With the recent increases in bunker prices the question of the quantity of received bunkers has re-appeared creating the problems of alleged short deliveries of this costly material. Some of the methods and techniques which are used by the bunker barges delivering fuel to avoid full delivery, or at least make the vessel believe that it has received its full contracted amount, appear to range from at best most devious to the outright scandalous.
During the past months DNVPS have issued their Bunker Alerts warning their customers of the devious use of compressed air or nitrogen that was used by certain bunker barges in Singapore for the apparent clearing of pipelines upon completion of delivery of bunkers to a vessel. Although on face value such a technique may be valid from a pollution prevention perspective to avoid the potential of any residue leaks from the bunker hose when disconnecting from the receiving vessel, clearly, such barges carrying out this technique do not have drip trays of adequate capacity or have systems in place to drain the delivery hose back to the bunker barge upon completion of bunkering. This being the apparent or potential reason, one must ask the question as to whether the barge is seaworthy for the function or service it is performing within the confined waters off Singapore and the potential pollution problems to be associated with a bunker spill.
Notwithstanding the foregoing, the consequences for the measurement of the delivered bunker quantity onboard the receiving vessel could be large. By entraining air or nitrogen within a viscous bunker the resulting observed volume will be artificially increased over a short period of time until the entrapped gases evolve from the liquid bunker. Furthermore the use of nitrogen can cause an artificial drop in the viscosity of the bunker over a short period thereby impacting the apparent quality of the material received.
In contrast to this type of procedure an alternative bunkering event was reported by an INTERTANKO member that took place off Gibraltar. (source: Intertanko)