Summary
The engineering staff completed an ice navigation checklist. Opened the steam valve to the lower sea chest as they thought this would prevent ice build-up.
During the night, the electrical officer of the watch (EOW) noticed a rise in temperature in the fresh water cooling system. The chief engineer, identified a blockage in the low sea chest suction. Arrangements were made to use water from the forepeak ballast tank to lower the cooling water temperature.
To clear the ice, engine staff unbolted the cover of the housing containing the low sea water strainer. As the crew were working they noticed water beginning to overflow from the seawater strainer housing. They attempted to tighten the valve, but the valve operating mechanism failed. Hydrostatic pressure forced the valve disc, allowing seawater to enter in an uncontrolled manner and overflow into the engine room. This flooded the engine room With 4m deep water on just ten minutes.
Cause and Consequence
The cover on the sea water strainer housing was not in good condition. The water reached the level of the grating deck. The Master ordered the vessel be blacked out and evacuated as they found sparks from the electrical system in the engine room.
Measures Taken
The crew were mustered on the upper deck and briefed on the situation. The emergency generator was started and put on line and the crew readied for possible abandonment.
Result
The vessel drifted and, despite having anchors down and a rescue tug on scene, touched some shoals before it could be towed to safety.
Damages Sustained
The hull sustained tears, punctures and dents. The engine room machinery and electrical components located below the flooded waterline were all rendered inoperable.
Technical Findings
- Warmed sea water from the heat exchanger was being both discharged overboard and returned to the pump, rather than being recirculated into the low sea chest. As a result, the seawater strainer became plugged with ice and slush, causing the vessel to lose seawater suction from the low sea chest.
- Without a working indicator, the crew had no visual means to confirm that the low sea chest valve was fully closed.
- The brass and steel collars around the valve stem, were poorly fitted.
- The collars separated when the low sea chest valve operating mechanism was overstressed while being tightened.
Reasons Identified
- Lack of knowledge on the operation of a vessel’s sea water cooling system when navigating in ice.
- Carelessness led to overheating of main engine that eventually ended up in loss of propulsion.
- The crew were not adequately familiarised with the cooling system, nor had they properly prepared the cooling system for operating in ice-covered waters.
- Lack of adherence of the indications in documentation from local authorities
- Ineffective training.
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Source: The Nautical Institute
