Ship's Propulsion Safety System

Snowgoose-1

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Just wondering what the above actually means other than stopping the engine damaging itself.
Perhaps due to excessive rolling, yawing etc ?

"The ship’s crew took the decision to head to Portsmouth when the ship’s propulsion safety system was activated in the poor weather, causing it to veer suddenly to the left and bringing the vessel to a sudden halt."

Link to press report MSN
 
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Bilgediver

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Is it possible the ship started to suffer synchronous rolling caused by the conditions and the brain sensed this and did what an experienced skipper would do in the old days and killed it by drastically reducing revs a d the selection g a course where this phenonimum did not occur.

I experienced this once when crossing the Pacific. We were riding the swells with no problem at 19 knots. There was a problem on deck up forward so a course alteration was made to keep the for deck dry. Almost immediately synchronous rolling started and built up to the point the ship was rolling to the extent I was very concerned, however I could not get to the phone to request the engineers reduce speed. Fortunately the watch engineer had the presence of mind and slowed down to slow ahead. The rolling immediately subsided. No instructions from them upstairs. ;) The problem on deck was sorted and we came back to the original course and speed.

This IS NOT Parametric rolling. That ti's something else more complicated.
 

Bilgediver

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Same problem as experienced by the Saga cruise liner in Biscay, maybe?


I think it could have been a similar situation and possibly modern ships detect the incident taking place and reduce speed automatically which then totally reduces the rolling.

It is possible to demonstrate this phenomenon on a small yacht. Stand in the cockpit with legs apart facing forward or aft and then alternate whole weight from one leg to the other and in time with the roll. You will soon get ghe boat rolling with minimum effort and to quite anangle of heel.
 
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bikedaft

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I wondered if one engine had automatically shut off, due to the waves setting off low oil alarms, and hence the ship did a sudden turn?

Like the cruise ship off Norway whose engines turned off due to low oil alarms going off - oil.levels were fine, but the oil in the sump.was splashing about with the waves...

Or, just my paranoia/cynicism? :)
 

DFL1010

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I wondered if one engine had automatically shut off, due to the waves setting off low oil alarms, and hence the ship did a sudden turn?

Like the cruise ship off Norway whose engines turned off due to low oil alarms going off - oil.levels were fine, but the oil in the sump.was splashing about with the waves...

Or, just my paranoia/cynicism? :)
Highly unlikely.

For a start losing power to one prop wouldn't result in a sudden turn.

Second, that's not how it works - it's not two engines, each connected to a shaft. The ship has 4 engines connected to 2 azipods. So, if all four were running and one failed then the balance of power would be distributed between the two azipods (and all other electric demands).
 

Bilgediver

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I wondered if one engine had automatically shut off, due to the waves setting off low oil alarms, and hence the ship did a sudden turn?

Like the cruise ship off Norway whose engines turned off due to low oil alarms going off - oil.levels were fine, but the oil in the sump.was splashing about with the waves...

Or, just my paranoia/cynicism? :)
The ships I sailed on used the oil pressure for alarm purposes but low oil level gave a warning. These engines have dry sumps and the oil is in tanks and of such a shape that this should not normally be a problem. I notice that in all the videos I have seen on social media covering this event the ship is hardly rolling at all but is a following sea. A slight alteration could produce severe rolling.
 
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capnsensible

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The ships I sailed on used the oil pressure for alarm purposes but low oil level gave a warning. These engines have dry sumps and the oil is in tanks and of such a shape that this should not normally be a problem. I notice that in all the videos I have seen on social media covering this event the ship is hardly rolling at all but is a following sea. A slight alteration could produce severe rolling.
Simply go below 200 feet to remove the vessel from all the floppy about stuff. :cool:
 

oldharry

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I know little of big ship handling, but looking at the wave size in a following sea, and the speed of the ship downwind, , could she have started to broach, causing the 'brain' to apply an emergency course correction? It seems hard to believe a vessel of that size could make such a violent move from its power plant that people are thrown about and injured, even with the modern propulsion pods?
 

Snowgoose-1

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I know little of big ship handling, but looking at the wave size in a following sea, and the speed of the ship downwind, , could she have started to broach, causing the 'brain' to apply an emergency course correction? It seems hard to believe a vessel of that size could make such a violent move from its power plant that people are thrown about and injured, even with the modern propulsion pods?
Seems logical.
Perhaps a sensor picks up some kind of death role . Fortunately a cruise ship has loads of lateral bouncy.
 

boomerangben

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Given the significant roll our beloved CalMac ferry generates when manoeuvring in and out of port simply through balancing centripetal force in a turn, I can imagine that a combination of this, windage, waves and automatic changes to the stabilisers might cause an unforeseen dynamic response resulting in injury and damage. Sounds like there might be a case where the skipper was caught between a rock and a hard point where automated systems and the forces of nature combine to do what was imagined in design as a safety feature instead turns out to be a unimaginable flaw.
 

RunAgroundHard

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It might be prop over speed shutdown caused by the waves lifting a prop partially, fully clear of the water.

The sudden turn happens because the other thrusters can’t power up to counter wave and windage on the hull because they are already working hard.

I have knowledge of this from one of my employers DP ships near a hurricane. In this case, the aft thrusters over speed, engine shuts, remaining thrusters can’t cope, and vessel ended up beam on.

It took a lot of skill, after restart, to get the vessel heading back into the waves and work the thrusters to stop it repeating.

The fact that it was the propulsion system suggests thruster over speed to me.
 

Bilgediver

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I know little of big ship handling, but looking at the wave size in a following sea, and the speed of the ship downwind, , could she have started to broach, causing the 'brain' to apply an emergency course correction? It seems hard to believe a vessel of that size could make such a violent move from its power plant that people are thrown about and injured, even with the modern propulsion pods?
That thought did occur and compared to older passenger ships the thrusters are nearer the surface which may not have helped as another poster has suggested.
 
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