Is anyone aware of any data that compares frictionl losses of the P.S.S. system with the frictional losses of the conventional stuffing box/flax packing? I have read some of the past forums on the P.S.S. but most deal with the dripless feature. Although this is a good feature, I would consider using this system if it has other benefits besides just the dripless, no leak performance that everyone craves about. I have used the Syntef Drip-Less packing system which also results in less water coming into the boat, but I have no idea of what the frictional losses are of either system. The Syntef system indicates that it should not be used in systems where the shaft speed results in a 900 FPM speed. (FPM not RPM) The 3GM engine with the 2.61 transmission reduction gear would result in a shaft FPM of 300 at an engine speed of 3000 rpm, which is 3 times below the recommended upper limit. Is there an upper shaft speed limit specification for the P.S.S. system? I am still looking for sources for additional loading on my 3GMD engine at the higher rpms and have not seen any reference to power losses from the shaft seal vs rpm. Would appreciate any comments/suggestions on this. Thanks, Ernie H-36
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Very Little Friction
Ernie, I don't have any figures, but the force/friction of a soft rubber bellows compressed 3/4" of its possible 3" with a wet graphite bearing pressing on a mirror polished SS collar would be so little that it would be negligable on my PSS. I think it would be less than the original or any special packing if only because it doesn't need adjustment as often and the bellows has give for irregularities. As for the high speed PSS makes a motorboat model with water injection. Stan "Christy Leigh" c320 #656
Ernie, I don't have any figures, but the force/friction of a soft rubber bellows compressed 3/4" of its possible 3" with a wet graphite bearing pressing on a mirror polished SS collar would be so little that it would be negligable on my PSS. I think it would be less than the original or any special packing if only because it doesn't need adjustment as often and the bellows has give for irregularities. As for the high speed PSS makes a motorboat model with water injection. Stan "Christy Leigh" c320 #656
Red Hot!
Ernie, If there were any significant frictional losses in shaft seals they would become extremely hot. In use most seals might just become slightly warm to the touch - indeed if they get hotter there must be something wrong. As far as loss of power from the engine, it is negligible. When the engine is stopped you should be able to turn the shaft by hand without too much resistance.
Ernie, If there were any significant frictional losses in shaft seals they would become extremely hot. In use most seals might just become slightly warm to the touch - indeed if they get hotter there must be something wrong. As far as loss of power from the engine, it is negligible. When the engine is stopped you should be able to turn the shaft by hand without too much resistance.
PSS Failure mode
So, I will assume that one of the failure modes of the PSS dripless system is the failure of the rubber bellows, which will result in a dramatic ingress of water. 1. True? 2. Can the bellows be repaired/replaced from insie the boat? How? 3. What emergency procedures are effective? Thanks, jv
So, I will assume that one of the failure modes of the PSS dripless system is the failure of the rubber bellows, which will result in a dramatic ingress of water. 1. True? 2. Can the bellows be repaired/replaced from insie the boat? How? 3. What emergency procedures are effective? Thanks, jv
Response to John Visser
Answer to John Visser re possible bellows failure ORIGINAL COMMENT: So, I will assume that one of the failure modes of the PSS dripless system is the failure of the rubber bellows, which will result in a dramatic ingress of water. 1. True? ANSWER: Essentially, No. Probably less than the probability of failure of a hose on your Yanmar engine. The PSS bellows on my boat appears to be made of thicker material than the engine hoses and appears to have more reinforcing material. The bellows hose is better built than most hoses from a sink to a seacock. This has been discussed before in this forum and I don't recall anyone saying their bellows failed so that represents a lot of users so I personally don't think this is a matter of concern but then everybody has a different threshold of what they consider prudent. My bellows is about 13 years old now. 2. Can the bellows be repaired/replaced from insie the boat? How? ANSWER: The standard method is to do this work with the boat out of the water. It's possible to do it with the boat in the water but that depends on how savey one is with hands-on work and what risk you would accept and if you panic easily. I helped a friend replace a below-the-water seacock on his C&C 36 while in the water and there was no problem. I could change the bellows, too, if necessary but in 13 years of use there has never been an opportunity to do so. "How?": Remove the coupler and PSS ring then slide the old bellows off. Plug the gap with a rag each time but realize some water will come in. Reverse the procedure to install the new bellows. 3. What emergency procedures are effective? ANSWER: Stuff the hole or wrap the bellows with a rag and call a mechanic.
Answer to John Visser re possible bellows failure ORIGINAL COMMENT: So, I will assume that one of the failure modes of the PSS dripless system is the failure of the rubber bellows, which will result in a dramatic ingress of water. 1. True? ANSWER: Essentially, No. Probably less than the probability of failure of a hose on your Yanmar engine. The PSS bellows on my boat appears to be made of thicker material than the engine hoses and appears to have more reinforcing material. The bellows hose is better built than most hoses from a sink to a seacock. This has been discussed before in this forum and I don't recall anyone saying their bellows failed so that represents a lot of users so I personally don't think this is a matter of concern but then everybody has a different threshold of what they consider prudent. My bellows is about 13 years old now. 2. Can the bellows be repaired/replaced from insie the boat? How? ANSWER: The standard method is to do this work with the boat out of the water. It's possible to do it with the boat in the water but that depends on how savey one is with hands-on work and what risk you would accept and if you panic easily. I helped a friend replace a below-the-water seacock on his C&C 36 while in the water and there was no problem. I could change the bellows, too, if necessary but in 13 years of use there has never been an opportunity to do so. "How?": Remove the coupler and PSS ring then slide the old bellows off. Plug the gap with a rag each time but realize some water will come in. Reverse the procedure to install the new bellows. 3. What emergency procedures are effective? ANSWER: Stuff the hole or wrap the bellows with a rag and call a mechanic.
John Nantz, I have heard of 1 PSS bellows failure
it happened after a diver was cleaning the boat and the presumption is that it got air in the shaft seal (They didn't think about "burping the seal again to get water back up there). They ran the engine and shut the boat down and suspected that the stainless steel collar got very hot due to no water cooling & "fused" to composite on the bellows and later (next day?) when they went to put the boat in gear it just ripped the bellows open. They were at the marina so luckily they hailed the people and they got a lift to haul the boat. It was a very large ingress of water and they noted that there would have been no way for thier bilge pumps to keep up or and they really did try and stuff/wrap the bellows. They thought of what might have happened if it was farther away from a marina facilites and he said it makes him shiver. I agree that the hose material on the PSS is exceptionally high quality and is much better built than most hoses from a sink to a seacock. But that's just it. On the hoses on your boat you have a seacock, but there is no seacock for your Shaft. Can the bellows be repaired/replaced from inside the boat?.....I guess anything is possible but would REALLY not want to try and do this I think most people don't realize how much water would be coming in that stern tube when the bellows is off. I would think the best way is to use some "plumbers toilet bowl wax" on the outside of the hull and plug it in where the shaft enters and then CAREFULL uncouple the shaft from the transmission (thats if you can even undo the bolts and shaft!!!). Extreem care must be taken not to loose the shaft and propeller into the deep blue sea (I guess somebody might need to be in the water just in case)....All this really depends on your boat and the stern log and all the geometry , e.g. long shaft, etc, etc.... With that said I had a PSS Shaft seal on my old boat for 6-7 years and it worked very well. The only problem I had (which scared me until I figured out what was wrong) was that over the years the dual set screws (grub screws) in the stainless collar must have worked loose and due to vibration the collar "shimmy"ed up the shaft and cause a sized leak. Very easy to fix.....just slid the colar back back and retight (and "locktight"en) the set screws.
it happened after a diver was cleaning the boat and the presumption is that it got air in the shaft seal (They didn't think about "burping the seal again to get water back up there). They ran the engine and shut the boat down and suspected that the stainless steel collar got very hot due to no water cooling & "fused" to composite on the bellows and later (next day?) when they went to put the boat in gear it just ripped the bellows open. They were at the marina so luckily they hailed the people and they got a lift to haul the boat. It was a very large ingress of water and they noted that there would have been no way for thier bilge pumps to keep up or and they really did try and stuff/wrap the bellows. They thought of what might have happened if it was farther away from a marina facilites and he said it makes him shiver. I agree that the hose material on the PSS is exceptionally high quality and is much better built than most hoses from a sink to a seacock. But that's just it. On the hoses on your boat you have a seacock, but there is no seacock for your Shaft. Can the bellows be repaired/replaced from inside the boat?.....I guess anything is possible but would REALLY not want to try and do this I think most people don't realize how much water would be coming in that stern tube when the bellows is off. I would think the best way is to use some "plumbers toilet bowl wax" on the outside of the hull and plug it in where the shaft enters and then CAREFULL uncouple the shaft from the transmission (thats if you can even undo the bolts and shaft!!!). Extreem care must be taken not to loose the shaft and propeller into the deep blue sea (I guess somebody might need to be in the water just in case)....All this really depends on your boat and the stern log and all the geometry , e.g. long shaft, etc, etc.... With that said I had a PSS Shaft seal on my old boat for 6-7 years and it worked very well. The only problem I had (which scared me until I figured out what was wrong) was that over the years the dual set screws (grub screws) in the stainless collar must have worked loose and due to vibration the collar "shimmy"ed up the shaft and cause a sized leak. Very easy to fix.....just slid the colar back back and retight (and "locktight"en) the set screws.
Now we're getting somewhere!
Thank you John and thank you Tom, I would like to say that I am sincerely interested, w=from a technical perspective, in the failure modes. This has nothing to do with rationalizing a decision I may have made, or knocking someone else's decision or product. I just want to know what would happen if it DID fail, and what could be done about it. John makes an interesting observation - that his has held up well for 13 years. Good testimony. It brongs up another quesotn - what is the service life of the bellow? Is there a recommended maximum service life? I was wondering - has anyone installed, or is it possible to install, a PSS unit AND left the ordinary packing gland in place? I was thinking the old thing could be slackened to reduce friction, and left as a backup in case the bellows let go. I don't know if this is possible. jv
Thank you John and thank you Tom, I would like to say that I am sincerely interested, w=from a technical perspective, in the failure modes. This has nothing to do with rationalizing a decision I may have made, or knocking someone else's decision or product. I just want to know what would happen if it DID fail, and what could be done about it. John makes an interesting observation - that his has held up well for 13 years. Good testimony. It brongs up another quesotn - what is the service life of the bellow? Is there a recommended maximum service life? I was wondering - has anyone installed, or is it possible to install, a PSS unit AND left the ordinary packing gland in place? I was thinking the old thing could be slackened to reduce friction, and left as a backup in case the bellows let go. I don't know if this is possible. jv
By the way, John Nantz, ...
you're really no tanswering the queastions. The engine hose and the seacock have nothing much to do with this. Answer 3 - yes, call a mechanic when you're half way to Bermuda; I'm not really concerned about this failing while I'm sitting at the dock. What could you do if you were offshore? I would be concerned that if I had to disconnect the coupling that if I lost control of the shaft it could slide back and jam my rudder.
you're really no tanswering the queastions. The engine hose and the seacock have nothing much to do with this. Answer 3 - yes, call a mechanic when you're half way to Bermuda; I'm not really concerned about this failing while I'm sitting at the dock. What could you do if you were offshore? I would be concerned that if I had to disconnect the coupling that if I lost control of the shaft it could slide back and jam my rudder.
John V..some of my observations to your questions
"is it possible to install, a PSS unit AND left the ordinary packing gland in place?" Gosh ...I *guess* you could..IF there was an extra 6 inches space between the existing Packing Gland and the Transmission coupling .. Which is very rare on most sailboat's I have ever seen.....typically it is very tight between the back of the engine and where the shaft exits. And THEN you have feel VERY confident that the PSS bellows attaches to the packing gland very securely. AND THEN you have to ENSURE that there is ample water flow through the existing packing gland to cool the PSS shaft seal (or you will increase the likelyhood of failure!)......I wouldn't do it!!..what a KLUGE and I would never even contemplate doing it.. 2nd question---- What could you do if you were offshore? ".....Like I said before. Go to your local hardware store and purchase some "plumbers toilet bowl wax" . IF (and a VERY BIG IF) there was a catastrophic failure then I would just cut away the rubber bellow and pack alot of this wax to stem the leak (And don't run your engine again)...and Then I would SAIL the boat into the closest port (well it IS a SAILBOAT) people do that ALL the time. Question really is....would I feel comforatble sailing my boat on the Ocean with a PSS dripless system.... YES...anything can fail but I beleive this is one of the less likely items and with keeping on eye on things you wont have a problem. Many high end boats and manufacturers use this system......if your super conservative then go by some GORE dripless flax packing material (I wonder what Kevin from PSS has to say about EVER hearing about a PSS failure)
"is it possible to install, a PSS unit AND left the ordinary packing gland in place?" Gosh ...I *guess* you could..IF there was an extra 6 inches space between the existing Packing Gland and the Transmission coupling .. Which is very rare on most sailboat's I have ever seen.....typically it is very tight between the back of the engine and where the shaft exits. And THEN you have feel VERY confident that the PSS bellows attaches to the packing gland very securely. AND THEN you have to ENSURE that there is ample water flow through the existing packing gland to cool the PSS shaft seal (or you will increase the likelyhood of failure!)......I wouldn't do it!!..what a KLUGE and I would never even contemplate doing it.. 2nd question---- What could you do if you were offshore? ".....Like I said before. Go to your local hardware store and purchase some "plumbers toilet bowl wax" . IF (and a VERY BIG IF) there was a catastrophic failure then I would just cut away the rubber bellow and pack alot of this wax to stem the leak (And don't run your engine again)...and Then I would SAIL the boat into the closest port (well it IS a SAILBOAT) people do that ALL the time. Question really is....would I feel comforatble sailing my boat on the Ocean with a PSS dripless system.... YES...anything can fail but I beleive this is one of the less likely items and with keeping on eye on things you wont have a problem. Many high end boats and manufacturers use this system......if your super conservative then go by some GORE dripless flax packing material (I wonder what Kevin from PSS has to say about EVER hearing about a PSS failure)
Wax seal
I am certainly going to get a coupl eof those wax toilet rings - I'd never heard of that before, adn it sound slike an excellent material. I think this has been a very useful discussion, thanks to all. jv
I am certainly going to get a coupl eof those wax toilet rings - I'd never heard of that before, adn it sound slike an excellent material. I think this has been a very useful discussion, thanks to all. jv
What I learned....
1. If someone has measured the frictional losses of either the PSS system or the conventional stuffing box system, the data is not readily available. 2. In either system there is some heat generated by the frictional losses and this heat is removed by the water. Lack of water in either system can be a severe problem in either case. Lack of water to remove the heat and lubricate the seal can be caused by air entrapment in the PSS system, and overtightening in the case of the conventiional stuffing box. One reported case of lack of water from air entrapment in the PSS caused considerable damage to the PSS system from the heat generated. 3. Either system could have a failure of the bellows or the hose,leading to lots of water leaking in for which the bilge pump may not be able to handle. 4. Both systems place a rotational torque load on the hose or bellows from the friction at the seal. In the case of the PSS system the friction occurs between the stainless steel collar and the carbon face. In the case of the conventional stuffing box, the friction occurs between the prop shaft o.d. and the packing material. If I could measure this amount of torque while underway, I would have some idea of how much horsepower is being consumed in the seal. All I need to figure out is how to measure this torque. Maybe a small fish scale may come in handy. Thanks to everyone who responded to this question. I have learned quite a bit from the ensuing discussion. For the time being, not seeing a big advantage with the PSS type of seal in terms of frictional losses, I will stay with the conventional stuffing box and use the teflon lub. Happy motoring, Ernie
1. If someone has measured the frictional losses of either the PSS system or the conventional stuffing box system, the data is not readily available. 2. In either system there is some heat generated by the frictional losses and this heat is removed by the water. Lack of water in either system can be a severe problem in either case. Lack of water to remove the heat and lubricate the seal can be caused by air entrapment in the PSS system, and overtightening in the case of the conventiional stuffing box. One reported case of lack of water from air entrapment in the PSS caused considerable damage to the PSS system from the heat generated. 3. Either system could have a failure of the bellows or the hose,leading to lots of water leaking in for which the bilge pump may not be able to handle. 4. Both systems place a rotational torque load on the hose or bellows from the friction at the seal. In the case of the PSS system the friction occurs between the stainless steel collar and the carbon face. In the case of the conventional stuffing box, the friction occurs between the prop shaft o.d. and the packing material. If I could measure this amount of torque while underway, I would have some idea of how much horsepower is being consumed in the seal. All I need to figure out is how to measure this torque. Maybe a small fish scale may come in handy. Thanks to everyone who responded to this question. I have learned quite a bit from the ensuing discussion. For the time being, not seeing a big advantage with the PSS type of seal in terms of frictional losses, I will stay with the conventional stuffing box and use the teflon lub. Happy motoring, Ernie
Thanks Tom - Quick on the Feet
Thanks for your reply, Tom, about the bellows failure. I've been on this site for several years and never heard anyone say anything about a problem so it is theoretically possible. Guess I was starting to get worn out about providing detailed answers to possible problems which are a remote possibility. I've had my share of problems with mechanical failures and the like over the years but have always managed to come up with a fix, permanent or short term. If I had to write a manual for every conceivable situation I'd never make it to the boat! When our boat was new, or maybe a couple months old, we were sailing along nicely and my wife asked why there was water coming out of the side of the boat. !!! It was a hose to the engine and I had practically no tools on board. Found the problem and fixed it - improvised. Had water up to the cabin sole. Wasn't supposed to happen but it did. Checked all the hose clamps and found several that needed additional tightning. On a boat - things happen. If a person wants to enjoy boating or cross oceans it helps to be quick on the feet sometimes and the ability to improvise is very helpful.
Thanks for your reply, Tom, about the bellows failure. I've been on this site for several years and never heard anyone say anything about a problem so it is theoretically possible. Guess I was starting to get worn out about providing detailed answers to possible problems which are a remote possibility. I've had my share of problems with mechanical failures and the like over the years but have always managed to come up with a fix, permanent or short term. If I had to write a manual for every conceivable situation I'd never make it to the boat! When our boat was new, or maybe a couple months old, we were sailing along nicely and my wife asked why there was water coming out of the side of the boat. !!! It was a hose to the engine and I had practically no tools on board. Found the problem and fixed it - improvised. Had water up to the cabin sole. Wasn't supposed to happen but it did. Checked all the hose clamps and found several that needed additional tightning. On a boat - things happen. If a person wants to enjoy boating or cross oceans it helps to be quick on the feet sometimes and the ability to improvise is very helpful.
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