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150 ft yacht with 130mm shafts. Problems with shafts.
2

150 ft yacht with 130mm shafts. Problems with shafts.

150 ft yacht with 130mm shafts. Problems with shafts.

(OP)
Hello Everyone,

I am new to this site and could really use some information. I have two shafts 130mm with heavy pitting that I need to have resurfaced and machined. I am probably not using the correct terminology please bear with me. Some of the pitting is 1/2" deep but I have heard that the shafts can have a new surface applied through a welding process and machining. Is there a depth of corrosion that decides when it is time to scrap the shafts? The yacht is in Miami,FL, if someone knows of a reputable machine shop that can handle this type of job please let me know. Or if I am missing important information about the process I am all ears. The spots in question are between two bearings. Please see the attachment for a picture of the corrosion.

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

Florida has a lot of coastline, and a lot of marine service centers. If you want local info, you need to define your locale a little more specifically.

Or, you could just ask the nearest yacht yard, or the one you're in; they all have trusted suppliers for most everything, including weld repair of shafts.

Mike Halloran
Pembroke Pines, FL, USA

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

I would think twice, 1/2" into a shaft is deep, and you will not have as good of strength or corrosion resistance as you started with.
What material are they?
It sounds like you really need to consider an upgrade in the alloy.

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P.E. Metallurgy, Plymouth Tube

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

(OP)
Thanks guys for the response. The shafts were replaced in Italy July 2012, I had to use google translator to get the basic information of replacing shafts and bearings. No other info was given on the invoice. If you look at the picture it doesn't even look like SS. I am in Miami would prefer to hear someone say they know a shop that is reputable. What would they have to do to test the metal for type of SS?

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

We can't look at the picture, because there's no attachment.

Mike Halloran
Pembroke Pines, FL, USA

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

(OP)
Not sure why the pics didn't upload. Will try again. Behind the packing gland is the first bearing then 4 ft further is the stern tube bearing. It seems as though the bearings are trapping water. Research indicates in time the salinity increases as well as oxidation lowering the O2 content accelerating the corrosion process. Is that correct? Is there a formula for distance between bearings for a 130mm shaft? I have never seen bearings so close together and that is where the heavy pitting has taken place. I also noticed the first bearing is worn substantially more than the other 3. I see your location is Pembroke pines do you do SS shaft work there?
Thanks again for sharing your professional experience and advice.




RE: 150 ft yacht with 130mm shafts. Problems with shafts.

Often for seawater service yachts are equipped to pump a small amount of fresh water into the bearings, to help keep salinity down.
I don't know any boat people down there, but there are a lot.
I'll ask a friend in Palm Beach who he uses.

There are special alloys used for seawater service. A low alloy stainless grade would last forever in fresh water and even handle occasional runs in seawater. But sitting in seawater take a different class of material.

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P.E. Metallurgy, Plymouth Tube

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

Wow, that is nasty. I can't say I've ever seen corrosion that highly localized and deep. Given that, I wouldn't trust the remainder of the shafts.

No, I don't do shafts. I worked on yacht exhausts all over SoFla for a few years, so I got to see a bunch of them spinning, none like yours.

You might consider mechanical seals to replace the packing glands.

Mike Halloran
Pembroke Pines, FL, USA

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

(OP)
Thanks for responding guys, I like the idea of pumping fresh water through the gland while we are just sitting alongside. There is a fitting from the engine raw water cooling side that goes to the backing of the packing which could be tied into. This would push the salt water out and keep the shafts in good shape. Thanks for a simple remedy. I have never see SS shafts do that type of deterioration I wonder if the Italians got their steel from the Chinese??? I will approach a few shops in the am to see if they can do anything with them. Will update as things move along.

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

The shaft shown in the photos looks like it already had some weld repairs performed on it. And given the current state of the shaft I can't imagine it would be cost effective to try to salvage it versus machining a new one.

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

(OP)
In Italy they supposedly replaced the shafts July 2012 for the same issue. Unless they told the owner they were new shafts and machined the old ones? What do you see that makes you think they have been machined before?

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

First determine the alloy. There are NDE Labs in the area that can perform XRF PMI (Positive Material Identification. I also believe that at least one lab in S. Florida can perform PMI with optical emission spectroscopy. Then a more corrosion resistant material can be selected or additional operating parameters (fresh water injection proposal) can be installed. From its past history, localized welding repair with matching weld filler metals or more corrosion resistant weld filler metals will not provide increased service life.

Is this yacht operated frequently or does it sit at dock for long periods?

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

(OP)
The yacht traveled the world but now sits and waits for a new owner. I have talked with F&J propeller in Miami who will look at making new shafts with better material. Talking about turning 5.5" shafts to 130MM. How does that effect the SS once it has been turned down to size. Thanks for all of the great info this is what the web was meant for!

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

Unless the shafts are heavily cold worked to make them stronger turning them down will have no impact.
You should be looking at alloys with high Cr and Mo.
Such as Aquamet 22, here:
http://www.aquamet.com/home.nxg

This isn't a commercial plug, but I have seen their stuff used successfully in many applications.

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P.E. Metallurgy, Plymouth Tube

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

Do you have cathodic protection on the shaft?

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

(OP)
Guys thanks for leading me to Brian at Aquamet, it appears the Italians put in the 17 instead of the 22HD or 25. This is why the magnet sticks to it like it does the hull plating. There is Cathodic protection and monitoring which is within the normal range. I will be adding a potable water flush to keep the salinity down in the space and replace the shafts with a higher quality. Thanks for all of the great advice and input greatly appreciated.

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

But the way, I have been wanting to ask, what is the boat?
A pair of 1,500 hp engines in a 150' boat is quite a package.

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P.E. Metallurgy, Plymouth Tube

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

(OP)
She is an Italian built full displacement hull and can be seen at www.goldencompass.biz

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

Nice boat.

Mike Halloran
Pembroke Pines, FL, USA

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

"Nice boat."

No kidding! I just took a look at the website for this boat (or "private estate" as described in the brochure), and it does not look like the owners are hurting for money to pay for repairs.

The cost of machining a new pair of prop shafts from a premium material like Aquamet 25 would probably be less than $40K. Which seems like a relatively modest expense compared to the cost of paying salaries of the Golden Compass's ten crew members.

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

Where were the sacrificial zinc anodes, or were there any?

Mike McCann, PE, SE (WA)


RE: 150 ft yacht with 130mm shafts. Problems with shafts.

In the first picture posted above you can see a MIG welder sitting below the corroded prop shaft. I hope they weren't using the MIG welder to rework the corroded sections of the shaft in-place. 17-4 stainless can readily be welded, but the shaft would need to be heat-treated after welding, re-machined/straightened, and balanced.

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

tbuelna,
Looks more like an SMAW welder to me.
What makes you think it is GMAW ?
Cheers,
DD

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

(OP)
Very observant guys. The welding machine is being used for hull plating replacement. The shafts are at F&J Propeller in Miami. They will be machining and welding the deep intrusions and buffing back down on non bearing surface. See attached pictures of test area. They will be doing an overlay on the bearing and packing surface. They have a 50 ton press for straightening the shafts. Thanks again for all of the input.



RE: 150 ft yacht with 130mm shafts. Problems with shafts.

(OP)
BTW- There were no anodes on the shafts. The had a bonding rider on the shaft but that is it. Will be investing in 130mm ID zincs. Anyone know a good place to get the zincs at wholesale?

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

Quote (DekDee)

...Looks more like an SMAW welder to me. What makes you think it is GMAW ?

Definitely a Miller machine based on the blue paint. The only reason I assumed it was not a stick welder is because there are three cables attached to the machine face.

Also, if you look at the second photo in the post above from captstaats, you can clearly see the remnants of a piece of errant MIG wire just to the upper left of the weld repair.

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

Was there any NDT performed? As I see the repair, I wouldn't OK it. I'd like a bit more certainty than just a visual inspection on those shafts. I would also be hesitant on using GMAW/MIG for this type or repair.

RE: 150 ft yacht with 130mm shafts. Problems with shafts.

A piece of wire and a lot of oxidation.
And what about all of the little pits? Those need to be done away with also.
What material is being used as weld filler?

Looking at the boat specs it says that the engines are 750hp. That makes these very low strength shafts.
Which is good news, since the repairs will not be highly stressed.

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P.E. Metallurgy, Plymouth Tube

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