Tanker Familiarization Inert Gas Systems 2

Question 1

What does 'gas-freeing' of a cargo tank involve?

Accepted Answer

Ventilating the tank with fresh air to replace inert gas and reduce hydrocarbon vapors for safe entry

Answer

Filling the tank completely with inert gas to purge residues

Answer

Purging hydrocarbon gas with pure nitrogen before loading

Answer

Testing the tank atmosphere for flammable vapors only

Question 2

What is the primary function of the scrubber in an inert gas system?

Accepted Answer

To cool and clean the flue gas by removing sulfur dioxide and soot particles

Answer

To remove oxygen from the inert gas before it reaches the tanks

Answer

To compress the inert gas to the required delivery pressure

Answer

To continuously monitor hydrocarbon levels in the gas supply

Question 3

Before personnel enter a tank that has been held in an inerted condition, what action is absolutely essential?

Accepted Answer

Gas-free the tank until oxygen is at least 19.5% and hydrocarbon levels are below the LFL

Answer

Top up the inert gas supply to maintain positive tank pressure

Answer

Confirm that the oxygen analyzer shows 8% before entry

Answer

Seal all tank openings except one entry hatch

Question 4

What is the correct procedure before loading flammable cargo into a tank that currently contains a normal air atmosphere (21% oxygen)?

Accepted Answer

Inert the tank to reduce oxygen below 8%, then proceed with loading

Answer

Load directly since the cargo will displace air naturally

Answer

Purge with additional fresh air first to ensure cleanliness, then load

Answer

Gas-free the tank to remove all traces of previous cargo, then load with air inside

Question 5

What does a pressure/vacuum (P/V) valve on a cargo tank protect against?

Accepted Answer

Both excessive over-pressure and excessive vacuum within the cargo tank

Answer

Backflow of inert gas toward the engine room

Answer

Oxygen ingress into the inert gas supply line

Answer

Sulfur dioxide contamination of the cargo

Question 6

What minimum oxygen percentage must be present in a tank atmosphere before personnel may safely enter?

Accepted Answer

19.5% or above

Answer

8% or above

Answer

12% or above

Answer

16% or above

Question 7

What is 'purging' in the context of an inert gas system?

Accepted Answer

Using inert gas to dilute and displace hydrocarbon vapors until they fall below the lower flammable limit

Answer

Adding oxygen to a tank to bring it to normal atmospheric levels

Answer

Removing inert gas from tanks using fresh air before personnel entry

Answer

Cleaning the inert gas scrubber with seawater to remove soot deposits