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SKIP-WAY TRAM 36 E&MJ; • APRIL 2016 www.e-mj.com ed suspension of the skip in the support frame and subsequently also by the yield- ing of the track rope line (Figure 3). After the skip is positioned in the top station, the discharge fap of the skip is opened by two side-mounted hydraulic cylinders with slowly increasing extension speed. Finer material empties through the initial opening. As the opening be- comes larger, coarser material and indi- vidual boulders slide out of the skip into the crusher station bin or onto a waiting truck. The hydraulic closing and opening mechanism is mounted on the skip and is activated in discharge position by a plug in power/control contact (Figure 3). Opening and closing of the discharge fap takes place fully automatically above a crusher station, whereas operator control is envisaged for truck re-loading. Characteristic design data for a Skip Way System in a kimberlite mine are shown in the example in Figure 9. In the example presented, uncrushed kimberlite with a density of 2.5 mt/m 3 is transported by a tandem skip way system a vertical distance of 410 m over a slope with an average incline of 45°. The mine trucks have a maximum payload capacity of 42 mt, so the skips were designed for a maximum capacity of 22 m 3 or 45 mt. With a conveying distance of 580 m and a chosen travel rope speed of 12 m/s, this results in 11.2 travel cycles per hour and rope system for a handling capacity of 1,000 mt/h. Due to the heavy masses to be accel- erated and positioned, the drive motor is designed for a power output of 3,000 kW. During the steady-state phase, i.e., during constant skip travel, skip deadweight compensation comes into play, so the average power requirement—over the full travel cycle—will be only 1,400 kW. The deadweight of a skip including defector sheave and tandem carriage for a maxi- mum payload of 45 mt is 37 mt; of this, as much as 22 mt is accounted for by the skip and hydraulic unit. This relatively high deadweight is necessary to absorb the heavy impacts of individual boulders during loading, but also serves to tension the travel rope in the wrap drive (Figure 6). The dead loads of the two skips do not need to be considered, as the masses cancel each other out in operation. The travel rope connecting the skips runs over the traction sheave with a speed of 12 m/s and moves the skips after single de- fection by a sheave in the skip carriage with a maximum speed of 6 m/s. The travel rope is 50 mm in diame- ter and the two full-locked track ropes in each strand are 96 mm in diameter. In accordance with the relevant design stan- dards, the design of the rope and the rope diameter require a traction sheave diam- eter of 3,200 mm and defector sheaves with 3,000 mm diameter. Depending on vertical lift and travel distance, a Skip Way System can handle up to 2,000 mt/h. The actual handling capacity and hence the maximum truck payload is limited to 60 mt per skip and is determined by the rope construction, rope breaking strength, rope diameter and the allowable wheel pressure on the track rope. The thyssenkrupp Skip Way System is highly adaptable to the topography of the mine. Depending on the location of haul roads, the confguration of the pit rim, the slope and space conditions at the bottom, the drive station can be arranged in differ- ent ways relative to the unloading stations in the mine. The spacing and orientation of the two masts and thus of the truck loading and crushing stations can also be varied to suit local conditions. Examples of possible layouts at the rim of the mine are shown in Figure 10. The thyssenkrupp Skip Way System has been designed for effcient use as a steep-angle conveying system in smaller but deep open-pit mines. The system ide- ally complements the "Integrated Crush- ing and Skip Conveying System" 1 with handling rates of up to 5,000 mt/h for uncrushed ore or overburden (Figure 11) previously developed by thyssenkrupp. In that system, skips run in opposite directions on a steel track over a steep slope and can either empty their pay- loads of up to 250 mt into the feed bin of a semimobile crusher or reload ore or Figure 9—Example design data for a skip system with 1,000-mt/h handling capacity. Figure 10—Examples of fexible layouts for unloading/loading stations and drive station arrangement.