Why We Need To Purge The Cargo Tanks Before Making Them Gas Free
Summary
TLDRThis educational video from 'My Time Genie' delves into the critical process of purging hydrocarbons from oil tanker cargo tanks to ensure safety. It explains the dangers of hydrogen sulfide and hydrocarbons, and the importance of using inert gas to purge these gases before introducing fresh air. The video outlines three purging methods: displacement, dilution, and positive displacement, aiming to reduce hydrocarbon levels below 2% to avoid flammability. It emphasizes the use of HC detectors to measure the safety of the tank's atmosphere and inert gas, ensuring a safe environment for gas freeing operations.
Takeaways
- 🚢 The atmosphere inside a cargo tank on an oil tanker can be lethal due to gases like hydrogen sulfide and hydrocarbons.
- 🌬️ 'Perching purging' is a procedure used to expel dangerous gases from cargo tanks by introducing inert gas.
- ⛔ Hydrogen sulfide is purged to reduce its level to a point that is safe for human life.
- 🔥 Hydrocarbons are purged to prevent the risk of explosion when mixed with oxygen.
- 🔍 Punching a cargo tank is necessary before purging to avoid creating a flammable mixture with the introduction of fresh air.
- 🔄 The three stages of purging a cargo tank are: too rich (can't catch fire), flammable range (risk of fire or explosion), and too lean (safe from fire or explosion).
- 🛠️ There are three methods for purging hydrocarbons: displacement, dilution, and positive displacement.
- 💡 Inert gas is used because it lacks both hydrocarbons and oxygen, preventing the atmosphere from becoming flammable.
- 🔍 A hydrocarbon (HC) detector is crucial to ensure the atmosphere in a cargo tank is below 2% HC before introducing fresh air.
- 🌟 Once the HC level is confirmed to be below 2%, it's safe to introduce fresh air and proceed with gas freeing the cargo tank.
Q & A
What is the primary danger of the atmosphere inside a cargo tank on an oil tanker?
-The atmosphere inside a cargo tank can contain hydrogen sulfide, which is dangerous for human life, and hydrocarbons, which are not only harmful if inhaled but can also lead to an explosion.
What is the purpose of purging in the context of oil tankers?
-Purging is done to expel dangerous gases like hydrogen sulfide and hydrocarbons from a cargo tank, making it safe for human entry and preventing potential explosions.
Why is it crucial to reduce the hydrogen sulfide level in a cargo tank?
-Reducing the hydrogen sulfide level ensures that it is no longer dangerous to human life in case it escapes onto the main deck of the tanker.
What is the significance of reducing the hydrocarbon percentage in a cargo tank before making it gas-free?
-Reducing the hydrocarbon percentage prevents the atmosphere inside the tank from becoming flammable when mixed with oxygen, thus avoiding the risk of fire or explosion.
Why is it incorrect to assume that introducing fresh air into a cargo tank will automatically expel all dangerous atmospheres?
-While fresh air will expel the atmosphere, it also raises the oxygen level, which, when combined with existing hydrocarbons, can create a flammable mixture if not properly managed.
What are the three stages an atmosphere in a cargo tank goes through during purging?
-The three stages are: 1) Too rich, where hydrocarbons are too much and cannot catch fire; 2) Flammable range, where the hydrocarbon percentage is just right to cause a fire or explosion with a heat source; 3) Too lean, where hydrocarbons are so low that a flammable atmosphere does not form.
What is the 'lean level' referred to in the context of purging a cargo tank?
-The 'lean level' is when the hydrocarbon percentage in a cargo tank is so low that introducing oxygen will not create a flammable atmosphere, thus preventing fire or explosion.
What are the three methods used to purge hydrocarbons from a cargo tank?
-The three methods are: 1) Displacement method, 2) Dilution method, and 3) Positive displacement method. Each method aims to expel the existing atmosphere in the cargo tank.
Why is inert gas considered safe for introducing into a cargo tank?
-Inert gas is considered safe because it lacks both the hydrocarbon fuel and oxygen, preventing the atmosphere inside the cargo tank from becoming flammable.
What is the target hydrocarbon level in a cargo tank before introducing fresh air, according to the script?
-The target hydrocarbon level should be below two percent by volume to ensure that introducing fresh air will not make the atmosphere inside the cargo tank flammable.
What is the final step in making a cargo tank safe for gas freeing, as described in the script?
-The final step is to confirm with gas detectors that the hydrocarbon level is below two percent by volume and that the inert gas has less than five percent oxygen before introducing fresh air into the cargo tank.
Outlines
🚢 Understanding Cargo Tank Purging
This paragraph explains the dangers of the atmosphere inside a cargo tank on an oil tanker, which can contain lethal gases like hydrogen sulfide and hydrocarbons. It discusses the process of purging, which involves introducing inert gas to expel these dangerous gases. The main goals of purging are to reduce hydrogen sulfide levels to non-dangerous levels and to make the tank gas-free by reducing hydrocarbon percentages. The paragraph also explains why fresh air cannot be introduced directly into a cargo tank without first purging it of hydrocarbons, as the presence of oxygen could lead to an explosion if a source of ignition is present. The three stages of purging a cargo tank are described: when the atmosphere is too rich, in the flammable range, and too lean. The goal is to reach a lean level where the hydrocarbons are below 2%, making it safe to introduce fresh air and proceed with gas freeing.
🔍 Safely Introducing Fresh Air into Cargo Tanks
This paragraph emphasizes the importance of ensuring that the hydrocarbon level in a cargo tank is below 2% before introducing fresh air. It explains that once this level is confirmed by gas detectors, it is safe to proceed with gas freeing. The paragraph concludes with a reminder of the main purpose of purging hydrocarbons from a cargo tank, which is to avoid the flammable range. The speaker encourages viewers to share, subscribe, and like the video if they found it informative, and ends with well-wishes for the viewers' safety and learning.
Mindmap
Keywords
💡Hydrogen Sulfide
💡Hydrocarbons
💡Perching Purging
💡Inert Gas
💡Flammable Range
💡Gas Freeing
💡Displacement Method
💡Dilution Method
💡Positive Displacement Method
💡HC Detector
Highlights
The atmosphere inside a cargo tank on an oil tanker can be lethal and dangerous due to the presence of gases like hydrogen sulfide and hydrocarbons.
Perching purging is a procedure used to remove dangerous gases from cargo tanks by introducing inert gas.
The primary purposes of purging are to expel hydrogen sulfide and hydrocarbons to make the atmosphere safe for human life and prevent explosions.
Introducing fresh air into a cargo tank can be risky because it raises the oxygen level, which combined with hydrocarbons can lead to an explosion.
Punching a cargo tank is necessary before purging to reduce the hydrocarbon levels to avoid creating a flammable atmosphere.
A flammable atmosphere in a cargo tank is defined as the presence of a correct percentage of hydrocarbons that can ignite with a source of heat.
The atmosphere in a cargo tank goes through three stages during purging: too rich, flammable range, and too lean.
The goal of purging is to reach a lean level where the hydrocarbons are below 2% to prevent fire or explosion even with a heat source.
There are three methods to purge hydrocarbons from a cargo tank: displacement, dilution, and positive displacement.
Inert gas used in purging lacks both fuel (hydrocarbons) and oxygen, preventing the atmosphere from becoming flammable.
A flammability diagram is used to ensure that hydrocarbon levels are reduced below 2% to avoid trouble when introducing fresh air.
A good hydrocarbon (HC) detector is essential to measure the atmosphere inside a cargo tank and confirm the inert gas has less than 5% oxygen.
Once the hydrocarbon level is confirmed to be below 2%, it is safe to introduce fresh air and begin gas freeing the cargo tank.
The main purpose of purging hydrocarbons is to avoid the flammable range, ensuring safe gas freeing operations.
The video concludes with a reminder to stay safe and continue learning about the safety procedures on oil tankers.
Transcripts
hello and welcome back to my time genie
all of you people who are already
serving on the oil tankers they already
know that the atmosphere inside a cargo
tank is not only lethal for a human life
it can also be dangerous for your ship
more specifically the atmosphere inside
a cargo tank can contain hydrogen
sulfide which is obviously a dangerous
gas for any human being
it can contain hydrocarbons that is not
just dangerous for a human being if
inhaled
but it can also lead to an explosion
to get rid of all of these gases that
are inside the cargo tanks the normal
procedure that is adopted on an oil
tanker is called as perching purging
simply means that you are introducing
the inert gas into a cargo tank
for the purpose of expelling the
atmosphere inside a cargo tank out
and the two main purposes for which the
purging is done is to expel the hydrogen
sulfide
from a cargo tank and also the
hydrocarbons from a cargo tank the
hydrogen sulfide is purged from the
cargo tank for obvious reasons the main
purpose is to reduce the hydrogen
sulfide level in a cargo tank to such a
level
that is not dangerous to human life
anymore in case
it escapes on the main deck and the
hydrocarbon percentage in a cargo tank
is reduced before the tank is made
gas free now you may be asking yourself
why is it required to punch a cargo tank
before caspering i mean in any case
if we introduce the fresh air into a
cargo tank it will expel
all the atmosphere of a cargo tank out
right wrong it is true that once you
introduce the fresh air into a cargo
tank
once you push the fresh air into a cargo
tank obviously it will expel the
atmosphere of the cargo tank out
but there is another thing and that is
when the fresh air goes inside a cargo
tank the oxygen in the cargo tank is
obviously
raised because the fresh air when it's
coming
from the fresh atmosphere outside it is
bringing the oxygen that is 20.9 percent
into a cargo tank
now inside a cargo tank there is already
hydrocarbons so
the fuel is there the oxygen is there
now the only thing that is remaining to
complete the fire triangle and cause an
explosion or
fire is the fire spark or any source of
heat or ignition so just as a precaution
and before the introduction of the fresh
air in a cargo tank
the atmosphere of the cargo tank is
basically purged out of the hydrocarbons
the hydrocarbons on a cargo tank are
reduced to such a level
that when they are mixed with 20.9
percent of oxygen the atmosphere of a
tank does not
go into a flammable range now you might
be asking yourself
what is a flammable range and how are we
going to know about it usually the
atmosphere of a cargo tank goes through
three stages when you are purging a
cargo tank the first stage is obviously
when the atmosphere is too rich
it basically means that the hydrocarbons
inside a cargo tank are too
much the atmosphere is so rich that it
cannot catch fire
the second stage would be when the
atmosphere is in a flammable range
it means that once a source of heat or
ignition is introduced in a cargo tank
the percentage of hydrocarbons in a
cargo tank is
just right to cause a fire or explosion
and the third stage is when the
atmosphere is too
lean too lean means that the percentage
of hydrocarbons in a cargo tank is
so less that if you introduce the oxygen
into a cargo tank the flammable
atmosphere is not going to form
and once the flammable atmosphere is not
going to form it's not going to catch
fire or cause an explosion in case a
source of heat
or ignition is introduced now our main
purpose when we are purging a cargo tank
is to reach
this lean level we want to reduce the
hydrocarbons to such an extent
that in case the source of heat or
ignition is introduced in a cargo tank
it does not catch fire
there are usually three methods that are
adopted to purge the hydrocarbon from a
cargo tank the first is
displacement method the second is
dilution method and the third is
positive displacement method all of them
are basically done in a little different
way
but the basic purpose is exactly the
same that is to expel the atmosphere
that is already in a cargo tank
now you might ask that if you are
reproducing the inert gas into a cargo
tank then
how is the inert gas safe basically
these are the gases that are produced
after burning the fuel that means that
they do not only lack
the fuel itself the hydrocarbon itself
but it also lacks in
oxygen and thus it prevents the
atmosphere that is inside a cargo tank
to fall into that flammability range
if you see this flammability diagram
then basically the basic purpose of all
of this operation
is to bring the hydrocarbon to below two
percent of hc
if the hc in a cargo tank are above two
percent and you introduce the fresh air
inside a cargo tank
then basically you are inviting a
trouble for yourself by making the
atmosphere inside a cargo tank
flammable
so you have to use a good hc detector
not to just measure the atmosphere
inside a cargo tank
but also to measure that the inert gas
that is going inside a cargo tank
has an oxygen that is less than five
percent once the atmosphere in a cargo
tank is achieved
that is it is below two percent by
volume of
hc once it is confirmed by your gas
detectors that it is actually so
it is safe to introduce fresh air inside
a cargo tank and then
you can actually start gas freeing a
cargo tank so all in all the basic
purpose of purging the hydrocarbons from
a cargo tank is basically
to avoid flammable range that's the main
purpose
once the desired hydrocarbon travel is
reached that is less than two percent by
volume
it is safe to introduce fresh air inside
a cargo tank and this way
we can carry out the gas spring
operation of a cargo tank
safely that's all for today i hope you
have learned something out of it if you
did
consider sharing consider subscribing
and consider liking this video stay
happy
stay safe stay well and happy learning
تصفح المزيد من مقاطع الفيديو ذات الصلة
How LNG Carriers (Gas Tankers) Work - Design Types, Loading & Discharge
DUAL FUEL ENGINES PART 5 - DOUBLE WALL PIPE VENTILATION SYSTEM
كورس أساسيات صناعة النفط والغاز: الجزء #1 : مقدمة عن صناعة النفط والغاز
Video Assogastecnici Le proprietà dei gas - Esperimenti di laboratorio
Kuliah Online - Basic Petroleum System & BATUAN INDUK (Source Rock)
Storage Tanks: What are Storage Tanks | What are Storage Tank Uses and Types | Design
5.0 / 5 (0 votes)