After completing a crude oil wash, what should be done with the oil in the lines running to the washing machines?

After completing a crude oil wash, the appropriate action is to open a COW (Crude Oil Washing) nozzle and drain the oil from the lines into the after tank by gravity. This method is effective because it ensures that any residual oil remaining in the lines is properly disposed of and returned to the cargo tank system instead of allowing it to remain in the lines or requiring more complex procedures to clean the lines. Draining by gravity takes advantage of the natural flow due to the elevation and helps prevent any potential contamination or leftover oil from affecting the operational cleanliness and safety of the cargo tanks.

This practice also ensures compliance with safety and environmental regulations, as it minimizes the risk of spills and ensures that all residual oil is accounted for. Properly handling the oil in this manner is critical for maintaining the integrity of the vessel's systems and effectively managing the cargo.

Other methods, such as using compressed air to blow out the lines or pulling suction with the supply line pump, can introduce complications in managing the oil and may not ensure complete removal of all residual oil, leading to potential issues later on. Leaving oil in the lines, even if they are left primed, poses risks for contamination and non-compliance with industry standards.