Audit of trackless system

4. Horizontal transportation

4.9 Trackless Transportation

4.9.1 Audit of trackless system

4.9.1.1 Overview

Load haul dump trucks (LHD) and small articulated dump trucks (ADT) have been used in underground mining for several years. Drill rigs, utility vehicles and light delivery trucks are also in use for the purposes of mining. Recently, light-duty commercial vehicles (LDV) have been commissioned for use in some mines for use as utility and light delivery vehicles (Figure 4-56). The personnel carrier's dimensions are 5,5 m (I) x 1,8 m (w) x 2,1 m (h).

PER (Manriding)·

Personnel compartrrient:

Cushioned seatsfor 16PElirsons

Figure 4-56: Personnel carrier

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Carrier:.6

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.10 tonne

Mines that are currently utilising LDVs for underground transport include Koornfontein, New Denmark and Tavistock collieries. AngloPlats and Impala Platinum Mines also make use of LDVs in their inclines, but this is for the use of officials and for the transport of small emergency materials, and not for the transport of personnel or materials on a regular basis.

4.9.1.2

Capacity

Theoretically, any size diesel or electrically powered vehicle can be used for underground transportation, as long as the haulages are of sufficient size to accommodate them. In practice, however, only those mines with direct surface access to the levels via declines make use of the larger vehicles. In the ultra deep mine application, the ability to transport any trackless vehicle down the shaft imposes size limitations on the vehicles, and so larger vehicles are not practical.

Smaller vehicles with a maximum length of 3 m that can fit inside the cages could be used, and larger vehicles slung under the cages. The most likely type of vehicle is a specially adapted bakkie with either load carrying or personnel carrying abilities. Bakkies are limited to a maximum of 12 passengers per vehicle.

Thus to transport an entire shift would require a fleet of vehicles running several trips each to achieve this feat. The bakkies are able to attain speeds of up to 60 km/hr in theory, but in practice, this is likely to be 30 km/hr or lower.

Figure 4-57: Kiruna Electric Truck (Dreyer, 2001)

4.9.1.3 Limits on length

There are no practical limits on the operational length, as diesel powered vehicles can. operate for as long as their fuel capacities allow. Battery powered vehicles are also able to operate over long distances with the only limiting factor being the recharge times for the batteries. Electric vehicles can be used in conjunction with overhead trolley wires, which would allow unlimited range within trolley line equipped haulages. Hybrid battery and electric vehicles give a limited operational range beyond the end of the trolley lines, allowing some flexibility in terms of being able to service cross cuts and development ends.

4.9.1.4 Environmental compatibility

Diesel powered trackless vehicles have the same limitations as those attributed to diesel locomotives (Section 3.2.1.3). Electric and battery powered vehicles do not produce exhaust gases and their heat output is significantly lower than that of the diesel engine. Stray currents and arcing are however one of the features of an overhead trolley line, which need to be considered similar to those discussed in section 3.2.1.2.

4.9.1.5 Powering systems

Diesel engines are the most common type of power units utilised for trackless vehicles. These types of powering units are required to be equipped with f1ameproofing measures, noise and emission retardation systems.

Electric power units make use of an overhead power supply in the form of overhead trolley lines. Electric power units can also be equipped with nickel cadmium batteries, which are continually charged while the vehicles are connected to the overhead trolley lines. This enables use of the vehicles for limited periods in areas where no power supply is available.

4.9.1.6 Boarding and alighting

For personnel riding purposes, no special boarding and alighting arrangements are required as personnel riding vehicles are able to stop at any point in the haulages to pick up or let off persons.

4.9.1.7 Maintenance

A systematic maintenance procedure is required in order that the vehicles are not allowed to deteriorate to a point where they may become unsafe to operate, or unreliable. Such a maintenance philosophy includes the systematic monitoring of the engine oil for contaminants in the case of diesel vehicles and the scheduling of regular maintenance for the vehicles. These maintenance intervals should be based on hours of use, or be of a set period. Maintenance intervals based on hours in use is the preferred method, as vehicles that have a higher usage are maintained more frequently, and unnecessary maintenance of light duty vehicles·

is avoided.

Tyres are the highest cost item after labour in the running of a trackless fleet. .The abrasive nature of the footwall necessitate that tyres be monitored and replaced on a regular basis. The rocks associated with hard rock mining have sharp edges; tyres, therefore need to be regularly checked for cuts in the tread and sidewalls, and replaced when necessary. Care must be taken in the selection of tyres, as inappropriate tyres will need replacement more frequently than ones suited for their intended purpose.

4.9.1.8 Installation considerations

Trackless mining vehicles for the transport and handling of rock typically require haulages with a minimum size of 3 m by 3 m cross section. Materials handling vehicles and personnel carrying cars on the other hand can be of a smaller size than this, and can be made to require very little headroom. Tunnel sizes can therefore be smaller than those required for LHDs. A minimum size of 2,5 m by 2,5 m cross section is sufficient for the operation of such vehicles, although parallel haulages may be required for traffic moving in opposing directions.

Alternatively, passing bays may be provided to allow vehicles to move in both directions in a single haulage.

Footwall and sidewall heave should have little impact on the operation of these vehicles, as they are able to handle undulating footwalls and can negotiate obstacles. Smaller vehicles, such as light utility vehicles, can be particularly effective in negotiating obstacles due to their small turning circles.

Where diesel powered vehicles are utilised, ventilation in the haulages must be such that exhaust gases are quickly removed from the environment. Roadways need to be constructed and maintained to prevent unnecessary wear or damage to the tyres. Therefore, good roadway surfaces are key to the successful operation of trackless vehicles.

4.9.1.9 Compatibility with other systems

Trackless vehicles are able to run in conjunction with other systems. Where track construction is such that it permits roadways to be constructed on the rail tracks, vehicles can operate over the railway tracks. However, where trackless vehicles operate in conjunction with conveyor systems, bridges are required for the·

conveyors system to operate over roadways and in some instances separate haulages are constructed for trackless vehicles and conveyors. Where this is not possible, roadways can be constructed adjacent to the conveyor systems, but this requires haulages large enough to accommodate both systems.