Flammability Composition Diagram - (With more detail explanation using animation) -Watch until end..

FLAMMABILITY COMPOSITION DIAGRAM
This is the most important diagram to understand the concept of flammability.
Every point on the diagram represents a hydrocarbon gas/air/IG mixture in terms of its hydrocarbon and oxygen content.
When the tank is clean, the oxygen level inside the tank will be 21% by volume.
As hydrocarbon is introduced in the tank, the oxygen level will reduce until reaches the point where hydrocarbon is 100% by volume and oxygen is 0%. Line AB slope reflecting the reduction in oxygen content as the hydrocarbon content increases.
Any points to the left of the line AB represent mixtures with their oxygen content further reduced by the addition of Inert Gas (IG)
The point of “C” and “D” represent the lower and upper flammability limit mixture for hydrocarbon gas in the air.
As the IG content increases, the flammable limit mixtures change as indicated by the lines CE and DE, which coverage at the point E.
Only those mixtures in the shaded area within the loop CED can burn.
The possibility of the composition gas mixtures enters the shaded area of flammable mixture whenever an inerted mixture is diluted by air (During gas freeing operation). At this moment, the DANGER OF EXPLOSION may happen.
It is best practice to dilute the mixture in the tank with additional IG (by purging) to remove hydrocarbon gas and bring the level below line GA (critical dilution with air). Then after that, the inerted mixture is diluted by air in order to prevent the mixture become flammable on dilution
Hydrocarbon gas in petroleum tankers cannot burn in an atmosphere containing less than about 11% oxygen by volume (ISGOTT Chapter 11.1.1),
As a safety margin, SOLAS requires that the IG system keep positive pressure in cargo tanks and have an oxygen content of not more than 8% by volume (ISGOTT Ch. 11.1.3)
The minimum concentration of a particular combustible gas or vapor necessary to support its combustion in air is defined as the Lower Explosive Limit (LEL) for that gas. Below this level, the mixture is too "lean" to burn.
The maximum concentration of a gas or vapor that will burn in the air is defined as the Upper Explosive Limit (UEL). Above this level, the mixture is too "rich" to burn.
The range between the LEL and UEL is known as the flammable range for that gas or vapor where the concentration of a particular combustible gas or vapor is sufficient to support its combustion in air.
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[@melgiewaisalqornic8209]

Thank you capt, this's new knowledge I've got, very detail for explanation, thank you for sharing , 🙏

[@tomtomshyu]

I have searched for some diagram info on youtube. Your explanation is the best.

[@l-marineservices6749]

@tomtomshyu thank you for your comment, glad to know that the content and explanation can be useful and be understood.

[@user-ek3ex6pp2m]

Thanks.. Much more infomative... Want to see more of your videos

[@l-marineservices6749]

Thank you for your comment and feed back...👍🙏

[@amritanjay5017]

Well Explanation.

[@l-marineservices6749]

Thank you for your comment and feed back.👍🙏

[@aksansetiawan9116]

👍👍👍

[@user-sm8hg9ol3n]

Sir,firstly i want to thank you for your video.Why the Oxygen decreases when you add IG.Can you please explain the part 3:10

[@l-marineservices6749]

Thanks for your question.
Essentially, you're asking about how adding inert gas (IG) reduces the oxygen levels in the tank atmosphere to the left of line AB. To delve deeper into this, it's important to note that purified argon and nitrogen gases are commonly used as inert gases due to their abundance and low cost.
When you inert a compartment like a tank, you're replacing the oxygen-rich air inside with an inert gas such as nitrogen or argon. This is done to create a safe environment by reducing or eliminating the presence of oxygen or other reactive gases. This is crucial in situations where the risk of fire, explosion, or unwanted chemical reactions is high.
When you introduce the inert gas (IG) into the compartment, it displaces the oxygen present in the air. This occurs because the inert gas is denser than air, causing it to sink to the bottom of the compartment and push the oxygen-rich air upwards and out of the compartment.
Moreover, if the inert gas is introduced at a sufficient flow rate or pressure, it can quickly displace the air, leaving minimal oxygen behind. This decrease in oxygen concentration makes it challenging for combustion to occur, which is vital in scenarios where fire prevention is paramount, such as in storage tanks for flammable liquids or gases.
In essence, adding inert gas to a compartment reduces the oxygen concentration by displacing the air, thereby creating a safer environment where combustion is less likely to occur.