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-   -   Dripless Shaft Seal versus Stuffing Box (http://www.sailnet.com/forums/gear-maintenance/91194-dripless-shaft-seal-versus-stuffing-box.html)

Cruisingdad 08-21-2012 12:52 PM

Dripless Shaft Seal versus Stuffing Box
 
I took a tour of the Catalina facility last week. Really enjoyed meeting the folks and was shocked at the systems they have in place there. For those that have not see it (catalina lover or not), it is interesting - especially when compared to something like Valiant which only put out 8-12 boats/year.

Anyways, Catalina has moved away from the dripless shaft seals. My previous boats (320 and 380) had a traditional stuffing box but my C400 has a dripless. all the new vessels out of Catalina are back to a traditional stuffing box.

I inquired with them about this and they responded that effectively they changed because a stuffing box gives some warnings before going out and is not necessarily a big deal when it does. However, the dripless may fail with little notice and can become a, "water hose" down below.

I thought about that, and I tend to agree with them. I saw another Catalina 400 when I had my boat pulled and the yard owner told me the 400 had an emergency pull becuase their dripless failed and threatened the boat.

On the flip side, keeping a dry boat sure has its advantages too. Sure makes tracking down any potential leaks easier.

I am curious what others think about this? Opinions?

Brian

tommays 08-21-2012 01:04 PM

Re: Dripless Shaft Seal versus Stuffing Box
 
I use the wonder packing :) and it gets wet BUT it does not really drip faster than it can evaporate from all the motor heat

BUT even a small drip would go to the small deep part of my bilge that has a big capacity BUT with the pump i installed there is never even a gallon of water in the boat

The REAL issues i see are boats like a C&C 35 Mark I that literally do not have ANY bilge

casey1999 08-21-2012 01:41 PM

Re: Dripless Shaft Seal versus Stuffing Box
 
I cannot imagine why anyone would install a Dripless Shaft seal. Why install somthing on your boat that could fail at any moment and sink your boat? I thought about installing one until a friend whom has one tells me how rapidly they can fail. Dripless not for me.

CalebD 08-21-2012 01:42 PM

Re: Dripless Shaft Seal versus Stuffing Box
 
Think about it it like this.
It is probably cheaper for Catalina to go with the traditional stuffing box then a dripless shaft seal. The traditional stuffing box gradually exhibits failure mode as more water gets in as packing wears away. (New packing is < $20) If the Dripless Shaft Seal rubber bellows ever cracks, rips or otherwise fails you may need a haul out and a new bellows.
I'm with Catalina on this one. The traditional stuffing box is a tried and true, hundred+ year old technology. Using this method saves them money and makes their boats a little bit safer. It is a no brainer.

PBzeer 08-21-2012 01:49 PM

Re: Dripless Shaft Seal versus Stuffing Box
 
My boat came with a dripless shaft seal. I've had no problems with it.

casey1999 08-21-2012 01:50 PM

Re: Dripless Shaft Seal versus Stuffing Box
 
Quote:

Originally Posted by PBzeer (Post 912532)
My boat came with a dripless shaft seal. I've had no problems with it.

Until you boat sinks...

jameswilson29 08-21-2012 01:52 PM

Re: Dripless Shaft Seal versus Stuffing Box
 
Are there any statistics supporting the assertion that a traditional stuffing box is safer than a dripless shaft seal (DSS)?

I would think the insurance companies would consider a DSS an additional risk factor and increase the premium if this were true, especially if its failure results in a total loss.

I have read and heard merely anecdotal evidence of DSSs failing, including an article in Boat/US magazine. A DSS is a moving part, which needs periodic inspection and replacement in due time (10 years?).

I am not surprised that a production builder would use a less expensive traditional part based on an unsubstantiated belief among buyers.

casey1999 08-21-2012 02:16 PM

Re: Dripless Shaft Seal versus Stuffing Box
 
Quote:

Originally Posted by jameswilson29 (Post 912534)
Are there any statistics supporting the assertion that a traditional stuffing box is safer than a dripless shaft seal (DSS)?

I would think the insurance companies would consider a DSS an additional risk factor and increase the premium if this were true, especially if its failure results in a total loss.

I have read and heard merely anecdotal evidence of DSSs failing, including an article in Boat/US magazine. A DSS is a moving part, which needs periodic inspection and replacement in due time (10 years?).

I am not surprised that a production builder would use a less expensive traditional part based on an unsubstantiated belief among buyers.

I am not sure on the statistics. But I hear a lot of bad things:
Emergency advise needed on a leaking pss dripless shaft seal ! [Archive] - Boat Repair Forum, Classifieds & Photo Gallery

I do not think insurace companies get that involved with how you boat is made, although maybe they should. Insuranace companies do not care if you use plastic through hulls or chinese carbon steel chain for you anchor rode. Like your car they do not raise your rates because your SUV has tires on it that have been recalled and are known to blow out at highway speeds. Buyer beware.

jrd22 08-21-2012 03:28 PM

Re: Dripless Shaft Seal versus Stuffing Box
 
I've had both. From my perspective I can't see a lot of difference as far as risk to the boat goes. The stuffing box uses a piece of heavy duty hose to hold the packing gland and there is arguably more torque on that hose from the friction of the packing than from the carbon block sliding on the stainless ring of a dripless type. Which is more likely to rip or tear and create a large leak? How often do you change that hose, I'm guessing most people have never changed it or even thought about the torque put on it. Dripless types recommend that the bellows (which is very thick and heavy duty) be changed every 8-10 years IIRC and that includes the hose clamps, and I just can't see one failing in that short amount of time. Another aspect is shaft wear, not a safety issue, but an expense over time from wear at the packing. There is no wear on the shaft of the dripless type. I'm not convinced that there is a big difference either way from a safety perspective but if there were any statistics that compared failures of the two types I'd be interested to see them.

eherlihy 08-21-2012 03:44 PM

Re: Dripless Shaft Seal versus Stuffing Box
 
I believe that jrd22 hit the nails on the head. Less wear & tear on the shaft is a major positive attribute of a dripless system.

I swapped my stuffing box over to a PSS dripless last year. I was impressed by the quality of the components, and the statement that most PWCs use them (anything that can survive a PWC is a good thing). I was, however shocked at the price, and the fact that the recommended replacement interval is 6 years, although I believe that they could run for 10.

Quote:

As with any rubber hose below waterline, the PSS bellows must be inspected on a regular basis for any sign of wear, aging or chemical deterioration. PYI suggests preventative maintenance. The PSS bellow should be replaced in six year intervals. During bellows replacement it is recommended the o-rings & set screws in the stainless steel rotor also be replaced.

Bellows may need to be more frequently inspected in an environment where non-sealed batteries emit sulfuric acid. Sulfuric acid vapor will accelerate rubber deterioration, as will an ozonater.
Ever since replacement I have had NOT A DROP of water in the bilge.


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