Features: - Tanker Operator

TECHNOLOGY - TANK CLEANING
manufacturers were used, but as can be seen,
the names of the manufacturers and the
specific product names are not disclosed for
reasons of confidentiality and also because the
objective of the project was not to say that one
cleaning chemical manufacturer was better
than another, rather that different cleaning
chemicals do not behave the same way under
the same conditions.
Consideration should also be given to the
concentration of use of the respective cleaning
chemicals, as this will have a direct impact on
the total cost of tank cleaning, assuming it
was carried out on board a vessel.
Results
The following results were noted:
The results are extremely interesting and very
clearly show that not all cleaning chemicals
are as efficient as each other under the same
conditions.
The first and most noticeable observation is
that even the best cleaning materials still
result in a hydrocarbon failure, which
confirms the fact that cleaning zinc silicate
from persistent hydrocarbons is indeed very
challenging.
It is also interesting to note that five out of
the top eight performing cleaning chemicals are
used at a concentration of less than 1% and
four out of the top eight are actually used at a
concentration of 0.5% or less. This does not
particularly justify the fact that most effective
detergents are effective at low concentrations,
but it does suggest the same. With this in mind
it would be interesting to note whether the
products 1, 2 and 3 from Company E
performed equally as well at lower
concentrations, which would of course make
them far more cost effective to the vessel.
If one considers that re-circulating a cargo
tank with a solution of tank cleaning
chemicals will usually require a minimum
volume of 10 cu m of liquid to maintain
suction on the pump, it is clear that a product
used at an active concentration of 0.5% will
utilise 50 litres of pure cleaning chemical,
whereas a product used at an active
Cleaning Chemical Concentration Average Hydrocarbon
of use Reading in FTU
(LIM spectrometer)
Hot water only 645
Company A – Product 1 0.5% 179
Company B – Product 1 0.5% 230
Company E – Product 1 3% 268
Company E – Product 2 3% 280
Company E – Product 3 3% 285
Company C – Product 1 0.4% 320
Company E – Product 4 0.8% 322
Company D – Product 1 0.4% 325
Company C – Product 2 2% 335
Company E – Product 5 3% 352
Company E – Product 6 0.5% 363
Company E – Product 7 3% 370
Company B Product 2 3% 400
Company G – Product 1 0.5% 415
Company E – Product 8 3% 438
Company E – Product 9 3% 450
Company F – Product 1 0.4% 498
Company F – Product 2 3% 530
Company E – Product 10 3% 535
Company E – Product 11 3% Aborted due to excessive foaming
Company F – Product 3 3% Aborted due to excessive foaming
concentration of 3% will utilise 300 litres of
pure cleaning chemical.
If this figure is then multiplied by the
number of cargo tanks that need cleaning on
each vessel and the number of tank cleaning
operations carried out on that vessel in a year
and the number of vessels in any particular
fleet, it is easy to see how quickly the costs of
cleaning chemicals alone can run into tens or
even hundreds of thousands of dollars/euros
each year.
So clearly the correct choice of tank
cleaning chemical for the owners/operators of
tankers is extremely important and not one
that should be taken without a better
understanding of efficiency and the fact that
actually, not all cleaning chemicals are the
same, even though at first glance, they may
appear to be very similar.
To close, it is fair to say that while answering
a number of points, projects like this also tend
to raise many more questions and LIM would
be very interested to hear from any parties
interested in taking this project further. Of
particular note are the following points:
1) The use of the appropriate cleaning
chemical for the particular tank cleaning
procedure. This project specifically looked
at the efficiency of ‘hydrocarbon
removers’ on cleaning a hydrocarbon from
a zinc silicate matrix, but there are many
different cleaning chemicals that are
specifically sold for particular tank
cleaning jobs and identifying whether
these cleaning chemicals are actually
suitable for the job is perhaps of equal
importance to how efficient they are.
2) The subject of cleaning chemical
concentration was touched upon in the
main report, with specific reference to the
overall cost of any tank cleaning
operation. Clearly this is an important
factor that could very well be studied
further, particularly under the control of a
laboratory based project.
3) Washing water temperature is also a very
important factor that could have a
significant impact on the efficiency of any
tank cleaning chemical. Again, this factor
would benefit from a laboratory based
study under controlled conditions; as
opposed to “on-board” experimentation,
which from experience tend to be costly
and cannot really be expected to produce
the same level of certainty in the results as
compared to a laboratory based study. TO
*This article was written by Guy
Johnson, director L&I Maritime (UK)
operations@limaritime.com
Tel: +44 1909 532 003.
30
TANKEROperator November/December 2009