IV. Translate the following sentences into English:

' 1. Простейшие подъемные устройства применялись более чем 2000 лет до нашей эры. 2. В Древней Греции применялись устрой­ства, являющиеся прототипом простейшего подъемного крана. 3. В конце XX в. появился электрический привод, который быстро вытесняет другие виды приводов. 4. Для питания электродвигате­ля применяется постоянный и переменный ток. 5. В Одесском порту много береговых кранов. 6. Современные краны могут об­рабатывать грузы на довольно высокой скорости. 7. Электриче­ский привод является самым распространенным типом привода. 8. При электрическом приводе, как правило, все механизмы име­ют самостоятельные моторы. 9. В настоящее время строительство кранов идет по пути дальнейшей стандартизации отдельных уз­лов, уменьшения веса, повышения степени безопасности работы. 10. В новых портовых кранах гидравлический привод применен не только для подъема стрелы, но и для подъема груза и поворо­та крана. 11. Подъемный механизм является основным в грузо­подъемных машинах. 12. Для механизации погрузочно-разгрузоч- ных работ со штучными грузами используются, главным обра­зом, краны различных типов грузоподъемностью до 50 т.

Lesson seven

HEAVY LIFT CRANE

In the foregoing pages, the description has been confined to the cargo quay crane of normal capacity. There are, however, occa­sional lifts to be dealt with, exceeding the normal limits. For these it is customary to provide a few heavy-powered cranes at each port and one or more floating cranes, which can lie alongside a vessel or a quay, as the case may be. The cost of a floating crane is, of course, greater, both as regards construction and working, but it has corresponding advantages. Floating cranes range in power from 10 or 15 tons to 50 or 100 tons. There are cranes of 200 to 500 tons capacity. A 50- or 60-ton crane, however, is generally capable of handling almost everything. Fixed quay cranes are of equivalent capacity.

FLOATING CRANES FOR BULK HANDLING

The grabbing floating cranes are mainly employed to handle bulk goods, such as ore, coal, phosphate, fertilizers, etc.

The use of floating cranes reduces demurrage as well as the harbour dues to be paid. In addition, very considerable costs can sometimes be saved on the warping or towing of sea-going vessels.

Fig. 8. The balancer-type design ensures a horizontal movement of the load

Floating cranes can be employed at the ship's berth in the harbour, for example when the loading or unloading of ships is to be accelerated. The floating cranes are also suited for assisting quay cranes in cargo handling, particularly for lifting cargo weigh­ing up to 12.5 tons, which is too heavy for the usual 3-ton harbour cranes.

These cranes are notable for their extremely accurate auto­matic weighing equipment.

For the rope-pull-operated weighing equipment, a compression member consisting of a lattice girder has been provided.

The axles of the guide pulleys at the front are supported by this compression member and by the upper compression girder located in the platform. The bottom end of the compression member is sup­ported in the weighing direction at some point.

Positions, which result from the operation of the balancer, are also compensated for by a special device, as is the influence of the pontoon's heel.

An automatic weighing machine installed in the operator's cab enables the weight of the load to be recorded with an accuracy of approximately 10 lb. The automatic weighing machine is equipped with a tare weight beam for balancing out the deadweight of either the grab or the hook sling, so that only the weight of the bulk material or cargo being lifted is measured, recorded and sum­med up.

The resultant is obtained from the total load consisting of the weights of the grab bucket contents, the bucket and the ropes them­selves as well as of the rope pull.