Exercise 6. Discuss the following topics.
1) Reasons of derangements in operation of engines.
2) Of what factors does the choice of engine (diesel/steam) depend on?
3) Comparison of steam and diesel engines (advantages and disadvantages).
4) How long have diesel electric systems been used?
5) What are the advantages of DEP?
6) Explain why different sizes of diesel generators are so important.
7) What should be done in order to reduce noise and vibration?
Lesson 2.
WRONG FITS AND CLEARANCES
Exercise 1. Read and learn the following words and expressions:
Synonyms:
1. design / construction - конструкция
2. to investigate / to consider / to examine – рассматривать, расследовать
3. volume/ capacity / bulk – емкость, вместимость
4. to discharge / to use up / to run down – разряжать
5. to develop / to evolve / to expand – развивать, расширять
Vocabulary notes:
1. crank – кривошип
2. crosshead – крейцкопф
3. bearing – подшипник
4. surface – поверхность
5. gripping – заедание
6. cam – кулачок
7. roller – ролик
8. ring slot – зазор/паз кольца
9. crank pit – лоток для кривошипа
10. vernier – нониус
11. caliper – штангенциркуль
12. jaw – фиксатор/зажим
13. to distort – искажать
Exercise 2. SCAN THE TEXT AND BE READY TO DISCUSS IT.
The principal source of trouble from this cause is the large bearings of the main shaft, cranks and crossheads. In general, the bearing pressures are higher in the DE than in the steam engine and more careful and accurate fitting is required, so that the maximum bearing surface will be obtained. All bearings must be relieved at the sides enough to prevent gripping and to assist the spread of the lubricating oil around the bearing but not enough to reduce the bearing surface too much when they expand with the heat. All of the bearings, large and small, about the engine are subject to wear and looseness may develop in any of them in service but the large bearings just mentioned have the most severe duty to perform and require adjustment more often than the others.
MEMORIZE THE FOLLOWING MINDMAP TO EASE DERANGEMENT UNDERSTANDING
Mechanical defects resulting in failure of parts in service may be due to errors in design, errors in machining or defects in the material itself.
Errors in design have been too numerous to catalog but in the case of most well established builders such errors have been eliminated by experience in operation.
Errors in machining are not the rule in any engine, if the manufacturer has an efficient inspection department, but they do occur and sometimes cause a great deal of trouble. Such errors are usually difficult to discover because they are not expected and the troubles resulting are assigned to other causes. Sometimes careful investigation and analysis will reveal that a breakage that was apparently caused by a mechanical defect was due to bad work or neglect on the part of the engineers.
Defects in the material do still occur due to neglect on the part of ship owner or repairmen while using improper and cheaper spares for major or minor repairs thus violating the manual requirements and specifications of ship builder.
MEMORIZE THE FOLLOWING MINDMAP TO EASE DERANGEMENT UNDERSTANDING
Exercise 3. Answer the following questions.
1) What is the principal source of trouble from wrong fits and clearances?
2) Why may looseness or slackness develop in any of the bearings in service?
3) What are the sources of mechanical defects?
4) What errors are usually difficult to discover?
5) What will sometimes careful investigation and analysis reveal?
6) Why is more accurate fitting of bearings required in DE?
Exercise 4. Translate into English.
1. Большие подшипники главного вала, кривошипов, крейцкопфов являются основными источниками аварий.
2. Все подшипники подвержены износу в процессе эксплуатации двигателя и поэтому требуют периодической подгонки.
3. Механические дефекты возникают вследствие конструктивных ошибок, погрешности при механической обработке деталей, дефектов в самом материале.
4. Это следует иметь в виду во время работы двигателя.
5. Такие погрешности трудно обнаружить, потому что на них не рассчитывают, и возникшие неисправности приписывают другим причинам.
6. Иногда тщательное расследование и анализ аварии показывает, что она произошла вследствие небрежной эксплуатации, хотя на первый взгляд кажется, что авария была вызвана конструктивным дефектом.
7. Давление на подшипники в дизельном двигатель выше, чем в паровом, поэтому требуется их более тщательная подгонка.
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