At times, a vessel has to load bunkers from two or more barges or from trucks. In such cases, collecting bunker drip sample is always a challenge. In an ideal case, for each such parcel being delivered, it is recommended to draw a continuous drip sample throughout the bunkering operation. Each such sample should be analyzed and checked for its specifications against the BDN or the ordered specifications.
In one such case, the vessel collected one common bunker drip sample and sent it for analysis. The tested results did not match with the BDN specifications. Though the tested parameters fell within specifications, the difference in density was high enough to cause a commercial loss Viswa Lab tests fuel samples and reports the difference in density if it is significant.
Below is an extract from the Viswa Lab fuel oil test report –
“Amount of shortage of fuel supplied based on the difference between the received density and test density _____MT”.
Though the fuel parcels bunkered are from the same supplier, it is essential to test the drip sample of every such parcel bunkered to determine the exact fuel quality. It is possible that the first parcel of bunker may be of good quality and the intermittent ones may be of a bad quality. When a common drip sample is collected, it may not represent the true quality of each of the parcel supplied. At times, it might not match with the BDN specifications. The risks involved may vary from off-spec fuel being supplied to unstable or incompatible fuels causing severe machinery problems.
How to Identify if the fuel supplied is of the same source?
When a vessel bunkers from two or more barges or trucks, as a first step, it is highly essential to verify that the fuels being bunkered are from same source or supplier. If otherwise, there is a probability that the two different fuels supplied might not be compatible with each other. One way to verify it is to check the BDN specifications of all such parcels. The difference in density and sulphur values might not be significant and they will be close to each other. Did you know that every fuel has a fingerprint?
Viswa Lab states that testing a fuel for fingerprint parameters would reveal whether the fuel is from same or a different source. This is applicable when the bunker drip samples are drawn from each of the parcels being supplied to the vessel. If a drip sample is collected common for all parcels, then the fingerprints of each fuel might not be a representative one.
So What are Fuel Fingerprint Parameters?
Every fuel has its own fingerprint. The fingerprint parameters are:
- Density
- Viscosity
- Sulphur
- Vanadium
- Carbon Residue
It is to be noted that Viscosity is not a mandatory parameter to be specified in the BDN. Marpol Annex VI does not include BDN in its list of mandatory BDN specifications. However, it has to be noted that the viscosity will resemble close if each of the samples from the parcels is tested. At times, a variation in viscosity is possible if the bunker supply barge supplies fuel with ‘in-line blending’ during bunkering.
If the fuel supplied is from the same source – then the above five fingerprint parameters would closely resemble each other. If the fuel supplied are not from the same source, then they would vary and prove that the fuels are from the different source. This fingerprinting is also applicable for vessels sending samples from tanks, before and after purifiers.
Source: Viswa Lab
