The "Cappuccino Effect" (also sometimes known as the "Coca Cola Effect") essentially may be described by a frothing/bubbling effect caused by compressed air blown through the delivery hose.
The aerated bunkers when sounded will give the impression that the fuel is delivered as ordered.
In fact after some time when the entrapped air in suspension settles out of the fuel oil the oil level drops and a short fall is discovered.
In large bunker deliveries this could be considerable with huge financial implications.
We have often been asked why the flow meter cannot detect the air being introduced in the system and compensate accordingly.
Well, most flow meters in use today are of either the wrong type or the wrong size. In other words are not technologically advanced.
Coriolis meters take direct mass flow measurements using the Coriolis Effect
All the standard flow meters will only measure the volume of throughput and not the actual mass of fuel being delivered. As a result when air is introduced into the system, which is essentially 'small air bubbles' - the flow meter will register it as volume.
However, there are flow meters out in the market which are capable of measuring the true quantity (mass) of the fuel delivered.
One such meter is the 'Coriolis Mass Meter' - it has been in existence for quite some time now and is only getting better.
Coriolis meters take direct mass flow measurements using the Coriolis Effect (a deflection of moving objects when they are viewed in a rotating reference frame – we won't be discussing this effect as this is beyond the scope of this article).
Coriolis meters are less sensitive to pressure, temperature, viscosity, and density changes, allowing them to measure liquids, slurries and gases accurately without the need for compensation.
These meters having no moving parts require little maintenance however, the initial cost and line modifications is usually a deterrent for many ship operators for not installing it.
Cappuccino Effect can be eliminated by sounding the fuel tanks prior to blowing through.
Look out for any signs of foam on the surface of the fuel or excessive bubbles on the sounding tape.
Look out for any unusual noises from the bunker barge or excessive vibration of the bunker delivery hose (especially if you know that the tanks on the bunker barge will not be empty and thus stripping of the tanks could be safely ruled out)
Remember whenever in doubt or have concerns always issue a letter of protest
Kaivan H. Chinoy is the Founder and Principal Marine Surveyor of AVA Marine Group, owners of Petro
Inspect and The Bunker Detectives.