Text 7. Mine tubs and cars in britain

Some 80 per cent of the containers used to transport coal from the face to the surface in British mines had, until recent­ly, a capacity of less than 15 cwt, the bulk of these carrying between 10 and 15 cwt. The size of tub adopted has in the past depended on the natural conditions, particularly the thick­ness and inclination of the seams and the method of working employed. With the advent of increased mechanization particularly where trunk conveying is adopted and the tub need not leave the main roads, the size of tub has greatly increased to between 2 and 6 tons, and in one case to 10 tons; and such larger cars will continue to replace tubs of 25 cwt or less ca­pacity when more installations of locomotive haulage, now in development stage, come into operation.

Where main roads are driven through the measures in the so-called horizon system of mining, mine cars are necessary to exploit the system to the best advantage.

The inherent advantage of mine cars over tubs are that the capacity of the whole transport system is increased and becomes more economic, since the useful load is increased relatively to the gross load, the power required is reduced since the friction is lessened, and the number of cars in circulation and in conse­quence the men required to manipulate them - is also reduced.

(1100)

NOTES:

• tub - бадья, вагонетка (до 0,7 м3);

• car - вагонетка (емкостью 1 тонна и более);

• bulk - объем, основная масса;

• gross load - общий вес.

Text 8. Conveyers

A system of conveyers is commonly divided into two sec­tions: (a) transport on the face; (b) transport by gate or room and trunk conveyers.

There are three main types of face conveyers: 1) jigging or shaker conveyers; 2) belt conveyers; 3) scraper conveyers.

Each of these suits best certain conditions of inclination, output or custom in the coal-field.

The shaker conveyer is essentially a downhill conveyer and although it may function satisfactorily in level conditions it is rarely suitable for even a slightly rising gradient.

This conveyer consists of a line of troughing in 10 or 11 ft sections connected to each other by bolts and nuts, ropes, or by wedges and other quickly-connected fasteners. The pans (troughing) are mounted on rollers and cradles shaped to give an abrupt stop at the end of the forward stroke of the conveyer, or on steel balls confined in frames which give only a horizon­tal motion to the troughing.

For a high concentrated output whether the coal is deliv­ered uphill or downhill, the belt conveyer, consisting of a driven drum, a double length of belting and a tension drum, is generally preferred for face work. The width of the belting employed varies from 20 in. to 26 in. and exceptionally 30 in., and the speed is from 100 to 200 ft per minute. The output from a 20-in. wide belt conveyer is about 50 tons per hour when running at 10 ft per min. and 85 tons at 175 ft; a 26-in. belt at the same speeds will give 65 and 110 tons per hour re­spectively. The height varies from 6 ft to 13 in. according to the thickness of the seam. The rollers supporting the top belt are at intervals of 3 ft, those-supporting the return belt every 6 ft.

A feature of recent years has been the return to popularity of the scraper chain conveyer. Its simplicity, robustness and reliability in its modern form has led to its increasing use in both longwall, and bord and pillar systems of mechanized mining.

In the latter the room type of easily extendible scraper conveyer is used to receive the output from loaders where shuttle cars cannot be employed, and this can deal with an output of 1.2 tons a minute with a chain speed of 126 ft per minute.

For longwall work either the single chain or the double chain type is used with capacities from 32 to 100 tons per hour _On the level, using 12 in. and 20 in. troughing and motors of 8 to 35 hp.

On the Ruhr an armoured scraper conveyer of this type has been developed for use with the coal plough. It is driven by motors of 50 hp at each end of the face with a 50 hp com­pressed-air engine which can be clutched in if an overload occurs. Resonance conveyers are also used with the plough and other power loaders.

(2200)

NOTES:

• shaker (or jigging) conveyer - качающийся (или вибрационный) конвейер;

• belt conveyer - ленточный конвейер;

• troughing - 1) лопатки, 2) система рештаков;

• longwall - сплошной забой;

• bord and pillar systems - камерная и столбовая системы разработки;

• room type - камерный тип разработки;

• armoured scraper conveyer - бронированный скребковый конвейер;

• plough - струг.