OCR

Truck and Conveyor Operation Looked Best Early in the deliberations it was obvious that the combination of trucks and conveyors offered several immediate and long range advantages. For example: 1) Conveyors would eliminate the steepest grades and free the relatively flat portions of the haul for the existing truck fleet. In other words, the haul would be divided to obtain optimum performance with the two methods . 2) This arrangement would permit a staged retirement of the trucks as me conveyor was extended in either direction. The years were taking their toll on the trucks, and this method would allow a stepped changeover and still satisfy the anticipated annual increase in tons to be hauled. 3) The downhill conveyor portion could be designed to convert the mechanical energy of braking into usable electrical energy. At some partial loading of the conveyors, the load would pass the threshhold from power-consuming to power-generating. At this point the drive motors, would function as generators or continuous brakes. The decision to pursue further the possibility of a long downhill conveyor system was followed shortly by feasibility studies and engineering proposals. In addition to the challenging problems of length and drop, an additional obstacle was included. To permit deferment of some part of the capital expenditure without jeopardizing immediate or future hauling needs, it was requested that the haulage system include the provision to conveniently and economically double capacity at some future date. System Would Have Four Flights The experts were unanimous in their affirmative response to the feasibility question. They were not unanimous, however, on the question of how many conveyors or flights would be required for the distance of approximately 7900 ft. and the drop of approximately 1700 ft. Proposals ranged from two to nine flights, with the majority recommending six. Con- veyer belting strength was the largest single factor in determining the least number of conveyor sections that would be required to safely and efficiently handle the proposed tonnages. The final decision was for a system having four flights. Fewer flights would mean fewer transfer points, and consequently less wear and tear on the ore. This would also minimize the problems inherent at a transfer, such as wear steel and belting abuse.