Short answer: bunker quantity disputes arise when the quantity on the bunker delivery note differs from what the receiving vessel measures. Common causes include measurement differences between meters and tank soundings, temperature and density errors, air entrainment, meter or seal problems, and documentation errors. Mass flow metering has reduced disputes in Singapore, but claims still depend on evidence gathered at delivery.
Why figures differ
Different measurement methods
The supplier’s figure comes from the bunker tanker’s mass flow meter. The vessel’s figure comes from tank soundings, converted to mass using temperature, density and tank calibration tables. Each has its own uncertainty. A small difference is normal; a large one needs explaining.
Temperature and density
When quantity is calculated from volume, errors in temperature readings or in the density figure used for conversion change the result. The vessel’s own figure is particularly sensitive to tank temperature and to the accuracy of its calibration tables, trim and list corrections.
Air entrainment
Air blown into fuel during delivery, sometimes called the “cappuccino effect”, inflates volume readings. It was a major issue with tank-gauged deliveries. Mass flow meters measure mass directly and modern systems detect aeration, but irregular flow and line clearing still need to be watched.
Meter integrity
A mass flow meter is only reliable if it is sealed, verified and correctly installed. Under SS 648 in Singapore, the system is sealed and subject to periodic verification by the MPA. A broken or questionable seal is a serious issue to record immediately.
Documentation errors
Wrong vessel details, mismatched sample seal numbers, or a quantity on the BDN that does not match the meter printout all weaken the record, whichever side they favour.
How to protect your position
- Appoint a bunker surveyor for large stems, new suppliers or any history of disputes.
- Take opening and closing soundings carefully, with temperatures and trim recorded.
- Record meter readings and seals before and after delivery, and keep the meter printout.
- Issue a letter of protest before signing if there is a discrepancy. Note it on the documents.
- Notify the supplier promptly in writing, within the time bar in its terms.
- Keep everything: BDN, printouts, survey report, sounding records, protest letters and correspondence.
What happens next
Most quantity disputes are settled commercially between buyer and supplier, using the survey report and meter data. Where the figures cannot be reconciled, the contract’s dispute resolution clause applies. A well-documented claim made quickly is far more likely to succeed than one raised weeks later.
Read what happens during a bunker survey for the surveyor’s role in detail.
Frequently asked questions
Do mass flow meters eliminate quantity disputes?
They greatly reduce them because they measure mass directly and are sealed and verified. Disputes can still occur over meter integrity, operating conditions and documentation, so independent oversight is still valuable.
What is a letter of protest in bunkering?
A formal written notice from the vessel to the supplier recording a disagreement, for example about quantity or sampling, issued at the time of delivery. It preserves the buyer’s position for a later claim.