SKF agri-hubs, fitted to replace bushes on rollers of a LandPac scraper unit, have effectively eliminated major maintenance, reliability problems, minimised downtime and significantly increased active operating hours.
The extremely robust SKF agri-hub units, developed for independent tillage discs, were fitted to a LandPac T500 dynamic compactor roller scraper unit. The tractor-towed 500 compactor, valued at approximately R2m (including the tractor), has an operating speed of around 12 km/h and is used to improve (compact) ground for the construction of foundations, roads and airport runways.
According to LandPac South Africa Director, Charles Davis, the pre-agri-hub design has been used for approximately ten years and historically, a number of maintenance related problems were encountered with the LandPac scraper blades in UK and European operations. Previously the roller was mounted to the frame with a bush arrangement and major difficulties, relating to the bushes in particular, were encountered. The very brief life span of the main sealing element (approximately 40 hours), lead to water contamination to the bush arrangement. Bushes were prone to failure within relatively short operational periods and therefore required regular lubrication.
In addition, the stub axle surface running in the bush could not be hardened sufficiently, due to the welded stub axle/roller interface, resulting in premature wearing of the stub axle. Depending on working conditions, bush failures would typically occur within 200 or sometimes even less operating hours.
Prior to introducing the agri-hubs, eight parts per roller had to be replaced, with the two left hand rollers usually failing first i.e. sixteen parts required replacement. Parts cost per roller equalled around R10,000.
The SKF agri-hubs replaced the bushes on the scraper unit as a potential solution to the unacceptable frequency and length of downtime period. The modification was implemented on the scraper blading unit on a trial basis in Malmo, Sweden. According to LandPac UK Operations Manager, Jarlath Costelloe, the site was selected because it represented the very harsh and diverse conditions ideal for testing purposes, including abrasive materials as well as a wide variety of soil moisture contents ranging from dry to extremely wet and muddy.
The scraper unit was fitted to the machine for approximately 700 hours of operation and 400 hours of active engagement with the ground, dramatically increasing uptime and production. In addition, the agri-hubs did not require any maintenance during this period and, after the trial period, still showed no sign of wear or damage.
When considering the low cost for the redesign, the agri-hub is one of the most cost effective solutions for reducing downtime and increasing production. The machines operate for approximately 3000 hours per annum and agri-hub has so far largely eliminated down time. Production targets were easily reached by removing associated cost and time lost on offsite equipment repair. Davis has no doubt that replacing the bushes with agri-hubs will, in future, lead to extensive savings in time, effort and cost.
SKF agri-hub's lubrication is life-long as hermetic sealing ensures that no lubricant loss will occur over the complete life span of this plug-and-play unit. The unit also makes a positive contribution to the environment as there is zero lubricant leakage into the soil. Central to the sealing principle is the "mud block" seal and the special labyrinth, which SKF already uses in applications where an absolutely tight seal is required and provides dynamic sealing against stones, mud and any kind of dust. A special cup and O-ring system provides the static sealing of the disc side in the SKF agri-hub unit, rendering it impervious to snow, water or mud.
The outstanding characteristics of SKF agri-Hub render it virtually maintenance-free and extremely reliable in operation. The specially designed surface geometry prevents grasses, stems or roots from becoming entangled in the unit. To combat unavoidable dirty conditions during field cultivation, the surface of SKF agri-hub is coated with an ecologically compatible zinc layer that enables relatively light cleaning of the units with a high-pressure hose.
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