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Friday, November 23, 2012

PowerPoint Presentation On Cargo Tank Atmosphere

PPT On Cargo Tank Atmosphere

Cargo Tank Atmosphere Presentation Transcript:
1. A tank is an enclosed space which is sealed and may not have any ventilation. As a result, there is a accumulation of gases which can be dangerous and harmful to humans.

 2. What do we FEAR MOST when we speak about Cargo Tank atmospheres ?

3. There are Different types of Tankers.
Such as: Crude Oil Tankers
Product Tankers
Chemical Tankers
Bitumen Tankers
Fruit Juice Tankers (stainless steel tanks)
Wine Tankers (stainless steel tanks)

4. Fire hazards can be best explained by a Fire Tetrahedron
It describes the four different factors required for ignition of a fire. Essentially all four elements must be present at the same time for a fire to occur. Removal of any one of these essential elements will result in the fire being extinguished : Air (Oxygen) Heat ( Internal / External Spark) Fuel (Cargo vapours) Chain Reaction The Inert Gas is introduced into a tank to remove the Oxygen side of the tetrahedron by reducing the Oxygen content below required percentage for combustion.

5. General Policy of Cargo tank atmosphere control
Tankers fitted with an inert gas system should maintain their cargo tanks in a non-flammable condition at all times.
It follows that: Tanks are kept inerted when they contain cargo /cargo residue The atmosphere within the tank should make the transition from inert condition to gas-free condition without passing through flammable condition. In practice before any tank is gas freed, it would be purged with inert gas until the hydrocarbon content of the tank atmosphere is below the critical dilution line. When a ship is in a gas-free condition before arrival at a loading port, tanks should be re-inerted prior to loading.

6. Dilution method
Dilution theory assumes Incoming inert gas / air, mixes with the original gas mixture in tank to form a homogenous mixture throughout the tank, In result concentration of original gas decreases gradually. For complete replacement the entry velocity of incoming gas should be high enough for the jet to reach the bottom of tank.

7. Displacement method
For ideal replacement a stable horizontal interface should be formed between the lighter gas entering at the top of tank and heavier gas being displayed from the bottom of tank through some suitable pipping arrangment. In result the tank atmosphere is changed gradually. For complete replacement a relativley low entry velocity of gas is required. In practice more than one volume change is necessary

8. For more please refer our PPT. Thank You.
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