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50 E&MJ; • MAY 2018 www.e-mj.com OPERATING STRATEGIES Destroying or dismantling something that is designed to be indestructible is always a formidable task, and nothing epitomizes a nearly indestructible object more than the giant tires used on large mining trucks and loaders. Living up to the image of their robust construction and massive weight, with prices to match, the industry's 59- inch (in.) and 63-in. tires carry many mil- lion tons of ore and waste over a wide range of pit bottom and haul road surfaces each year, enduring tremendous stress from heat, internal pressure and external haz- ards. Over time, they tend to get damaged, repaired, possibly retreaded and returned to service, but eventually they wear out. Often the decision is made to fi nd a con- venient spot to stack or bury them on-site. Salvadori Srl, an Italy-based supplier of tire "downsizing" equipment, recently reported that a sample of 1,300 working surface mines revealed a rough total of 38,000 mining trucks in operation. The giant tires mounted on these trucks have an operating life of 5 to 10 months. Once these tires can no longer be repaired or retreaded, they require disposal. Multiply this volume of potential "waste" tires by the total population of surface mines, and the numbers become startlingly large. Piles of huge tires pose many health and environmental concerns. In warmer climates, a waste tire will catch rainwa- ter and become an ideal incubator for mosquito larvae, thus increasing the risk of spreading diseases such as dengue, malaria and zika. In addition, tire fi re risk is very high in terms of environmen- tal impact and safety to people and ani- mals. During a tire blaze, toxic emissions can include sulphur, polycyclic aromatic hydrocarbons (PAHs) and benzene emis- sions with potential carcinogens. In more severe blazes, the combustion of tires can cause oxygen defi ciency. In these cases, the pyrolytic process releases oils, ben- zene, phenols and other substances ca- pable of contaminating not only the atmo- sphere, but also the soil and water table. The need to recycle waste tires has been recognized by regulators. In progres- sive countries and regions, legislation has mandated recycling, such as: • European Union (EU) Directive 1999/31/EC, which requires all EU countries to ban the disposal of both whole and shredded tires to landfi ll. The initial focus was on passenger and truck tires, but there is a growing aware- ness of the need of address this pro- blem in mining tires. • The 2014 Waste Amendment Act in South Africa, which limits residues of mining operations. • Chile's 2016 Law 20.920 introduced the "extended responsibility of the pro- ducer" scheme for tires. • Australia's ESR/2015/1836, which man- dates the disposal and storage of scrap tires at mine sites. In countries without legislation, fl eet operators have two options for dealing with waste tires: stockpiling or landfi lling. Neither approach actively manages the environmental liability. However, some mining companies are proactively begin- ning to downsize waste OTR tires. Until now, there have been two downsizing al- ternatives: • Destroying the tires with a demolition shear mounted on an excavator; or • Implementing multiple pieces of manu- ally operated downsizing equipment. Meeting the Challenge Giant OTR tires would overwhelm downsiz- ing equipment made for even large on-road tires. The volume of rubber, steel and tough synthetic materials in OTR tire carcasses and the physical stresses involved in han- dling and shearing them is beyond their capacity. Salvadori recently introduced a new OTR tire downsizing system to meet the challenge. But fi rst, it might be helpful to understand the downsizing process, at least in the way that Salvadori envisions it. Salvadori said it has been on the fore- front of tire recycling equipment for more than 30 years, and has engineered an in- tegrated solution that converts waste OTR tires into a valuable and reusable resource, crumb rubber. Downsizing is the fi rst step in recycling a waste tire, whereby the tire is cut into multiple sections that can be processed by a traditional shredding line that separates the components: steel, tex- tiles and granular rubber. The third and fi - nal step is converting granular rubber into moulded products using other equipment. The company's MT-REX system is de- signed to perform four downsizing jobs using a single piece of equipment: load- ing, positioning, cutting and conveying. It is claimed to deliver a number of benefi ts to mines and mine service companies in need of tire disposal and recycling solu- tions: These include: System Effi ciently Downsizes Giant OTR Tires for Recycling Tire recycling equipment supplier Salvadori Srl says its MT-REX system can cut a 63-in.-diam OTR tire into consistently sized pices for shredding in less than an hour.