Common causes of marine diesel engines overheating

Overheating is a common symptom of marine diesel engine blockage. Marine diesels should run at 180 degrees Fahrenheit. When the temperature goes above 200, start getting worried. Dialing down the RPM’s may allow the engine to recover and run well at a more leisurely pace. Overheating is difficult to diagnose, and the only real way to solve the problem is a systemic examination of every engine element, i.e. trial and error. Here is a starter list of parts to examine:

1) Raw Water Impeller – the most common source. A spoke of the plastic impeller breaks off and clogs the raw water flow. Easy fix: buy a new impeller.

2) Mixing Elbow – Corrosion here blocks the flow. Solution is a new or boiled out elbow.

3) Heat Exchanger – Scale builds up in the heat exchanger. Solution is to snake with a wire and dip in acid.

4) Thermostat Sensor/Receiver – Is the thermostat stuck? Or is the engine even overheating? Check the exhaust temperature. How hot is the water? Shoot a heat sensor on the water reservoir.

5) Fresh Water Tank – Is it leaking?

6) Hoses – Delamination inside engine hoses restricts the flow, causing the engine to overheat.

7) Fresh Water Pump – An aluminum impeller inside the pump can corrode and limit flow.

8) Oil Cooler – Similar to the heat exchanger. You cannot snake her out because the tubes narrow at the ends but dipping the cooler in an acid bath does the job.

9) Over-propped – Too large a diameter or too much pitch can cause an engine to overheat prematurely.

10) Aeration – Air getting in from a leak in the line anywhere can lead to overheating.

 

Exercise 6. Answer the following questions.

 

1. What is normal temperature of marine diesel engine?
2. What is its abnormal temperature?
3. What should be done in order to prevent engine overheat?
4. Why is it difficult to diagnose the engine overheating?
5. What parts of the engine should be examined?
6. What other advice can you give in order to prevent engine overheat?

 

Watch the video “Marine engine starting difficulties” and discuss the following topics.

[ https://www.youtube.com/watch?v=NZT0yZUL3qU ]

1. Reducing the amount of vibration of an engine.
2. The methods of refining of the oil.
3. Why it's important to check the sea water temperature regulary?

 

Lesson 6. ENGINE SHIPYARD REPAIRS

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

Vocabulary notes:

1. conscientious – добросовестный

2. recourse – обращаться за помощью

3. bedplate – станина

4. cast iron – чугун

5. misalignment – смещение

6. chock – подпорка

7. filler piece – прокладка

8. cylinder liner – рабочая втулка цилиндра

9. prolific – продуктивный

10. casuality – случайность

11. abrasive – абразивный

12. impurity – примесь

13. to fit a replacement part in-situ – устанавливать сменные запасные части на месте

14. to predict by computer – прогнозировать с помощью ЭВМ

15. spare parts – запасные части

16. wear and tear - изнашиваться

 

Exercise 2. Read, translate and discuss the text.

The conscientious engineer who is responsible for the operating efficiency of his ship takes pride in maintaining the machinery in good condition without recourse to outside help. There are conditions, however, under which this becomes impossible. The operating schedule may be such that the engineers must be available for operation most of the time and many repairs requiring the engines to be disabled cannot be done within the short time available for such work. In this case repairs are restricted practically to such items as may be carried out at sea. As the size of marine Diesel engines increases the individual parts become more massive and even routine examinations become too great a task for a small number of engineers and the limited equipment on shipboard. As a result, a large proportion of motorship repairs is done in shipyards. Such repairs may, in general, be grouped into three classes as follows: (1) maintenance repairs, or those resulting from ordinary wear and tear in service; (2) repairs required as a result of faulty design, or changes due to improvements in design; (3) repairs required as a result of accident, stress of weather, or other unusual conditions.

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.