The examples shown here are the actual results of bunker operations which, through INtegrity, reveal the nature of some of the problems with fuel quality. Undoubtedly some of these problems not show a failure to achieve “Value for Money” but they also illustrate some of the sources of quantity problems. Note that all the examples shown are from inline blending on a barge.
Integrity and the digital viscometer can highlight these problems as they are occurring and because operators can tell at a glance that there is a problem and what that problem is, many of these problems will be resolved simply due to better operator information,.allowing them better control of bunkering.
Equipment problems or operational procedural problems are resolved by a one off action to remedy the identified problem..
Fraud becomes very visible and much more difficult to perpetrate.
Fuel quality is assured and, in conjunction with tank dipping, tank gauging or flow metering, most fuel quantity problems are managed or eliminated.
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In any bunking operation there are three distinct elements in the log:
This chart illustrates what may be expected when monitoring fuel properties as the fuel is flowing. The results are apparent in real time allowing real time decisions and actions.
Initially INtegrity will respond to whatever was in the pipe work at connection. Once flow starts the fuel will arrive at the digital viscometer and its properties will become apparent.
If the fuel is a pre-
If the fuel is being blended as it is being bunkered then dependent on the method, the it will be apparent that the blender must first arrive at its control condition. In the case of meter blending (red trace) the system should rapidly reach the set point values. Some mechanical blenders (blue trace) may require longer to reach the set points and may show some slight drifting.
A good bunker:
:More precisely, an acceptable bunker. Discounting the start and end sequences and despite some evident instabilities in the middle of bunkering, the overall result, as shown by the mean and standard deviation results, is for a good blend. It is not as good as it could be but far from being atypical.
Any time the fuel is not maintained homogenous in storage or if it is crudely adulterated then the density and viscosity will show variation during bunkering the fuel.
In this example, the cause f the problem is not clear and it is also relatively slight (note the scales) and could simply indicate that the fuel, or one of its components, most probably the residual oil, has partially stratified in storage. It might also indicate some problem on the barge. Note that because this is an inline blender, some of the effects have been moderated by the response of the blender to changing viscosity.
Common practice for some operators has been to follow the “ISO in, ISO out” principal that if all the fuels put into a common storage tank are of the same grade and are ISO 8217 compliant, then any fuel bunkered from that tank will also be ISO 8217 compliant.
Unfortunately, this is not good enough for MARPOL. The fuels may have differing sulphur contents and densities. Density is not only an important parameter for accounting for the amount of fuel bunkered (which is the density that will be reported here?) it must also be accurately reported in the vessel logs.
Here it is evident that a more dense fuel has been consolidated with a less dense fuel and the more dens has been pumped from the bottom of the compartment (or a separate compartment) first. What does the fuel calculation show?
Air in the Residual fuel component:
In this example there is a significant amount of air dispersed in the residual fuel component on the barge. This may have been inadvertently introduced during loading of the barge.
In this case we not only see evidence of bubbles in the fuel but also of pockets of air.
The effects are dramatic, instantly evident and recognisable. Samples taken and measured with offline instruments (e.g. Hydrometers and falling ball viscometers) will report false low densities and false high viscosities. The digital viscometer also will show false high viscosity and false low density but most importantly, the entrained air will also result in false metered flows (especially pockets of air) and false tank dipping values on the barge or on the vessel.
In this case the air is present just as a dispersion of bubbles and is consistent with air being drawn into the blender as the fuels are being pumped. Even though this is a low viscosity intermediate fuel, there is no evidence of the air being in the fuel in the compartments. Evidently the problem has been detected and the cause found (possibly a partially open valve or a leaking gasket in the pump suction) and remedial action taken with instant effects.
Notice the quality of the density and viscosity signals after the air has been eliminated. These are very stable and consistent as the blend continues and these should match the fuel blend calculation if the component certificates are valid. Note also that the effect of air on the values is to increase the viscosity and reduce the density.
These are all real data from actual bunkering operations. In normal operations the data is not processed nor evaluated in this manner, the viscometer is simply to provide viscosity trim control. INtegrity allows automatic comparison of fuel density and viscosity with the certificate values, air detection and some diagnostics to suggest possible causes when the fuel quality is not consistent with the certificate or blend calculation.
Any problem of quality or any operational problem such as entrained air is instantly detected, is recognisable and allows immediate remedial actions. When first used INtegrity problems associated with equipment or operational procedure can be identified and remedied for once and for all.
All parties to the bunkering operation have access to full and instant data on the
problem and its possible causes and appropriate action can then be taken, even if
that action is to reject the bunker. Rejecting a bunker can save the vessel having