FUEL SYSTEM Along the discussion please make a list of requirements to fuel system
Pureness of the fuel • High pressure pump and injectors • Unit injectors • Electronic unit injectors Contaminated fuel ruins the fine components
Sulphur • Converted to sulphur trioxide during combustion • But react with liquid water. The result is H2SO4 – highly corrosive agent • React with Zn – White cloud of Zink sulphate
Water • Wears fuel system • Filter media go to swell cutting off the engine fuel supply • React with sulphur – H2SO4
Steps to overcome effects of water • Drain water from fuel tanks • Obtain fuel from reliable sources • Use water separators
Water separators • Sediment type
Water separators • Coalescing type
Catalytic Fines • Small , hard particles which originate at the refinery. • Cause very rapid abrasive wear on injection pumps, Piston rings and cylinder liners • Centrifuging and filtration
Micro organisms in Fuel • Cause corrosion and filter plugging • Bioside added to the fuel will kill them but not remove the remained of their bodies • Clean tanks and filter the fuel
Steps to minimize problem • Avoid long fuel storage periods • Drain water from fuel tanks regularly • Purchase fuel from reliable sources • Dose all fuel inventory with biocide at the first sign of micro organism contamination
Filters • Primary Fuel Strainer – 0.1x 0.2 mm • Secondary Fuel Filter – 10 microns Advised by engine manufacturer
Air in the fuel line Interruption of the flow
Heat in the fuel Power loss 1% of each 6 o C (10 o F) above 29o C (85 o F)
Fuel Coolers Factors affect the need for fuel cooling equipment: • Length of periods of continuous operation • Length of time between periods of operation • Volume of the fuel tank (larger than 11000L) • Ability of the fuel tanks to dissipate the heat of stored fuel
REQUIREMENTS • Pureness of the fuel • No air in the fuel line • No excessive heat in the fuel • As less restriction in the line as possible • Storage • If more then one tank – transfer • Stop flow when engine stop • How much fuel available • Isolating branch in case of contaminating
Fuel tanks • Size • How many tanks • Location • Materials • Requirements to the tank arrangement
Size • Fuel consumption f x hp (of kW) F = ------------------- S x 1000 S – Specific gravity of diesel fuel – 0.83 f – Specific fuel consumption: g/hp-hr or g/kW-hr F – Fuel consumption: l/hr • Proposed hours work without refill
How many tanks? • One – small boats • Two – Starboard and Port – stability maintenance • More than two • Day tank
Day tanks Factors affect the need for fuel cooling equipment: • Length of periods of continuous operation • Length of time between periods of operation • Volume of the fuel tank ( larger than 11000L) • Ability of the fuel tanks to dissipate the heat of stored fuel
Location of the day tank • The level of the fuel is to be no higher than the fuel injection valves on the engine • Close enough to the engine so the total suction lift is less than the suction head of the fuel pump.
Location • On the bottom or close to the hull side provides good cooling but could create too great stability • Close to the engine provide small resistance of the lines but weight distribution could suffer • Level – 1.Lower than engine injectors or shut off valve to be provided - solenoid or manual; 2.No lower than suction head of the fuel pump or transfer to additional higher tank is to be provided
Materials • Sheet steel • Marine aluminium • Nickel-copper • Fibreglass • Polyethylene Galvanized material should never be used Cu react with the sulphur in diesel as well
Requirements to the tank • Fill • Ventilation • Gauge • Drain • Cleaning access • Discharge line • Return line • Baffles • Grounding/Bonding
Tank construction
Tank arrangement
Fuel return line • Pressure limit – acc. manufacturer • Size at least same size as a supply line • A shutoff valve is not recommended
Test • 3 psi or more depends of rules complied Clean and flush fuel system prior to start the engine
