FREE Tanker Familiarization Tank Atmosphere Control Questions and Answers

Question 1

According to SOLAS regulations, what is the maximum permissible oxygen content by volume for a cargo tank's atmosphere to be considered effectively inerted?

Accepted Answer

8%

Answer

15%

Answer

11%

Answer

5%

Question 2

A tanker is discharging cargo when the Inert Gas (IG) system fails, causing the pressure in the tanks to drop. What is the most critical and immediate hazard created by this situation?

Accepted Answer

Air being drawn into the tank, potentially creating a flammable atmosphere.

Answer

Structural damage to the tank deck from over-pressurization.

Answer

The cargo pumps overheating due to loss of back-pressure.

Answer

A significant increase in toxic vapor concentration at the vent mast.

Question 3

Which of the following correctly describes the primary purpose of 'purging' a cargo tank with inert gas immediately after cargo discharge and before commencing gas-freeing?

Accepted Answer

To reduce the hydrocarbon vapor concentration to a level below 2% by volume before introducing air.

Answer

To introduce fresh air until the oxygen level reaches 21% for safe entry.

Answer

To use high-pressure water jets to clean the tank bulkheads of cargo residue.

Answer

To increase the tank pressure significantly above atmospheric pressure to test for leaks.

Question 4

When preparing a tank for man-entry, what is the primary objective of the 'gas-freeing' operation that follows purging?

Accepted Answer

To displace the inert gas with fresh air, raising the oxygen level to 21% and ensuring hydrocarbon levels are safe.

Answer

To reduce the hydrocarbon gas content below the critical dilution line using more inert gas.

Answer

To fill the tank with water to remove any remaining cargo residue.

Answer

To lower the tank temperature to ambient conditions after a heated cargo.

Question 5

A tanker is loading at a terminal equipped with a Vapor Emission Control System (VECS). A high-pressure alarm for the cargo tanks sounds. Which of the following is the most probable cause related to the VECS operation?

Accepted Answer

A blockage or closed valve exists in the vapor return line to the shore facility.

Answer

The cargo loading rate is too slow.

Answer

The inert gas system is supplying gas with a high oxygen content.

Answer

The P/V breaker on the mast riser has lifted.

Question 6

When purging a tank using the 'dilution' method, what is the key principle for it to be effective?

Accepted Answer

Injecting inert gas at a high velocity to promote thorough mixing with the existing tank atmosphere.

Answer

Introducing inert gas at a very low velocity to create a stable interface with the tank vapors.

Answer

Using an inert gas that is significantly denser than the hydrocarbon vapors.

Answer

Simultaneously introducing fresh air from the bottom of the tank.