Assalamoalikum and welcome back to Orange Shots
I'm very certain that most of you must have enjoyed playing with
the balloons at some point in your life
you must be thinking that why am I referring to a balloon
what is its similarity to a ship?
just wait for 5 minutes and I’ll explain everything
a balloon is an incredible object with a special property
that is, it expands with the rise of temperature of the air inside
and it shrinks when the air inside is cooled
in simple words, a balloon's structure is capable
of handling incredible amount of expansion
and contraction
a ship can also handle contraction and expansion
but to a limited extent, unlike balloon.
a ship can't expand or contract
in the same proportions as a balloon does
and that's a big problem for a Ship
a balloon may expand or contract until the expansion limits are reached
until the time you don't cross the expansion or contraction limits
a balloon will keep expanding or contracting
but ships are incapable of expansion to a balloon's proportions
Airplanes are also very capable when it comes to contractions or expansions
that's because the planes need to fly
and the air becomes thinner in the top parts of our atmosphere
and hence atmospheric pressure is less
this results in expansion of an airplane
and when the plane is landing
the atmospheric pressure rises
and the plane contracts as a result
a plane's structure is built to withstand these volumetric changes
but even if we consider the lesser volume changes in an airplane
a ship can't even be stretched to those proportions
but does a ship contract or expand?
just like any other thing
Ships also contract and expand
usually, the structure of ships
is rigid, made of steel
so naturally it cannot expand or contract like a balloon
if you consider all different parts of a ship
every part is designed to
withstand the usual contractions or expansions
they are capable to tolerate those changes
Thing is, the vessels don't run in restricted parts of the world
sometimes we have to call the ports where snowfall is usual
temperature can be -20 to -30 with Chill factor
and then there are ports where temperatures soar to 50 deg C
can you imagine this temp difference?
extreme cold temperature of -20
and scorching heat of +50!!
but our ship's structure can withstand these temp changes
every part of vessel is designed to adapt to these temperature changes
except ONE
This one thing cannot completely adapt to these temperature Changes
and they are our Cargo tanks
Our vessel is an oil tanker Ship
this means that all of her cargo tanks are completely sealed tight
so even if you dip the forward part of the ship in water
there will be no ingress of water, until and unless
an opening of the tank is compromised
or the cargo tank is damaged
but this excellent sealing comes with it's own drawbacks
thing is the cargo tanks usually contain OIL
we carry all sorts of Crude oils and diesel oil etc
and the quantity is quite a lot as well
0.15 million tons
now imaging that you have so much of oil on board in sealed cargo tanks
with the rise of atmospheric temperatures not only will the cargo tank expand
the oil contained within will expand too
I’m sure being conversant with physics, everyone knows that
solid and liquid do not expand in similar proportions at same temperature
the expand or contract differently
simply speaking, our cargo tanks do not expand as much as the oil inside it
on top of it, the biggest danger is posed by the gases and vapours in the tank
Now consider a loaded tank
in fact consider a fully loaded tanker instead
with the rise in temperature the oil will expand
along with the volumetric expansion of oil
it will give off more gases and vapours
and gases already in space will expand even more
Now the cargo tanks are not like Balloon
they do not have the capability to expand to 6,7,or 8 times of their size
these cargo tanks can contract or expand a bit, but they can't become balloons
This expansion of gases can lead to a potential disaster
Once the pressure inside a cargo tank increases it will tend to push the walls of tank outwards
and if you're unable to manage this increased pressure inside tanks
it may cause these tanks to Explode
and these sort of incidents have happened in our industry
in the case of cargo contraction, the gases and vapours inside the tank will contract
and pull the cargo tank walls inwards
this can lead to potential implosion of cargo tanks
and by the way if you guys want to know the difference between explosion and implosion
it's called explosion when a thing bursts outwards
and when something collapses and bursts inwards it’s called implosion
both of these have happened in our industry many times
so, it is very much necessary to monitor and manage this vapour pressure
if you don't do it, you're potentially running your vessel into danger
and that's the point where these things come in
They're called PV valves
or pressure - vacuum valves
I's standing on top of the vacuum side of the valve
in case there is build up of negative pressure in the tanks
meaning, the oil and vapours inside tanks have contracted
and they're trying to pull in the tank plating
this side of the valve will come into action
There is a small disc inside this valve
when negative pressure build up inside a tank
This disc will lift due to suction effect of vacuum¬¬¬¬¬
and the air will be sucked in
but in fact, you shouldn’t allow this build up of vacuum inside your tanks
because there is hydrocarbon gases in your tanks
this fresh air when sucked in can lead to formation of flammable mixture
that can cause potential fire and explosion too
but in case if somehow the tanks are in vaccuum then this valve helps
vaccum side will open, air will be sucked into the tank
the vaccuum will be broken and implosion will be averted.
Then comes this side This is called "Pressure Side"
similarly, there is another disc here on the pressure side
when the pressure in cargo tanks will exceed certain limit
the pressure will be exerted on this disc
this pressure will lift this disc up
The gases from the tanks will be released in the air
and pressure inside tanks will be reduced
This will save your ship from implosion and explosion
and just to inform you
PV valve is our last resort when it comes to managing the tank pressure
we fill our cargo tanks with inert gas if the tanks are about to go in vacuum
Similarly, when the pressure inside tanks are rising
PV valve is not our first choice when it comes to releasing the pressure
For releasing gases, we have Mast Riser
we can manually open mast riser and release all the gases in air
The reason for using Mast riser is, the Mast riser is quite high
it releases gases well clear of the deck
high enough to be safe for vessel's crew
because the petroleum gases contain not only hydrocarbons
but Hydrogen Sulphide, Chlorine, Benzene
and even mercaptans amongst others
These all gases may be very dangerous for human life
Hence our first priority is to release these gases from Mast Riser
if the pressure inside cargo tanks is rising
and hence this equipment saves our ship from implosion and explosion
and there is at least one PV Valve on each cargo oil tank
in case you guys want to know what happens when the fresh water
on ship is finished
tap here
to watch a video about lightening striking a ship,
Tap here
until the next video, take care & keep me in your prayers
with tonnes of love for my orange shots family and to be orange shots family
this is me "Zahid Nisar"
You are watching "Orange Shots"
& Until the next video
Allah Hafiz