SKF Xtra Power Belts save £420k in one year for Fonterra Te Rapa
An SKF power transmission overhaul has brought major cost and maintenance savings to multinational dairy company Fonterra Te Rapa, including a maintenance cost saving of £420k over 12 months. By identifying design problems and misalignment that was causing over-tensioning and high running belt temperatures SKF executed a system redesign using the SKF belt design programme and SKF Xtra Power Belts, bringing significantly reduced downtime as well as improved energy efficiency.
Reliability Engineers at Fonterra Te Rapa initially contacted SKF for assistance with the belt drives located on the blowers of their D5 Drier, which is used to cycle the evaporators and concentrate system that control the specification of milk powder. The existing drive belts were operating within a very high ambient temperature of approximately 60˚C. As a result, the belts required frequent replacement, typically lasting no more than 4 to 5 weeks. Worse still, during the previous twelve months the belts had failed twice before they could be replaced, leading to costly unplanned shutdowns of the entire plant. On both occasions urgent maintenance caused a four-hour shutdown, each costing £53,000 per hour in lost production. To prevent further losses, Fonterra Te Rapa approached SKF to come up with a suitable solution.
SKF began by conducting a comprehensive evaluation of the belt drive, starting with an inspection of some of the failed belts. Having concluded the inspection, SKF confirmed that failure was due to very high running temperatures that were causing the rubber to cure and harden, resulting in the belts cracking and breaking.
On further inspection of the drive, more issues were uncovered. Firstly, it was noted that the drives were significantly over-designed. The over-belting of the drive made it difficult to maintain tension correctly, further elevating the temperature. Secondly, there were tensioning issues; the frames on which the motors were mounted were spring loaded with the full weight of the motor being used to apply tension. SKF checked the belt tension with the SKF Belt Frequency Meter and found the tension to be higher than that recommended for this belt type. Thirdly, SKF found that the motor was not correctly aligned, causing high running belt temperatures.
The solution was a system redesign using the SKF belt design programme. Since there were multiple blowers running under the same condition, SKF designed and trialled two different solutions. The first featured SKF Xtra Power belts, which were selected for their ability to withstand slightly higher temperatures, smooth operation, high running efficiency leading to lower running temperatures, and the capacity to resist stretch and retain the correct tension without constant maintenance. The second utilised SKF 8M timing belt drives, which also offered a higher maximum temperature rating and increased running efficiency over the existing belt.
The two trial drives were fitted along with a ‘control’ set – a configuration using existing belts. During fitting of the trial belts, the tension arrangement of the frame was altered so that the correct tension could be applied. The SKF Belt Frequency Meter was used to fit the belts at the correct tension, while the motors and pulleys were correctly aligned using SKF alignment tools.
At the next scheduled maintenance interval 28 days later, the three drives were inspected. The two redesigned drives showed no signs of abnormal wear or heat deterioration. A thermographic image (infra-red) determined that the internal running temperature of the belts had been reduced by up to 10˚C. In addition, the tension was checked and found to be within specification. In contrast, the belts of the control set had hardened and cracked through to the tensile cords. The rubber had completely cured and the belts required replacement as failure appeared imminent.
When Fonterra Te Rapa began using the SKF belts the results were far-reaching, bringing significantly reduced downtime and maintenance costs as well as improved energy efficiency. The upgrade has not only reduced maintenance costs incurred by repeated replacement and re-tensioning of belts that failed prematurely, but also prevented massive losses as the result of lost production, which in the previous 12 months had amounted to £420k. Further savings have been made in terms of energy as a result of the belt drives running efficiently.