In an event of a short delivery be wary that empty tanks may not be empty even with zero dip and that substantial pumpable may exist.
Verify the tanks claimed to be empty - don't take the supplier's word for it.
Zero Dip Volume Application Principle
The bunker surveyor or the vessel representative should notify the barge representative that the zero dip volume of the tank(s) shall be included in the bunker tanker calculations.
The condition shall deemed to apply when the closing gauge would indicate no oil cut whereas the visual inspection of the bunker tanker cargo tank indicate free flowing oil at the aft of the tank.
To avoid zero dip volume application, sufficient bunkers should be retained in cargo tanks such that it touches all four sides of the tank.
To apply zero dip correction, it is assumed that the tank is rectangular where the sounding is not constrained by a sounding pipe – i.e. sounding should be taken in an "open sounding" position (from the hatch) where the sounding tape bob is free to travel with the trim of the barge and not restricted by the sounding pipe.
However, if the tape is used inside a sounding pipe this correction would be invalid.
Liquid cargo should only be trim and/or list corrected if the liquid is in contact with all bulkheads.
When the liquid is not in contact with all bulkheads, a wedge correction should be applied.
*Cut - The oil level on the tape or bob or the water level marking on a tape or bob coated with water indicating paste. "Taking a cut" is taking a measurement of the oil or water level.
Do not assume any tanks to be empty even when reaching stripping level
Check tank calibration tables to verify the unpumable
Apply correct list / trim corrections during calculations
Remember whenever in doubt or have concerns always issue a letter of protest
Kaivan H. Chinoy is the Founder and Principal Marine Surveyor of AVA Marine Group, owners of Petro
Inspect and The Bunker Detectives.