Some tests are offered to detect cat fines in the field. 80ppm is very low level and the effectiveness of these tests is dubious.
Operational experience has shown that if there are greater than 80mg/kg of aluminium and silicon in the fuel before treatment, it is likely that the fuel treatment plant will not be able to reduce the level sufficiently and abrasive wear will take place.
The graph shows the distribution of Aluminium and Sodium for residual fuel.
Info Centre >> Fuel and Lube Oil Technical Manual >> 2. Fuel Oil - Characteristics >> 2.11 Aluminium & Silicon
It is generally accepted that an indication of aluminium represents the potential presence of catalyst fines. These fines are particles of spent catalyst arising from the catalytic cracking process in the refinery. The fines are in the form of complex alumino-silicates. Depending on which catalyst is used, the fines vary both in size and hardness. If not reduced by suitable fuel treatment, the abrasive nature of the fines does damage to the engine, particularly fuel pumps, injectors, piston rings and liners.
Historically, the parameter used for limiting the amount of catalyst fines was by specifying a limit of 30mg/kg of aluminium. The generally accepted way of limiting the amount of catalyst fines is by limiting the combination of aluminium and silicon in elemental form to 80mg/kg. The reason for this change is because it is considered more realistic in limiting the presence of catalyst fines, which on a world-wide basis are of variable composition. The percentage removed by fuel treatment depends upon the size and density of the particulate matter.