Task 1: Synthetic Fibre Ropes
1.Polypropylene (Characteristics,Advantages,Disadvantages) Is
the most popular of the man-made fibres at sea. Is
reasonablyeconomical very cheap. Has same strength even if its wet
or dry. Is used for mooring ropes. Is permanently damaged and
weakened from exposure to heat and UV radiation such as that
present in sunlight. Affects acids,alkalis and oils. A by-product
from polypropylene called fibrefilm, is a very cheap version of the
fibre and it is very common used on board ships. Is lightweight and
easier to handle in thicker diameters. Is not the strongest rope
around; its not recommended for safety ropes which might be exposed
to very high stresses. Is stiff and slippery and is notorious for
coming undone because it slips out of knots and cleats. It is
highly flexibile and has minimum stretch. It has the lowest melting
temperature from all synthetic fibre ropes ( 150 F).
Fig.1: Polypropylene Ropes
2.Polythene (Characteristics,Advantages,Disadvantages) It
absorbs only 0.01 % water. Its used on mooring tails and mooring
ropes. It doesnt float and in cold climates they tend to stiffen up
and become difficult to handle. They are not that economic in
comparation with polypropylene. Due to its materials, it has a good
resistance to UV radiation and sunlight. Is very close to nylon in
strength when a steady force is applied. It stretches very little
and cant absorb shock loard as well. It is also as equally
resistant to moisture and chemicals as nylon, but is superior in
resistance to abrasion and sunlight.
Fig.2: Polythene Ropes
3.Nylone (Characteristics,Advantages,Disadvantages) Is the
strongest of all the man-made fibre ropes. It has a very excellent
elasticity and a good schock absorber; this makes it a good choice
for live loards, including towing and anchoring. It does not float.
It is transparent to infrared light. It has a good resistance
against UV radiations, oil and organic solvents. It does not burn
when it break down in fire it forms hazardous smoke, or ash. It is
sensitive to high temperatures and will degrade releasing toxic
materials including cyanide. Because it absorbs water it is liable
to stain; this is not necessarily harmful but can be unsightly. It
resists rot and mildew but can stain particularly in water soluble
stains. It looses strength when its wet. If it is repeatedly cycled
at high percentage of its breaking strength, it generates a large
amount of internat heat,which degrades the performance of it and
can cause failure at high loads, such as anchor rodes during a
hurricane.
Fig.3: Nylon RopesTask 2
In the fig4, we deal with a Direct Pipeline System. Direct
Pipeline is the simplest type of pipeline system that uses a few
valves than the other types. Its main role is that it takes oil
directly from the tank to the pump and it reduces friction. This
has an affect of increasing the rate of discharge. It is easy to
operate and less crew is required. The role of the few valves is
that it takes less time to set it the valve system before
commencing a cargo operation. Also, it is a very inflexible system,
which makes it very difficult to plan for a multiportdischarge.
Block stowage has to be used which makes it difficult to control
the trim operation. Washing in the direct pipeline system is pretty
difficult because there is no circular system and the washings must
be flushed into the tanks. In my point of view, the Direct Pipeline
System is the most efficient system, when we speak about
discharging and loading the tanks with the cargo. I think that
because it takes less time and it doesnt cost to much to maintain
it.
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