02 medium speed diesel engine

8/2/2019 02 Medium Speed Diesel Engine

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Medium Speed Diesel Engines

Defined as those having rated speeds

within the range of

300 to 1000 rev / min.

In recent years the geared multiple engine marine mainpropulsion plants have been used in certain types of ships. There

are a number,of advantages which have prompted development

of these compact power units. The developments that have taken

place for these new, higher output four stroke, main propulsiongeared units are towards high piston and engine speed, higher

mean effective pressure with high degree of turbo charging and

vee arrangement of cylinders.


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According to Speed.

Slow Speed Engines: 100 to 150 r.p.m.

Medium Speed Engines: 300 to 1000 r.p.m.

High Speed Engines: More than 1000 r.p.m.


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In Diesel engines also, there is tough

competition between medium and slow speed

engines.

The worse quality of fuels available and

increase in the cost of oil has led to renewed

interest in coal-fired ships. Keeping in viewthe limited world reserves of oil, coal fired

ships seem to provide a good alternative in

2000s but at present the position of Dieselengines remains unchallenged.


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Compact engine room


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Medium speed engine shaft drive


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Vee type engine


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Medium speed engine crankshaft


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Friction clutches A and

B are pnuematically

controlled from some

remote positions. Gears

1,2,3 and 4 would haveto be the same size if the

gear were to be single

reduction.


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Advantages of medium speed engines:

(a) Low weight of engine and reduced space

requirement - In the present state of technology,

with turbo - supercharging there is about 30%,

saving in space of engine room and 300% saving in

weight compared with slow, speed diesel engineplant with comparable output. 35 kg. per h.p. for

Slow Speed crosshead engine. 12 kg. per h.p. for

Medium Speed geared unit.

(b) Low head space - The low. height of

engine room enables the shipbuilder to provide a

continuous deck which may be useful for laying out

of workshop, auxiliary engines, control. room,

stores etc. A continuous deck may prove useful for

carriage of cargo in some special type of ships.

(c) Location of engine as far aft as possible is

advantageous for best utilisation of space in the

carriage of cargo. Low machinery weight enables

the ship, light or laden, to maintain a level trim

which is hardly possible for a ship fitted with slow

speed crosshead engine.

(d) The speed of engine and propeller. shaft being

independent to each other, best designed speed can

be selected for both. A free selection of propeller

revolutions ensures maximum propeller efficiency.

(e) The medium speed

application affords possibilities of

number of combinations, such as, in

line and vee engines in single or.

multi-engine layouts. The same engine

can be used for other duties like driving

alternator or cargo pump in ports.

Multi-engine plant enhances the

reliability and safety factor. It also

combines the advantage of certain

routine work being carried out at sea.

(f) The initial cost of a geared

installation may be 30 p.c. less than that

of the conventional two-stroke

crosshead engine. The spare parts are

not only cheaper, but also easier to

handle store or transported.

(g) As the engines are worked on

clean distillate or light blended heavy

oil, the rate of wear of pistons, rings

and liners are considerably less.


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Disadvantages to use these engines in ship for

main propulsion purpose.

High lubricating oil consumption (1.2 gm per b.h. p.

hour as against 0. 5 gm. per b.h.p. hour in crosshead

engines).

Short service life of exhaust valves.

More maintenance work

High load on bearings needing more frequent attention

and replacement,

Very high noise level.

02 medium speed diesel engine

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