In the last week FOBAS has tested a number of fuel samples bunkered in Fujairah which have tested Aluminum and Silicon (Al+Si/Cat fines) at levels above the 95% confidence limit of the ISO8217(2017) RME/RMG and RMK grades.
Results have ranged from marginally above at 75 mg/kg up to nearly double at 139 mg/kg. Al+Si at 75mg/kg can be difficult to reduce but may be manageable; however Al+Si at levels up to 139mg/kg would prove extremely difficult to bring down to acceptable levels for engine entry (<15mg/kg). Carry over of abrasive Al+Si material at high levels may lead to damage to fuel pumps/injectors and cylinder components.
FOBAS data suggests that in general purifier's performance onboard is approx 60-65 % which means that even if catfines are within specification i.e. at 60 mg/kg purifier efficiency of approx 80% plus will be required to reduce these catfines to acceptable lower levels for engine entry . Following graph suggests the required purifier efficiency against level of catfine sin fuels. FOBAS strongly recommends that special attention is given to the operation of purification plants whenever catfines are found in excess of 30 mg/kg.
There are few steps that can be taken to maximize the Al+Si reduction:
Fuel should remain in settling tanks for the maximum possible time, with elevated heating as appropriate, to facilitate gravitational separation of Al+Si through settling. Both settling and service tanks should be drained off at regular intervals.
Separators should be operated using optimum arrangement and settings, ensuring optimal fuel flow rate and steady state fuel through-put temperature of 98 Deg C to enhance separator efficiency. The de-sludge cycle frequency may be increased to optimise bowl cleanliness and separation efficiency in removing Al+Si from the fuel oil.
And further recommendations for monitoring performance and signs of increased wear:
Additionally during the use of any fuel with high Al+Si attention should be given to any increase in fuel rack position needed to maintain set engine revolutions/load, which may indicate increased wear rates of fuel pump/injectors.
Spot checks on ring packs and liners should be carried out at the earliest opportunity for signs of Al+Si abrasive wear.
As ever it is extremely important to take representative bunker drip samples during bunkering process so that quality of the bunkered fuel can be ascertained. In case that a vessel bunkers a fuel with a tested Al+Si off-spec as above the first action we would recommend is that further samples are taken from upper, middle, lower and bottom of the respective bunker tanks to confirm the original result and to establish the distribution of the catfines in the tank(s). Additionally the suppliers should be contacted and requested to comment on the results.
As good general practice we would recommend regular checks of purifier performance by having samples taken from inlet and outlet of all purifiers analyzed for at least water, ash and element concentration, including Al+Si, to be confident of purifier performance at all times.
FOBAS Specialist for Europe
Lloyd's Register EMEA
T +44 (0) 3304140578, M +44 (0) 7966233440