Watch the video “Diesel Engine Startup” and discuss the following topics.

[https://www.youtube.com/watch?v=4_IrG9vzb-A]

1) Describe the process of starting the engine

2) Why the right fits and clearances are so important?

3) What types of bearings we can find in common motorship's engine?

Lesson 4. SYSTEM DEFECTS

 

Exercise 1. Read and learn the following words and expressions.

Synonyms:

1. accumulation / pilling / assemblage - накопление, аккумуляция
2. to lubricate / to smear / to oil – смазывать
3. frequent / rapid - частый, повторяющийся
4. to plug up / to clog / to obstruct - засорять(ся)
5. to bind / to grip – заедать
6. to lift / to heave / to raise - поднимать

Vocabulary notes:

1. shoal/shallow water – мелководье

2. stroke – ход, такт

3. suction – всасывание

4. particle – частица, комок

5. micrometer – микрометр

6. hiss – посторонний шум, шипение

7. air pocket – воздушная пробка

8. indicator cock – индикаторный кран

9. fuel nozzle – форсунка

10. valve stem – шток клапана

11. discharge valve – выпускной клапан

12. jellyfish – медуза

13. air injection engine – компрессорный двигатель

14. pipe – труба

15. copper – медь

16. devastating – разрушительный

17. public system – коммунальная система водоснабжения

18. joint – место соединения

19. stopcock – кран

20. blowlamp – паяльная лампа

 

Exercise 2. Read, translate and discuss the text.

F uel system defects

Derangements in the fuel system are most likely to occur at the fuel measuring pumps. These pumps must handle a very small amount of oil at high pressure on each stroke and in order to do this the suction and discharge valves must be kept in perfect condition. A frequent source of trouble with these valves is dirt or grit in the oil. A small particle of sand or a thread qf waste under a valve will cause it to leak. Good strainers should be provided in the fuel oil supply line to the pumps and the strainers should be cleaned frequently. The pump plungers should be very carefully packed to prevent leakage of oil outward and air inward. Accumulation of air in the pumps will cause either irregular supply of fuel to the engine or stoppage. Stoppage of fuel supply to any one cylinder throws extra load on the other cylinders when the governor acts to increase the pumps discharge. Repeated regrinding of the pump suction valves will require careful checking of the pump timing.

Combustion defects

Normally the combustion in each power cylinder should be smokeless and complete and occur early in the stroke. Insufficient breaking up of the oil during injection will cause slow and incomplete burning and may be the result of clogged fuel nozzles, oil too cold or incorrect timing. Other causes of incomplete burning are compression too low, injection valves not correctly timed and air inlet pipes clogged.

Cooling water system defects

Complete stoppage of the cooling water supply can hardly occur unless the circulating pump breaks down or the ship grounds in shoal water where mud may plug up the sea injection valve, thus stopping the supply of raw water to the coolers of a closed fresh water system or the jacket supply of a sea water cooling system. In the event of the rare occurrence of pump breakage there is always an auxiliary pump available. Most well designed ships, especially when designed to operate in shoal water, have high and low sea suctions. The high suction is used in shallow water where mud might be drawn in through the low suction. The low suction should always be used at sea as the rolling of the ship is likely to throw the high suction out of the water and admit air into the system. It not infrequently happens when ships anchor in tropical harbors that the sea suction becomes clogged with jellyfish. When this happens it can be cleared by blowing out, if a steam or air connection on the body of the sea valve is available.

Failure of the water supply to any individual cylinder or piston may be caused by an air pocket in the supply line to that point or in the upper part of the cylinder head. Where all of the cooling water is passed through the coolers on the air compressor before reaching the engine jackets a leak in a cooler will allow air to blow into the water and stop the supply to all cylinders.

Lubricating system defects

All Diesel engines today are lubricated by the forced feed method and no hand oiling of any part is required. This requires that the engine housings be closed in, to prevent loss of oil through splashing, and the oil piping, with the oil circulating pump, forms a closed circuit through which the same oil circulates repeatedly. Of course the most serious derangement in such a system is loss of pressure.

Air system defects

The most serious derangement that can occur in the air system of an air injection engine, aside from the remote possibility of an explosion, is loss of injection air. Assuming that the compressor suction is open and the bleeder valve in the first stage properly adjusted, a falling off in the air pressure may be due to leaky, broken or stuck compressor valves, an injection valve sticking open, leaky air valve stem packing, leaky joints in the air piping or failure of the cooling water supply. If the air pressure falls to somewhere near the compression pressure in the power cylinders, unless the trouble can be located immediately, the engine should be stopped. If the engine is kept running, there will be a possibility of an explosion inside the injection valve body.

 

Exercise 3. Answer the following questions.

1) What derangements in the fuel system are most likely to occur?

2) What will cause the valve of the fuel measuring pump to leak?

3) When should combustion occur in each power cylinder?

4) What are the causes of incomplete burning?

5) When can complete stoppage of the cooling water supply occur?

6) What sea suctions do most well-designed ships have?

7) When is the high suction used?

8) Which sea suction is used in shallow water?

9) How are all Diesel engines lubricated today?

10) What is the most serious derangement that can occur in the air system of an air injection engine?

 

Exercise 4. Translate into English.

1. Неисправности топливной системы чаще всего встречаются в клапанах топливных насосов.

2. Скопление воздуха в насосах либо нарушит регулярную подачу топлива к двигателю, либо совсем прекратит ее.

3. Повторные притирки всасывающих клапанов требуют внимательной проверки.

4. Как правило, сгорание топлива в цилиндре должно быть полным, бездымным.

5. Неполное сгорание может происходить вследствие очень низкой компрессии.

6. Большинство судов, предназначенных для плавания на мелководье, имеют нижние и верхние приемные патрубки забортной воды.

7. При стоянке в тропической гавани приемный патрубок забортной воды может быть забит попаданием в него медузы.

 

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

A.: What are some of the causes of loss of injection air pressure?

В.: Leaky, broken or stuck compressor valves, injection air valve sticking open, leaky spray air valve stem packing, leaky joints in air piping, loss of cooling water.

A.: How can a start be had if there is no compressor available?

В.: Procure a bottle of CO2 gas and connect it to the starting air line. This gas is non-explosive and safe to use for this purpose.

A.: What are some of the causes of failure of an engine to start firing after it begins to turn on air?

В.: Fuel pumps not discharging oil, incorrect timing of fuel valves, low compression, injection air pressure too low and cylinders too cold.

A.: What are some of the causes of cracked cylinder heads?

В.: Unequal heating, due to poor design, air pockets in jacket, insufficient cooling water and overloading.

A.: How does wear on main bearings cause crank shaft to break?

В.: By throwing the shaft out of line and causing it to be bent in alternate directions twice in every revolution.

A.: Give the valve timing for the average and large 4-cycle engine.

В.: Injection valve opens 5 degrees before top center, injection valve closes 49 degrees past top center, exhaust valve opens 140 degrees past top center, air inlet valve opens 15 degrees before top center, exhaust valve closes 10 degrees past top center, and air inlet closes 214 degrees past top center. When in use, the air starting valve opens at top center and closes at 128 degrees past top center.