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Go Back   SailNet Community > On Board > Gear & Maintenance > Dripless vs Flax Stuffing Boxes
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Thread: Dripless vs Flax Stuffing Boxes Reply to Thread
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Topic Review (Newest First)
11-07-2009 08:31 PM
BELLATRIX1965
Flushing line

Mine is rigged with a "flushing" line that is teed into my raw water pump discharge. This is a common arrangement in industrial mechanical seal set-ups (lots of seawater pumps on ships are set up this way). The flushing water constantly cleans and lubricates the faces of the seal - never a problem with mine. Just be aware that this small (3/8"?) line will leak seawater back into the boat if disconnected!

***Also, PSS recommends renewal of the bellows every 6 years, no matter what it looks like. This is due to the characteristic of all elastomers (rubber or otherwise) to continue curing over time. Think about the nasty, cracked hose that you replaced in the engine room when you first bought the boat. . .

Seals are great if properly maintained (yeah, like everything else!) and they will not fret the shaft like packed stuffing boxes will - regardless of the type of packing. Shop before you buy - some of the well-advertized retailers charge a fair amount more for the PSS seals than what you will find them for elsewhere.
11-06-2009 07:01 AM
rk6johnson What is the best procedure for "Burping" a dripless system? The one on my Catalina 350 recently leaked and maybe that is the problem (gets cleaned by diver each month). Any other maintenance needed on them? Should the seal be flushed periodically?
11-06-2009 07:00 AM
rk6johnson What is the best procedure for "Burping" a dripless system? The one on my Catalina 350 recently leaked and maybe that is the problem (gets cleaned by diver each month). Any other maintenance needed on them? Should the seal be fluched periodically?
09-26-2009 10:56 AM
Sabreman A clarification - if the vent hose is open at the top as it should be, then burping is not needed. This is why PSS started using them for all their applications regardless of shaft speed. On our last boat, one without the vent hose, I would not allow a yard to launch our boat without me being present to make sure that the seal was burped. There were many other reasons why I wanted to be there at launching, but keeping my shaft from burning up was definitely one of them! I was very glad when I found out that PSS made the vent universal.
09-23-2009 02:59 PM
tommays As far as burping the vent hose is a MUST as i know somebody who got air in theres form the divers air tanks when cleaning the bottom
09-23-2009 02:26 PM
Valiente No, that's not far-fetched. I put a simple ABUS hose clamp between the coupler and the stuffing box on my Viking 33, plus a second one between the cutlass bearing and the hull. Shafts spinning out happen more often than people admit. My wife did a delivery in June where the shaft actually BROKE about an inch aft of the coupler...a clamp forward of the cutlass bearing kept it in the boat, and the water (mostly) out.

As they were offshore at the time, this was a good thing.
09-23-2009 02:07 PM
Sabreman Rich - A clarification.

Shaft seals are self adjusting by their nature so they will not need to be adjusted once installed. Once the collar goes on and is locked, it's not going anywhere. We've never had to perform any adjustment in 20 years.

PSS no longer sells seals that need burping. They all come with a 3' hose that is led above the waterline. I was initially disconcerted to have an open hose in my engine compartment, but quickly realized that if I simply led it straight up and attached it to the underside of the cockpit floor, there would be no problem. Of course, I could take the hose off requiring burping, which is ok too. Do it once when the boat goes in the water and that's it.

One advantage to a shaft seal - you can't lose your shaft! I saw it happen once and the boat nearly sunk at the dock. The owner had engine work done and the mechanic forgot to tighten the coupling bolts. Slid right out the stuffing box when the engine was put into reverse. The collar on a seal would have prevented that. Pretty far fetched, but true!
09-23-2009 01:24 PM
justified I have a PSS shaft seal on both of my Newports. the 28' had one installed twenty yrs ago and it still is drip free. you do need to check that the clamps are tightened but other than that happy drip free sailing.
09-23-2009 01:21 PM
RichH The traditional STUFFING BOX
Cons: needs periodic adjustment, needs smooth shaft surface to work well (no burrs, no galling or anyother shaft surface irregularities). Shaft should be removed and 'dressed' by a machinist when replacing packing.
Pros: can be packed (temporarily) with virtually any 'lubricated rope' that fits when in a dire emergency ... and still affect a 'seal' with the propshaft turning.
Inexpensive to operate. Technology is over 200 years old; therefore, quite reliable. Easy DIY changeout of packing.
Better pros: can be packed with braided PTFE (Gore-tex) for 'virtually dripless' operation.
Cheap, even when using GFO packing.
Virtually Dripless Packing by Gore GFO


SHAFT SEAL .....
Cons: CANNOT be fixed/adjusted while underway. If it fails while underway, you usually must stop the leak by 'draconian methods' ... and that all stop the shaft seal from working thus you cant use the engine. Those that have 'auxiliary' water cooling need to be 'occasionally burped' - installation of the high-speed seal requires careful 'precision'.
Expensive
Pros: dry bilge.
09-23-2009 01:11 PM
Sabreman We replaced the traditional stuffing box on both our Sabres with a PSS shaft seal. It's what Sabre installs on their new boats. While the issues that others in this thread raise are valid, they are of low likelihood. We have never had an issue with our PSS, I check the bellows regularly, and made sure that the area around it was clear (should be anyway since there is a spinning shaft). Besides being dripless, another benefit of shaft seals is that they reduce the effects of minor engine misalignment since there are only two points holding the shaft vs. three with a stuffing box. The effect is increased cutlass bearing longevity. I don't plan to go back to stuffing boxes; if shaft seals are good enough for the Navy, that's good enough for me! IMHO, stuffing boxes are more worrisome because you always have to keep after that drip, and I HATE leaks of any sort!

I describe the benefits and process to install the shaft seal in the following two links:
http://www.sailnet.com/forums/gear-m...ffing-box.html
http://www.sailnet.com/forums/gear-m...nder-33-a.html

BTW, I agree with others that flax in a traditional stuffing box should be avoided. Use the synthetic stuff. Flax is the traditional material because they didn't have anything better in the old days.
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