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Old 10-19-2020, 05:46 PM   #1
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Dripless shaft seal maintenance ??

Previous owner of our boat installed a dripless shaft seal. it must be 2 years old now and has not had any maintenance or adjustments made. Should I be doing any maintenance? no leaks or water entry into bilge now. Anyone have any advise?
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Old 10-21-2020, 05:38 AM   #2
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"Anyone have any advise?"

Only an opinion, if it is the style that has a thin flexible bellows , I would contemplate going back to the ancient style stuffing box but with modern Duramax packing .

If the thin rubber gets torn it can easily allow water flow that can overpower most bilge pumping systems.
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Old 10-21-2020, 07:06 AM   #3
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Coalman - you may want to post a picture so folks can identify. PSS systems - a very common stuffing box with bellows, recommends the bellows be replaced at about 7-years I believe. These bellows are quite stout, reinforced with wire, and would be difficult to tear.

If there is no leak, and at 2-years old, unlikely you need to do anything. I will voice a different opinion to FF: where a stuffing box is easily accessible and the owner is comfortable with routine maintenance, I recommend a traditional stuffing box with modern packing as FF suggests. Some stuffing boxes are very difficult to reach and service (V-Drives often fall into this category). In those cases, dripless system makes more sense. Also, where owners want nothing to do with maintenance, it's a good idea too.

Personally, while my first choice on your boat would probably be a traditional stuffing box, I'd keep the dripless and not worry about it. It's sort of a "Ford vs Chevy" debate - personal preference.

Peter
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Old 10-21-2020, 07:40 AM   #4
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I concur with leaving the PSS unit in place. they have been around now for more than 20 years. Have yet to hear of boats sinking specifically because of a tear in the bellows, though others here probably have opinions!! Provided it is not leaking or spraying droplets of water, the only maintenance worth doing is to check to make sure that the cooling water flow is running correctly. If you are getting any sort of light spray, the carbon seal faces may need to be adjusted to a closer fit by slightly extending the bellows. When you do this be sure to replace the small allen bolts used to lock the flange in place - according to PSS, these should not be re-used. The bellows is easily inspected for cracking but should be good for at least 10 years.
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Old 10-21-2020, 02:27 PM   #5
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There was a Pursuit years ago that sank when the bellows came loose, or maybe it was a Tiara. Another that nearly did so when the collar slipped, both I think were recent installation issues. So catastrophic issues while rare are not unheard of. As you say, they have been around for a long time, so have run enough numbers to have incidents. That by itself means little, though be aware that there are failure points that can, however rare, result in a lot of water, really fast.

Iíve had PSS not long after they came out. Local company, good support. Personally Iíve gone back to a traditional stuffing box since gore packing became available, but nothing wrong with the PSS design. They have some failure potential, but mostly related to install and usually donít give problems unless some grit gets in the sealing surfaces which if you canít polish in place can have the nuisance of needing a haul out to replace, which in the three instances I had a unit give me trouble, only once did we eventually give up and replace the ceramic seal.

Overall, they are good units with a good history. I wouldnít put it on the list unless it was giving me trouble. Really good chance you go years before it gives you any grief whatsoever. I see no reason to add things to the maintenance list without a valid reason. There will be plenty of candidates that announce themselves soon enough if you worry about being bored.
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Old 10-21-2020, 02:59 PM   #6
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These seals have been used on large pumps and other shoreside applications for at least 30 years, probably longer, and are proven. Mine is coming up on 3 years old so I also wondered what was needed maintenance wise. As others have said, it looks like a bellows replacement and check every 6 years, at least for the PSS mechanical seal I have. Also, apparently the seal can get air bound when the boat is hauled. The Helmsman website has an article how to “burb” it manually (PSS) to remove any trapped air after a haul out.
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Old 10-21-2020, 03:14 PM   #7
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Hi, I have Vetus dripless seal in my boat. Works well - is dripless indeed and have been happy with it. Official instruction is to add some silicone grease once a year.
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Old 10-21-2020, 03:50 PM   #8
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Quote:
Originally Posted by ghost View Post
There was a Pursuit years ago that sank when the bellows came loose, or maybe it was a Tiara. Another that nearly did so when the collar slipped, both I think were recent installation issues. So catastrophic issues while rare are not unheard of. As you say, they have been around for a long time, so have run enough numbers to have incidents. That by itself means little, though be aware that there are failure points that can, however rare, result in a lot of water, really fast.

Iíve had PSS not long after they came out. Local company, good support. Personally Iíve gone back to a traditional stuffing box since gore packing became available, but nothing wrong with the PSS design. They have some failure potential, but mostly related to install and usually donít give problems unless some grit gets in the sealing surfaces which if you canít polish in place can have the nuisance of needing a haul out to replace, which in the three instances I had a unit give me trouble, only once did we eventually give up and replace the ceramic seal.

Overall, they are good units with a good history. I wouldnít put it on the list unless it was giving me trouble. Really good chance you go years before it gives you any grief whatsoever. I see no reason to add things to the maintenance list without a valid reason. There will be plenty of candidates that announce themselves soon enough if you worry about being bored.
I have seen one failure and was due to install error. I was aboard a boat when the one next to suddenly has the owner pop up telling for me. I go aboard and there's an alarming amount of water streaming in. Took me a moment to figure out what was going on, but figured it was from the PSS. Within a minute or so, I'd figured out the collar had backed off.

There are two stepped set screws to secure the collar, the second one jamming down into the first one that secures against the shaft. The simple fix is to put a hose clamp around the shaft as an extra security step. There was no second set screw in the bilge so I'm pretty sure it hadn't been installed in the first place.

Personally, I do not fault PSS for this. It's an install error. I still prefer traditional shaft packing, but don't have a complaint with PSS.

Peter
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Old 10-21-2020, 03:56 PM   #9
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I clamped a shaft zinc forward, but snug against the seal to prevent that.
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Old 10-21-2020, 06:38 PM   #10
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PSS make a very good, dependable shaft seal. There is nothing wrong with them, and they have a proven track record. Like a lot of things, they can be installed wrong, and if not tended to periodically can lead to trouble.
PSS has a recommended service interval for a "major" service (bellows replacement). I did mine a few years ago and used the newer "longer life" model that has a recommended 10 year replacement interval. For insurance purposes, you might want to follow this recommendation .
The system works by compressing the bellows (so that the "spring" in the bellows pushes the carbon stator against the SS ring), so if the "retaining" grub screws "let go" and the compression is released, you will develop a leak. So, like others have suggested, a preventive measure is a good idea. You can use a shaft zinc, a hose clamp, or the purpose built retaining collar from PSS to backup the normal grub screws. The grub screws are not to be reused, and 2 per hole are used as described above.

Regular routine maintenance would include:
- checking all hose clamps to ensure they are correctly tightened.
- inspecting the bellows for signs of damage.

- checking for signs of leaks or spray. The bellows can be adjusted if needed.
- checking for cooling water flow.
- checking the "extra" retaining device if installed.
- occasionally taking a temperature check of the PSS system to look for signs of overheat (use an Infared gun) while underway. It is usually very cool.

So, other than the every 6? or in my case 10 year maintenance, they are fairly maintenance free (not meaning they should be ignored).
As far as the cooling water goes, at the speeds (and RPM's) that Nordic Tug and Monks tend to operate, cooling water from the engine is not really needed (assuming that there is no air lock in the bellows after a haulout). There is a cooling hose installed anyway. The bellows can be "burped" after a haulout if needed, but I have never found it necessary.
The ordinary bellows is very tough, and the longer life one is even tougher. Yes it is remotely possible that under crazy circumstances a bellows tear could sink your boat, but you could also have a Humpback whale breach and land on your boat. Does that stop you from boating?
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Old 10-24-2020, 10:07 AM   #11
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What ever maintenance is needed is dependent on the type of pss system you have. As mentioned in an earlier reply a picture would help. All I know about is the Tides Marine dripless shaft seals. When I first purchased my Mainship the seals were replaced due to leakage. Unfortunately this never really completely stopped the leak, it still dripped a little. A few years later I found out that the insides of the assembly had been scored due to lack of water flow through the cooling channels. Scale built up and blocked the water. I replaced the assemblies myself on a short haul in the yard. The water flow for the system is tapped off the bottom of the engine air coolers. Scale had clogged the port in the air cooler that the pss hose is attached to.
So to prevent this from occurring again when I change my air cooler zincs I make sure this port is clear and I have good water flow into the pss system. The only other thing I do is check hose clamps. Since the replacement of the assemblies I have not seen one drip.
Again your maintenance will depend on your system.
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Old 10-30-2020, 11:09 AM   #12
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I have a PSS dripless seal on my 2006 NT32. The only thing I have done is keep the bellow clean, with occasional wipe of 3M 303, check the hose clamps, and an occasional "burp" to make sure no debris builds up between the carbon and SS rotor. While I have a PSS maintenance kit, I have yet to install the kit in this original 15 years old seal ( 2,300+ hours). The seal works flawlessly. I've never had any leaks. The bellow still retains the original pressure, and I've never had to compress the bellow (push the rotor aft) to increase pressure. PSS recommends the bellow, o-rings, set screws, and hose clamps (the maintenance kit) be replaced every 6 years. On several occasions, I've asked PSS reps at boat show..."without any failure, deterioration, or leaks, when should I install the maintenance kit?". The usual response is... if periodic inspection shows no leaks, deterioration, let it be.

Now after 15 years, again without any issues with the PSS seal, I'm getting a little antsy, and thinking about installing the maintenance components. On any of these maintenance kit installations, removing the coupling from the shaft is the major challenge. This Winter when I haul, I'll disconnect the coupling from the transmission flange. I need to take a template of the coupling face to make up or purchase a puller, basically a steel plate ring with bolt holes that line up with your coupling, and a large center bolt to work off coupling from shaft. The old-school method of longer nuts and bolts and a spark plug socket might work to push off the coupling, but there's some potential to deform the coupling.
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Old 10-30-2020, 01:47 PM   #13
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The PSS are fine if you (or your mechanic) stays on top of the maintenance and visually inspects them frequently. Most of the commercial guys here and Maine have gone to the RE Thomas ISB/SA self-aligning shaft seal for the failures mentioned above.



It's a traditional bronze stuffing box, yet water fed and able to self-align on the shaft. The newer style packing allows you to tighten the nut so it doesn't have to leak to keep the packing cool. The unit also has a cutless bearing in it to support the shaft whereas traditional stuffing boxes act as a bearing and a seal... Here's video:

https://youtu.be/0rRDPatjbHI
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