." Chetty adds that savings on design costs were also achieved due to SKF performing the design verification as part of a value added service. "We also recommended high viscosity and high temperature SKF grease as the lubricant for the application."
"This was a good learning experience for SKF's Application Engineering Services and their knowledge and expertise are invaluable due to the solutions that they provide. We are able to offer other SKF customers the benefit of this expertise gained through hands-on experience," continues Chetty.
"We are willing to work hand in hand with our valued customers to ensure the optimal bearing arrangement design for a specific application," concludes Chetty.
| Product Model | Inside Diameter | Outside Diameter | Thickness |
| 7305BDF NACHI | 25 | 62 | 17 |
| 7305DF NACHI | 25 | 62 | 17 |