ISO 8217 has been significantly amended and with this in mind we feel it important to share the background into these parameters making their way into the new specifications.
It is important to specify ISO 8217:2010 if, when purchasing fuels, you require the latest specifications as ISO 8217:2005 is still widely available.
Acid Number, ASTM D664
Acid numbers significantly higher than indicate possible contaminants (e.g. Fatty Acids etc. from Bio Fuels) or the presence of acidic compounds.
There is NO correlation between Acid Number and Corrosive Activity of Fuels – The Key issue remains to ensure Inorganic Acids are not present in the fuel, in other words ensuring the Strong Acid Number is NIL.
Calculated Carbon Aromaticity Index, CCAI
Calculation determined from the Density and Viscosity of the Fuel. It Does NOT provide information regarding combustion characteristics
Included in Specification to avoid Residual Fuel Oils with an uncharacteristic Density / Viscosity Relationship which can lead to ignition delays.
CCAI with regard RMG grades is not a parameter that gives cause for concern, as it would take a corresponding viscosity of 83cSt with a 0.991 kg/Ltr Density to reach the limit of 870 maximum – values that are in practice extremely unlikely.
It is however more applicable for RMK and lighter fuel oil grades.
Should fuel Ignition quality problems be reported then a suitable technique for further investigation would be Fuel Ignition and Combustion Analysis, using the FIA 100/FCA analyser to obtain an ECN (Estimated Cetane Number)
Hydrogen Sulphide
Guidance limit of 2 mg/kg in the liquid phase currently in place. Specification comes into force on the 1st July 2012.
IP 570 is currently under review with respect technical issues.
H2S is a highly toxic gas with a Short Term Exposure Limit (STEL*) of 10 ppm in vapour.*STEL is the maximum concentration an individual could be exposed to in a 15 minute period.
No correlation exists for the conversion of H2S concentration in liquid to vapour concentration due to many influences, movement of product, temperature and size of vapour space etc however it is widely accepted that 1 ppm in liquid has the potential to evolve as much as 100ppm in the vapour phase.
The 2 ppm limit is therefore being questioned by many industry experts.
Sodium
Fuels rich in Sodium (Na) and Vanadium (V) form oxides once burned and the ash particles can become fluid and stick to surfaces (Stiction Temperature). This temperature is lowest for ashes rich in Na and V. These deposits can cause damage to components such as piston crowns and exhaust valves in Diesel Engines by processes such as hot corrosion.
The common source of excessive Sodium in bunker fuels is from Sodium Chloride in Sea Water. As a rule of thumb a 1% by volume contamination of Sea Water would add about 100mg/kg (ppm wt) of sodium to the fuel.
Essentially “water free” fuels may contain between 10 and 50 mg/kg Oil Soluble Sodium, this derived from Crude Oil and the refining process.
Note – older medium speed engines are more at risk for such processes to occur. More modern engines are made from corrosion resistant Nimonic steel alloys.
Inorganic Sodium, such as from salt water can be removed along with the water by centrifuging or in settling tanks.
Total Sediment Accelerated (TSA) & Total Sediment Potential (TSP)
Allowance has now been made for the TSA (accelerated) test to be used in the standard. This involves a chemical ageing process rather than heat treating for 24 hours and subsequently results will be available in a shorter timescale.
Should a dispute occur the TSP method must be performed.
Changes to Existing Specifications – See table for more details
Ash Specifications have been tightened for many Grades.
Vanadium Limits have been generally reduced, Aluminium and Silicon specifications have been reduced.
Criteria for Used Lubricating Oils being present has been amended.
Grade Changes
RMA 10 – A new grade has been added replacing DMC.
RMG and RMK have now been expanded to allow for different Viscosity grades.
RMF and RMH have been removed.
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Cockett Marine Oil Limited can supply both ISO 8217:2005 and ISO 8217:2010 specifications.
For a quotation contact: Enquiries@Cockett.com
For more information relating to this article contact:
Chris Turner - Group Technical Manager – Email: C.Turner@cockett.com
Cockett Marine Oil Limited
