LUBRICATING OIL SYSTEMS
It is important that not only that the proper type of
lubricant is used, but also that the lubricant is supplied to the sliding or
rolling parts in proper quantities, at the proper temperature, and that
provisions be made to remove any impurities which enter the system. The engine
lubricating systems are designed to fulfill these requirements, as the life and
reliability of the engine depend on good lubrication.
Most conventional marine diesel engines use three
separate lubricating systems. They are the following: (I) the crankcase oil
with its pump, filter and cooler used for the crankshaft, connecting rod and
camshaft bearings, and for piston cooling; (2) the cylinder oil and the
cylinder lubricators adjusted to meter a specific number of drops per minute;
(3) the valve-gear centralized lubricating system in which lubricant is drained
separately in order to prevent contamination of the crankcase oil by leaking
fuel, injector cooling water, or exhaust gas.
2-cycle and 4-cycle diesel engines are supplied with
lubricating oil under pressure to all bearings and moving parts. Therefore,
such systems are called pressure-lubricating systems whose essential parts are
the following: (I) Tanks and sumps used to hold the oil that is continuously
circulated. (2) Lubricating oil pumps, which provide pressure for forcing
"the oil through the oil passages and the bearings. Maximum system
pressure is set by a relief valve. It must be adequate to provide the required
oil flow through bearing clearances. The lube oil pumps are driven by chains or
gears from the crankshaft, or by extension of the crankshaft or camshaft. They
are located either inside or outside the crankcase.
When a centrifuge or oil-treatment system is installed
to maintain clean lubricating oil, additional pumps are required to deliver oil
to the treating equipment. (3) Lubricating oil circulating in the engine picks
up friction heat from the bearings, heat from oil-cooled pistons, and also heat
transferred from the combustion space to the oil film on the cylinder walls.
This heat is removed by contact with water-cooled surfaces in the oil cooler of
shell-and-tube construction.
No matter what system of filtering is employed,
filters should provide the required flow rate at an acceptable pressure drop.
Mechanical straining is usually accomplished by a fine-mesh screen.
Absorbent filters remove contaminants from the oil by
sucking up or swallowing, as a sponge. Material used in them includes cotton
waste, mineral wool, paper wood pulp, wool yarn, and felt.
Absorbent filters are those which hold, in a very thin
layer, by adhesion, the molecules of dissolved substances, or liquids, to the
surface of the solid filtering material.
Centrifugal filtering, or centrifuging, removes
abrasive particles from the oil when the oil is rotated in an
electrically-driven cylinder, at a very high velocity. The conventional
centrifuge may be used to remove sludge, dirt, carbon particles and water from
the lubricating oil.
I. Read the text and watch the video.
II. Answer the questions.
1.
What are the principal functions of the lubricating systems?
2.
What is the crankcase oil used for?
3.
How does a lubricator work?
4.
Why is the valve-gear lube oil drained separately?
5.
What are the parts of the pressure-lubricating system?
6.
How may the lube oil pumps be driven?
7.
What is the principle of centrifuging?
8.
Where is the circulating lube oil cooled?
9.
What types of filters are used for cleaning lubricating oil?
III. Translate into English.
1. Існують різні способи подачі мастила до рухомих
частин дизеля.
2. Для запобігання прямого контакту тертьових
поверхностей кожна робоча частина повинна змащуватися.
3. Масляні фільтри необхідні для очищення циркулюючого
масла.
4. Після змащення всіх робочих поверхонь масло стікає
в піддон, завершуючи цикл.
5. Якщо в'язкість масла занадто низька, воно не
розділяє рухомі поверхні, а це призводить до металевого контакту і зайвого
зносу.
6. Мастило має містити мінімальну кількість кислот,
лугів і сторонніх часток.
FUEL SYSTEMS
If an engineer wants to do his job effectively he must
have a good knowledge of the engine fuel system. The equipment used on board a
diesel-driven ship for handling and controlling fuel oil belongs to several
separate systems.
Fuel injection system performs the following functions:
(1) it meters the quantity of the fuel required by the engine and maintains
this quantity constant; (2) it injects fuel at the correct point in the cycle
at all engine speeds and loads; (3) it begins and ends injection very quickly;
(4) it injects fuel at the rate necessary to control combustion; (5) it
atomizes fuel in the combustion chamber of each cylinder. The most important
devices of this system are high- pressure fuel pumps and fiiel injection
valves.
The engineer who has the main engine in his charge is
responsible for the efficient operation, maintenance, adjustment and repair of
the fuel injection system. Fuel fill and transfer system has the necessary
tanks, piping, valves and pumps to receive fuel oil aboard, store it and pump
it into the day tank. On either side of the main deck there is a ship's
fuelling station equipped with one or more fill pipes. A fill pipe must be
terminated with a connecting flange of international standard.
One end of the flexible hose passed over from a
bunkering facility: fuel barge, fuel lighter, another vessel or shore fuelling
facility, is connected to the ship's fill pipe. A container, called "drip
tray" or "drip pan", must be placed under this flange-bolt
connection to collect any leaks. The fill pipe runs from the fuelling station
downward to the engine room where it is connected to a valve manifold. From
that point, fuel oil transferred through the hose is directed to the various
storage tanks.
When fuel oil is coming aboard, a specially designated
rating, motorman or oiler, keeps a close watch on the levels in all tanks. He
must keep the personnel stationed at the ship's fuelling station informed, by
telephone or other means, of tank levels so that the delivery (rate) can be
slowed down or stopped when necessary. A fuel tank must never be filled beyond
the 95-percent level. Special overflow arrangements are provided for this
purpose.
In most ships, storage tanks are located in the double
bottom. The tanks, which are designed for heavy fuel oil (HFO), are provided
with steam heating coils.
Every day the 3rd engineer transfers the amount of
fuel consumed in a day from a storage tank to a settling tank by means of a
fuel transfer pump. Water and sediment contained in the HFO settle out to the
bottom of the settling tank.
The fuel treatment system starts where a fuel service
pump takes suction from the settling tanks. HFO discharged by this pump flows
through a strainer and fuel oil heater. Heated HFO is centrifuged (purified) in
order to remove impurities and then it is pumped into a day tank.
A booster pump takes suction from the day tank and
supplies it to the high-pressure fuel pumps through a filter.
Summing up the functions of the fuel systems of a
diesel engine burning HFO one can say that they are designed for taking on,
transferring, storing, settling, measuring, heating, straining, centrifuging,
filtering, and supplying fuel oil into the engine's cylinders.
Before receiving fuel oil aboard, the person in charge
of bunkering operations must take soundings or meter readings on all fuel
tanks. It is his duty to know how much fuel is available on board, where it is,
how much more can be taken on and the order in which the tanks should be
filled. He maintains special records for this purpose and informs the chief
engineer accordingly.
I. Answer the questions.
1. What are the five actions performed by the fuel
injection system?
2. What jobs must the engineer responsible for the
main engine do to maintain the fuel injection system in good working order?
3. What is the ship's fuelling station designed for
and what is it equipped with?
4. The hose flange size is standardized, why?
5. What are the English names for the facilities,
which deliver bunkers to the ships?
6 . Why is one of the tanks called the day fuel tank?
7. What professionals assist to bunkering operations
and what are their duties?
8. What is an overflow arrangement needed for?
9. What are the functions of the transfer pump,
booster pump, centrifuge and filter?
10. Did you understand the meaning of the terms
"to take soundings", "to take meter readings", and "to
maintain records"? Can you explain them at length?
11. Can you sum up the functions of the fuel systems?
II. Translate into English.
1. Сорт палива залежить від його головних складових
частин.
2. Теплота згоряння визначається калориметром.
3. В'язкість характеризується швидкістю витікання
палива.
4. На в'язкість палива впливає зміна температури.
5. Важке паливо зазвичай характеризується високою
в'язкістю.
6. Паливо повинно спалюватися в розпиленому стані.
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