Exercise 5. Read dialogues and reproduce them then make up your own dialogues based on topics given below.
1. Preparation requirements.
A.: If all the stored air is lost how the engines can be started?
В.: In most cases a small emergency compressor is provided, driven by a very small oil engine that can be started by hand. After a small amount of air is pumped up an auxiliary engine can be started and air pumped up to start the main engine.
A.: How much starting air capacity should the tanks have?
В.: The usual requirement is enough to start the engine 12 times. A better rule is to provide at least 35 times the volume swept through by one piston for each main engine.
A.: Describe the preparations for starting the engine.
В.: Jack the engine to see that it is clear for running, start lubricating oil pump and see that oil reaches all bearings, open by-pass valves in fuel oil lines to injection valves and pump oil through by hand to clear out all air and fill the pipes with oil, open stop valves in starting air and injection air lines, give cylinder lubricators a number of turns by hand to get some oil into the cylinders, start jacket cooling water pump and see that the propellers are clear. If means for heating the cylinders are available and the weather is cold, warming up should be started in time to have all the cylinders hot before starting.
2. Common troubles.
A.: Why should the bearings of a new engine be gone over after 800 to 900 hours of running?
В.: То take up looseness due to the initial wearing in.
A.: Why will a piston sometimes run without trouble at normal load and drag or stick if the load is increased?
В.: Because the clearance in the cylinder may be sufficient at normal load but when overload causes all parts to become hotter the increased temperature of the piston causes it to expand more and reduce the clearance.
A.: What is the effect of too much or too little clearance between a cam and its roller?
В.: Too much clearance causes late valve opening, early closure, decreased lift and noisy operation. Too little clearance causes early opening, late closure, increased valve lift and may prevent complete closure.
A.: What are some of the common troubles experienced with fuel measuring pumps?
В.: Leaky suction and discharge valves, due to grit in the oil or to particles of dirt or lint becoming caught under the valves; pump becoming air bound; incorrect clearance between suction valve stems and tappets; leaky plungers, and change in timing, due to looseness in the operating gear.
A.: Why is it desirable to have thermometers so located that separate temperature readings of the cooling water discharge from the cylinders can be taken?
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В.: If merely the temperature of the common discharge from all cylinders is taken, a single cylinder jacket may become air bound and the flow of cooling water through it stopped altogether without giving any indication at the common outlet.
A.: What are the effects of too many or incorrectly placed oil grooves in a bearing?
В.: The bearing surface is reduced and the oil escapes from the bearing without spreading over its surface.
A.: What is a common trouble with the cylinder lubricating system?
В.: Excessive feed of lubricating oil into the system, causing collection of gum and carbon in the ring slots and leakage of black oil into the crank pits.
Topics for discussion:
1. Process of engaging and disengaging of turning gear.
2. Excessive fuel consumption.
3. Excessive lube oil consumption.
Comprehensive reading. Read, translate into Russian and discuss the following text
Application of calipers
A caliper is a device used to measure the distance between two opposite sides of an object. A caliper can be as simple as a compass with inward or outward-facing points. The tips of the caliper are adjusted to fit across the points to be measured, the caliper is then removed and the distance read by measuring between the tips with a measuring tool, such as a ruler.
It is used in many fields such as mechanical engineering, metalworking, forestry, woodworking, science and medicine.
A caliper must be properly applied against the part in order to take the desired measurement. For example, when measuring the thickness of a plate a vernier caliper must be held at right angles to the piece. Some practice may be needed to measure round or irregular objects correctly.
Accuracy of measurement when using a caliper is highly dependent on the skill of the operator. Regardless of type, a caliper's jaws must be forced into contact with the part being measured. As both part and caliper are always to some extent elastic, the amount of force used affects the indication. A consistent, firm touch is correct. Too much force results in an underindication as part and tool distort; too little force gives insufficient contact and an overindication. This is a greater problem with a caliper incorporating a wheel, which lends mechanical advantage. This is especially the case with digital calipers, calipers out of adjustment, or calipers with a poor quality beam.
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Simple calipers are uncalibrated; the measurement taken must be compared against a scale. Whether the scale is part of the caliper or not, all analog calipers—vernier and dial—require good eyesight in order to achieve the highest precision. Digital calipers have the advantage in this area.
Calibrated calipers may be mishandled, leading to loss of zero. When calipers' jaws are fully closed, it should of course indicate zero. If it does not, it must be recalibrated or repaired. It might seem that a vernier caliper cannot get out of calibration but a drop or knock can be enough. Digital calipers have zero set buttons. Vernier, dial and digital calipers can be used with accessories that extend their usefulness. Examples are a base that extends their usefulness as a depth gauge and a jaw attachment that allows measuring the center distance between holes. Since the 1970s a clever modification of the moveable jaw on the back side of any caliper allows for step or depth measurements in addition to external caliper measurements, in similar fashion to a universal micrometer.
Exercise 6. Discuss the following topics.
1) What is caliper? Give a definition
2) In what fields calipers are used?
3) How to measure the thickness of plate correctly?
4) What causes underindication and overindication?
5) What can indicate that caliper is mishandled?
6) Describe the modification of calipers.
Lesson 3.
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
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4. to plug up / to clog / to obstruct – засорять(ся)
5. to bind / to grip – заедать
6. to lift / to heave / to raise – поднимать
7. shoal/shallow water – мелководье
Vocabulary notes:
1. stroke – ход, такт
2. particle – частица, комок
3. hiss – посторонний шум
4. air pocket – воздушная пробка
5. cock – кран
6. valve stem – шток клапана
7. jellyfish – медуза
8. pipe – труба
9. copper – медь
10. devastating – разрушительный
11. joint – место соединения
12. stop cock – стопорный кран
13. blowlamp – паяльная лампа
MEMORIZE THE FOLLOWING MINDMAP TO EASE DERANGEMENT UNDERSTANDING
Exercise 2. SCANTHE TEXT AND BE READY TO DISCUSS IT.
Fuel 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 of 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.
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MEMORIZE THE FOLLOWING MINDMAP TO EASE DERANGEMENT UNDERSTANDING
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. The only remedy in this case is to eliminate the passage of air into this particular system which may be due to the following reasons: defective gaskets or glands, leakage through bursts or breakage of pipelines and also cracks of cylinder liners.
MEMORIZE THE FOLLOWING MINDMAP TO EASE DERANGEMENT UNDERSTANDING
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.
The most serious derangement in the referred system aside from aging and leakage through different joints, elbows and pipelines as well as due to burst of pipes is loss of oil film thickness.
MEMORIZE THE FOLLOWING MINDMAP TO EASE DERANGEMENT UNDERSTANDING
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.
MEMORIZE THE FOLLOWING MINDMAP TO EASE DERANGEMENT UNDERSTANDING
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 DEs 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.
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