What happened

During voyage, a main engine No. 1 cylinder exhaust gas temperature lower alarm occurred. Hammer- ing sounds following knocking sounds were confirmed from the cylinder interior. The main engine was stopped and after replacing the No. 1 cylinder fuel valve, inspection and adjustment of the exhaust valve and fuel pump was carried out. Although voyage was recommended, the same knocking and hammering sounds occurred. These sounds stopped when the speed was reduced to below 53 RPM, at which point the compression Pressure, P-max and exhaust gas temperature were on a par with other cylinders. The speed was established at less than 53 RPM and the amount of cylinder lubrication was increased as emergency measures. In order to meet the schedule for port entry, voyage was continued and the ship entered port a few hours later than the scheduled time. After arrival at port, an analysis of a drawn piston confirmed cylinder liner biased abrasion (maximum 3.3mm abrasion,) piston ring abnormal abrasion and piston ring tension reduction.

Root Causes

As the center of the cylinder liner and piston was eccentric from the time of engine manufacturing, the piston skirt was contacting the cylinder liner. It is surmised that abnormal abrasion occurred as the piston ring slid over the surface of the cylinder liner which had run out of oil film. It is surmised that the knocking sounds and hammering sounds occurred because the piston with an eccentric center started contacting the cylinder liner due to the abrasion of the piston ring and cylinder liner.

Repair

The following repair was administered under manufacturer guarantee.
• Cylinder liner replacement
• The piston rod was moved 30/100mm toward the stern side in order to align the piston and cylinder liner centers.

posted 05 Dec '18, 10:17

Dec. 5, 2018, 10:17 a.m.
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