What should be the status of the cross-connection valve when tanks are carrying liquid with a free surface?

When tanks are carrying liquid with a free surface, the cross-connection valve should be closed. This is crucial because having the valve open could allow for the mixing of liquids between tanks or compartments, creating a potentially hazardous situation. The presence of a free surface in the tanks can significantly affect the stability of the vessel. Free surface effects can increase the center of gravity and decrease the metacentric height, which in turn can lead to a greater risk of capsizing, especially in rough weather or during maneuvers.

By keeping the cross-connection valve closed, it helps to maintain the integrity of the fluid in each tank, minimizing the free surface effect and promoting better handling and stability of the vessel. Ensuring that each tank operates independently prevents the undesired redistribution of liquid that could compromise the vessel's stability. Establishing this practice is essential for safe operations during journeys or when facing adverse conditions at sea.