25
FUELS & LUBES INTERNATIONAL
Quarter Two 2015
THE STORY BEGAN ABOUT
10 years ago. That’s when carmakers
throughout Europe started to see
sticking fuel injectors in light-duty
diesel vehicles. By 2011, the problem
and the associated warranty repairs
had grown serious, raising alarm
among vehicle makers and fuel
injection equipment suppliers.
They faced a rising tide of costs and
increasing customer complaints
across the Continent.
“The worst affected country was
France, although sporadic problems
had been reported in Denmark,
Germany and Spain,” said Ortwin
Costenoble, secretary of technical
committee CEN/TC 19. The
committee deals with gaseous and
liquid fuels, lubricants and related
products of petroleum, synthetic and
biological origin, for the European
Committee for Standardisation
(CEN). This technical committee
was coordinating efforts to find
the source of the problem and its
solution. Costenoble is a senior
consultant with NEN, a Delft,
Netherlands-based organisation that
supports the standardisation process.
At meetings, vehicle makers
made presentations about the
severity of the problem. The charts
they used had an unlabeled y-axis for
the number of warranty fixes, and so
it was impossible for non-carmakers
to determine howmany vehicles
were coming in for repairs. But, the
trend line was clearly going up.
An ad-hoc task force began
looking into the issue, which was
dubbed IDID. The designator came
from the first letters of “internal
diesel injector deposit,” a description
of what was going on. After some
detective work, the investigators
discovered that the source of the
problemwas sodium carboxylate
soap deposits. As to why the deposits
were suddenly causing trouble, there
were several contributors. Some
came about because of fuel changes
made to reduce emissions.
“This problem is probably
aggravated by sulphur-free diesel
with lower aromatic levels, resulting
in reduced natural fuel solvency, [as
well as] increased biodiesel blending
up to 7%, providing an additional
source of sodium and weak acids,”
Costenoble said.
Advanced engine hardware
introduced to boost fuel efficiency
also played a role. Smaller,
turbocharged engines and a push
for fuel efficiency meant that
injector tolerances shrank. On
top of that, these smaller engines
operate at higher injector pressure
and higher fuel temperature.
Consequently, deposit build-up
that in an earlier generation of
injectors might not have been an
issue proved to be problematic.
Looking at the fuel in the
country most severely impacted,
France, gave the investigators a
critical clue. Pipeline operators had
used a particular sodium-based
additive to inhibit corrosion. That
provided the final piece of the
solution to the mystery.
“The root cause of the internal
injector deposit problem that
has resulted in vehicle failures
in several EU countries is due to
different chemical interactions
between fuel corrosion inhibitor
additives and contaminants
present in the diesel fuel from the
production process,” Costenoble
said in summing up the task force’s
findings, which were published in
2014.
With the mystery solved, the
question then was how to fix the
problem. An option was to set a
maximum sodium limit in diesel
fuel. However, that was not deemed
practical for two reasons. The first
was that the proposed limit would
have to be very low, 500 parts per
billion (ppb). Second, the limit
would need to apply at the pump
where drivers fill up, which would
be operationally difficult.
Another proposal was to
remove the chemical causing
the problem in France, possible
because of little evidence of
internal corrosion with modern
fuels. That fix was implemented
with good results.
“Reports of injector sticking
problems have reduced dramatically
since the water soluble sodium
nitrite pipeline corrosion inhibitor
was removed in France,” said Nigel
Elliott, chair of the IDID task force.
THE SEQUEL?
If this were a Hollywood movie,
it would be time for the words “The
End” to appear. Unfortunately,
there might be a sequel, perhaps
more than one. As fuels and
engines change, problems like this
could continue to crop up. After
all, there could be other sources of
sodium or even other chemicals or
elements that by interacting with
fuel could cause deposits to form.
French pipeline operators
are not alone in using corrosion
inhibitors. It’s possible that one of
these corrosion inhibitors might
react to what’s in a given fuel and
that could lead to the creation of
particulates, soaps and deposits.
Investigators have started
looking into other possible
trouble spots along the fuel supply
chain. The Alpharetta, Ga.-based
Coordinating Research Council
(CRC) is looking into this issue
with regard to historic pipeline
inhibitors being used in the U.S.A.,
according to Elliot.
There is convincing evidence
that other corrosion inhibitors,
such as alkenyl succinic acids,
also react with sodium in diesel
fuel to form sodium carboxylate
soaps, according to Costenoble.
Other additives could also create
problems.
“Dimer acids at higher treat
rates of more than 30 parts per
million by volume have also been
shown to cause inline fuel injector
pump sticking when the pump is
lubricated with engine oil and the
fuel and oil come into contact on
the fuel pump plunger and react to
form a sticky deposit,” Costenoble
said.
The fuels industry must, in
effect, perform a balancing act
with every fuel and additive blend.
For instance, a corrosion inhibitor
needs to do its part to improve
corrosion resistance. At the same
time, it cannot react to what is in
the fuel and create problems.
To protect against this
possibility, the Coordinating
European Council (CEC) is
developing a standardised engine
test to recreate, and thereby detect,
the IDID problem. The test can
then be used to judge the impact
of different mitigation strategies,
as well as the effect of fuels and
additives.
“The objective is to develop a
test that will discriminate between
fuels that differ in their ability to
produce IDID in direct-injection,
common rail diesel engines,”
Costenoble said in discussing the
goal of this test development.
Courtesy of Ortwin Costenoble, NEN
Ortwin Costenoble
