Question 11 TK01 - Tank Vessel Assistant - Dangerous Liquids

The Correct Answer is C **Explanation for Option C (8%):** The maximum allowable oxygen content within the ship's cargo tanks, inert gas piping, and the vapor recovery system is mandated by international regulations, primarily the International Convention for the Safety of Life at Sea (SOLAS) and the International Code for Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code) and related codes (such as the FSS Code for fire safety systems). For tankers requiring an Inert Gas (IG) system, the IG system's primary function is to prevent flammable atmospheres from forming by reducing the oxygen concentration below the limit required to support combustion. The universally accepted regulatory limit for maintaining an inert atmosphere in cargo tanks of oil and chemical tankers (and LNG/LPG carriers during certain operations) is **8% by volume**. This 8% limit provides a significant safety margin below the critical oxygen level (the Limiting Oxygen Concentration or LOC) needed for most hydrocarbon vapors to ignite, which is typically around 10-11% for petroleum products. **Why other options are incorrect:** * **A) 4%:** While the Inert Gas system is typically designed to maintain the oxygen content significantly lower than the 8% maximum (often aiming for 5% or less during normal operations), 4% is not the *maximum allowable* limit set by regulations. It represents an ideal operational target, not the regulatory ceiling. * **B) 5%:** Similar to 4%, 5% is a common operational target for Inert Gas systems to ensure a robust safety margin. However, the regulatory maximum limit that must *not* be exceeded is 8%. * **D) 10%:** 10% is too high and would be considered critically unsafe. Since the Limiting Oxygen Concentration (LOC) for common petroleum products is around 10-11%, allowing the tank atmosphere to reach 10% oxygen would eliminate the required safety margin, putting the atmosphere dangerously close to or within the flammable range during cargo operations.