Tanker Familiarization Inert Gas Systems 3

Question 1

What automatic safety action is triggered if the oxygen content of the supplied inert gas rises above the set alarm point (typically 8%)?

Accepted Answer

The system automatically shuts down and isolates gas flow to the cargo tanks

Answer

The inert gas blower automatically increases its speed to compensate

Answer

Fresh air is automatically mixed in to dilute the oxygen content

Answer

The cargo pumps are automatically stopped to prevent loading

Question 2

Why must the deck water seal be verified as operational before starting the inert gas system?

Accepted Answer

To prevent flammable cargo vapors from back-flowing through the inert gas main and reaching the engine room

Answer

To confirm the scrubber has adequate cooling water flow for operation

Answer

To maintain the required delivery pressure in the inert gas distribution main

Answer

To ensure the flue gas is adequately cooled before reaching the cargo tanks

Question 3

Why is nitrogen blanketing used on some chemical and product tankers instead of flue gas inerting?

Accepted Answer

Pure nitrogen provides an inert atmosphere without the impurities (SO₂, soot, CO) found in flue gas that could contaminate sensitive cargoes

Answer

Nitrogen is cheaper to produce than flue gas on smaller tankers

Answer

Nitrogen blanketing is faster than flue gas inerting during cargo loading operations

Answer

Nitrogen is used only for tanks that carry refrigerated liquefied gases

Question 4

What minimum oxygen concentration in the tank atmosphere is required before personnel may occupy the space for extended work?

Accepted Answer

19.5% by volume

Answer

8% by volume

Answer

12% by volume

Answer

16% by volume

Question 5

What is the main function of the high-velocity vent (P/V breaker) fitted on a tanker?

Accepted Answer

To relieve excess tank pressure at high velocity so that vapors are dispersed well above deck level

Answer

To maintain a continuous positive pressure in all cargo tanks at all times

Answer

To rapidly depressurize the inert gas main in an emergency

Answer

To measure the pressure differential between individual cargo tanks

Question 6

Under what condition should the inert gas in cargo tanks be 'topped up'?

Accepted Answer

Whenever the oxygen content rises above 8% or tank pressure drops below the minimum set point

Answer

Only before every scheduled cargo loading operation

Answer

On a fixed schedule of every 24 hours regardless of actual tank conditions

Answer

Only after a tank has been opened for inspection or repair

Question 7

What specific hazard does carbon monoxide (CO) present in flue gas pose to tanker personnel?

Accepted Answer

It is a highly toxic, colorless, odorless gas that can cause unconsciousness and death at low concentrations

Answer

It raises the oxygen content of the inert gas, reducing its effectiveness

Answer

It reacts with hydrocarbon cargo vapors to form additional explosive compounds

Answer

It corrodes stainless steel inert gas piping and deck seals over time