Final answer:
According to maritime practices and environmental considerations, it appears a flow-through system on container ships may allow a valve to remain open during transport to manage ballast water. However, specific valve operations must align with maritime regulations and the ship's ballast water management plan.
Step-by-step explanation:
The question concerns the operations of valves on cargo tanks during transportation, specifically within the context of container ships and ballast water (BW) management. According to the information provided, container ships can maintain stability during cargo operations by transferring ballast water internally among tanks instead of discharging it. This management approach can allow container ships to hold their ballast water without discharge, which is important from an environmental perspective.
About the question, it appears that the valve permitted to remain open during transport may be a flow-through system for ballast water, as described in the first information block. The flow-through process involves drawing water in through a lower valve and out through an upper opening, allowing a large volume of water to be pumped through, potentially exceeding 300% of the ballast tank capacity. This system would be used while the ship is voyaging to flush out organisms and sediments in ballast water that could be harmful if introduced into new ecosystems.
However, the information provided does not explicitly state which specific valve is permitted to remain open on container ships during transportation. Therefore, it is essential to consult the relevant maritime regulations and the ship's specific ballast water management plan to determine the exact valve operation procedures during transport.