Critically "Off Spec"
In the most serious of cases where critical parameters are off-specification other advice will be supplied by the testing agency. In the very worst cases, advice will be given that a fuel should not be used and a claim will be recommended to be lodged against the supplier of the fuel.
It must however be noted that a de-bunkering of the vessel should always be the last resort. However, there are some cases where there are no other options and no possible fuel treatment possibilities such that burning of the fuel may lead to serious damage to the ships engines.
Example of “Critical Off Spec”
One of the most critical test parameters carried out by testing agencies is that of aluminium and silicon. In the ISO8217 standard, the two elements combined have an allowable maximum level of 80 mg/kg in Marine Fuel Oil. This has been set at 80 mg/kg because through intensive research over many years, it was determined that fuels delivered to vessels with a combined aluminium plus silicon content of no more than 80 mg/kg can be treated with the efficient running of the vessels fuel pre-treatment plant to reduce the contaminant to an acceptable level. This is usually defined as less than 20 mg/kg as per most engine manufacturers recommendations for levels at the point of injection to the engine).
Aluminium plus silicon are not naturally occurring in fuel oil and are only found in residual fuel oil as a result of catalysts that are used during the refining process and are generally referred to ‘catfines’. The level in the fuel supplied to vessels is extremely critical because the aluminium plus silicon particles are known to be very abrasive. Should the levels going through the engine be higher that engine manufacturer’s recommendations then increased wear levels could be expected to the moving parts of the engine. These parts include the fuel pumps, injectors, cylinder liners and piston rings.
Generally the levels can be considered:
| <20 mg/kg | = OK |
| 20 – 50 mg/kg | = Pre-treatment must be efficient |
| 50 – 80 mg/kg | = Pre/post purifier samples should be checked to confirm full efficiency |
| > 80 mg/kg | = Fuel must be segregated pending further investigation |
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