MATERIALS HANDLING
of conveyor design, inspection, maintenance and having a clean working environment, when it comes to rip, tear and impact damage, the most significant factor is the conveyor belt itself. Even if the conveyor set up is perfect and continuously monitored and inspected, accidents will still happen. This is why the conveyor belt itself also needs to be a central focus of attention. There are three methods of approach – sacrificial belts, thicker, heavier belts, or specialist belts engineered for purpose. It is estimated that in mining and
quarrying especially, up to 80% of belts are replaced prematurely as a result of accidental catastrophic damage. Such damage is regarded by some as being inevitable, in which case the use of ‘sacrificial belts’ is the chosen approach. The most popular source of ‘cheap’ belts is Southeast Asia. The line of thinking seems to be that as the belt is going to be destroyed anyway, why fit more expensive, better-quality ones? The arguments against this view are, in my opinion, overwhelming. Firstly, there is the cost in time and money spent regularly buying replacement belts. Add to this the very significant cost of loss of output due to stoppages to make repeated repairs, the cost of the repairs themselves and, ultimately, the conveyor downtime and cost of fitting the replacement belts. Another increasingly important
argument against sacrificial belts is its environmental impact. Manufacturing industrial conveyor belts uses a lot of energy and materials, much
of which are oil derivatives, so it produces a big carbon footprint. Add to this the considerable impact on the environment caused by discarded industrial belting. Rubber constitutes at least 70% of the material mass of a conveyor belt, most of which is synthetic. The inner plies are mostly polyester and nylon and are therefore not biodegradable. Recycling conveyor belts remains a complicated and expensive process so nearly 90% of conveyor belts end up on scrapheaps and in landfill.
THICKER IS NOT THE SOLUTION Although fitting belts with thicker covers and heavier carcasses may seem entirely logical, it is rarely the best solution. Firstly, if the cover rubber is not resilient enough, then adding more of the same will make little or no difference. Neither will increasing the number of plies or the tensile strength because thicker, heavier belts are much less flexible. Reduced longitudinal flexibility
normally requires an increase in the diameter of the drive pulley. Increasing tensile strength by just one step usually means an increase in diameter of 25% or more. Failure to increase the pulley (drum) diameter can lead to dynamic stress failure, especially in splice joint areas. Reduced horizontal flexibility causes a decrease in troughability. There is also a price to pay in terms of increased power consumption, which can be quite significant.
The biggest cause of rip damage is trapped rocks or other foreign objects
ENGINEERED FOR THE TASK The only practical solution is to fit a conveyor belt that has been specifically engineered to withstand the kind of punishment that would destroy a conventional belt. The genuinely specialist belts that are available use uniquely designed fabric plies that allow the transversal (weft) nylon strands to stretch. As the trapped object is being pulled through the belt, the strands gather into a bundle that eventually becomes strong enough to stop the belt in its tracks rather than propagate over a much long distance. The design of the fabric also allows the energy created by heavy impact to be dissipated over a much wider area rather than rupture the inner carcass. Specialist belts such as Fenner
Dunlop’s UsFlex and Ultra X range, are proven to provide more than three times the rip and impact resistance and last up to four or five times longer than conventional multi-ply conveyor belts. There are a number of imitators, but tests show that they typically have some 60% less rip and tear resistance. Although the initial purchase price may appear high, they are, without doubt, the most cost-effective solution. Over the lifetime of the belt, the cost will be substantially less than even the cheapest, thickest sacrificial belt with the added benefit of significantly fewer repairs, replacements and stoppages. As they say, price is what you pay but cost is what you actually spend. ●
Belts engineered for the task last up to four or five times longer
36
www.engineerlive.com
Rob van Oijen is manager for Application Engineering at Dunlop Conveyor Belting.
www.fennerdunlopemea.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56
