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  #21  
Old 08-22-2012
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Re: Dripless Shaft Seal versus Stuffing Box

Quote:
Originally Posted by eherlihy View Post
My mast is keel stepped too, and the bilge is completely dry with the PSS Shaft Seal.
Somehow rain water always finds it's way down my mast and into the bilge. So, I figure a few more drops won't matter much.
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  #22  
Old 08-22-2012
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Re: Dripless Shaft Seal versus Stuffing Box

Quote:
Originally Posted by alturia View Post
Not all dripless shaft seals use bellows like PSS. Take a look for instance at the Lasdrop Gen II dripless shaft seal. There is no bellows to tear or give way.

Nautical Specialties manufacturer of Lasdrop Shaft-Seals
So its either bellows or "O" rings, neither of which are second generation technology. I think I would rather have packing material than "O" rings.
"O" rings can be a challenge.
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  #23  
Old 08-22-2012
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Re: Dripless Shaft Seal versus Stuffing Box

I had a "failure" of a PSS seal. First hand! Still sweat thinking about it.

In the PSS design, a carbon bushing on the bellows rubs against the rotor, a steel ring, to provide the watertight seal. The rotor is held in place on the propshaft with two grub screws - each with a second grub screw behind the first to prevent backing out,

In my case, the grub screws loosened over time, and while moving into my slip the rotor slipped about 1". I am guessing the engine moved on the engine mounts when I put her into reverse, putting pressure on the loose rotor. Luckily I heard the rushing of water before I left her, or she could have sunk at the dock. Within 5 minutes the water level was within 1/2 of the cabin sole. Think 3-4 hosepipes fully on.

People have alluded to this in this thread, but just in case anybody here has a PSS seal I want to be perfectly clear: ENSURE THAT THE ROTOR IS LOCKED IN PLACE. Check next time you are in the boat; a hose clamp, zinc, or stainless steel collet will work. http://ct4.pbase.com/g1/84/622984/3/...1.5lrRHrj9.jpg (from MaineSails excellent PSS Shaft Seal Installation Photo Gallery by Compass Marine at pbase.com)

The two grub screws are not enough. it's like driving without airbag, seatbelt - or doors. Beats me why PSS doesn't recommend this - reputable yards add a backup as a matter of course - they seem like nice folk, and set me free grub screws to re-attach my rotor to the shaft. CHECK YOURS. Sorry to rant, but that was a lot of water.....

Last edited by paul323; 08-22-2012 at 12:53 PM.
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  #24  
Old 08-22-2012
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Re: Dripless Shaft Seal versus Stuffing Box

Quote:
Originally Posted by eherlihy View Post
You may not care, but I, and several others, do. I do not want stagnant water to collect in the bilge. For more on why see this thread. It can also lead to that "boaty smell."

If you don't mind water in your bilge, that's your business...
I would like a dry bilge if possible and keep my stuffing box. My plan is to build a small bilge area around the stuffing box with its own bilge pump. That way the main bilge will keep totally dry while this small bilge will take care of the small amount of shaft seal leaks. I would use a shower type sump / pump package like previous poster mentioned, but the V drive makes the fit too tight. Project is underway Saturday.

Fininshed dam and installed Whale low profile bilge pump (in addition to the automatic bilge pump in the now dry main bilge. Everything works like a champ.

Last edited by casey1999; 09-04-2012 at 02:23 PM.
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  #25  
Old 08-30-2012
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Re: Dripless Shaft Seal versus Stuffing Box

I would suspect Catalina moved back to a traditional stuffing box because they are about 1/3 the cost of a PSS (based on wholesale pricing and Catalina pays less than I do I am sure).

The installation is also less costly for Catalina with a traditional gland not having to run an extra hose for the vent.

The PSS seals are extremely reliable and are used by the USCG and the world best builders. I know of some in commercial used with over 10k hours on them.

All the failures of PSS I have read of have been due to installer or owner error. The stainless rotors do not slip if properly & competently installed. I have seen 20 year old PSS seals still working perfectly. I have one customer who still has the old cloth covered bellows, this despite my very strong suggestion he replace it. I don't think PYI has made those bellows for about 15-20 years.

The term "properly installed" means the grub/set screws that contact the shaft are only ever tightened once. ONCE!!!! Tightened and used are two different things. They also need to be tightened to the proper torque with the proper Allen key.. PSS ships the proper Allen key but I still see grub screws molested by using the wrong Allen key.

Often times installers mess up the adjustment or compression of the bellows. Sadly they think nothing of loosening the set screws and simply moving or re-adjusting the rotor and snugging up the set screws. PLEASE DO NOT DO THIS! If this is done it is no longer a proper installation and you have just increased the risk of the rotor slipping and a leak. If you need to adjust the bellows you need to use brand new set screws.

These set screws can only be tightened once because the shaft, usually Aqualoy or Nitronic, is harder than the grub screw. These volcano head screws rely on the initial "cut" or bite into the shaft for the grip. Loosen the screw and move the rotor, even 1/8" and you need new screws.

PYI Says this right in the installation instructions:

"Do not re-use the supplied cupped pointed sets screws."

What is a one time use? If you tighten the set screws onto the shaft even once, that is your use. For example if you are installing the PSS and adjust it, tighten the set screw then realize the adjustment was wrong you now need to use new set screws. This is installer error numero-uno with PSS seals....


For years I have installed PSS seals with "clamp collars" from McMaster Carr as added insurance. Hose clamps and zincs are really not the ideal solution but a clamp collar is designed for this:


Here's a better view:


PYI saw me using these and they now offer their own "clamp collars". IMHO all PSS seals should come standard with a clamp collar, and a bag of extra set screws, but I digress. It would virtually eliminate installer error and slipping rotors and help eliminate the "I had a PSS failure" threads, which were really "installer error".

Both standard glands and PSS seals are reliable. I have however seen and know of plenty of sinkings related to traditional boxes. They are also highly prone to installer or user error. Hoses on traditional boxes also need to be changed so a traditional gland is not immune from hose replacement maintenance.


Despite misleading marketing messages by packing manufacturers traditional boxes should not be run "dry" or "dripless" but they can be "drips-less" than older plant based packings.. They, all PSS type or traditional glands, need to pass some water (traditional) or vent air (PSS type), or they can overheat. Trapped air or not passing of water can also lead to stagnation and corrosion of the shafting up inside the log.

This is what stagnant water on a traditional box set to not drip can do:


Some boats are more prone to trapped air in the log hence PYI's move to all vented/plumbed seals even on slow moving craft. "Burping" on some boats was more than just at launch time so vents make a lot of sense on all sailboats.

Newer packings can be pretty darn drips-less but should not be 100% dripless. it can be so minimal that engine warmth evaporates any drips before it accumulates.

Unfortunately I can't count the number of times an owner or yard mechanic has said to me "Yeah when I adjusted the PSS." and I ask "Did you replace the set screws?" and am treated with a blank stare? Scary stuff!

If a failure were to occur with a slipping rotor, in this scenario, it is installer error not the fault of PYI or the PSS seal.

I also very often see the vent holes plugged with brass or ss plugs. The vents should always be plumbed (power) or vented/used on sailboats. Metallic plugs should never, ever be used in the carbon rotor. There is a reason PYI uses a nylon hose barb and that is because the carbon is the most noble element in the galvanic scale and the differing expansion contraction characteristics between brass or SS and the carbon...

PYI says this in the instructions but many people choose not to read or heed them:

"Do not tighten or replace the installed nylon hose barb fitting with a metallic fitting (bronze or stainless steel). Metal hose barbs will damage the carbon and destroy the PSS."

Again, this type of failure, overheating of the seal, dissimilar metals corrosion or a split carbon would clearly get blamed on the PSS seal. Sadly on the "net" PSS takes the hit not the dolt who caused the failure by not following the installation instructions. These are examples of installer error not a failure on the part of the seal. I see the metallic plugs and set screw errors frequently.
Cruisingdad, tdw, T37Chef and 5 others like this.
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Last edited by Maine Sail; 08-30-2012 at 10:46 AM.
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  #26  
Old 08-30-2012
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Re: Dripless Shaft Seal versus Stuffing Box

Adding to Maine Sail's excellent post above;

When I purchased my PSS seal in April of 2012, it included 6 set screws. I believe that the reason there were so many is; 1 set (2 screws) were intended to hold the rotor in position, 1 set are meant to be snugged against the first set (thus locking the first set in position [See Maine's "better view" pic above], and allowing them to be used as spares) and the third set as spares. All of the set screws had thread locking compound pre-applied. Also included was the proper size allen wrench, and two sets of O rings.

The only part that PSS did not include was the Clamp Collar, which I have since purchased from McMaster-Carr.
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Last edited by eherlihy; 08-30-2012 at 10:49 AM.
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  #27  
Old 08-30-2012
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Re: Dripless Shaft Seal versus Stuffing Box

[QUOTE=Maine Sail;916052] I still see grub screws molested by using the wrong Allen key.

I love it. What a tactful way to put FUBAR. Do you know how hard it can be to removed "molested" set screws?
The rest is also very informative.
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  #28  
Old 08-31-2012
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Re: Dripless Shaft Seal versus Stuffing Box

Quote:
Originally Posted by Maine Sail View Post
I would suspect Catalina moved back to a traditional stuffing box because they are about 1/3 the cost of a PSS (based on wholesale pricing and Catalina pays less than I do I am sure).

The installation is also less costly for Catalina with a traditional gland not having to run an extra hose for the vent.

The PSS seals are extremely reliable and are used by the USCG and the world best builders. I know of some in commercial used with over 10k hours on them.

All the failures of PSS I have read of have been due to installer or owner error. The stainless rotors do not slip if properly & competently installed. I have seen 20 year old PSS seals still working perfectly. I have one customer who still has the old cloth covered bellows, this despite my very strong suggestion he replace it. I don't think PYI has made those bellows for about 15-20 years.

The term "properly installed" means the grub/set screws that contact the shaft are only ever tightened once. ONCE!!!! Tightened and used are two different things. They also need to be tightened to the proper torque with the proper Allen key.. PSS ships the proper Allen key but I still see grub screws molested by using the wrong Allen key.

Often times installers mess up the adjustment or compression of the bellows. Sadly they think nothing of loosening the set screws and simply moving or re-adjusting the rotor and snugging up the set screws. PLEASE DO NOT DO THIS! If this is done it is no longer a proper installation and you have just increased the risk of the rotor slipping and a leak. If you need to adjust the bellows you need to use brand new set screws.

These set screws can only be tightened once because the shaft, usually Aqualoy or Nitronic, is harder than the grub screw. These volcano head screws rely on the initial "cut" or bite into the shaft for the grip. Loosen the screw and move the rotor, even 1/8" and you need new screws.

PYI Says this right in the installation instructions:

"Do not re-use the supplied cupped pointed sets screws."

What is a one time use? If you tighten the set screws onto the shaft even once, that is your use. For example if you are installing the PSS and adjust it, tighten the set screw then realize the adjustment was wrong you now need to use new set screws. This is installer error numero-uno with PSS seals....


For years I have installed PSS seals with "clamp collars" from McMaster Carr as added insurance. Hose clamps and zincs are really not the ideal solution but a clamp collar is designed for this:


Here's a better view:


PYI saw me using these and they now offer their own "clamp collars". IMHO all PSS seals should come standard with a clamp collar, and a bag of extra set screws, but I digress. It would virtually eliminate installer error and slipping rotors and help eliminate the "I had a PSS failure" threads, which were really "installer error".

Both standard glands and PSS seals are reliable. I have however seen and know of plenty of sinkings related to traditional boxes. They are also highly prone to installer or user error. Hoses on traditional boxes also need to be changed so a traditional gland is not immune from hose replacement maintenance.


Despite misleading marketing messages by packing manufacturers traditional boxes should not be run "dry" or "dripless" but they can be "drips-less" than older plant based packings.. They, all PSS type or traditional glands, need to pass some water (traditional) or vent air (PSS type), or they can overheat. Trapped air or not passing of water can also lead to stagnation and corrosion of the shafting up inside the log.

This is what stagnant water on a traditional box set to not drip can do:


Some boats are more prone to trapped air in the log hence PYI's move to all vented/plumbed seals even on slow moving craft. "Burping" on some boats was more than just at launch time so vents make a lot of sense on all sailboats.

Newer packings can be pretty darn drips-less but should not be 100% dripless. it can be so minimal that engine warmth evaporates any drips before it accumulates.

Unfortunately I can't count the number of times an owner or yard mechanic has said to me "Yeah when I adjusted the PSS." and I ask "Did you replace the set screws?" and am treated with a blank stare? Scary stuff!

If a failure were to occur with a slipping rotor, in this scenario, it is installer error not the fault of PYI or the PSS seal.

I also very often see the vent holes plugged with brass or ss plugs. The vents should always be plumbed (power) or vented/used on sailboats. Metallic plugs should never, ever be used in the carbon rotor. There is a reason PYI uses a nylon hose barb and that is because the carbon is the most noble element in the galvanic scale and the differing expansion contraction characteristics between brass or SS and the carbon...

PYI says this in the instructions but many people choose not to read or heed them:

"Do not tighten or replace the installed nylon hose barb fitting with a metallic fitting (bronze or stainless steel). Metal hose barbs will damage the carbon and destroy the PSS."

Again, this type of failure, overheating of the seal, dissimilar metals corrosion or a split carbon would clearly get blamed on the PSS seal. Sadly on the "net" PSS takes the hit not the dolt who caused the failure by not following the installation instructions. These are examples of installer error not a failure on the part of the seal. I see the metallic plugs and set screw errors frequently.
Another outstanding post. I was curious your thoughts. Thanks.

B
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  #29  
Old 08-31-2012
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Re: Dripless Shaft Seal versus Stuffing Box

Quote:
Originally Posted by Cruisingdad View Post
Another outstanding post. I was curious your thoughts. Thanks.

B
I got your PM but we were off cruising with limited "fast" data....
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Old 08-31-2012
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Re: Dripless Shaft Seal versus Stuffing Box

I was so excited to hear from the broker(friend of the owner) when we bought the boat last Spring, "and hey, you've got a dripless shaft seal to go along with that fancy feathering prop". Now I'm not so sure.. I guess I gotta add it to fall maintenance.
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