Name: Mr V Rajaram
Ship came out of drydock (routine drydocking). On coming out of the dry dock, the main engine was started and found working well. After few minutes, Unit 5 exhaust valve was found knocking, and the sound was increasing. Suspected air lock, the hydraulic system of purged off air, but found no improvement. Master was informed and requested to anchor the vessel for investigation and rectification. On investigation it was found that no oil was coming to the piston. The lines dismantled and thoroughly cleaned. Waste pieces were found to block the passage. Same cleared and the system tried out, found satisfactory.
Lesson learnt: proper filtration is required in the hydraulic circuits. Filters should be cleaned at regular intervals or replaced as the case may be, to avoid such problems.