Tank Atmosphere Control Flashcards
7 cards from real Tanker Familiarization practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Tank Atmosphere Control flashcards as text
What does the term 'inerting' a cargo tank mean?
Answer: Reducing the oxygen content below 8% to prevent a flammable atmosphere
Inerting is the process of introducing inert gas to reduce and maintain oxygen content below 8% by volume, preventing the formation of a flammable atmosphere.
Which condition must be checked before allowing personnel to enter a gas-freed cargo tank?
Answer: Oxygen level is between 19.5% and 23.5% and hydrocarbon vapors are below 1% LEL
A safe entry atmosphere requires sufficient oxygen for breathing (19.5%-23.5%) and hydrocarbon levels below 1% LEL to prevent explosion risk.
What is the purpose of the 'pressure/vacuum (P/V) breaker' on a tanker?
Answer: To protect cargo tanks from excessive pressure or vacuum by venting to atmosphere
The P/V breaker is a safety device that opens automatically if tank pressure or vacuum exceeds safe limits, protecting the tank structure.
During cargo loading on an inerted tanker, what should happen to the tank pressure?
Answer: Positive pressure should be maintained by venting inert gas as cargo fills the tank
As liquid cargo enters and occupies tank volume, the inert gas above the cargo is vented through the IG vent system to maintain safe positive pressure.
What does 'HC content' refer to when measuring tank atmospheres?
Answer: The concentration of hydrocarbon vapor expressed as a percentage of LEL
HC content is the hydrocarbon vapor concentration measured as a percentage of the Lower Explosive Limit, indicating the risk of flammable atmosphere.
Why is it critical to monitor inert gas quality continuously during inerting operations?
Answer: To detect if oxygen content rises above 8%, which could create a flammable atmosphere in the tank
Continuous monitoring ensures that the oxygen content of gas entering tanks never exceeds 8%, which would risk creating a flammable atmosphere.
What precaution must be taken when venting cargo tank vapors to atmosphere?
Answer: Vapors must be vented at high velocity through mast risers to disperse safely above the deck
High-velocity venting through mast risers ensures vapors are dispersed well above deck level, reducing the risk of accumulation and ignition near personnel or ignition sources.