Establishing the pros and cons of underground dump trucks and conveyors cannot be based on one subject but a wide range of factors. In summary form, overall findings about safety, productivity and economics are outlined below. Safety system of conveyor is more detailed than that of a dump truck although dump truck safety the user of the equipment and the machine itself. The conveyor safety system, however, is centred mainly on protecting itself rather than people since it is a fixed plant with moving parts unlike a dump truck. The assumption is that in both cases people have the right to make a decision when not to do what they do. In addition, a conveyor is environmentally friendly as opposed to a dump truck that produces high noise levels and exhaust emissions. The productivity has been discussed in terms of depth, gradient, distance and capacity by which it is affected. Trucks will produce efficiently at a short distance of up to 100 metres and gradient of -10°or less where it is not economically viable to invest in a conveyor system. On the other hand a conveyor will be ideal for a massive long term project due to high recovery rate and return on high initial investment. In the investigation the belt conveyor runs at a steeper gradient of -12° as compared with -9° for a dump truck. Steep gradient results i n shorter distance while shallow gradient for like that of a dump truck increases the distance. To be more specific as calculated, a conveyor decline running at a grade of -12°and dump truck ramp mined at -9° and both targeting a depth of 100 meters wil l result is distance difference of 158.2 meters. A dump truck will travel a longer distance and the trend continues even further as the mine deepens and gradient becomes steeper. The negative effects of increased distance are: - rising production costs and increased cycle time. Both conveyor and dump truck are designed to handle different capacities however, continuous transportation by a conveyor gives a competitive edge over dump truck cyclic operation. On the other hand particle size distribution limits use of a conveyor unlike a dump truck that can carry almost any broken rock while a belt conveyor will not transport oversize fragmented material in excess of 300 millimetres. The decision of truck verses conveyor is based on economic factors such as initial cost of investment, running cost and life of mine. However, the decision is limited by mine depth and gradient and, length of conveyor. Economically, trucks have an advantage when it comes to initial investment as it does not compare with high initial investment in a conveyor system. Although the conveyor is inflexible and has initial cost of investment, the low cost of running the system pays back within a short period. Conveyor systems experience low labour requirement, low energy demand and low spare parts cost while the opposite is true with trucks. Other factors such as depth, gradient and distance have an economic effect on production costs. Any increase in distance affects energy consumption, tyre and belt wear. While filling of material on a belt conveyor is certain, a dump truck dump box filling capacity does not exceed 95% due to among other factors operator competence and condition a bucket lip on an LHD. General mining conditions affect both modes of transport as the geo-mechanics of the mine must be clearly understood before haulage is made. In particular the rock strength and hydrology remain a critical issue. Unlike conveyors, dump trucks are at a higher risk of being damaged as a result of fall of unsupported ground. The summary above is explained in the body of the report.
|Translated title of the contribution||Pros and Cons of Underground Conveyors and Trucks|
|Publication status||Published - 2016|