150-Ton floating crane

This type of crane has many uses. It oftea carries out work which cannot be done by any other handling equipment. It is usual­ly mounted on a steel platform, which draws nearly seven feet of water. A weight of 150 tons can be taken to a height of 178 ft. with the main hoist, and 50 tons to a height of 216 ft. with an auxiliary hoist. Other details are as follows: height of base 84 ft., length of steel jib 140 ft., the main hoist can lift at a distance of 60 ft. from the pontoon and the auxiliary hoist has a maximum out­reach of 100 ft. from the pontoon.

When required, this crane can be towed by two or three tugs; the large parts and heavy lifts can be carried on the pontoon if necessary as the deck has been specially strengthened.

DOCKSIDE CRANES

One of the new types of cranes introduced in recent years is the mobile and flexible level-luffing slewing crane which is completely ousting the old type of crane with fixed jib. These modern level- luffing slewing cranes with luffable jib can alter their radius quickly under load.

They can cover from a central point a wide circular area and therefore do not need to be travelled to and fro at each working cycle.

The transhipping performance of these cranes is still further enhanced by measures which permit of the slewing gear running quicker at short radii and of the hoisting speed with light loads and empty hook being increased to three or four times that of the speed with heavy loads.

WORDS AND PHRASES

heavy lift crane тяжелый кран

occasional [э'ке!зпэ1] случайный

fertilizer ['fa:tilaizaj удобрение

warping 'w3:pig] верпование

towing ['touig] буксирование

to accelerate [ak'selereit] ускорять

notable ['noutabl] известный, славящийся

accurate ['sekjunt] точный, правильный, тщательный

the rope-pull-operated weighing equipment взвешивающее устрой­ство с канатными блоками compression member элемент, работающий на сжатие

lattice girder ['laetis 'ga:da] решетчатая ферма

axle [asksl] ось

guide pulley ['gaid 'puli] направляющий шкив

In the weighing direction в направлении взвешивающего эле­мента

to result (from) являться результатом (ч.-л.)

balancer ['baslansa] стабилизатор, уравнитель

to compensate уравновешивать

automatic weighing machine автоматические весы

cab кабина

to record [ri'kDrd] регистрировать

lb. (лат. librum) = pound фунт

tare weight beam противовес, уравновешивающий тару

grab грейфер

hook sling подвеска с захватом

to sum up суммировать, подводить итог

resultant - итог

grab bucket храповой ковш

auxiliary - вспомогательный

hoist -таль, лебедка

pontoon - понтон

level-luffing slewing crane - поворотный кран с горизонтальным

перемещением груза при изменении вылета стрелы

toalter['о:Нэ] (из) менять

tooust [aust] вытеснять

performance - действие, производительность

to enhance [in'hct:ns] повышать, увеличивать, усиливать

EXERCISES

I. Answer the following questions:

1. What capacity of the cargo quay crane is considered normal?

2. In what case are heavy-powered cranes provided?

3. What are floating cranes used for?

4. Why is the cost of a floating crane greater?

5. What are the advantages of a floating crane?

6. What is the average capacity of the floating crane?

7. What are the grabbing floating cranes used for?

8. Does the use of floating cranes reduce demurrage?

9. What does the compression member support?

10. Where is an automatic weighing machine installed?

11. What is an automatic weighing machine equipped with?

12. How is the resultant obtained?

13. What does the total load consist of?

2. What are the functions of the -ed form in the following sentences? Translate the sentences into Russian:

1. In this manner we achieved an important economy of time compared with the old method. 2. Soviet dockers are skilled machine operators. 3. The main advantages gained by the new installation can be summarized as follows. 4. This type of floating crane was designed by a Soviet engineer. 5. Wagons were unloaded by two electrically operated side-discharge tipplers and weighers located between the tracks. 6. This complex equipment incorporated numerous improvements.

2. Translate the following sentences into English:

1. Поворотные краны с постоянным и переменным вылетом стрелы были созданы в XIV в. 2. Поворотные краны бывают ста­ционарными и передвижными. 3. Краны с горизонтальным пере­мещением груза изменяют вылет с подвешенным грузом. 4. Сред­няя скорость изменения вылета для кранов до 10 т— около 0,5 м/сек. 5. Скорость подъема груза в кранах небольшой грузо­подъемности равна 1 —1,5 м/сек. 6. В кранах большой грузоподъ­емности скорость меньше. 7. Максимальная рабочая нагрузка это­го крана равна 10 г на вылете стрелы 12 м. 8. Известно, что наи­больший вылет стрелы этого крана 40 м, наименьший—10 м, 9. Плавучие краны большой грузоподъемности применяются для перегрузки тяжеловесов. 10. Плавучие краны монтируются на плавучем понтоне и передвигаются внутри порта с помощью бук­сиров или собственным ходом. 11. Плавучие краны бывают как самоходными, так и несамоходными. 12. В плавучих кранах при­меняется как паровой, так и моторный привод. 13. Моторный при­вод имеет более высокий к.п.д., чем паровой. 14. Кран поднимает груз на высоту 1 м над комингсом люка. 15. В конце 1958 года в Ленинградском порту была организована выставка, на которой демонстрировались новые грузоподъемные устройства. 16. Наш завод отправляет краны в страны народной демократии. 17. Со­вершенствуя процесс погрузки угля на суда, портовики добились высоких результатов. 18. Современные причалы следует оснащать новыми типами береговых кранов. 19. В нашем порту есть пла­вучий кран грузоподъемностью 100т.

Lesson eight

MOBILE CRANES

Safeguarding stability is the most important factor for mobile cranes.

The overloading of a mobile crane may result in: —

1. Fracture of a component due to overstress.

2. A condition of instability followed by overturning.

In practice, failure due to (a) is extremely rare, certainly far less frequent than failure due to (b), the reason being that the de­signer practically does not know weight distribution when dealing- with load stresses on the crane structure and mechanical com­ponents. Therefore he is able to adopt normal factors of safety of not less than 4'/₂ or 5 for structure and 6 or 7 for gearing and ropes.

The factor of stability is synonymous with the factor of safety. A mobile crane must travel over average road surfaces, perhaps on a gradient with load suspended from the hook. It may be, and more often is, without outriggers, draw beams or other aids to stability. There are limitations the designer must observe regarding wheel loads, axle loads and tyre pressure. Wind velocity and gradients must be allowed for and care taken that an „excess of tail weight does not render the crane unstable backward when the jib and fit­tings are removed.

Cranes operating grabs or flat-bottomed skips encounter in­determinate overloads due to suction or to the grab jaws closing on some submerged object such as a pile.

Similarly, when operating with an electromagnet an overload may be imposed due to the magnetization of the billets in contact with the magnet.

Again, where cargo is being handled from a wharf or elevated gantry there is no chance of recovery from an overload by allowing the suspended load to rest on the ground. In many other classes of work, such as the handling of miscellaneous scrap metal, the weights lifted are often more guesswork. With reasonable care it will generally be found possible to pick up any load at the ap­propriate radius which, of course, is better not only for the machine but for the goods handled.

A HEAVY MOBILE CRANE

This crane embodies a number of new and original features. High speeds are required for duties such as grabbing and magnet operation.

The controls of this crane are simple in operation and are so placed as to avoid fatigue of the driver. There are only three foot pedals (for engine clutch, travelling brake and engine speed) and steering is by a large diameter steering wheel, set at the optimum angle for easy manipulation. The levers are light in operation and are placed conveniently to hand so that any chance of confusion is avoided. The weatherproof saloon cab has large safety-glass wind­ows all round which give an exceptionally wide range of vision. A cab heater for use in cold weather can be fitted if required.

The crane is a full-circle slewing type and uses the direct mechanical transmission system with diesel prime mover. The four motions of hoisting, slewing, travelling and luffing are indepen­dently operated and reversible.

A new feature, the advantages of which will be readily appre­ciated by engineers, is the application of unit construction to the various crane motions. Each motion, i.e. hoisting, slewing, luffing and travelling, has its own gearbox with enclosed bearings and gears with oilbath lubrication. The hoisting and luffing brakes, which are semi-automatic in operation, are arranged for manual adjustment without tools, in order to facilitate regular attention.

The maximum load of six tons can be hoisted at speeds up to 1220 cm. per minute, but lighter loads up to two tons can be handl­ed at 3,648 cm. per minute, enabling high outputs to be attained when the crane is used for grabbing. For accurate placing of loads an inching movement is provided, either for lifting or lowering, bv a small movement of the joy-stick type lever.

The crane slews on a large diameter ring of live-rollers, which give extremely smooth action. The slewing speed is variable up to 2'/2 r.p.m. in either direction and slewing can be carried out simul­taneously with hoisting if this is desired for fast operation.

The luffing gear, which is completely independent of the other motions, will raise the jib, with load if necessary, from maximum to minimum radius in 20 seconds.

A full load of six tons can be carried on level ground at speeds of up to 3 miles an hour. Without loads, on level ground the crane can travel at six miles an hour and can turn in a circle of 699 cm. radius. Travelling speed is operated by accelerator pedal, and large plate clutch in conjunction with a three-speed gearbox gives extreme­ly smooth flexible control. Brakes of 2-leading shoe-type are fitted on all four travelling wheels, which make for maximum safety under all road conditions. The brakes are operated by foot pedal.

Pneumatic tyres are employed on wheels of special design which are slightly smaller in overall diameter than the tyres. Such wheels have many proven advantages. They limit deflection of the tyres when slewing and thus obviate instability which might arise if, for example, the tyres were under-inflated. They provide a large addi­tional bearing area which prevents the cranes from sinking in soft ground. They protect the side walls of the tyres from damage when the crane is working in, say, steel stock-yards, scrap yards, or alongside the kerb.

Finally, in the event of a sudden blow out the resistor wheels take the weight immediately, so avoiding what might be a serious accident.

The standard power unit is a diesel engine of 37 b.h.p., fitted with maximum speed governor in addition to the variable speed control operated by the accelerator pedal in the driver's cab.

WORDS AND PHRASES

stability [sts'bihti]устойчивость

fracture ['frsektja]разрыв

overstress перенапряжение

overturning опрокидывание

the reason being that по той причине, что

to adopt допускать

factors of safety факторы безопасности gradient уклон

outrigger укосина

draw beam стрела для поднятия тяжестей

regarding относительно

tyre [taia] шина