Bedplates

Most bedplate troubles arise from surprising flexibility of what is usually a massive structure of cast iron. An example of this was the bed of a 500hp. engine that had been carefully reset to correct an original misalignment. After accurate alignment was complete and the bed was resting on permanent steel chocks, the spaces between chocks were closed with wooden filler pieces, as is a usual custom in marine work. It was found that a too thick filler piece driven under the bed at about its center with an ordinary hand hammer bowed up the bed enough to throw the coupling on the end of a crank shaft measurably out of line. This flexibility seldom results in any injury to the bed itself, but often has a serious effect on other parts of the engine structure, particularly the crank shaft.

Framing

Frames are subject to the same sort of deflection as the bed, and in many cases this deflection is caused by the bending of the bed.

Cylinders

Cylinders, or what may more precisely be termed cylinder jackets, give very little trouble, although on some of the of the older engines an occasional cracked cylinder will be found. Cylinder liners, however, are a prolific source of work for the repair yard. Liner casualities a occur either from wear or cracks. Wear is a normal result of engine use, but it sometimes assumes abnormal proportions if operating conditions are not right. Of course, the liner material has some bearing on rate of wear in service and there is some variation in the quality of liner iron found in different makes of engines, but there is not enough variation to make this an important factor in differences in length of liner life found in service. What appears to be the most important factor is the fuel used. Some fuel will contain more abrasive impurities than others, but it is believed that all fuel oil, even the highest commercial grades, should be passed through a centrifuge before being used in the engine.

Exercise 3. Answer the following questions.

1) What does the good condition of the engine depend upon?

2) What repairs can be done at sea?

3) Why are repairs at sea restricted to a certain amount of insignificant items?

4) What does the conscientious engineer take pride in?

5) What are the conditions under which maintaining the machinery becomes difficult?

7) What do most bedplate troubles arise from?

8) Why should all fuel oil be passed through a centrifuge?

9) Why are frames subject to the same sort of deflection as the bed?

10) What appears to be the most important factor in the length of a liner line?

11) How does the quality of liner iron influence the length of liner life?

Exercise 4. Translate the sentences from English into Russian

1. Fuel pumps should be examined and adjusted if necessary.

2. the condition of the cylinder bore is one of the main factors affecting the operation of a high speed oil engine.

3. Cylinder liners must be examined externally for deposits of scale.

4. The liner should be measured for wear and renewed, if the limit for wear has been reached.

5. The clearance of connecting-rod top and bottom ends should also be examined and adjusted.

6. At intervals of one year the maneuvering gear must be examined for wear at the joints of levers and rods.

7. Piston heads must be inspected for deposits of carbon in cooling spaces and cooling pipes.

8. Engine rooms and particularly the the floor areas between the underneath engine seatings and bilge areas, are frequently in need of coating maintenance.

9. All carbon deposits must be removed from cylinder ports.

10. When excessive lubricating oil consumption or excessive blow- by is observed the cylinder heads should be removed and the cylinder bores checked for wear.

Exercise 5. Translate into English.

1. Многие экипажи гордятся тем, что могут длительное время эксплуатировать силовую установку своего судна без ремонта.

2. Однако существуют условия, при которых становится невозможным обойтись без посторонней помощи.

3. Часть ремонтных работ выполняется непосредственно на судоремонтном заводе.

4. Многие ремонтные работы, требующие вывода из строя машины, не могут быть выполнены в море.

5. Ремонт двигателя практически ограничивается теми работами, которые можно выполнить в море.

6. Рубашки цилиндров в современных двигателях доставляют много хлопот.

7. Если условия эксплуатации двигателя неправильные, износ некоторых деталей превышает нормальные допуски.

8. Качество используемого топлива является важным фактором в эксплуатации двигателя.

Exercise 6. Make up a dialogue of your own based on the one given below.

ENGINE DAMAGE

A: Which of the several causes of ignition failures is most likely to occur?

B: Failure of the fuel supply is the most common cause, for the reason that the fuel pump is very sensitive to the presence of air and unless great care has been exercised in cleaning air out of the fuel lines, the pump will not deliver oil to the injection valves. This is especially true after the fuel lines or pump have been opened up for any reason.

A: How is air cleared out of the fuel lines?

B: Most installations include a by-pass valve in each fuel oil discharge line, adjacent to the injection valve. By opening these valves and operating the hand pumps on the fuel measuring pump, oil is forced through the pump and pipe line out through the by-passes, carrying the air with it. When only oil flows from the by-passes the valves are closed and few strokes given to the hand pumps to force some oil into the injection valves.

A: How is the compression pressure measured?

B: With the indicator, cutting out one cylinder at a time and indicating that cylinder while the rest of the cylinders operate on fuel or starting air. Both methods should be used in order to determine the difference in compression with hot cylinders and with cold.

A: How is the compression pressure adjusted?

B: By decreasing or increasing the linear clearance between piston and cylinder head. This is usually done by increasing or reducing the thickness of shims under the foot of the connecting rod.

A: What are the principal sources of knocks in the Diesel engine?

B: The large bearings, the valve gear, or the interior of the cylinders. Bearing knocks are caused by too much clearance. Valve gear knocks may be caused by excessive roller clearance, worn or broken rollers, or sticking valve stems. Knocks inside the cylinder are caused by too early injection, valve at low speed, injection air pressure too high, or stuck piston rings.

A: How is the separation of the two halves of the box usually obtained?

B: By placing sheet metal shims between the abutting surfaces.

A: How is bearing usually measured?

B: By placing strips of soft lead wire in the bearing and setting up the bolts. The thickness to which the lead wire is mashed will be equal to the clearance.

A: How is bearing refitted?

B: By scraping surface of the boxes with steel scrapers until all the high spots are removed and even contact is obtained between bearing and boxes.

Comprehensive reading. Read, translate into Russian and discuss the following text.