Operating troubles in general.
Water may get into the fuel oil by leakage through defective riveting of tanks, through alternate use of tanks for fuel oil and water ballast, or the fuel oil as delivered into the tanks may contain considerable moisture that will settle out. The degree of seriousness of the resulting troubles will vary with the amount of water in the oil, but among the possibilities are cracked heads and pistons, burned out exhaust valves, low compression due to wear of rings and liners, and irregular running of the engines.
Improperly refined oil.
Fuel oil must, during the refining process, be treated with sulphuric acid and this acid must later be neutralized with soda. If this neutralizing agent is not thoroughly washed out of the oil, its presence cannot be detected without chemical analysis nor is it removed by the filtering and straining methods ordinarily used on shipboard. When the engine is opened up after running on this insufficiently washed oil the entire surface of the combustion spaces in the cylinders will be found to have a coating of gritty material which looks and feels like sand but which is mostly sodium sulphate. It does not cause any immediate derangement of the engine but it does cause considerable wear of piston rings and cylinder liners. When such deposits are found the only remedy is to stop using the fuel from that particular refinery.
Loss of power or slowing down of engine.
When this occurs the first possibility that should be investigated is hot bearings. Other causes are failure of fuel to one or more cylinders, derangement of valves of valve gear or a fall in cooling water temperature. A decided reduction of the sea water temperature will often be experienced when entering a river from the sea, passing out of the Gulf Stream or leaving tropical waters. When this occurs the cooling water supply should be cut down until the jacket water temperature is up to normal. A distinct loss in efficiency sometimes results from the idea that the jacket water should always be kept as cold as possible.
Cracked cylinders and cylinder heads.
Cracks may result from unequal heating due to poor design, bad castings, air pockets in jackets, lack of cooling water and overloading. Modern practice in design and construction has greatly reduced the probability of cracking from the first two causes and watchfulness on the part of the engineers eliminates the other causes, so that cracked heads and cylinders are not nearly as common as they were in the early days of Diesel engineering. If cracks are found they must be repaired immediately by means available on board, but if it’s impossible to repair in-situ or these cracks are devastating, proceed on DEP (if any) or order tug assistance to the nearest port for shipyard repairs.
Cracked crank shafts.
During the early development period cracked crank shafts were so common that it was considered one of the inevitable hazards associated with DE operation. This trouble has become very rare, however, in modern practice. But still these cracks may result from misalignment with steering shaft, couplings and other gears. To minimize such derangements all engine personal shall maintain all operating parameters and check alignment of all rotating parts. Unfortunately, such cracks may not be eliminated on spot thus complete renewal in a shipyard is required.
Vibration.
The amount of vibration of an engine and of 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 DEs, 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 and bolts, shaking off small fittings, breaking pipes and even breaking of the crank shaft, if continued long enough. Another cause of vibration may result from air in fuel system which leads to engine misfire.
Exercise 3. 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 as 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 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.
7. На заре дизельных двигателей считалось, что трещины в цилиндрах – неотъемлемая часть эксплуатации данного типа двигателей.
8. При работе двигателя на максимальной скорости вибрации особенно опасны.
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