The bunkering ports for North Pacific Ocean route were U.S.A. West Coast and Asia, and those for Europe route were Rotterdam and Singapore. And the output of main engines was almost the same in these two routes.
In this example, the correlation between the cylinder liner wear and the fuel oil is very clear.
3. Investigation results and cause of these excessive wears
A thoroughgoing investigation had been executed in cooperation with shipowners, MHI and their R & D centers, especially for combustion, tribology, fuel oil and chemical analysis.
Hereafter, the detail on these features is specified.
3.1 FCC catalytic fines
Fig. 3 shows the typical FCC catalytic fines on the cylinder liner running surface.
Fig. 3 FCC catalytic fines on the cylinder liner running surface
Catalytic fines are small hard particles of alumina (Al2O3) and Silica (SiO2) and used as catalysts in fuel refining process. And those catalytic fines often leaks in residual fuel.
Fig. 4 and Fig. 5 show the two typical wear patterns, which were taken on the same engine at the same time. These surface conditions indicate that;
Pattern 1: Abrasive wear but no remarkable wear amount
The catalytic fines scratch cylinder liner running surface, but no remarkable wear amount yet. (Fig. 4).
Pattern 2: Adhesive wear with heavy wear amount
FCC catalytic fines are scraped off and could scarcely observed on the liner surface (Fig. 5).
In the first stage FCC particles cause abrasive wear on the sliding surface and it deteriorates local bearing capacity between piston ring and cylinder liner (Pattern 1). Thinner oil film changes the condition of cylinder liner running surface from abrasion to adhesion, then the wear amount is suddenly increased (Pattern 2).
Fig. 6 shows that there were time lags between the occurrence of excessive wear of each cylinder liner on an engine in every case. This means that cylinder liners could endure to some extent under abrasive condition without remarkable wear (Pattern 1 ). However, if FCC particles continuously come on the cylinder liner surface, sudden heavy adhesive wear (Pattern 2) could consequentially occur.
This could be the case for any type of diesel engine because of the following reasons;
i) Hardness of FCC particles is much higher than ones of cylinder liner and piston ring.
ii)The size of FCC particles is much larger than minimum cylinder lubricating oil film thickness.
