Tanker Familiarization Tank Atmosphere Control 3

Question 1

When purging a cargo tank from inert to gas-free, what is the correct procedure?

Accepted Answer

Ventilate the tank through the top while monitoring hydrocarbon levels at the bottom

Answer

Purging displaces hydrocarbon-rich inert gas from the top while monitoring at the bottom ensures vapors pass through the explosive range as briefly as possible.

Question 2

What is the danger of introducing air into a cargo tank that is in the 'rich' condition (above UEL)?

Accepted Answer

Diluting with air can bring the mixture into the explosive range

Answer

Adding air to a rich tank dilutes the hydrocarbon concentration, potentially passing through the explosive range between UEL and LEL.

Question 3

Which type of inert gas is considered the highest quality source for tanker IG systems?

Accepted Answer

Nitrogen gas from a dedicated nitrogen generator

Answer

Nitrogen generators produce very high-purity inert gas with extremely low oxygen content, making them superior to boiler flue gas systems.

Question 4

What does a 'scrubber' do in an inert gas system?

Accepted Answer

Cools and cleans the flue gas by removing sulfur dioxide and soot particles

Answer

The scrubber cools the hot boiler flue gas and removes corrosive impurities like SO₂ and particulates before the gas enters the cargo tanks.

Question 5

A ship's IG deck seal serves what primary function?

Accepted Answer

To prevent cargo vapors from flowing back into the IG system machinery

Answer

The deck water seal acts as a non-return device preventing flammable cargo vapors from backflowing into the inert gas plant and ship machinery spaces.

Tanker Familiarization Practice Test

Tanker Familiarization Practice Test

Tanker Familiarization Tank Atmosphere Control 3