Marine Maintenance Technology International - April 2016

FUEL MANAGEMENT (^) ⠿
MARINE MAINTENANCE TECHNOLOGY INTERNATIONAL | APRIL 2016 ⠿ 69
Density determination for assessment
of fuel volume
For fuel quantity verification, it is important
to determine the density of bunker fuel
as this specific property directly relates
to the volume and denotes the cost of a
particular HFO. Sometimes the volume of
heavy fuel oil is intentionally or accidentally
increased through air ingress (the so-
called ‘cappuccino effect’) and on-site
measurement of density can help to detect
and occurring discrepancies efficiently.
Substantial financial losses can be avoided
when one considers the total amount of
heavy fuel oil supplied.
Identifying stability of bunker fuel
As a rule, HFO burned in ship engines
contains a blend of several oil types in
order to obtain the required low-sulfur
level. Sometimes during transport, as well
as due to the long periods of storage in a
tank before actual use, asphaltenes that are
present in fuel oil in various concentrations
can precipitate, causing sludge formation.
This results in a considerable reduction in
quality of bunker fuel.
Therefore it is important to regularly
assess the condition of fuels delivered and
stored on board in order to detect possible
oil instability before introducing it to the fuel
system and engine. Determining on board
whether the heavy fuel oil is stable (resistant
to diverse temperature, transportation and
storage stresses), can help to prevent the
blockage of filters and pipes of the engine
fuel system.
Compatibility check before blending
There is a current trend to mix various
marine fuels on board after delivery, but it is
important to first assess their compatibility.
Even if diverse fuel oils are confirmed as
stable, it does not nevertheless constitute
a guarantee of their compatibility when
commingled.
Various compositional structures of fuel
oils (i.e. different origins) can potentially
cause incompatibility problems such as
shown in the example of IFO and HDME
(above right). Two fuel oils of the same
grade, but of different origins, can prove to
be incompatible when they are blended in
the storage tank.
ABOVE Very dark solid area in the center of the
spot indicates incompatibility of the fuel oil
samples (IFO 380 and HDME 50) analyzed with
Martechnic’s Compa Dens Check
Another possible incompatibility
can occur during the change-over from
one specific fuel oil grade to another.
Even though the bunker fuels are stored
in separate storage tanks on board,
incompatibility can appear in the settling
tank and subsequently in the service tank.
Additionally, incompatibility can also
emerge in the pipelines when switching from
residual fuel oil to marine gas oil.
To avoid the risk of sludge formation, it is
therefore recommended that bunker fuels be
stored in different tanks when delivered on
board and that tests be conducted to assess
their compatibility before mixing them.
Detecting cat fines on board
Another major challenge currently occurring
is the increased concentration of cat
fines in the residual oil as a result of the
catalytic cracking technology used in the
refining process. As cat fines are extremely
abrasive particles that can substantially
harm the components of the engine system,
the bunker fuel undergoes a purification
procedure in a separator system on board.
However, the amount of cat fines
contained in a particular bunker fuel
might not correspond with the maximum
acceptable level and the purification cannot
always guarantee their further reduction.
It is necessary to conduct onboard test
analysis to quickly determine the presence
of these particles in the bunker fuel before
introducing it to the engine system.
Conclusion
Current legislation restricting sulfur
content in marine fuel oils has intensified
refining and blending of fuels to achieve
the prescribed specifications. This creates
challenges to stability and compatibility of
bunker fuel and increases cat fines, which
are extremely damaging to engine systems.
In situations like these, Martechnic’s oil
quality management solutions provide
effective on-site decisions for the
assessment of fuel oil quality. \
Free reader inquiry service
Martechnic GmbH
To learn more about this advertiser, visit
http://www.ukipme.com/info/mmm NOW!
Reader inquiry no. 102
ABOVE: The test device Compa Dens Check
enables an on-site measurement of density,
stability and compatibility of fuel oils