What does "On board quantity (OBQ)" refer to?

"On board quantity (OBQ)" specifically refers to the quantity of residual material left in a vessel after loading operations have been completed. This term is crucial in the shipping and tankerman industry as it helps determine the amount of usable capacity of a vessel for carrying cargo. Understanding OBQ is important for accurate cargo measurements and for assessing the vessel's performance and efficiency during loading and unloading operations.

In tankerman operations, recognizing the amount of OBQ allows operators to ensure that they are complying with regulations and managing inventories correctly. This balance is vital as it influences the planning for future voyages and the costs associated with transporting oil or other liquids.

The other choices presented do not accurately depict what OBQ encompasses. The total amount of cargo loaded onto a tanker pertains more to the cargo intake rather than residuals. Fuel discharged relates to operations after the vessel has completed its loading or discharging sequence, and the amount of usable fuel focuses on fuel management rather than the complete understanding of OBQ as it pertains to residuals in the tank.