Fig.5. General arrangement of property for dragline mining

The best arrangement of hopper, grizzly, and launder will depend on local conditions and will probably require a certain amount of experiment in each case; the points to look for are simplicity and lightness in construction, and a satisfactory rejection of stones from the grizzly and of the pebbles from the top part of the launder, which will not travel with the tailings.

A suggested size of hopper mouth for working with a ½-yard dragline bucket will be about 10 feet by 10 feet, with sloping sides to the grizzly bars, having an area of, say, 6 feet by 8 feet; below the grizzly bars, a box 6 feet by 6 feet with a bottom slope of 1 in 25 corresponding to that found necessary for the launder. The bottom end of this box would be open, leading direct to the launder. The grizzly bars will slope at right angels, to the slope of the box below so that the stones are rejected at right angles to the line of launder and in direction from which the dragline is feeding the hopper. The importance and value of this provision is that, when the stones ejected from the grizzly and shovelled out of the launer have reached a sufficient pile, the dragline bucket can be fowered alongside the hopper unit to pick up these stones and deposit them on the overburden dump as explained previously. (http://ru.scribd.com/)

COMPREHENSION CHECK

Exercise 8. Complete the sentences using the information from text 2.

1. Excavating machinery usually consists of ...

2. The dragline is practically identical with the mechani­cal shovel as far as …

3. Almost any property will have a definite downstream boundary and fairly well-defined side boundaries can be drawn, which determine ... .

4. A first cut commenced on the downstream boundary, with its side limit resting on ...

5. The disposal of the overburden in the second series of cuts is the same as in the first series; the disposal of tailings is effected by ...

6. The best arrangement of hopper, grizzly and launder de­pends on ...

Exercise 9. Find the English equivalents of the words and word combinations in the text:

вскрышное оборудование, длина стрелы, выгружать породу (из ковша), продвигать экскаватор вдоль уступа, гусеницы, вращающаяся часть экскаватора, подъемный канат, длина отвалообразования, борт разреза, пустая порода, отбросы, гарантировать полную отработку, простота и легкость конструкции

LANGUAGE REVIEW

Exercise 10. Use it can… or it can’t:

If something is washable, it can be washed.

If something is

1. unbreakable, it ________

2. portable _____________

3. unusable _____________

4. invisible ______________

Exercise 11. Write the sentences in another way, beginning as in the example:

Example: It is predicted that the mine will be able to access over 12.5 million ounces of gold. - The mine is predicted to be able to access over 12.5 million ounces of gold.

1. It is expected that the weather will change tomorrow. The weather is______

2. It is believed that the company will increase the output, The company is ___

3. It is reported that two miners were seriously injured. Two miners are____

4. It is said that the enterprise will buy new mining equipment. The enterprise is ________

5. It is reported that the building was badly damaged by the fire. The building is ________

SPEAKING

Exercise 12. Discuss the questions with the partner.

1. There are four main kinds of excavating machines. (What are they?)

2. There are some common machinery units of dragline and power shovel. (What are they?)

3. The digging action of the dragline is performed by the jib. (How is it performed?)

4. The first cut is made at the downstream boundary of the property and provision must be made to dispose of the tailings. (How are those tailings disposed?)

5. As soon as the cut is opened, a pump would be installed. (Why?)

Exercise 13. Give a short description of a dragline excavator. Use the words below:

dragline excavator; base; revolving frame; main machinery units; the digging part of the machine; jib; the digging bucket; the steel rope; the hoist; payable ground; mining cuts.

VOCABULARY

conjunction - связь

trucks - грузовики

rails - рельсы

expenditure - расходы

carrier - грузовой транспортёр, автомобиль

water supply - водоснабжение

delay - задержка, простой

a derrick - вышка, эстакада

a sheave - ролик, шкив

a rack - зубчатая рейка, стеллаж, решетка

a pinion - малая шестерня, зубчатое колесо

to handle - перекидывать

unsuitable – неудобный

anchorage - анкерное укрепление, заякорение

pick and shovel methods of excavation - выемка грунта с при­менением кайлы и механической лопаты

drum - барабан

to ensure - гарантировать

to haul up - поднять, затащить

to fee – питать

to discharge - разгружать

to avoid - избегать

paddock – шурф с прямоугольным сечением

brake - тормоз

clutch – муфта, зажимное устройство

tower - башня

mast – мачта, эстакада

fixed - фиксированный

carriage – несущий элемент, салазки,

load carrier – поддерживающее устройство

self dumping – самоопрокидывающийся

slack-line - провисающий канат

conveying - транспортирование, перекидка, перевалка

washing plant - промывочная установка

to be mounted - быть смонтированным

trommel - барабан, барабанный грохот

a jig - отсадочная машина

scarce - бедный, некондиционный

classifiers - классификаторы

Exercise 14. Find the meaning of the word combinations and make up sentences with five of them:

a haulage system; in conjunction with; to be employed to excavate; to load into trucks; a washing plant; to increase the expenditure; a cost per yard; to deliver the excavated material; a storage bin; to be available; inadequate water supply; gravel banks; costly delays; the digging unit; a boom (jib) carrying the dipper; to move in vertical (horizontal) plain; with respect to; to handle a load; within the radius; unsuitable for scraping; to result in more economical working; to be operated by; head and tail ropes; to be driven by; overburden stripping; scrape-hauler “Tandem”.

READING

Exercise 15. Read the text below looking for the main ideas concerning characteristics of power shovels, cableways and washing plants.