A Day Of Tendering.....

At GSC......Its interesting how the thrusters are use to hold the ship in position all day instead of dropping anchor.

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Looking at all the sediment that gets disturbed I wonder what does the bigger damage to the sea floor an anchor or the thrusters? we already know what is more detrimental to the air we breathe.

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Looking at all the sediment that gets disturbed I wonder what does the bigger damage to the sea floor an anchor or the thrusters? we already know what is more detrimental to the air we breathe.

 

 

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Sitting back in Spice H20 later in the day their was a lot of soot at one point coming down

Sitting back in Spice H20 later in the day their was a lot of soot at one point coming down

Specially and probably worse if the ship is not underway.

https://www.dw.com/en/hoping-for-a-fresh-sea-breeze-aboard-a-cruise-ship-better-hold-your-nose/a-37284464

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Specially and probably worse if the ship is not underway.

 

https://www.dw.com/en/hoping-for-a-fresh-sea-breeze-aboard-a-cruise-ship-better-hold-your-nose/a-37284464

 

 

 

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this is why they are some ports in the US require ships use a low sulfur fuel and/or exhaust scrubber systems.

Yikes....I just found out about "the caverns" at Spice H2O on the Escape, and was planning to spend the GSC day at sea instead of land. Well, plans have changed!

this is why they are some ports in the US require ships use a low sulfur fuel and/or exhaust scrubber systems.

I don't think it was soot from fuel, more like burning trash (paper). Pieces from 1/16 - 1/4 inch

They also drop the anchor

First off, I suspect that the ship does in fact anchor. They will use the thrusters during tendering so that they can ensure that the same side of the ship faces leeward to provide shelter for the boats when coming alongside. If they didn't use the thrusters, then at some time during the day, as the tidal currents change, the ship would swing around the anchor and the other side tender port would be the lee or sheltered side. This would require opening up that platform, rigging the handrails and such, setting up the security station (card scanner, etc) at the new port, and closing up the other port.

As for the soot, it is not "some US ports" that require low sulfur diesel or scrubbers, but any time the ship is within 200 miles of the North American coastline (except in places like the Bahamas, EEZ (exclusive economic zone, 200 miles out) impinges on another nation's territorial waters. In the Florida Strait, the ECA limit is halfway between Florida and the Bahamas, or about 20 miles. Now, the emissions requirements are for sulfur oxide and nitrous oxide emissions, not particulate matter, so even burning low sulfur diesel fuel, you can and will get some soot particles, and this is perfectly legal. Probably more of this comes from the ship's boilers than the diesel engines. And the problem is exacerbated by the ship not moving, and likely having no wind or a wind off the stern.

Now, having said that most of the daily soot comes from the boilers, while using the thrusters for tendering, the load on the diesels will increase and decrease quite a lot and quite quickly as the thrusters are used and then idled. This rapid, large change in load will always cause a turbocharged diesel engine to build up soot, for two reasons. First, they have to keep a second diesel running to provide the power for the thrusters (one diesel typically has enough power for the hotel), so when the thrusters are idle, the diesels are running under low load conditions, and this leads to soot. And secondly, when the load changes quickly, the turbocharger takes a second or two to react, causing insufficient air for complete combustion, and soot. Just like when a bus or truck accelerates from a stop light, and there is a brief cloud of gray/black smoke.

The ship is not allowed to incinerate trash while not underway.

The ship is not allowed to incinerate trash while not underway.

Interesting, does "Soot" from fuel still burn once its leaves the stack? The reason I ask is because we were on our balcony one night about 10pm while heading back. Port side rear 1/3 of ship. The wind was blowing from the east (starboard side causing the exhaust to drop over the port side). For a while their were lots of what I consider embers being blown around. It looked like the after effects of a big campfire when you throw a log on, embers were lighting up the sky. I remember taking a tour on the BA and we went to the trash room. They were explaining how hot and well the paper trash burns, didn't look like it was burning to well that night lol

I was on the Sky in June. We definitely anchored at GSC. I'm pretty sure I have a photo of the anchor line. I thought it was neat how the ship "moved" throughout the day.

Interesting, does "Soot" from fuel still burn once its leaves the stack? The reason I ask is because we were on our balcony one night about 10pm while heading back. Port side rear 1/3 of ship. The wind was blowing from the east (starboard side causing the exhaust to drop over the port side). For a while their were lots of what I consider embers being blown around. It looked like the after effects of a big campfire when you throw a log on, embers were lighting up the sky. I remember taking a tour on the BA and we went to the trash room. They were explaining how hot and well the paper trash burns, didn't look like it was burning to well that night lol

What you are seeing typically at night is the cleaning process for the diesels and boilers. This is done at night, so it is less visible to the guests, and as you say, most typically done so that the wind is on the beam so that the soot is more quickly blown away from the ship. As I said, the combustion process will cause the products of incomplete combustion (soot) to form on the heat exchange surfaces in a coating, which will then decrease heat transfer, losing efficiency. So this soot must be removed from the surfaces. For boilers, steam is sprayed onto the heat transfer surfaces, blasting the soot off into small flakes, and the forced draft fan pushes this up and out the stack. For diesels, the soot tends to adhere to the turbocharger turbine blades, and to remove it, the engineers will inject ground walnut shells into the exhaust gas just before the turbo, acting as a "sand blasting" agent, it removes the soot particles, and the exhaust gas carries this up the stack. Now, particularly for the diesels, the exhaust gas is so hot that the fine flakes of soot, now have so much surface area in comparison to their volume, that they quickly heat up and start to burn, causing the glowing "embers" that you see. Also, the spent walnut shells will tend to burn as well.

For trash incineration, the unit uses a double combustion chamber, where the trash is burned in the first chamber, and then the exhaust gas and any unburned particles are led to the second chamber, where another burner increases the temperature to the point where everything burns. Only then is the exhaust gas led up the stack. The incinerators, since they are not trying to gain anything from the combustion (either heat to form steam, or mechanical power to drive a generator) can be much more effective at reducing particulate emissions, since there isn't any "fuel efficiency" involved (you are really wasting fuel to burn the trash, so not efficient).

What you are seeing typically at night is the cleaning process for the diesels and boilers. This is done at night, so it is less visible to the guests, and as you say, most typically done so that the wind is on the beam so that the soot is more quickly blown away from the ship. As I said, the combustion process will cause the products of incomplete combustion (soot) to form on the heat exchange surfaces in a coating, which will then decrease heat transfer, losing efficiency. So this soot must be removed from the surfaces. For boilers, steam is sprayed onto the heat transfer surfaces, blasting the soot off into small flakes, and the forced draft fan pushes this up and out the stack. For diesels, the soot tends to adhere to the turbocharger turbine blades, and to remove it, the engineers will inject ground walnut shells into the exhaust gas just before the turbo, acting as a "sand blasting" agent, it removes the soot particles, and the exhaust gas carries this up the stack. Now, particularly for the diesels, the exhaust gas is so hot that the fine flakes of soot, now have so much surface area in comparison to their volume, that they quickly heat up and start to burn, causing the glowing "embers" that you see. Also, the spent walnut shells will tend to burn as well.

 

For trash incineration, the unit uses a double combustion chamber, where the trash is burned in the first chamber, and then the exhaust gas and any unburned particles are led to the second chamber, where another burner increases the temperature to the point where everything burns. Only then is the exhaust gas led up the stack. The incinerators, since they are not trying to gain anything from the combustion (either heat to form steam, or mechanical power to drive a generator) can be much more effective at reducing particulate emissions, since there isn't any "fuel efficiency" involved (you are really wasting fuel to burn the trash, so not efficient).

Wow, thanks for the inside knowledge! Great info!