Vibration

The amount of vibration of an engine and of the ship's hull in which it is installed will depend on how well the reciprocating and rotating masses in the engine are balanced and the position of the engine relative to a nodal point in the hull. These are both matters over which the operating engineer has no control. Normally Diesel engines, especially in the large sizes, run with very little vibration but it sometimes happens that an engine will have a critical speed, a speed at which the twisting impulses imparted to the crank shaft by the pressure acting on the pistons coincide with the natural period of vibration of the crank shaft. When the engine operates at this speed violent vibration will occur that may result in loosening nuts, shaking off small fittings, breaking pipes and even breaking of the crank shaft, if continued long enough.

Exercise 1. Answer the following questions.

1) Due to what causes may the engine fail to start on air?

2) How can water get into fuel oil?

3) What is the only remedy against improperly refined oil?

4) What may a distinct loss in efficiency sometimes result from?

5) Why are cracked heads and cylinders not so common as they used to be in the early days of Diesel engineering?

6) What does the amount of vibration of an engine and of the ship's hull depend on?

7) Why was a cracked crank shaft considered one of the inevita­ble hazards associated with Diesel engine operation?

8) When may violent vibration occur?

Exercise 2. Give the Russian equivalents of the following.

1) Air pocket.

2) To start on air.

3) Starting air valves.

4) Exhaust valves.

5) Unequal heating.

Exercise 3. Use the correct words from the text.

1) Mechanical defects may be due to errors in ...

2) There are errors which are difficult to ... because they are not expected.

3) A careful . . . revealed that the engine trouble was due to neglect on the part of the engineers.

4) A thread of waste under the valve caused it to ...

5) Stoppage of fuel supply to one cylinder throws extra ... on the other cylinders.

6. ... of cylinder heads often results from unequal heating.

7. When ... of power occurs the first possibility that should be investigated is hot bearings.

Exercise 4. Translate into English.

1) Неисправности в двигателе, связанные с пневмозапуском, могут быть вызваны неправильной регулировкой воздушно­го пускового клапана и другими причинами.

2) Вода может попасть в топливо вследствие переменного ис­пользования цистерн для топлива и водяного балласта.

3) Резкое снижение температуры забортной воды влияет на мощность двигателя.

4) Трещины цилиндров происходят вследствие неравномерного нагрева, из-за конструктивных недостатков, плохой отливки, воздушных пробок.

5) Самой серьезной неисправностью, которая встречается в воз­душной системе пневмозапуска, является падение давления воздуха, поступающего в цилиндр.

6) Бдительность со стороны механиков может исключить при­чины, вызывающие аварии двигателя.

Exercise 5. Make up a dialogue of your own based on the one given below.