The majority of casualties at sea are caused by a chain of failures occurring at the same time. As Mr. Ansuman Ghosh Director of Risk Assessment at UK P&I Club explained, due to the nature of shipping and the heavy-duty equipment onboard, these casualties often involve some form of catastrophic machinery failure.
Following the situation, Mr Ansuman Ghosh shares several cases that involved some kind of catastrophic machinery failure.
The case
A vessel was on a passage through a narrow channel. The pilot boarded and requested full ahead shortly after his arrival on the bridge. The Master asked the engine room to increase speed.
All was running smoothly for the next half an hour. Suddenly, a large amount of water was seen leaking from main engine unit number 6 around the cylinder jacket area. Engine room (ER) staff tried to isolate the leakage at unit number 6 but failed as the outlet valve was not holding.
Due to the heavy leakage and low pressure on the cooling water system, the main engine (ME) automatic slowdown was activated.
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The bridge team quickly considered all the options that would prevent the ship from colliding with the approaching bridge. The team’s efforts were futile as the loaded vessel was not moving at sufficient speed to maintain steerageway.
Within a few minutes, there was an allison with significant impact and the bridge centre pillar fendering was splintered.
The water leakage from unit number 6 was identified from a crack on the cylinder cover cooling jacket. Often such cracks are associated with insufficient cooling water maintenance.
Lessons learned
- In such cases, heavy deposits of dirt and metallic particles i.e. rust are found in the system.
- Deposits are brought in by the circulating cooling water and tend to find their way into the clearances between the cylinder cover and the cooling jacket. This makes heat expansion of the cylinder cover impossible without exposing the cooling jacket to significant stress. Thus, insufficient cooling water treatment, combined with the heavy corrosion of the engine components, can also cause the cooling water jacket to crack.
- It is important to ensure that the valves are holding so that a particular unit can be isolated quickly.
- Additionally, like fuel oil and lubricating oil, the engine cooling water is a medium which must be carefully selected, treated, maintained and monitored.
