Propulsion Damage on the Anthem !!

[Aquahound]

I'm hoping our Chief Engineer comes back and explains the clutches.

 

Me too because for now, I'm thinking Anthem is a stick shift. ;)

[xpcdoojk]

Does that include single engine airplanes?

 

I think that is what he is implles. He flies a single engine, when he loses one, his plane is a glider. I would imagine it would apply to most posters here who might have their own plane.

 

JC<---- has no plane.

[chengkp75]

Been working, but saw Oceanboy's cry for help on another thread, so I came here and did a quick scan, but didn't read all posts, so apologies if I'm repeating info.

 

Please note the USCG's statement regarding the port azipod:

 

"during the storm the port azipod, which is one component of the vessel's propulsion system, burned out all four clutches," the statement said. "As a precaution, this azipod was shut down for the return voyage to Bayonne. Technicians are onboard replacing the clutches on both the starboard and port azipods as a precaution. Repairs and subsequent testing of the azipods is ongoing."

 

Highlighting, mine.

 

The azipod was still functional, but they did not want to do further damage to the clutches, so they let it freewheel.

 

Now, to some questions along the thread:

 

The tug escort was mandatory for any ship that does not have redundancy in steering, all the way from the Ambrose traffic separation scheme (arrival point for port of NYC, a few miles out), to the dock. It was not that Anthem could not dock on her own, but that the USCG requires a tug standing by in case the remaining steering method fails.

 

The reason for the small wake on the port side is that if you stop the one pod's propeller from turning, it creates a huge "barn door" of drag which will slow the ship, make steering difficult, and increase fuel consumption. Unless a bearing has gone bad in a pod, they will just turn the power off to it, and the motion of the ship will cause the propeller to turn freely, reducing drag.

 

If a pod loses a bearing, not Anthem's case, they will lock the shaft, to keep the free rotation from further damaging the bearings. If the bearing cannot be repaired quickly, they will pull the propeller blades from that pod, and the hub presents very little drag when locked. This is what Freedom did last year.

 

Ships that have more than 2 pods (with the exception of the Cunard QM2), only have 2 pods that steer. So, loss of a "fixipod" (one that does not steer), will reduce propulsion, but will not require the tug escorts that Anthem and other ships have had to use when entering/leaving port.

 

And as I've stated on other threads, while the USCG did in fact "detain" the Anthem (not allowed to proceed to sea), because RCI had no intention of sailing before Saturday anyway, it was a "non-affecting" detention (sort of made that word up, meaning it really did not affect their schedule). The USCG has a Port State Control Information Exchange, where they post a record of all visits by the USCG to foreign flag ships in US ports (Port State Control, or SOLAS inspections, that cruisers are frequently aware of due to delayed boarding), which Anthem had in January this year in San Juan. They will also post the report of this inspection, since it is technically a detention, but their site only updates weekly, so it will have to wait until Monday or Tuesday to see it.

 

Regarding the PVSA, etc, and the decision to return to NJ. The PVSA is almost universally waived in cases of weather or mechanical problems. Technically, even returning to NJ was a violation, but not of the PVSA, since CBP has banned all cruises to nowhere (which this was), but that has to do with work visa rules for the crew.

 

Probably didn't cover half the thread, but I'm subscribed now, and any questions I'll be available until its time to weight test my bunk. :D

[Cuizer2]

I think that is what he is implles. He flies a single engine, when he loses one, his plane is a glider. I would imagine it would apply to most posters here who might have their own plane.

 

JC<---- has no plane.

 

Commercial jets are required to be able to fly with the loss of one engine. Now if gliding is considered flying then yes, a single engine plane will fly with the loss of its engine. However, originally commercial jets that were more than two hours from land (like those that fly to Hawaii) had to have three or more engines. That requirement was increased to three hours, and thus now two engine jets can fly to Hawaii.

 

Clearly the loss of one engine in an eight engine jet, such as a B-52, is less of an issue than the loss of one engine in a single engine jet such as an F-16.

[shaun07]

If anthem had lost the other pod would it be dead in the water. I know it has bow trusters. But would it me able to make port with just them

[Clarea]

If anthem had lost the other pod would it be dead in the water. I know it has bow trusters. But would it me able to make port with just them

Bow thrusters just provide sideways force, not forward propulsive force. It's not like the Starship Enterprise.

Edited February 12, 2016 by clarea

[chengkp75]

Me too because for now, I'm thinking Anthem is a stick shift. ;)

 

Okay, Paul. Just saw you. And better news for those worried that the Anthem had limited propulsion.

 

The clutches are over-torque protection for the steering motors that rotate the pod. They have nothing to do with the propulsion motor or the pod's ability to provide propulsion. These clutches are only on steerable pods, and are there to prevent damage to the electric motors and reduction gears should the pod be rotated in such a way that the pod or propeller struck an obstruction, so that you could not continue to turn the pod further and cause damage. Sort of like an oscillating desk fan, and you stop it from going back and forth, eventually the gearbox will strip out.

 

The side and steering forces required to keep the ship's heading wore out the clutches.

 

The pod was usable, and even steerable, but they didn't want to damage anything further. End of discussion.

[Clarea]

Okay, Paul. Just saw you. And better news for those worried that the Anthem had limited propulsion.

 

The clutches are over-torque protection for the steering motors that rotate the pod. They have nothing to do with the propulsion motor or the pod's ability to provide propulsion. These clutches are only on steerable pods, and are there to prevent damage to the electric motors and reduction gears should the pod be rotated in such a way that the pod or propeller struck an obstruction, so that you could not continue to turn the pod further and cause damage. Sort of like an oscillating desk fan, and you stop it from going back and forth, eventually the gearbox will strip out.

 

The side and steering forces required to keep the ship's heading wore out the clutches.

 

The pod was usable, and even steerable, but they didn't want to damage anything further. End of discussion.

Thanks for the explanation. I'm impressed that the design of the azipod allows that kind of maintenance without taking the ship out of the water.

[Riff Sniff]

Thanks for the technical explanation of the azipod clutch problem. Your expertise is appreciated!

 

 

Sent from my iPad using Tapatalk HD

[Seago2]

Chengkp75 I came on to CC specifically looking for what you had to say. I thought I would have to wade through 1000 posts. Just my luck to get your answer quickly. You're the best thing on CC and have been since Concordia.

[beachnative]

Okay, Paul. Just saw you. And better news for those worried that the Anthem had limited propulsion.

 

The clutches are over-torque protection for the steering motors that rotate the pod. They have nothing to do with the propulsion motor or the pod's ability to provide propulsion. These clutches are only on steerable pods, and are there to prevent damage to the electric motors and reduction gears should the pod be rotated in such a way that the pod or propeller struck an obstruction, so that you could not continue to turn the pod further and cause damage. Sort of like an oscillating desk fan, and you stop it from going back and forth, eventually the gearbox will strip out.

 

The side and steering forces required to keep the ship's heading wore out the clutches.

 

The pod was usable, and even steerable, but they didn't want to damage anything further. End of discussion.

 

I've complimented you before and I want to do it again. Your knowledge is deeply appreciated. I hope you don't mind but I copy and pasted your statement to another thread and gave you full credit.

[Ocean Boy]

Could you comment on a discussion we had earlier about the Quantun class ships having only two pods? The point being that almost all of the Voyager/Freedom/Oasis class ships have sailed for a period of time with a pod out of service but since they have three of them if they lost another on a cruise they would still have propulsion. Does this mean if a pod goes down on Quantum/Anthem that they would not be allowed to sail since if the other pod goes bad then there is no backup and no propulsion? With the history that we have seem so far of pod problems not being uncommon could this be a design problem for these ships?

[antsnanny]

The 150mph winds is why we weren't making any headway. Before the storm, both were working fine. It was after the storm that the port pod was having issues. The ship was a champ.

 

At some point during the storm, the pods were damaged, right? So its possible that when the ship wasn't making any headway could have happened after the pods were damaged.

[loubetti]

If anthem had lost the other pod would it be dead in the water. I know it has bow trusters. But would it me able to make port with just them

 

In one word: No

 

Bow thrusters do not provide forward thrust, only sideways thrust to maneuver the bow left/right.

[shaun07]

In one word: No

 

Bow thrusters do not provide forward thrust, only sideways thrust to maneuver the bow left/right.

 

so if the quantum loses one pod. they are one pod away from being stranded at sea. There must be some sort of back up?

[Formula280SS]

Thank you so much for sharing this. Most informative thing I've read yet! It makes a lot of sense, too.

 

Hoping Anthem is "all better" and able to sail tomorrow.

 

You are welcome.

 

It's been a real nutty week for Anthem threads and really hard to get out 'just plain facts.

 

The azipods are now fine, replaced the clutches (there is a more experienced member commenting on such in this thread; thanks also).

 

Good luck to all on the next cruise.

 

Welcome home to those on the storm cruise.

[chengkp75]

Thanks for the explanation. I'm impressed that the design of the azipod allows that kind of maintenance without taking the ship out of the water.

 

Actually, those clutches, the steering electric motors and gearboxes are up in the hull, not even down in the pod.

[Peeker28]

Been working, but saw Oceanboy's cry for help on another thread, so I came here and did a quick scan, but didn't read all posts, so apologies if I'm repeating info.

 

 

 

Please note the USCG's statement regarding the port azipod:

 

 

 

"during the storm the port azipod, which is one component of the vessel's propulsion system, burned out all four clutches," the statement said. "As a precaution, this azipod was shut down for the return voyage to Bayonne. Technicians are onboard replacing the clutches on both the starboard and port azipods as a precaution. Repairs and subsequent testing of the azipods is ongoing."

 

 

 

Highlighting, mine.

 

 

 

The azipod was still functional, but they did not want to do further damage to the clutches, so they let it freewheel.

 

 

 

Now, to some questions along the thread:

 

 

 

The tug escort was mandatory for any ship that does not have redundancy in steering, all the way from the Ambrose traffic separation scheme (arrival point for port of NYC, a few miles out), to the dock. It was not that Anthem could not dock on her own, but that the USCG requires a tug standing by in case the remaining steering method fails.

 

 

 

The reason for the small wake on the port side is that if you stop the one pod's propeller from turning, it creates a huge "barn door" of drag which will slow the ship, make steering difficult, and increase fuel consumption. Unless a bearing has gone bad in a pod, they will just turn the power off to it, and the motion of the ship will cause the propeller to turn freely, reducing drag.

 

 

 

If a pod loses a bearing, not Anthem's case, they will lock the shaft, to keep the free rotation from further damaging the bearings. If the bearing cannot be repaired quickly, they will pull the propeller blades from that pod, and the hub presents very little drag when locked. This is what Freedom did last year.

 

 

 

Ships that have more than 2 pods (with the exception of the Cunard QM2), only have 2 pods that steer. So, loss of a "fixipod" (one that does not steer), will reduce propulsion, but will not require the tug escorts that Anthem and other ships have had to use when entering/leaving port.

 

 

 

And as I've stated on other threads, while the USCG did in fact "detain" the Anthem (not allowed to proceed to sea), because RCI had no intention of sailing before Saturday anyway, it was a "non-affecting" detention (sort of made that word up, meaning it really did not affect their schedule). The USCG has a Port State Control Information Exchange, where they post a record of all visits by the USCG to foreign flag ships in US ports (Port State Control, or SOLAS inspections, that cruisers are frequently aware of due to delayed boarding), which Anthem had in January this year in San Juan. They will also post the report of this inspection, since it is technically a detention, but their site only updates weekly, so it will have to wait until Monday or Tuesday to see it.

 

 

 

Regarding the PVSA, etc, and the decision to return to NJ. The PVSA is almost universally waived in cases of weather or mechanical problems. Technically, even returning to NJ was a violation, but not of the PVSA, since CBP has banned all cruises to nowhere (which this was), but that has to do with work visa rules for the crew.

 

 

 

Probably didn't cover half the thread, but I'm subscribed now, and any questions I'll be available until its time to weight test my bunk. :D

 

 

Absolutely excellent description, thank you!!

[sjn911]

I've complimented you before and I want to do it again. Your knowledge is deeply appreciated. I hope you don't mind but I copy and pasted your statement to another thread and gave you full credit.

IE Chengkp75....me too...I just happened to browse around more and it is just so great to be able to trust knowledge and have such clear repeat and patience..even when not speaking "the tech" language well enough he is so well stated and repeats answers kindly to those still learning or getting it...

 

Like the plugs in the room.

 

Thanks Mr. Chengkp75 and relieved on the new propulsion facts. It helps so much to be able to assess and keep up.

Edited February 13, 2016 by sjn911

[Cuizer2]

Bow thrusters just provide sideways force, not forward propulsive force. It's not like the Starship Enterprise.

 

The Starship Enterprise has side thrusters? :confused:

[sjn911]

I've complimented you before and I want to do it again. Your knowledge is deeply appreciated. I hope you don't mind but I copy and pasted your statement to another thread and gave you full credit.

IE Cheng....me too...I just happened to browse around more and it is just so great to be able to trust knowledge and have such clear repeat and patience..even when not speaking "the tech" language well enough he is so well stated and repeats answers kindly to those still learning or getting it...

 

Like the plugs in the room.

 

Thanks Mr. ChengKp and relieved on the new propulsion facts.

[Cuizer2]

so if the quantum loses one pod. they are one pod away from being stranded at sea. There must be some sort of back up?

 

Yes, the other pod.

 

Ever been on a twin engine jet?

[cruisenfever]

Thanks so much Chengkp75 for all the explanations that even a dummy like me can understand!!

 

If you don't mind my asking, what exactly does your screen name represent? Or is it TOP SECRET.

Edited February 13, 2016 by cruisenfever

[chengkp75]

Could you comment on a discussion we had earlier about the Quantun class ships having only two pods? The point being that almost all of the Voyager/Freedom/Oasis class ships have sailed for a period of time with a pod out of service but since they have three of them if they lost another on a cruise they would still have propulsion. Does this mean if a pod goes down on Quantum/Anthem that they would not be allowed to sail since if the other pod goes bad then there is no backup and no propulsion? With the history that we have seem so far of pod problems not being uncommon could this be a design problem for these ships?

 

Big difference with the Quantum class ships. These ships have the second generation XO azipods, which allow for the thrust bearings to be renewed without drydocking. These thrust bearings are the major headache with podded propulsion. What the thrust bearing does is provide the point where the "push" of the propeller shaft, which is rotating, forces against the stationary ship. So, the entire power of the propeller is pushing on this bearing, and the entire inertia of the ship is pushing back. The Voyager/Freedom/Oasis class have the older AO (I think it was) type pods, and the bearing could not be renewed from the inside, so a bearing failure required securing a drydock time slip, or in the case of Allure, a modification to the drydock to allow it to service a ship too big to fit. These new pods can renew bearings from the inside, so they carry spares, and the repair can normally be done within a long port stay, or with the shaft locked and calm weather, at sea.

 

There is no requirement for redundancy of propulsion (with a bit of a caveat with regards to cruise ships, more later). 90% of ships on the ocean today have only one engine and one propeller. The problem comes with steering. Ships with rudders will have two sources of hydraulics to turn the rudder, just like having two azipods (though cruise ships with twin rudders will have 4 steering motors, two on each rudder). The USCG says that you must have redundancy of steering to enter into restricted waters of the US (ports and traffic schemes). If a twin rudder ship loses one of 4 steering motors, she still has two rudders, so there is redundancy. But if a ship has two azipods (steerable pods), and one goes down, there is no redundancy, so the USCG will require a tug escort in case things go further south. The ship is perfectly capable of maneuvering on one rudder or pod, but the USCG wants a safety factor. Each time the ship enters or leaves a US port, it must report the loss of steering redundancy, and each Captain of the Port will determine measures required, but mostly it is a tug escort. This only applies to US ports, some foreign ports require it, some don't.

 

Now, the caveat about redundancy of propulsion for cruise ships. The recent (2010) Safe Return to Port regulations require redundancy of propulsion, but this is accomplished with one pod down by being able to power the one operational pod from either engine room/switchboard, so loss of one engine room, and one propulsion room will still allow the ship to proceed under power.

 

So, the USCG can allow a ship to proceed to sea with only one pod operational, if it was built before 2010, or if built after 2010 if both engine rooms are operational. Maritime regulations are never retroactive.

[chengkp75]

Thanks so much Chengkp75 for all the explanations that even a dummy like me can understand!!

 

If you don't mind my asking, what exactly does your screen name represent?

 

Cheng is the acronym for Chief Engineer, KP stands for Kings Point, the US Merchant Marine Academy, and 75 is my year of graduation.