MATERIALS HANDLING
‘Sacrificial’ belts sacrifice productivity, money and time
Conveyor belt damage is an expensive problem for mine
operators but it is possible to reduce its occurrence
case, their big weakness is that although the steel cords themselves are very strong, they provide little or no protection against ripping. Trapped foreign objects that penetrate through the rubber covers run parallel with the cords, ripping the belt longitudinally. Te only practical way to create rip resistance in a steelcord belt is by the use of breakers.
materials. It has little or nothing to do with lower labour costs in Asia. Low-grade belts are the result of a ‘pile it high, sell it cheap’ mentality so they lack the necessary durability and are very easily damaged. When you add the cost of incessant patch repairs, the splice repairs, the cost of replacement belt after replacement belt together with the invisible ‘un-invoiced’ cost of the lost production while all those unplanned stoppages are taking place, the true cost is several times higher than the price paid for the original belt. As the old saying goes, price is what you pay but cost is what you spend. Another answer might seem to be
replacing the multi-ply belt with a steelcord belt, but this is also extremely unlikely to be the right answer. Conveyors that use steelcord belts have to be designed differently from those that use multi- ply belts. Because of their innate tensile strength and low elongation (stretch), steelcord belts are typically only suited to conveying over longer distances. In any
USING BREAKER PLIES Te use of breaker plies can be a solution because they can provide a considerably increased level of resistance against longitudinal ripping, especially in the case of steelcord belts. Te breaker ply performs two functions – firstly it can help prevent the penetration of the belt by a foreign object. Secondly, it acts as a barrier if an object does penetrate between the steel cords or through the inner fabric plies and starts to rip along the length of the belt. However, before operators take this path, it is important to bear in mind that breaker plies have to be embedded in the rubber covers of steelcord belts during the manufacturing process, so each belt has to be custom-made. Tis means a much higher price per metre and invariably, much longer lead times. Tere are numerous types and strengths
of breaker. Te lighter weight versions are designed to simply absorb and dissipate energy whereas stronger, heavier weight breakers can actually limit the amount of damage. Tese are commonly referred to as ‘rip stop’ breakers. In this market, traders rather than manufacturers are
promoting the vast majority of rip resistant belting on offer, which means that most of these belts almost certainly originate from Southeast Asia. Secondly and almost without
exception, the technical reason given for the promised high level of rip resistance was the use of steel breakers within the top cover. However, steel breakers do have an inherent weakness because the thin steel strands used in conventional ‘ripstop’ breaker plies have a limited amount of stretch before they snap as the belt is pulled against the trapped object. Strange as it may seem, all the evidence points to (good quality) synthetic plies being much more effective than steel when it comes to actually minimising rip propogation.
ENGINEERED FOR THE TASK Although belts with an inbuilt ‘steel reinforced’ breaker ply will resist rip damage more than conventional multi-ply belting, the most practical and economical solution is to fit a conveyor belt that has a carcass that has been genuinely engineered for the purpose and that has a proven performance record. A good example of this is UsFlex, which has been a popular choice in the rip-resistant belt market for more than 20 years, and its much younger but well regarded stable mate, Ultra X. Both belts are manufactured in the Netherlands by Dunlop Conveyor Belting. Te company maintains that what makes these belts so effective in resisting damage is their innovatively designed fabric plies. Te company designs and manufactures
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