Mardi Gras Sea Trials

[chengkp75]

2 hours ago, ALWAYS CRUZIN said:

A new ship using LNG when it first starts its engines produces the usual black smoke out out the stacks. Take the Mardi Gras as an example. After the shake down. Does the black smoke exhaust cease to exist? Is their any visible exhaust. I think there would not be, but you say some diesel is needed also.

First off, I seriously doubt that the Mardi Gras, as pictured "starting engines for the first time", was operating on LNG.  Even if she had loaded LNG while in the builder's dock, the first start, would have been on full diesel.  Some of that smoke may have been preservative in the engines burning off, and the turbocharger preservative burning off, some of it may have been simply poor combustion due to the engines not being warmed up, and due to Carnival's funnel design it is difficult to determine whether that smoke was from the engines or the boilers.  Very low load operation of the engines, as having more than two diesels running with little to no propulsion (ship's propulsion is never used when any part of the ship is within the drydock) load can cause incomplete combustion as well.  The photos of the Mardi Gras does not show really "black" smoke, you can find many photos of ships that have just started a diesel, and the smoke is much more.  Exhaust smoke is also very subjective, and it takes a trained observer (some ports have "certified smoke observers") to determine what type of smoke is coming from a ship's exhaust.  Very often, a "white smoke", caused by excessive water vapor or low exhaust temperatures, can, against certain background sky conditions, look very black.

 

But, under most conditions, if the ship is operating on 95% LNG, there will be almost no smoke.  Bear in mind that the ship is not required to operate on LNG outside of designated ECA's, and certainly until the infrastructure is fully developed for bunkering LNG, the ship will likely be running on a much lower, to none, LNG ratio.

[ALWAYS CRUZIN]

7 hours ago, chengkp75 said:

First off, I seriously doubt that the Mardi Gras, as pictured "starting engines for the first time", was operating on LNG.  Even if she had loaded LNG while in the builder's dock, the first start, would have been on full diesel.  Some of that smoke may have been preservative in the engines burning off, and the turbocharger preservative burning off, some of it may have been simply poor combustion due to the engines not being warmed up, and due to Carnival's funnel design it is difficult to determine whether that smoke was from the engines or the boilers.  Very low load operation of the engines, as having more than two diesels running with little to no propulsion (ship's propulsion is never used when any part of the ship is within the drydock) load can cause incomplete combustion as well.  The photos of the Mardi Gras does not show really "black" smoke, you can find many photos of ships that have just started a diesel, and the smoke is much more.  Exhaust smoke is also very subjective, and it takes a trained observer (some ports have "certified smoke observers") to determine what type of smoke is coming from a ship's exhaust.  Very often, a "white smoke", caused by excessive water vapor or low exhaust temperatures, can, against certain background sky conditions, look very black.

 

But, under most conditions, if the ship is operating on 95% LNG, there will be almost no smoke.  Bear in mind that the ship is not required to operate on LNG outside of designated ECA's, and certainly until the infrastructure is fully developed for bunkering LNG, the ship will likely be running on a much lower, to none, LNG ratio.

Very informative. Thanks!

[BlerkOne]

As I understand it, the engines were really started a month or so before the smoky picture, anyway.

[chengkp75]

7 hours ago, BlerkOne said:

As I understand it, the engines were really started a month or so before the smoky picture, anyway.

Unlike most ships that will use a shore power connection while in drydock, a cruise ship requires so much power that the ship normally has a connection to the fresh water cooling system where shore water is supplied, and taken away through another connection, allowing one of the ship's diesels to run.  So, I kind of felt all along that the "first start" was a bit of PR, as they would have tested the power systems prior to sending the ship out of the dock.  Didn't want to spoil anyone's image of the moment by bringing that up.

Edited October 5, 2020 by chengkp75

[BlerkOne]