Features: - Tanker Operator

INDUSTRY - BUNKERS
From 1st January 2010, vessels berthed at European ports will have to use 0.1% sulphur
fuel oil, effectively meaning a switch to gas oil.
Sulphur Fuel Oils (MARULS) in collaboration
with the Research Council of Norway,
Marintek and 19 Norwegian shipowners. The
project’s aim was to develop technical
guidelines and new, simple indicators for the
ignition and combustion quality of bunker fuel
to aid in the process of making the complex
task of bunker purchasing more transparent.
Due to modern refinery processes and the
blending techniques used to produce a product
that meets regulatory sulphur levels, DNVPS
and its customers saw that the quality of some
LSFO had poorer ignition and combustion
properties than ‘normal’ fuel.
The heavier molecules in LSFO require
more energy for ignition and can delay
ignition and prolong combustion. “An engine
needs combustion energy at exactly the right
time, when the piston is in the right place. If it
doesn’t get that, then the energy is not utilised
to the maximum potential, and worse, we run
the risk of engine component breakdown,”
Stirling explained.
Fouling problems
Poor combustion leads to increased fouling
and, in extreme cases, moving parts such as
exhaust valves are inhibited. Excessive
fouling of the exhaust gas receiver, combined
with late ignition, or prolonged combustion,
has even led to exhaust gas fires.
The concentration of abrasive aluminium
and silicon particles (catfines) can also be
greater in LSFO. Catfines can lead to damage
to all moving parts of the engine that come in
contact with the fuel, such as high pressure
fuel pumps, fuel valves, piston rings/grooves
and cylinder liners.
“Of course, the effect of both poorer
ignition and combustion and high catfine
levels can be reduced if the vessel is aware of
the potential problem before use, and
procedures can be put in place to minimise
their effect,” said Stirling.
So how does this all tie in with EU and
Californian regulations, including ultra low
sulphur gas oil?
Engines in a worse condition than they
would otherwise be if only ‘normal’ HFO is
used can therefore be more vulnerable to
switching to low viscosity MGO, as the
quality of low sulphur gas oil is very different
from that of ‘thick’ fuel oil.
For example, as a result of the (possibly
too) low viscosity, internal leakages between
the pump cylinder and plunger can occur.
With reduced fuel supply to the engine, nonoptimal
atomisation and reduced starting
performance can be experienced.
The fuel is also acting as a lubricant
between the metal surfaces of the pump. If the
viscosity is too low, then there is the risk of
metal to metal contact and the vessel risks
either stopping or not being able to start (or
retstart) when switching.
Low viscosity is especially challenging for
larger boilers as it may cause a change in the
fuel/air ratio due to pressure changes and
increase the risk of smoke emissions.
Additionally, especially for rotary cup burners,
unless suitable heat shields are fitted, there is
increased risk of coke deposits.
Boiler problems
For larger boilers that are used for propulsion
and steam generation for cargo pumps on
LNGCs (to atomise fuel), there can be
relighting challenges after flame failure when
using gas oil. However, according to boiler
manufacturers, all the potential low sulphur
gas oil problems can be avoided if upgrades
are made to existing burners. They have also
reminded users that boiler pumps may not be
suitable for viscosities below a certain
minimum level and that a separate pump may
be needed for low viscosity MGO operation.
Looking at DNVPS statistics, MGO
viscosity has decreased in many ports in the
lead up to the EU and Californian regulations.
“As you reduce the viscosity, you generally
also reduce density. This can be both a
commercial and a statutory problem as lower
density, if not referenced properly on the
delivery note, can lead to less fuel received.
“More importantly, it can be a safety issue.
DNVPS statistics show you often also reduce
the flashpoint and if this falls below 60 deg C
then you are outside SOLAS regulations.
Your vessel loses its class and you have no
insurance,” said Stirling. “Upon receipt of
low flash point gas oil, you should contact
your classification society immediately for
instructions.”
Sulphur regulations are becoming
increasingly complex as more Emission
Control Areas (ECAs) are being discussed and
EU regulations enter into force. Even when
regulations are well established, local
variation in the application of rules can be
confounding and could lead to unnecessary
delays and detentions, said Stirling.
The European ports requirements, for
example, could see one country accepting
bunker delivery notes showing sulphur
content of 0.1% and allowing tested sulphur
up to 0.14% where other countries may
accept less statistical variation and insist on
0.1% maximum.
DNVPS constantly monitors fuel quality
around the world and helps bunker purchasers,
operators and crews to be up-to-date on local
regulations and any variations in bunker
quality. The organisation can pinpoint
emerging problems in specific ports and
specific supplier variations on a daily basis so
that its clients can avoid the worst problems,
or at least take appropriate action to guard
against risk. The Norwegian class society
subsidiary also provides support in training
and procedure development to cater for
different fuel qualities through adequate
housekeeping, fuel treatment and the
adjustment of engine operational parameters.
“Always, when using any fuel, we say that
the chief engineer should be vigilant and
regularly check engine state. If poor quality
fuel is received, we will then teach routines and
give advice on what we feel the chief engineer
should check for,” said Stirling. “Additionally,
we advise that all customers test all samples
and trend, historically, all fuel used.”
The purpose of the MARULS project was to
ensure that bunker purchasers can have
confidence in the quality of the fuel they buy so
that poor ignition and combustion properties
can be catered for through appropriate
procedures. “This will protect engine condition
and, ultimately, life and property at sea,” said
Stirling. “The better the engine condition, the
better the chance of avoiding switchover
problems and we continue to benchmark both
LSFO and MGO quality going forward in order
to inform our customers, the industry and the
IMO about the trends.”
TO
*This article was written exclusively for
TAKEROperator by DVPS.
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TANKEROperator November/December 2009