Marine Engineering Practice Question and Answer- Part 3

This is the third article in
this series. We have covered topics like Steam, Liner, Control air, Sea Water
Line, Expansion tank, Sump, Spanners, O- Rings, Mechanical Seal and Crankshaft
Deflections. Questions given here might be useful for you if you are sailing on
ship or giving your officers exam.

You can read about first and
second article in this series here:
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What Fittings are there on
Steam line?

Answer: Here are some of the
fitting that you find on a steam line:
1.      
Strainer
2.     
Steam Trap
3.     
Reducing Valve for low pressure applications
4.     
Blow Down Valve
5.     
Pressure and Temperature Gauge

What are the indications that
your liner is cracked?

Answer: These are the common
indications if your engine liner is cracked:
1.      
You will see pressure changes in the cooling
water system of jacket water. Mostly during compression, and expansion.
2.     
You will see that water is coming from the
scavenge drains.
3.     
At the expansion tank, you will see foaming taking
place.
4.     
Higher exhaust temperature and also the jacket
cooling water temperature.
5.     
Smoke will be little white in color.

What are the fittings on the
control air line from the main air bottle?

Answer: These are the fittings:
1.      
Pressure reducing valve
2.     
Strainer on the line
3.     
Drain Valve for moisture
4.     
Air Dryer to remove moisture
Marine Engineering Practice

 Five ways to stop leakage in the sea water
line

Answer: Here are some ways you
can stop the leakage,
1.      
With a wooden dart inserted in to the hole.
2.     
By welding plate or normal brazing.
3.     
Using rubber pad and circle clip.
4.     
Cement box is also one method.
5.     
Using material like davcon.
6.     
Making threads in the pipe and putting a stud or
bolt in it.

Auxiliary Engine sump going up
in your watch, what can be the reasons?

1.      
Valve for filling oil is not holding.
2.     
Valve arrangement from the purifier has been set
wrong.
3.     
Jacket water is leaking in to the sump.
4.     
Fuel oil is leaking in to the sump.
5.     
Too much blow by leading to the combustion
products to find their way to the sump.

Expansion Tank Purpose and what
it is called otherwise?

It is the low pressure point,
so all the water vapors generated in the cooling system, will be related here.
Also, compensation for any type of water will be made here. Chemical to the
system are made from here. The other name of this tank is De-Aerator.

Why spanner length increases
with size?

Spanner works on the phenomenon
of the torque. Since Torque is defined as the product of the force and the
perpendicular distance. So, more the distance, lesser the force that you have
to apply while opening or tightening. This is the reason why, spanner length is
increased as the size increases.

How to make o-ring if you don’t
have spare?

Ship is provided with a roll of
o-ring material. Cut a piece for it. Now cut the end, at a 45 degree angle, so
that maximum contact can be there when you will join the two ends together. Use
locatite or whatever joining adhesive you have onboard to join the ends. Keep
it for half hour, and you are ready with your O-Ring.
Diagram below shows how to cut it
O-Ring Material

Mechanical Seal leaking, you
don’t have spare, how to repair?

Take out the mechanical seal
carefully. Take the seal (mostly carbon made), clean with soft rag. Now put
some clean lube oil on the chart paper or glass. Smoother surfaces are always
welcomed. Now put the seal over it, and lap it. Generally it is advisable not
to use any lapping paste, even the fine ones.

Reason for taking crank shaft
deflection

Taking deflections give us the information
about the condition of main bearing. Consider a situation when a rod is placed
over two supports. These two supports are equal in height. So, if you apply
force and turn the rod, there will be no deflections.

But when these two supports are
in unequal height (consider two adjacent main bearings), the rod will hog or
sag depending on the difference of height. Same goes with the engine crankshaft.
When you take deflection, the crank web will either hog or sag, depending on
the main bearing clearances.

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Mark Eriscson

Love to write about topics related to maritime sector. Was born in sailor's family, so love to ride on those high seas. In free time i would like to go for a good sunbath and some soothing guitar music. Want to have my own boat one day.

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