Australasian Mining Review
Issue link: http://ebook.aprs.com.au/i/26056
13 Improve productivity and reduce tyre Wastage by reducing tyre tread depth “The more rubber the better” is a common misperception that most people have about tyre tread depth, but this misperception is costing the mining industry millions of dollars a year. A lmost every tyre failure resulting from casing separation, distinguished by the ominous bulging of the tyre on the shoulder or tyre sidewall is avoidable. For every application, there is, in fact, an optimum tread depth for a tyre, beyond which deeper tread will actually reduce tyre life rather than extend it. This is very well illustrated by the experience of an Ipswich mine that was using high-capacity heavy- ply 26.5-25 tyres with 100mm of rubber tread. The tyres were consistently lasting only 12 months before failing from case separation due to excessive heat build-up, which gradually destroys the internal tyre structure. Once a tyre dealer determined the cause of the problem, Big Tyre in Toowoomba was asked to remove half the tread of all new tyres for this application before they were fitted; thereafter the replacement tyres lasted three years before they wore out. The cost of removing half the tread cost 5% of the new tyre cost but yielded 4,000% return (or 200% ROI on the total tyre investment). This size tyre was not available from the tyre manufacturers in the strength and tread thickness required by the mine and it is not economical to custom make tyres to suit, so modifying new tyres is still the best option. The alternative option of slowing down the vehicles to reduce tyre heat no doubt costs the mines far more in lost productivity than it would cost in modifying the tyres. Consequently Big Tyre has been buffing excess tread off significant numbers of new tyres of all sizes including dozens of 33.00R51 and 40.00R57 tyres. All OTR tyres have, or should have, a TKPH rating relating to the average load on a tyre (T) for a given speed (KPH) that a tyre is capable of sustaining. Multiplying the tonnage on the tyre by the speed, determines the amount and rate of work the tyre is doing and therefore reflects the amount of heat being generated. Similarly a ‘Site TKPH’ can be calculated by multiplying the average weight on a tyre by the average speed over a complete cycle time. If the site TKPH is greater than 80 or 90% of the rated tyre TKPH then heat-related failures are likely to occur, resulting in unnecessary wastage and downtime. Tyres are a very significant cost, especially when in short supply. Typically the industry has concentrated on improving tyre life through improved road maintenance, correct loading, etc and blame the tyre manufacturers for any heat related tyre failures. The good news is that mines have the power to greatly reduce or prevent these premature failures and to significantly improve tyre performance through removing excess rubber on tyres. Excellent use can be made of tyre management reports to investigate all tyres that have been ruined through tyre separations, and arranging for tyre replacements to have less tread. Through trials, mines can actually determine their own tyre tread depth to help optimise their operations. To discuss these issues further contact Bruce Louden or Robert Ward at Big Tyre on 07 4699 9777 Australasian Mining Review 2011: issue 2.1