CHEMCO Exit Exam • Set 13 Question 9 of 30

The atmosphere in a tank is too rich when it is

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Direct Answer

Option D: incapable of supporting combustion because the hydrocarbon vapor content makes the atmosphere above the UFL (Upper Flammable Limit)

A tank atmosphere is "too rich" when the hydrocarbon vapor concentration exceeds the Upper Flammable Limit (UFL). In this state, there is insufficient oxygen to support combustion, rendering the atmosphere incapable of igniting, as defined in ISGOTT.

All Options

incapable of supporting combustion because the hydrocarbon vapor content

makes the atmosphere below the LFL (Lower Flammable Level) capable of supporting combustion

in a noncombustible state which can be relied on to occur naturally on a regular basis

incapable of supporting combustion because the hydrocarbon vapor content makes the atmosphere above the UFL (Upper Flammable Limit) (Correct Answer)

Detailed Explanation & Context

Relevant Framework: STCW 2010 Manila Amendments • DG Shipping E-Learning & Exit Exam Standards • Advanced Training for Chemical Tanker Cargo Operations (CHEMCO).

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