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Old 05-03-2011, 13:29   #1
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Lightbulb Need Help with PSS Shaftseal

I have a PSS Shaft Seal on my boat.
These seals are very good and there shouldn't be any water leaking into my boat.
But the ones I have are leaking, not all the time, some times when the engines are running, next time at anchor. I had mechanics on board, I spoke to dealer and I get the same answer, the PSS is a 100% watertight and totally maintenance-free seal.
Any sugguestions what I can do next.
Thanks
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Old 05-03-2011, 13:38   #2
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Re: Need help with PSS Shaftseal

check the engine alignment by backing off the coupling to see if the coupling moves off axis compared to the transmission. If that is good then verify that you have a sufficient length of the flexible blue silicon rubber between the hull and the end where the seal rides. IF too short there is not enough flexture to accommodate misalignment between the hull and the axis of the transmission.
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Old 15-03-2011, 14:40   #3
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Re: Need help with PSS Shaftseal

I too have a pss and it is a mighty tight squeeze on my boat. it also leaks.
I'm unsure where you got the 100% watertight from as I recall talking to pss a few years back and they were not perplexed about a small amount of water (mine is about a quarter of a pint max after using it when the boat has been unused a week or so, when dry and standing, it stays dry) If I recall it is caused by a minor imperfection on the stainless steel face and I was advised that I could pull the seal back and clean it with glass paper or just ignore it, I chose the latter.
It is the rubber boot/bellows integrity that is of paramount importance, if that is damaged or the hose clamps look suspect then it is a big deal.

I'm curious to see if someone posts to the contrary or if pss advise you differently. OBTW the cause for the imperfection was during a long motorsail it started to squeak, with hindsight I should have pulled the boot back to let any air out once a day during prolonged use, my pss predates the newer versions with an air outlet on a small barb.
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Old 15-03-2011, 14:46   #4
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Re: Need help with PSS Shaftseal

I've just installed one, part of the installation instructions were to measure the compression amount based on shaft diameter. If there was leakage the amount of compression could be increased......in 1/4" increments I beleive.
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Old 16-03-2011, 07:42   #5
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Re: Need help with PSS Shaftseal

I had a serious leak once when the s/s coller moved up the shaft about 1 1/4". when in gear it would spray lots of water but with the shaft stationary not a drop. Moving the coller back I replaced the 4 grub screws and put a hose clamp on the shaft, infront of the coller to arrest any movement should it happen again.
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Old 16-03-2011, 08:05   #6
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Re: Need help with PSS Shaftseal

I know I will get a rain of comments from PSS owners and the folks from the manufacturers and installers who monitor these posts and respond as individuals, but IMHO and experience, the modern packing materials you can put in a traditional stuffing box and stop leaking entirely, make this device unnecessary. There may have been a time when these devices were superior when all we had was flax packing materials, but the new packing materials do not require leaking and fit nicely in a traditional stuffing box.
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Old 16-03-2011, 08:42   #7
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Re: Need help with PSS Shaftseal

Quote:
Originally Posted by Pete the Cat View Post
... the modern packing materials you can put in a traditional stuffing box and stop leaking entirely, make this device unnecessary. There may have been a time when these devices were superior when all we had was flax packing materials, but the new packing materials do not require leaking and fit nicely in a traditional stuffing box.
Interesting!
Which modern packing materials don't require "leaking" for lubrication?
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Old 16-03-2011, 08:44   #8
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Re: Need help with PSS Shaftseal

Pete is right. I thought before I made the sizeable investment in a PSS that it might be a good idea to try a PTFE impregnated woven poly packing. There are no leaks and the packing gland remains the same temp. as the outside water. It works beautifuly for me.
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Old 16-03-2011, 08:53   #9
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Re: Need help with PSS Shaftseal

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Pete is right ...
I thought that PTFE packings should be allowed to leak more, to dissipate the heat the packings generate through thermal expansion.

Ie: ... When frictional heat is generated by contact with a high speed rotary shaft, pure PTFE has a tendency to absorb the heat, not allowing it to dissipate to the surroundings. Higher leak rates across the packing-shaft surface are required to keep a PTFE packing from burning or charring ...

Here ➥ When Should I Use Braided PTFE Packing, and In What Form? | Compression Packing

What brand of packing are you guys (Pete & Jesse) using?
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Old 16-03-2011, 11:10   #10
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Re: Need help with PSS Shaftseal

I get mine from a seal and gasket manufacturer who provides it for the military and have used it for a few years, no leak, no scoring, runs cool and is used widely by the lobstermen here in Maine--from whom I learned about it, but I have seen the same thing (black stuff) in chandleries recently. I think someone on the site can give you the brand name it is sold under as they have on another thread. A few years ago when I first used it, I was thinking about packaging it for recreational yachts, but someone beat me to it. Costs about double the teflon flax packing we used to use. I also understand that there is a brand sold that is black and is not designed to run without water, so--apparently, not all black packing has the same properties.

Before that I used to use the Dripless Packing (green clay) that has been around for 20 years. It was a little messy to set up--the clay is set in lubricant goop (the boatyard guys call it Elephant Snot) that oozes out at first and required gradually turning in the pressure on your fitting to stop the leak but not overtighten. Then it is dripless.
I used this for years and thousands of miles (a couple years in Central America and a lot of motoring with no adjustment) and it worked OK, too, once set up, but the black stuff is a great improvement. Simpler to set up, cheaper.

Word of caution: You need to tighten the nut with this stuff very gradually. I can imagine that it would not be something the boatyards would want to encourage as it requires some initial, sequential tighting as it wears in. You hand tighten the nut plus a 1/8th of a turn, run for a few hours and check, repeat until there are no leaks. Honking it down really tight and sending folks on their way is not going to work--I imagine it is possible to overtighten.

No mechanical device or packing material is going to work on a significantly misaligned drive train or out-of-true shaft.

Someone will have the brand name. I am told West Marine has it. My local chandlery has it.
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Old 16-03-2011, 11:29   #11
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Re: Need Help with PSS Shaftseal

i found pss to be a unique situation in and of itself. is a good way to sseal shaft -- but has failure issues. the hose clamps fail and he system fails and boat has inflow of water. ouch. ours failed last yr in gulf-- only slight inflow-- we repaired it-- someone else was reputed to have sunk in mid pacific due to failure of pss--i know th eman-- he stopped mid passage and replaced that pss in mid pacific--he is fine and so is boat--is a leaky teaky. as there is such a long shaft on our leakies, i was wondering if a support for the shaft in the form of a dry bearing in a support beam or plate -- would that help prevent some of the vibration/wobble from turning of the shaft--or is that an issue over 4 ft or so of length--mebbe 5 ft..i didnt measure--just a guesstimate....??????
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Old 16-03-2011, 12:31   #12
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Re: Need help with PSS Shaftseal

Quote:
Originally Posted by KatKokomo View Post
I have a PSS Shaft Seal on my boat.
These seals are very good and there shouldn't be any water leaking into my boat.
But the ones I have are leaking, not all the time, some times when the engines are running, next time at anchor. I had mechanics on board, I spoke to dealer and I get the same answer, the PSS is a 100% watertight and totally maintenance-free seal.
Any sugguestions what I can do next.
Thanks
I have had one for 15 years, it is 100% drip free, and I still like it! I have had my share of problems that I can share, as well as the cures.

I launched our boat with the "low speed" (= not irrigated model). These have to be "burped" when you launch, EVERY time, or an air pocket at the top of the stern tube may cause the rotor to be running "dry" rather than in water for it's cooling & lubrication effect. After 5 years of building, and in the excitement of first launch, I may have forgotten this, I'm not sure. (burping is where you rock the bellows' carbon flange, to let some water in, and let the air out of the stern tube).

Some months later, it was chattering a lot, especially at low RPMs, like the rotor was sticky or something. They are VERY sensitive to oil on the interface! I used a thin paper towel and Isopropyl alcohol to clean between the rotor and carbon flange. This helped for a while. (KEEP IT OFF OF THE RUBBER BELLOWS).

Later, when the noise came back, I was instructed to polish the interface this way:
Fold over 2000 grit wet/dry sandpaper once, stick it inbetween the rotor and carbon flange, and go around and around for about a minute. This gets petrochemicals off the interface. It helped a lot.

If it started chattering again, I would sometimes loosen the hose clamp on the bellows, and "cock it" to keep the carbon flange centered on the shaft. It has to be just right! The bellows pressure pushing on the rotor, does NOT need to be very tight, Perhaps one pound of continuous pressure!

Seeing fine black specs, indicating a fine carbon mist, around the seal, is normal. It is SO fine, and in SUCH small volume, that it dries on contact, and just looks like a sprinkling of graphite.

Later it did start dripping on occasion, and I just did the above procedures over and over, for a temporary fix.

A year later, at another marina, where we were to stand the mast... We came back to the boat after a night out, to find 1.5' of water in the main hull! If it hadn't been a Trimaran, it would've sunk! I bailed, pumped, washed, and dried. Then replaced the pressure pump, eng. battery, etc. I also installed automatic bilge pumps & bilge water alarms. I had originally omitted these, because with our normally "dusty" dry bilge, I didn't think them necessary.

What had happened was, when I was cleaning the engine compartment previous to the flooding, I turned the shaft by hand, with the rotor. It taking SO little pressure, I never gave the practice a second thought. WRONG! The rotor had later slipped an inch up the shaft when I was running in place, letting in a constant slow stream! Even without such provocation, the grub screw that holds the rotor in place on the shaft, isn't 100% fool proof.

The company sent me a new unit, and a special "reverse direction" drill bit, to get out the old stuck grub screw. (It worked perfectly). I installed the new unit IN the water. Luckily it went off well, but it was a bit risky.
To prevent this from EVER happening again, I put a standard doughnut zinc on the shaft, just on the engine side of the SS rotor, I put a small bead of caulk on it's face, so I wouldn't need to push on the rotor at all, possibly getting it out of square to the shaft. This was a perfect solution! There are fancier SS collar back up devices out there, I saw one here on CF, but a Zinc works fine.

When I sent them the old, somewhat leaky unit, they examined it under magnification, and said I had cracks on the bellows, and small pits on the SS rotor. They thought it had been run VERY hot! HMMM!

This made me think I MIGHT have forgotten to burp it on first launch, running it hard for a week... DRY! I still don't know? The new unit never chattered or dripped at all after that, for the next 7 years!

In '04, while doing a refit and the shaft was out, I called PYI for a conversation about my installation. I have a cutlass bearing on the far end of a 3' long stern tube, so very little water flow. I was advised that they don't recommend the NON irrigated "low speed" model anymore, so I upgraded to the new "high speed" carbon flange with a hose barb on it. Otherwise, it is identical. The irrigation hose goes to your engine's up turned cooling hose loop, but be sure it is on the correct side. You can flood the engine through this hose otherwise! I even put a petcock valve in the irrigation hose, should I need it.

The new model gets plenty of lubricating water flow, the backup zinc is still there, and it has been chatter and drip free for another 7 years now. I like them a lot, in spite of the learning curve! Obviously, Don't turn the shaft by the rotor, or let it run dry, and install a zinc rotor backup...

The "wet" version is best. If you have one, a CVA joint like ours, makes the installation even better, because the shaft only spins, never shakes... And you need a carbon flange size that has plenty of space between the shaft and inside of the carbon's hole, 3/16" on all sides is OK. I had a friend that had less than 1/8" and his worked fine, but chattered all the time!

By keeping a bone dry bilge, it not only cuts down on mold, mildew, and smells, but if I get a small eng. "or other" water leak, I know right away, before it becomes a big deal!

Good luck with your problem, and hope this helps. Mark
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