Summary
It was winter and the vessel was drifting outside Newfoundland waiting for an ice advisor to board and then proceed to Montreal. After a couple of hours the weather deteriorated. To stay clear of the heavy weather it was decided to sail to more sheltered waters and pick up the ice advisor.
For navigation the master used 20 black and white photocopies from the British Admiralty for the area. In preparation for entering ice-covered waters, the chief engineer prepared an ice checklist, gave night orders to the crew, checked all of the valves for the cooling system and opened the steam valve to the low sea chest.
Some hours later the third engineer standing watch noticed a rise in temperature in the freshwater cooling system. He called the chief engineer, who attributed the rise in temperature to a blockage in the low sea chest suction. The chief engineer closed the low sea chest valve and opened the high sea chest valve to lower the fresh water temperature; however, the flow of seawater through this line was obstructed.
The master agreed with the chief engineer to draw water from the forepeak ballast tank. The chief engineer arranged all the appropriate valves in the engine room. The master then went to the ballast control room, where he opened the necessary valves to allow water to begin circulating within the seawater cooling system, which in turn lowered the fresh water temperature.
Suspecting a build-up of ice, the chief engineer unbolted the cover of the housing containing the low seawater strainer. As the crew were clearing the ice and slush, they noticed water beginning to overflow from the seawater strainer housing. The second engineer went to the low sea chest valve, where he attempted to tighten the valve by hand, but he could not close the valve. This was probably because ice was blocking the valve disk. The crew were not aware that the valve disc had not fully closed, nor did they have the visual means to verify that the valve disc had reached its closed position, as the indicator was not working.
The second engineer, not being able to move the hand wheel, then attempted to tighten the valve by using an F-key, when the valve operating mechanism failed. The hydrostatic pressure on the valve disc pushed the unsecured valve operating mechanism upwards, allowing seawater to enter the uncovered seawater strainer housing uncontrollably, and overflowed into the engine room.
The chief engineer, along with the engine room crew, made multiple attempts to secure the cover on the seawater strainer housing but failed, which allowed more water to flow into the engine room and flood it. Within approximately 10 minutes, the water in the engine room was about 4 meters deep and had reached the level of the grating deck, from which the crew were still attempting to secure the cover on the seawater strainer housing. Upon seeing electrical sparks, the master ordered that the vessel be blacked out and the engine room evacuated.
The vessel drifted aground the following day as no salvage tug reached it in time.
Issues to be considered
- The charts the vessel had for the area were not sufficient for navigation. It is mandatory to have updated and correct charts onboard for the intended voyage.
- The seawater inlet should be kept at 20°C.
- The warmed seawater leaving the various main engine heat exchangers was not being recirculated to the low sea chest to melt ice.
- The steam valve to the low sea chest had been opened to prevent the build-up of ice and slush. This is ineffective and should not be done.
- The main seawater overboard discharge valve should be only kept open at 5% to 10%.
- Steam and/or compressed air to the sea chest is not a defence against ice and slush build-up, given that steam and compressed air will not be able to keep the sea chest ice-free during normal operations.
- It was found that the valve that permitted seawater to recirculate to the low sea chest was closed.
- The low and high sea chests within the seawater cooling system each have a valve that controls suction. These valves were each fitted with an extended drive shaft. The extended drive shaft was fitted with a valve position indicator to indicate whether the valve was open, closed, or somewhere in between. If the sea chest valve discs were not fully closed to create a watertight seal, seawater could enter the cooling system by seeping in around the valve disc. The vertical plate of the valve position indicator was bent upwards and therefore no longer fitted within the slot in the fixed vertical plate.
- Follow Transport Canada’s Mandatory Winter Navigation Information when sailing in Canadian waters. Furthermore these suggestions will apply to navigation in any icy waters.
Disclaimer: The above image is for representation of the below incident and need not be considered as an actual case image.
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Source: Swedish Club
