Fig. 42. Section of elevator pit (Joshua Hendy Iron Works)

Maximum height 0f lift. The natural head of water required for an elevator should be about five times greater than the vertical lift required, which means that the maximum height of lift would be about 20% of the effective head; in practice, on the other hand, it is found that the maximum height of lift is about 17% of the eff­ective head at the nozzle of the elevator. However, no definite rule can be given for the ratio between effective head and vertical lift, as the latter is dependent to some extent on the size of the gravel, the slope of the upraise pipe, and the pressure, as a high pressure or head of water is much more effective than a low head of water.

Capacity of elevators. The quantity of material and water lifted varies according to the ratio between effective head and vertical lift, the volume and head of water available, the flow of water and gravel to the intake of the elevator, and with the duty of the giant water, the latter being the most vital factor in calculating the size of the elevator. The solid material does not form more than 5% of the entire weight (water and gravel combined) lifted by the elevator, and in practice it is generally reckoned at from 2 to 3%, and so it is usual, when calculating the size of an elevator, to consider only the water capacity.

The table gives the capacity of Hendy hydraulic gravel elevators with the approximate sizes of sluices.

Diam. of up-raise pipe, inches	Total water (giants, elev. seepage), cu. ft.per/min	Suitable for use with one giant	Approximate width of sluices, inches
			Bedrock sluice		Surface sluice ah wood
			Steel	Wood
8 10 12 14 16 20	200-400 324-645 450-945 700-1300 1125-1725 1600-2700	1 1 2 3 4 5 or 6	10-12 10-12 12-14 12-16 16-24 24-36	12-18 12-18 14-18 16-24 20-30 30-42	24-30 30-36 30-36 32-42 40-60 48-66

EFFICIENCY OF ELEVATORS. The efficiency of hydraulic gravel elevators is very low, and varies from 10% to 20%.

Peele gives the following formula for calculating the efficiency of elevators:

E equals H (62∙4W+S)+62∙4N (H₁-H),

where:

E- equals % efficiency;

H- equals height of lift, in feet;

H₁- equals effective head at nozzle of elevator;

W- equals cubic feet per minute of water (giants, seepage, etc).

COMPREHENSION CHECK

Exercise 15. Complete the sentences based on the information from the text.

1. Hydraulic elevators are also used where … is not sufficient to use sluice boxes.

2. The gravel broken down by the giants, together with the spent giant water and seepage is delivered to … of the elevator by means of ... .

3. It is usually stated that the elevator nozzle water will lift 0,5 times its own … of ... .

4. The maximum height of lift is about ... of the effective head.

5. However, no definite rule can be given for ... between effective head and ... .

6. The efficiency of hydraulic gravel elevators is very ... , and varies from ... to … .

Exercise 16. Look through the text and find the English equivalents of the words and word combinations. Use five of them to make sentences.

гидромонитор; труба; насос; дамба; шлюз; водопровод; канава; землесосы; грунтовые насосы; насос; отбойка; выгонка; напор; струя; применять; годный; предотвращать; проход; скорость; благоприятный; продуктивность.

SPEAKING

Exercise 17. Make questions to the sentences below and ask them the partner.

1. It is vital to obtain information about the total length of leafs, flumes and pipe-lines required tor conveying the water to the giants at the working faces.

2. The main pipe from the bulkhead should be fitted with two vacuum valves.

3. A ditch 6 feet wide at the top, 3 feet at the bottom, and 3 feet 6 inches deep, will carry some 2500 to 3000 "miner’s inches" of water.

4. Liners reinforce the entrance section and the throat as these take the most severe wear.

Exercise 18. Render in English

1. Гидроэлеваторы применяются там, где уклон недостаточный для применения шлюзов.

2. Самая благоприятная глубина для работы гидроэлеваторов – 25 футов.

3. Наклон трубы изменяется в пределах от 40 до 90°, но обычный наклон от 60 до 70°.

4. Чтобы предотвратить засорение отверстия трубы крупными частицами, желательно установить грохот у конца шлюза.

5. Нельзя, руководствуясь каким-то правилом, определить продуктивность элеватора, так рак она изменится в зависимости от количества и напора воды, от работы гидромонитора, от количества промываемого песка и т.д.

6. Продуктивность гидроэлеватора очень невелика и изменяется в пределах от 10 до 20%.

Exercise 19. Answer the questions to the text "Hydraulic Elevators".

1. Where do the elevators have their greatest use?

2. To what part of the elevator is the broken gravel delivered?

3. To what depth has the gravel been successfully worked by means of hydraulic elevators?

4. What can you say about the water required?

5. Should the elevator be large enough to lift all that the giants can excavate?

6. What is the maximum height of lift?

7. What is it advisable to fit over the end of the sluice to prevent the throat of the elevator being choked and clogged up with large stones?

8. Is there any definite rule for determining the elevator capacity?

9. What can you say about the efficiency of hydraulic gravel elevators?

Exercise 20. Discuss the questions based on the information from the text and your own experience with the partner.

1. В каких пределах применяются наклоны трубы?

2. Каков обычный наклон трубы?

3. Почему желательно устанавливать грохот у конца шлюза?

4. Какова продуктивность гидроэлеватора?

5. Какова глубина для работы гидроэлеватора?

6. Где элеваторы чаще всего используются?

7. В какой части гидроэлеватора подается песок?

8. Что вы можете сказать о количестве требуемой воды?

VOCABULARY

free wash – обводнен, содержит свободную воду

tongue and groove joints – соединения в шип шпунтовке

log cribbing dam – касторовая плотина, сложенная из “кругляка”

as their name implies – как подразумевает само название

design - строить, конструировать

installation – устанавливать, располагать

consider - считать, рассматривать

affect - влиять

reduce - уменьшать, сокращать

lessen - уменьшать

width ширина

length - длина

ensure - обеспечивать

release - высвобождать

ditch - котлован, канава, ров

bedrock - котлован в коренной породе

bedrock cut - вруб в коренной породе

tailings stacker укладчик хвостов

tailings pile - укладка (складирование хвостов)

tailings disposal - уборка хвостов

watertight - водонепроницаемый

drop - падение, спад

rig - оснастка, буровая вилка

Exercise 21. Find the meaning of the words below and try to remember them.

proper construction; grade; vital importance; efficiency; obtain; design; consider; average; quantity; treatment; affect; reduce; calculate; state; sufficient; depend on; wash; supply; employ; utilize; passage; disintegrate upraise pipe; pollution; impounding; cribbing; fill up; brushwood.

READING

Exercise 22. Read the text below looking for the main ideas concerning sluice boxes.