Fuel Quality / Fuel Degradation
The shelf life of diesel fuel is 6 to 12 months under optimal storage conditions. Fuel degradation is an inevitable, natural process. And unless an adequate fuel sampling, testing, monitoring and maintenance program is implemented, fuel breakdown will continue to be a potentially expensive liability and a major contributor to your overall operation costs.
Diesel is a very complex fluid…
It is not homogenous and no two batches will ever be identical. Fuel deterioration, filterability and shelf life depend on a variety of factors including good housekeeping.
Dirt and water are the most significant contamination factors in diesel fuel degradation. In some cases fuel is replaced with water, kerosene, and other fluids between the refinery and the fuel pump. Much of the source of dirt and water originates from onsite storage tanks, delivery methods to equipment fuel tanks, and fuel tanks themselves.
Injector life is reduced by about half with water content above acceptable levels. Water content should optimally stay well under 0.05%. When fuel contains water it will begin to show a haze. Water content above 0 .05% will cause damage to the fuel injection system. The lubricating properties of diesel fuel are also affected by moisture displacing the fuel. When moisture is present, fuel combustibility is reduced when water becomes heated in the combustion chamber. Water immediately turns to steam under compression and heat damaging injector tips. Water promotes bacterial growth, which results in acidic conditions, which will cause corrosion in engine and fuel system components. Unstable fuels form asphaltenes. The Asphaltenes plug filters and damage injectors. They can also affect the combustion efficiency of the engine. Improper fuel droplet size due to damaged injectors combined with asphaltene particulates requires higher temperatures and compression to fully combust.
Poor physical properties of diesel fuel will affect the reliability of diesel engines. Diesel fuel is intended to cool and lubricate fuel injection systems. Poor lubricity will result in excessive wear and premature failure of injectors and fuel pump. Poor lubricity can be due to inadequate manufacturing of the fuel, using improper solvents or low quality additives. Severe processing of fuels can reduce the amount of surface protecting agents in the fuel. Fuels that are a heavier grade (require less refinement) will create combustion chamber deposits. These deposits which will reduce the life of cylinder liners and rings. Low cetane numbers will also damage engines damage over time. Low cetane numbers result in engine knock, trouble starting and black exhaust smoke.