Equipment options for stopping in gold mines

Choice of Stoping Equipment

Ideally, the hydraulic props will be Jightweight to facilitate handling and installation, and will be sufficiently blast-resistant to permit for installation close tball mill grinding mediaowards the face with no having to be removed before the blast. Preferably, the hydraulic props should be powered by plain water. Current hydraulic props demand a hydraulic pressure of 20 to 40 MPa for setting. Based on the kind of hydraulic power source used, a pressure intensifier might be necessary to enable this pressure to be attained in the prop. Appropriate compact intensifiers for insertion in the hydraulic provide line for the prop have been created for this purpose. Water-powered blast-resistant props are available commercially, but the smallest version has a 200 kN setting force, producing it relatively heavy and of unnecessarily high force for that dense assistance configuration proposed. So that you can attain the required help resistance, it really is considered that a setting force of as little as 50 kN could be sufficient with a configuration of a single prop per square metre. This would enable a lot lighter props to be used, which' will be more easily handled than these available at the moment. Being of smaller volume, these props would require less water for setting. Therefore the intensifier, if essential, may be even more compact compared to version presently accessible. Moreover to getting created for water powering, the props would need to exhibit sufficient resilience and robustness to avoid getting dislodged throughout the blast. Handful of difficulties are foreseen in the development of these units, since the essential technology is effectively established. The adoption of the dense support configuration proposed would drastically reduce the incidence of rock falls in the face, and would facilitate improved productivity of the stoping activities. However, for extreme rockburst circumstances, it might still be necessary to use heavier props with setting forces from 200 kN upwards, possibly in mixture with lighter, lower-force props.

Hand-held water jets for face cleaning have already been the topic of a specific quantity of engineering development to render them sufficiently protected, rugged, and reliable for use in stopes!. Suitable jetting guns are now obtainable to use with water at pressures which range from 9 to 18 MPa. Aside from making it achievable to handle face cleaning using the roof support program described above, the use of water jets enables a lot greater face-cleaning rates to be achieved. In trials conducted at Kloof gold mine over yesteryear three years, average monthly cleaning rates of typically 20 t/h (scraper delays included) happen to be recorded utilizing this cleaning technique, roughly twice the typical rate achieved elsewhere around the mine, where only face scrapers are used. The actual cleaning rates achievable obviously rely on panel length and on the problem and inclination with the footwall but, normally speaking, a noticable difference of a minimum of 50 % might be expected. Labour productivity can be considerably improved because the scraper does not have to be rerigged throughout the cleaning operation, and due to the fact another activity to sweep fines is no longer essential.

Conventionally, hand-held rockdrills and thrustlegs are powered by compressed air, but hydraulically powered versions operating on emulsion (98 % water) are actually available commercially. These hydraulic drills are comparable in size and mass with compressed-air drills but, due to the fact their penetration rates are considerably greater, they're capable of achieving greater than twice the quantity of holes drilled hourly. They're specifically powerful in heavily fractured ground, and are environmentally much much more acceptable because of reduced noise and removal of fog.

The drilling overall performance from the emulsion-powered rockdrills has been measured exhaustively, and Table I shows some typical outcomes obtained on various mines throughout a six-month period under various production conditions2.

The drilling rates offered in Table I are greater than twice these normally achieved with compressed-air drills. If complete benefit is taken with this. high efficiency, drilling labour productivities of as much as 100 holes per shift might be achieved regularly with one drill. In practice, values of up to 160 holes per shift with one particular drill have already been documented on occasions.

The hydraulic emulsion for these drills needs to be supplied in a pressure of 14 to 18 MPa. Emulsion pumps effective at generating these pressures are available either in a traditional form, powered electrically, or within a form generally known as the hydro-transformer in which high-pressure water is used as the driving medium. Hand-held rockdrills and thrustlegs powered by plain water are beneath improvement. A prototype version is shown in Fig. 3, and versions are required to turn out to be available commercially during 1991. With one of these, it's going to become possible to energy the drilling operations directly from the identical supply of high-pressure water as that used for props and water jets.

A widespread feature of all hydraulically powered devices handled manually in stopes, such as props, rockdrills, and water jets, is that they have to be powered through flexible high-pressure hoses connected for the powering installation. Regular hydraulic hoses do not survive effectively inside the stoping environment owing for the susceptibility with the rubber cover to cutting and abrasion, and with the reinforcing wire to corrosion. Hoses of improved style and materials have been developed specially for this application, and so are readily offered commercially.

In any consideration with the equipment and its particular method of powering for that face layout shown in Fig. 1, the type of equipment to become used within the gullies ought to even be borne in thoughts. Gully equipment is basically focused on rockhandling; conventionally, the scraper winch is used with this purpose, but the continuous scraper and loadhaul- dump car (LHD) are alternatives3. All the choices are completely compatible together with the proposed face layout. Even though scrapers are electrically powered at present, it's very possible to power them highpressure water, as well as a appropriate scraper-winch drive depending on a Pelton turbine has already been developed and proved, and is also available commercially. If face scrapers will also be powered this way, the chance then exists of powering the entire stope with water hydraulics. Using this in mind, a variety of ancillary devices (like items like ventilation fans, watering-down guns, winch signalling bells, and blasthole cleaners) continues to be created for operation on high-pressure water, enabling all external supplies of compressed air, electricity, and lowpressure service water to become eliminated from your stope if desired.