We don’t agree with this assertion that temperature control for heavy fuel oil operation on motor ships is adequate.
One side of our argument is that fuel supplied comes within a viscosity tolerance, not one specific value, and that the relationship between temperature and viscosity (Viscosity Index) does not follow a single ratio. Therefore, there is no specific temperature related to the required injection viscosity for fuels supplied. Depending on viscosity index and specific viscosity of fuel supplied the right temperature may lie within a 0 – 20oC temperature range, if the fuel is within specification.
The other side is the inverse of the above. Because the right viscosity may be within a 20oC range, the corresponding change in viscosity from this temperature range will be as much as 7cSt. This is a significant difference in viscosity, affecting fuel consumption and engine maintenance.
The larger the diesel engine, the slower the speed, the higher the cylinder output, the larger the fuel quantity injected per work stroke. The larger the engine the heavier the fuel. These are facts on ships, therefore tighter viscosity control becomes more important with increased engine size.
The right viscosity means
Good fuel injection with good fuel combustion,
No excessive loading of injection equipment and cam shaft,
Reduced maintenance of diesel engine = cost savings,
Reduced wear = cost savings,
Optimal fuel consumption = fuel savings.