Question 37 TK01 - Tank Vessel Assistant - Dangerous Liquids

The Correct Answer is D **Explanation for Option D (125%):** The regulatory requirements (specifically, the IMO SOLAS Convention, Chapter II-2, Regulation 4.5.5.3.3) for inert gas systems (IGS) on tanker vessels mandate a minimum capacity for the inert gas generating plant (or scrubber/fan system if flue gas is used) to ensure safety during cargo operations. The required capacity of the inert gas generating system must be sufficient to supply inert gas at a rate that is at least **125%** of the maximum rated capacity of the combined discharge rate of all the cargo pumps that are connected to the main cargo lines and which can be operated simultaneously. This margin of 25% above the maximum pumping rate is necessary for several reasons: 1. **Maintaining Positive Pressure:** When discharging cargo, the volume being removed is replaced by inert gas. The system must be able to maintain a slight positive pressure in the cargo tanks even when pumps are operating at maximum capacity, ensuring that no air ingress can occur. 2. **Handling System Losses:** It accounts for potential system losses, leaks, or demands during simultaneous operations (e.g., purging, tank cleaning preparation). 3. **Safety Buffer:** It provides a critical safety buffer to ensure a continuous and adequate supply of inert gas, even under fluctuating operational conditions or potential pump overloads. **Explanation of Incorrect Options:** * **A) 50%:** This capacity is far too low. Operating cargo pumps would rapidly draw down the inert gas supply, leading to negative pressure in the tanks and creating a severe safety hazard (the risk of drawing in atmospheric air and reaching flammable limits). * **B) 75%:** While closer than 50%, 75% is still insufficient. If the inert gas capacity is less than the maximum pumping rate (100%), the system cannot maintain the required positive pressure when the vessel is discharging cargo at full capacity. * **C) 100%:** A capacity of exactly 100% is insufficient because it provides no margin for maintaining positive pressure, accounting for system inefficiencies, or covering brief peak demands. Regulations require a safety margin above the maximum operational demand.