Ship’s Engine Room Flooded In 10 Minutes

A bulk carrier was entering ice-infested waters. In preparation, the engineering staff completed an ice navigation checklist and, among other things, 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. He called the chief engineer, who attributed the rise in temperature to an ice blockage in the low sea chest suction. Arrangements were made to use water from the forepeak ballast tank to lower the cooling water temperature.

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[quote=“DeepSeaDiver, post:1, topic:16308”][/quote]

Entering ice infested waters is similar to entering the Bangkok river. In both cases your seachest strainers are quickly clogged - wether with crushed ice or empty plastic bags. First thing will be the warning in seawater pressure drop for the main cooling seawater system. A quick look at the systems suction gauge will show a suction pressure drop to the vacuum side. The quickest action to be taken is changing the seawater suction to the other seachest.
As you know, you have two, high and low. Close inlet and outlet gate valves or flap valves at the clogged strainer, open the vent cock on top of the cover and wait until no more water flows out. Then open the cover, clean the strainer and refit everything. Do never remove the cover of the seachest if it’s still pressurized. Modern vessels have due to ballast water restrictions no more facilities to use ballast water as cooling water in circulation but if you have, you should be familiar with the system prior to reach infested waters. Using steam to melt the ice is useless and modern ships have no more fittings for this.They may have compressed air fittings. Recirculating warm water is of no effect because the seawater temperature outside is prob. 4 degrees C or less and the cooling water flow is very much bypassed at the cooler. My advice - have manpower stand by, watch the suction gauge of main seawater pump and change the high or deep suction strainers as soon as pressure drops to -0,3 bar.

I would think the cleaning frequency of the filters or strainers depends upon the type. Do you have much experience with magnetic type filters, and IG system scrubber type filters?

That’s correct. Automatic filters in oil and fuel circuits have timers and delta-pressure triggers (e.g. Boll&Kirch). They have magnetic capsules too, mostly inserted at the bottom frame. But strainers in seawater lines on bigger vessels are of the bucket type. Galvanized steel buckets with holes in it. The are cleaned according to the maintenance schedules or as I mentioned above in case the suction pressure of the seawater cooling pump drops. Sorry, I do not have experience with scrubber type filters.

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