Tricks of the Bunker Trade: Unpumpable Fuel, Zero Dip Volume Application

by Kaivan H. Chinoy, Petro Inspect / The Bunker Detectives
Thursday December 19, 2013

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.

Key Notes:

  • 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

About Petro Inspect and The Bunker Detectives

Bunker Detectives

Petro Inspect, previous known only as The Bunker Detectives, are a dedicated team who primarily help ship charterers' & bunker brokers deal with bunker quantity disputes (which do not fall under P&I cover for charterers'), and also offer an exclusive service to ship charterers' dealing with 'Bad' Bunker dispute claims, such as the supply of contaminated or off- specification bunkers.

The core services provided under the banner of 'Bunker Detective' are 221B Surveys (aka Bunker Detective Surveys), Bunker Stem Surveys (aka Bunker Quantity Surveys - BQS) and Charter On/Off Hire and Condition Surveys, as well as a bunker fuel concealment detection services.

About Kaivan H. Chinoy

A qualified Mercantile Marine Officer with an MSc Degree in "Technical Management of Ship Operations," prior to founding AVA Marine Kaivan spent over 15 years involved in extensive marine operations including vessel navigation, cargo handling, accident investigations, project cargo risk management, and marine cargo surveying.

To contact the editor responsible for this story email us at editor@shipandbunker.com