The surface of the slip rings must always be kept smooth & clean. The slip rings are cleaned with a dry cloth or, if necessary, with a cloth dipped in petrol. Special attention has to be paid to all insulating surfaces of the slip rings & brush holders. Also dry compressed air may be used for cleaning. Lubricants of any kind must not be used between the slip rings & the brushes.
If the surface of a slip ring is damaged, the slip rings must be turned.TIj.e turning is done by rotating the machine with the aid of the' auxiliary motor & the pulley at a speed below the rated speed. The recommended periphery speeds for slip rings are:
steel approx, 50 - 90 m/min
bronze approx.90 - 130 m/min
When turning the slip rings of a machine provided with sleeve-bearings, the min. periphery speed, however, is determined by the permissible min. speed of the machine.
25. /3 мин./ Парная работа. Обсудите Особенности ухода за оборудованием с контактными кольцами.
26. /5 мин./ а) Прослушайте/прочуйте и запомните содержание двух предложений, первое из которых предписывает выполнить операцию по уходу за машиной, а второе называет цель, б) Используя модель, объедините эти предложения в одну фразу, сделав необходимые преобразования.
Model. Keep the machine clean & dry. - Effective cooling & insulation. = For the effective cooling & insulation the machine must be kept clean & dry.
1. Clean the pipes from time to time with the brush delivered with the heat exchanger. - To reduce the cooling capacity.
2. Keep the water flow in the cooling pipes close to the value instructed by the manufacturer. - To prevent corrosion.
3. Keep the machines which have been unused for long periods of time in a dry place. - To prevent the moisture from penetrating to the bearings & windings.
в) Парная работа. Обсудите проблемы ухода за оборудованием /4 мин./.
27. /4 мин./ Прослушайте/прочтите вопросы и дайте на них ответы.
1. What indicates the water flow decrease? 2. How would you detect that the water flow decreased too much? 3. What in your opinion causes easily damages in the windings?
28. /4 мин./ а) Прослушайте/прочтите и постарайтесь запомнить информацию о порядке заказа щеток, б) Повторно прослу-шивая/читая информацию, отметьте, какие данные необходимо указать при заказе.
• Ordering New Brushes
When ordering new brushes, the quality, size & supplement accessories have to be quoted. When the brushes are ordered from our works, we shall deliver the correct brushes if the type designation & manufacturing number
of the machine are given to us. If the brushes are ordered elsewhere, the quality can be determined by the marking made on the brush by the manufacturer. The dimensions & accessories of the brush can be determined by comparing the form & dimensions of the worn brush to the enclosed dimension print & by giving the corresponding brush type. The mark of the brush to be replaced should correspond to the mark which is recommended for this type designation of the machine or, as an exception, the brush should possess close characteristics.
29. /14 мин./ Отработайте чтение основного текста сами или имитируя произношение и интонацию диктора.
30. / 2 мин./ а) Прослушайте/прочтите диалог, стремясь понять основное содержание; б) Повторно прослушивая запись или читай диалог, делайте заметки об основных смысловых моментах с целью последующего их использования в беседе.
A scientist: Have you got your doctor’s degree in science?
A pilot: No, I haven’t.
S.: This is very bad. If you had a doyctor’s degree you would be a lecturer in my college, I am sure you would. /Ten minutes later/
. Have you got a master’s degree in engineering?
P.: No, I haven’t. I haven’t a degree at all.
S.: This is very bad. If you had a degree in science or in engineering, you wouldn’t be just a pilot. You would be a manager of a factory or...
P. /inerrupting him/: By the way, have you got a parachute?
S. /a little surprised/: No, I haven’t. Why do you want to know?
P.: E... well. If you had a parachute I think you’d be much safer. You see, the plane’s developed engine trouble & I would not be at all surprised if it fell down...
