Vista repairs

[chengkp75]

2 hours ago, ew101 said:

Thank you Chengkp75.  This answers a million questions.  So the shipboard big loads (engines, AC chillers, bow thrusters) need the high voltage generators (big or small or all the same size) online.  The backup diesel only has 440V AC output so can only supply a few "hotel" loads- outlets, maybe toilets, hall lights etc.   The goal to me would be if a ship had an engine room fire, and the other engine room was OK you could "limp" home with lights, food/water, toilets and maybe 5 knots.  And I am remembering now- a lightly loaded diesel generator can "wet stack" - which is not good for it.  So the number of generators running should match the load.  Brilliant.  You are such an asset to us.  

Well, not quite.  Again, I don't believe there are "backup generators" anymore.  But, when there were, yes, they only fed specific 440/220/110v circuits.  And, because they were only going to feed these specific circuits, it was decided this was too complex.  You see, further complicating things, the ship is divided into "vertical fire zones", or fire zones that run from the keel to the mast top in a given section of the ship.  Generally, there are 5-8 of these spaced along the ship.  You can locate the fire zone boundaries by the fire doors in the passageways outside your cabin.  The fire doors separate the zones.  Now, in order to isolate a fire to a specific zone, the electricity, the ventilation, and the water can be shut off to each zone, without affecting other zones.  So, just dealing with electricity, there are 480v, 220v, and 110v switchboards in each fire zone that control the power to that zone, and which can be shut off at the main switchboard.

 

Now, the "Safe Return to Port" regulations of the IMO (applicable to ships built after 2010) requires that loss of one engine room, or one propulsion motor room, not disable either power generation or propulsion completely, so that a ship that has had an engine room fire can return to port under her own power.  I don't know the exact layout of the Vista's engine rooms, but I suspect that the three large generators are in one space, and the two small ones in the other, along with other machinery.  If there is a fire in one engine room, the power from those generators can be isolated from the switchboard, and the remaining generators can provide power to all services, both propulsion and hotel, but on a limited capacity.  So, you could provide all hotel functions, but only get 50% of propulsion power, and maybe only 50% of AC capacity (though there are almost always more AC chillers than needed).

 

Most cruise ships had features of the Safe Return to Port requirements long before they were required.  Even the Carnival Splendor and Triumph had two engine rooms, but the unfortunate design flaw was that the power cables from the forward generators ran over top of the aft generators, so a fire in the aft engine room would take out both engine rooms, even though there was no damage in the forward engine room.  Most ships also have separate switchboards for each engine room, located in the same fire zone as the engine room it serves (engine rooms are in different fire zones by design), and these two switchboards have a connecting circuit breaker which can be opened to isolate one engine room.  Now, in order to have power supplied to all services at all times, even with one engine room isolated, each of the two switchboards can supply power to each zone switchboard (those 440/220/110v circuits in each fire zone), with one supply being energized and one in standby, since the two main switchboards are connected most of the time.

 

Most ships also have the Engine Control Room separate from the two main switchboard rooms, but the Splendor and Triumph not only had both main switchboards in the same room, but ECR in the same room as well.  The fire in the aft engine room traveled up the cable ways and made the ECR too hot to remain in, so the ships lost virtually all control of engineering systems.

 

And, the power to speed relationship for a ship is exponential, so the first 50% of speed requires relatively little power, while the last 10% of speed at the top of the range will require 25% or more of the total power.

[ew101]

Thanks again.  We need you please on the Freedom thread 🙂  On a semi related and more urgent topic.  

Edited May 26, 2022 by ew101

[stevethepirate]

I have friends on the Vista now. They where told that the problem is fixed. I don't know if it's a permanent or temporary fix. They were doing over 20 knots. So, maybe it's fixed.

[Lee Cruiser]

1 hour ago, stevethepirate said:

I have friends on the Vista now. They where told that the problem is fixed. I don't know if it's a permanent or temporary fix. They were doing over 20 knots. So, maybe it's fixed.

That would be great news!  Hopefully it is true and permanent.

[groundloop]

Dang, what is it with Carnival recently?  There's these problems with Vista, reported problems with Miracle, and of course the issues with Magic and Freedom today.  And I believe I'm missing one or two others.

 

This is starting to feel like the manufacturing plant I used to work at that chose to cut preventive maintenance to save money in the short term (but of course wound up creating much bigger headaches down the road).

Edited May 27, 2022 by groundloop

[Lane Hog]

I think it's more a matter of the fact that when the ships were idle, that left more time for PM's to be done, so they've been in ultra-good shape for the last six months.

[quattrohead]

19 hours ago, ew101 said:

a lightly loaded diesel generator can "wet stack

Yes, British Rail found this out when they were testing the new Class 91 electric engines using Mk3 carriages. The Mk3 needed a different power supply system as provided by the Class 43 engine so they kept 1 attached for hotel power, but soon found out they started having exhause fires, so they had to run them at load as well during testing. There is a video showing this bad arse hybrid with a poorly maintained 43 in the front.

https://www.railforums.co.uk/threads/class-91-43-late-1980s-formations.141904/ - technical discussion here.

[talkorpi]

On the Vista right now. We were going up to 21 knots yesterday to get out of a bad storm in between Belize and Cozumel. It was just a brief time at that speed, but considering that our cruising speed for the rest of the cruise was just 17 knots, it was encouraging to see it hitting above 20!
 

I asked the cruise director today about the engines/repairs, and she told me that they loaded the necessary parts in Cozumel and that the technicians were already onboard to fix the problem. Hopefully we should have a fully-functioning ship again very soon!

 

I will be doing a review and hope to have it done by the end of the weekend. Stay tuned!