shaft gland

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robertj

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following a recent prob with my stern gland i am changing from the stuffing box type to a deep seal type.

there are a few on the market and wish to know the forums views on various deep sea seals volvo/pss etc?

bob
 
If you can fit a Volvo shaft seal then do - everyone says they are great and reasonably priced. If yoy dry out they need "burping" afterwards but if afloat then apply special grease once a year and forget.

There are limits of sizing in respect of stern tude and prop shaft - unforunately I couldn't fit one and went for a Tides Marine shaft seal which has been great. They are chunky self-aligning jobbies that do not rely on faces mating like the PSS. Worth every penny to get away from drippy greasers.

It does have to have a water feed to lubricate it but no servicing required.

shaftseal.jpg
 
stern seal

moodysabre,

can i ask the cost of your set up and where does the water feed come from?

bob
 
Be careful what you choose. There is no such thing as a "Deep Sea" type. That is a specific design.

There are two main types. Those that rely on lip seals such as the Volvo and the Tides Marine as in Moodysabre's post. If you can fit it, the Volvo seal is probably the preferred choice - it is used by most major boat builders who use shafts because it is simple cheap and reliable. If lip seals wear they do so slowly and give plenty of warning through drips when they need replacing. They will not fail catastrophically.

The alternative designs use mechanical face seals that don't actually seal the shaft but seal the housing around the shaft by pressure of a bellows. These are potentially less secure for a variety of reasons and in the case of the Deep Sea seal an "emergency" clamping mechanism is provided to lock them when the seal fails. Does not inspire confidence from my point of view.
 
robertj said:
moodysabre,

can i ask the cost of your set up and where does the water feed come from?

bob
Click to expand...


Two years ago it was about £120. There is a large selection of size variations as shown on their website. There is a UK supplier.

For the water feed I put a T in the raw water intake after the pump. I used brass hydraulic fittings and car rad hose. There has to be a specific rate of flow and to control this I put a jubilee clip on the feed hose and tightened it up until the flow was the rate recommended. This hasn't affected the engine cooling.

In practice I had to make a loop in the intake and T off that as there wasn't room for it straight in line.
 
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This is my cue.
Do not dismiss the PSS seal. Simple, elegant, requires no maintenance and can be used on a drying mooring as it needs no "burping" when launched. They are expensive. In a recent Yahcting Monthly top guru Nigel Calder called it his favourite modern seal, a sort of seal of approval he he.
 
The PSS seal relies upon a carbon face almost in contact with a stainless steel one, separated by a thin film of water. The small loading pressure required is provided by a rubber bellows. This is exactly the same technology as is used in mechanical seals in millions of industrial pumps throughout the world, (including your car coolant pump, washing machine, central heating, etc) where it has completely supplanted the old packed gland type of seal. My PSS seal is perfectly reliable, needs no burping or anything else and never drops even a drip of water. I see no reason why they should be 'less secure for a variety of reasons'.

By contrast, the Volvo is a lip seal type that enjoys less than perfect reliability in automotive crankshaft seals, raw water pumps, etc. I'm not saying that Volvo shaft seals are unreliable as there is loads of evidence that they are not. But let's have an unbiased view.
 
I changed from a Volvo seal because I dry out, and it is a complete faff to lift all the aft cabin matress and stuff to burp it.

So I went for the Tides marine seal as MoodySabre.

It works very well, but......

You must be careful to route the siphon loop to the height of your raw water strainer, or it siphons the water out of the strainer and prevents raw water being sucked into the system on engine startup.

I agree with MoodySabre that you need to regulate the flow with a jubilee clip on the small bore pipe, as it is drawn from a spigot on the pump, and therefore before the water has been through the engine. Too much flow through the small bore will starve the engine of cooling water, with the inevitable consequence.

In my case, I ran the engine flat out, and it sounded the alarm after 30 minutes. Small tweak on the flow jubilee clip - problem solved.

Tides marine seal well worth the money.

Volvo seals have been known to do thousands of engine hours if the shaft is in peerfect condition with no abrading areas of corrosion or similar.
 
Why Not Have Your Stuffing Box Refurbished

I have found stuffing boxes to be quite reliable. Could you have it refurbished?I had mine refurbished last year, works a treat. Took a wee while to bed in and leaked more than normal for the first few hours of use. Now turn down greaser before I leave the boat and every 10 hours of use.
 
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Just done the same, had a deep sea seal with no history of age, it never leaked but i decided to change it for peace of mind..
In the end i went for a PSS, very like the DSS but imo better made.
For simplicity and after reading post on hear I tried to get a volvo seal but my shaft & log sizes were not available.........

Before - the old Deep Sea
IMG_0007.jpg

After - the new PSS
IMG_0004.jpg
 
I am looking to replace the packing in my stuffing box while the boat is out this winter. I have read from time to time about "dripless" packing material being available- I think using Goretex or Teflon? Anyone tried this material?
 
I've had a series of lip seal type seals and on the latest boat have a Volvo one. It works well but has a life of about 5 / 7 years and so a cost of £10 / 15 pa. It requires burping if on a drying mooring. By comparison the previous seals with an oil reservoir cost very little for the three lip seals to be replaced from an industrial supply shop.

I'll be trying the Tides marine one next time round. No way would I go for the old style stuffing box - they went out with the ark in industry.
 
I'd suggest

Your PSS bellows is to tightly compressed.

If you read the supporting instructions they give you very specific dimensions for the bellows-compression.

After 12 years, I've just fitted a replacement bellows (though PSS in the US recommend changing every 7 years).
 
charles_reed said:
Your PSS bellows is to tightly compressed.
Click to expand...

I'll check it again but i'm sure its is as per the instructions.
I must admit it does look over compressed....:confused:

I have just checked, 1 1/4 inch shaft which is 1 inch compression from the neutral position according to the compression chart.
So it is right.......
 
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vyv_cox said:
The PSS seal relies upon a carbon face almost in contact with a stainless steel one, separated by a thin film of water. The small loading pressure required is provided by a rubber bellows. This is exactly the same technology as is used in mechanical seals in millions of industrial pumps throughout the world, (including your car coolant pump, washing machine, central heating, etc) where it has completely supplanted the old packed gland type of seal. My PSS seal is perfectly reliable, needs no burping or anything else and never drops even a drip of water. I see no reason why they should be 'less secure for a variety of reasons'.

By contrast, the Volvo is a lip seal type that enjoys less than perfect reliability in automotive crankshaft seals, raw water pumps, etc. I'm not saying that Volvo shaft seals are unreliable as there is loads of evidence that they are not. But let's have an unbiased view.
Click to expand...

The last time this subject came up here there were two well documented cases (at least if you believe the poster) of this type of seal failing. In one case the faces stuck together with deposits and in the second a piece of wood floating on bilge water jammed between the faces. In the first case just after launching when the engine was put in gear, the bellows tore and in the second, again after launching water entered through the gap between the faces without the owner realising. In yet another thread a couple of years ago there was a photo of a 45 ft Hunter in Florida for sale as a wreck - sunk due to failure of a face seal (make unknown). So, the problems seem to come not from wear when running (although this can be an issue in silty water) but from not being used. You get a similar problem on some boats' cutless bearings where they sit in water where deposits or marine beasties are common. The flutes in the bearings fill up and as soon as the shaft operates you get wear, or even difficulty in use.

I agree that the PSS is much better made than the Deep Sea Seal - and many earlier designs which were withdrawn from the market because of high failure rate. However, in my view any seal that relies on pressure to make the seal and can fail catastrophically is not a good idea - however well engineered to reduce the chances of failing - or as in the case of Deep Sea even having a device to lock should it fail.

Seals that seal around the shaft such as a lip seals or traditional stuffing boxes do not fail catastrophically but slowly become less effective. Comparisons with crankshaft oil seals are not really valid because they operate in much more hostile environments than a water cooled prop shaft seal.

As far as I know, there are no significant builders in Europe that use face seals, nor are there any manufacturers in Europe. I don't know about the USA except that many use Tides as OE (as do some builders here like Fairline). As I said most use the Volvo seal which lasts well - mine has just finished its 14th season. The Vetus system, which also uses lip seals is also popular, particularly in motor boats.
 
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Tranona said:
The last time this subject came up here there were two well documented cases (at least if you believe the poster) of this type of seal failing. In one case the faces stuck together with dep....
Click to expand...

I have done a quick search and think I have found the origianl story:

"Ours sticks if the prop shaft isn't moved for a week or so. When we’re on the boat I do a daily engine check and just give the prop shaft a quick turn by hand which releases it if it has stuck. Realistically you only need to do this once per trip as it does need a good few days before it sticks again. It doesn't stick particularly hard and it would come free when you put the engine in gear but I've heard a salty old sea tale of one on a MOBO that wasn't moved for 12 months. The story goes that it was stuck so hard that when the engine was put in gear the bellows tore which of course let the sea in. If it is true the seal must have been stuck far harder than I’ve ever known mine to be and the rubber bellows must have been old and quite brittle. Still, it focuses your mind on freeing it up by hand with the engine check rather than just putting the boat in gear. Must say I'm 100% happy with the seal which we've had for 2 years. This 'sticking' issue really isn't a big deal."
 
doug748 said:
I have done a quick search and think I have found the origianl story:

"Ours sticks if the prop shaft isn't moved for a week or so. When we’re on the boat I do a daily engine check and just give the prop shaft a quick turn by hand which releases it if it has stuck. Realistically you only need to do this once per trip as it does need a good few days before it sticks again. It doesn't stick particularly hard and it would come free when you put the engine in gear but I've heard a salty old sea tale of one on a MOBO that wasn't moved for 12 months. The story goes that it was stuck so hard that when the engine was put in gear the bellows tore which of course let the sea in. If it is true the seal must have been stuck far harder than I’ve ever known mine to be and the rubber bellows must have been old and quite brittle. Still, it focuses your mind on freeing it up by hand with the engine check rather than just putting the boat in gear. Must say I'm 100% happy with the seal which we've had for 2 years. This 'sticking' issue really isn't a big deal."
Click to expand...

That wasn't the actual one - that is rather too anecdotal, but may well be true. The two I was referring to both came from the same person. Reason it had some credence was because the poster checked back with the owners to determine the type. Originally it was just "modern type" but of course it is important to know which design because of the fundamental differences in concept.

Sticking can be an issue and just like not burping a Volvo you would soon know about it because it usually makes a horrible noise. There is also an issue with the faces parting either because the bellows is not set up properly or excessive forward movement of the engine when going into gear - or a combination of the two. I have heard of such cases and also cases of water pressure opening the faces when surfing, but only at the bar talk level.

My ideal stern gland would be the oil bath type with lip seals - I had one at one time. However they are complicated and expensive to make properly as well as being quite bulky. Why go to all that expense and complexity when as noted above a 1 inch / 25mm size Volvo is less than £70?
 
Stuffing Boxes Have Not Gone With The Ark In Industry

wotayottie said:
I've had a series of lip seal type seals and on the latest boat have a Volvo one. It works well but has a life of about 5 / 7 years and so a cost of £10 / 15 pa. It requires burping if on a drying mooring. By comparison the previous seals with an oil reservoir cost very little for the three lip seals to be replaced from an industrial supply shop.

I'll be trying the Tides marine one next time round. No way would I go for the old style stuffing box - they went out with the ark in industry.
Click to expand...

Not quite - every drilling rig I work on including brand new rigs all have a stuffing box with packing on centrifugal transfer pumps. All now use non lubricated graphite packing. The reason for this is low cost reliability and the ability fix without pulling the motor off the pump.

They also offer good shaft sealing on non toxic slurry mediums in preference to a more engineered elastomer type lip seal.

Stuffing boxes offer simple, effective, reliable technology with inherent redundancy in the 4 wraps of packing.
 
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