PSS type shaft seal

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NDG

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I’m looking for a bit of advice regarding a recently installed PSS type shaft seal, manufactured by Michigan Marine. It’s done about 20 hours of motoring and as you can see from the picture, it is still throwing out carbon dust. I know this is normal in the first few hours whilst the carbon collar polishes, but I think it should have stopped by now.

I am wondering if the compression is a bit too high and it needs to be backed off a bit. Could that be the case? I don’t know what the standard distance should be from the collar to the stern tube - I tried calling Michigan but they don’t seem to have an installation manual. It doesn’t seem to be dripping which is good - if fact it’s great when I think of the last packing gland which used to spray water everywhere.

I’m wondering if anyone has any similar experiences particularly with this manufacturer.

Thanks for any help.

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No expert, but the PSS seal in Jissel hardly produced any powder. The bearing surface is supposed to be water-lubricated, is enough water getting to it?

Jissel shouldn't have needed it, but on a mud mooring, I wanted to flush mud out of the stern tube, so took a feed from the cooling water to the PSS.
 
I would be concerned by that. Is water reaching the sealing faces to provide cooling and lubrication?
Otherwise, is the face of the SS rotor in good condition?
 
Last boat had a PSS seal, I fitted one to current boat myself. Zero detectable carbon dust on either

Like the previous respondents, my first thought is that it's running dry.

Try "burping" it (puling the faces apart) and you should get water. Although less copious than with an old fashioned stuffing box, there should still be a very modest amount of water escaping from the seal when running (so modest that you'd be hard pressed to see it but never the less it should be there)
 
Not sure that is actually a PSS seal but another make of face seal, and don't think that Michigan in the states actually make it. Their European distribution depot is at that address in Devon.

You need the installation instructions similar to those for PSS that gives the preload you need to put on the bellows. Wear suggests there is too much load. Worth trying to open the faces to allow water in, or moving the stator up the shaft a bit.
 
Thanks for the quick replies. The bellows are definitely supplied with water (i have pushed the bellows back and flushed them).

I am thinking that the compression is too high and there is no water reaching the face of the rotor to provide lubrication.

pvb said:
The OP said it was a "PSS type shaft seal". It's actually an Ercem seal, made in France. The detailed fitting instructions can be downloaded from the following link...

https://www.maucour.fr/en/cms/Notice_Montage_Ercem_std_Inf_55mmUKV230518.pdf
Click to expand...

That’s correct - it isn’t PSS but I wasn’t sure who the manufacturer was. I was told by the engineers who fitted it that it was made by Michigan but looking at that link, its definitely an Ercem seal so thank you very much for that reference. I’m not happy with the engineers as its been really hard to get them to attend to snagging items (they fitted a complete new engine, shaft and stern tube). Overall the job was ok but their follow up service is almost non-existent.

However…now that I have the manufacturers installation guide I can check the compression and adjust it if i need to - it should be quite straightforward.

Thanks again for all the help.
 
Happy to help! Note the comments in the instructions about always having water at the carbon/steel interface. Also note in the Troubleshooting the bit about "Premature wear of the graphite ring with strong projections" - I think by "strong projections" they mean it's hurling black dust everywhere![/I]
 
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I see what you mean - a literal translation from french I suspect! I think mine is certainly giving out ’strong projections‘ at the moment.
 
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Boater Sam said:
I would doubt that there is much carbon face seal left, they are only a couple of mm thick when new.
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I’m not concerned about that. It’s not leaking and it’s still doing its job. The manual which pvb has found suggests the carbon seal is a lot thicker than that anyway, unless I’m misunderstanding something.

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I have a Michigan marine PSS design and it did that at first also. It’s just the carbon face bedding in I think. Remember that the bellows on a Michigan don’t compress much. Only 10mm on mine and way less than other PSS types. Perhaps you compressed them too much and the friction is too high?
 
NDG said:
I’m not concerned about that. It’s not leaking and it’s still doing its job. The manual which pvb has found suggests the carbon seal is a lot thicker than that anyway, unless I’m misunderstanding something.

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I notice that there is an emphasis on the need for either a vent tube or water feed pipe. It’s not clear from the OP’s photo whether either has been fittted. If not, I would suggest that‘s where the problem lies.
Mike
 
mikegunn said:
I notice that there is an emphasis on the need for either a vent tube or water feed pipe. It’s not clear from the OP’s photo whether either has been fittted. If not, I would suggest that‘s where the problem lies.
Mike
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The water feed pipe isn’t mandatory and they sell versions with and without it. It’s personal preference but advised for high speed vessels, not for sailing. Personally I have one but if I replace I’ll get one without since I just see it as an added liability which is capable of sinking a boat.
 
Hoist said:
1. You cannot have too much compression on it, DONT BACK IT OFF. I have tried that when I incorrectly set up ours in the past after an engine change on the water. the more compression the better.
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That's not what the fitting instructions say. Why is it that we seem to have a spate of people who ignore manufacturers' instructions?
 
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