Wednesday, August 7, 2013
1. THERE
MIGHT BE A PROBLEM WITH LOW LUBRICITY OF
LOW SULPHUR DIESEL FUELS. FOR FUEL DESTINED FOR AUTOMOTIVE APPLICATIONS, THE
FUEL USUALLY HAS A MINIMUM LUBRICITY REQUIREMENT
SPECIFIED, AND WILL USUALLY CONTAIN LUBRICITY ADDITIVES TO RAISE PERFORMANCE
TO THE SPECIFIED LEVEL.
THE
SAME DOES NOT APPLY TO MARINE DISTILLATES. FOR MARINE APPLICATIONS, A MINIMUM
LUBRICITY IS NOT DEFINED IN FUEL SPECIFICATIONS. THERE IS LITTLE OR NO EXPERIENCE
OF USING VERY LOW SULPHUR FUELS WITHOUT LUBRICITY ADDITIVES IN MARINE APPLICATIONS.
WE BELIEVE FURTHER WORK IS REQUIRED TO ESTABLISH THAT SUCH LOW SULPHUR FUELS
REQUIRED BY THE REGULATIONS HAVE A SUFFICIENT LUBRICITY.
2.
DEEP-SEA SHIPPING ENTERING THE COASTAL WATERS HAVE TO SWITCH FROM HEAVY FUEL
OIL TO DIESEL FUEL. SUCH A SWITCHING IS
POSSIBLE, BUT REQUIRES THAT DETAILED PROCEDURES BE FOLLOWED EXACTLY, IF
PROBLEMS ARE TO BE AVOIDED. DURING OPERATION WITH HFO, THE FUEL PUMPS ARE HOT
(ABOUT 150°C). DIESEL FUEL IS INTRODUCED INTO THE PUMPS AT AMBIENT (ENGINE ROOM)
TEMPERATURE. IF THE CHANGING OF THE FUEL IS DONE TOO FAST, THE COMBINATION OF
THERMAL CONTRACTION OF THE PUMP ELEMENTS, AND THE LOW LUBRICITY OF THE DIESEL
FUEL (DUE TO ITS LOWERED VISCOSITY IN THE HOT PUMPS), COULD LEAD TO SUDDEN
SEIZURE OF THE FUEL PUMPS, AND HENCE LOSS OF PROPULSIVE POWER OR ELECTRICAL BLACKOUT ON THE VESSEL.
3.
THE THIRD POTENTIAL PROBLEM, AND THE ONE THAT GIVES MOST CONCERN, IS
COMPATIBILITY OF HFO WITH LOW-SULPHUR/LOW-AROMATICS DIESEL. WHEN SWITCHING FROM
HFO TO DIESEL FUEL (OR VICE VERSA) THERE IS A MIXING OF THESE TWO DIFFERENT
FUELS. (THIS CANNOT BE AVOIDED, BECAUSE OF THE GRADUAL CHANGEOVER PROCESS
REQUIRED TO AVOID THE PROBLEMS DESCRIBED UNDER ITEM 2).
IF
THE DIESEL FUEL IS NOT COMPATIBLE WITH THE HEAVY FUEL, THE ASPHALTENES OF THE HEAVY
FUEL WILL BE PRECIPITATED OUT. THE RESULT WILL BE FILTER CLOGGING, OR FUEL PUMP STICKING,
THAT AGAIN COULD LEAD TO LOSS OF PROPULSIVE POWER, OR ELECTRICAL BLACKOUT
ON
THE VESSEL.
THE
RISK OF AN INCOMPATIBILITY PROBLEM
BETWEEN HFO AND LOW-SULPHUR / LOW AROMATICS DIESEL FUEL IS SIGNIFICANTLY HIGHER
THAN FOR A “NORMAL” MARINE DIESEL FUEL (ISO-F-DMA
OR ISO-F-DMB). THIS IS BECAUSE THE LOW CONTENT OF AROMATICS MEANS
THERE IS LESS SOLVENCY IN THE HFO/DIESEL MIXTURE TO KEEP THE ASPHALTENES IN
SOLUTION.
