Final answer:
The tank likely has a mechanism that allows the operator to stop the oil flow for maintenance, similar to flow-through systems in ballast tanks where large volumes of water are cycled through.
Step-by-step explanation:
The tank in question seems to be equipped with a flow-control feature that permits the operator to halt the flow of oil. This functionality is crucial for performing routine maintenance like cleaning the strainer without having to empty the tank completely. A similar process is seen in ballast tanks which use a flow-through system, allowing water to be drawn in through a lower valve and expelled through an upper opening, where up to 300% of the ballast tank capacity can be pumped through for cleaning or maintenance purposes. This kind of system is essential for the efficient operation and upkeep of tanks that handle liquids like oil or ballast water.