Dripless Shaft Seal Inspection & Maintenance?

[chala]

Originally Posted by Dockhead

I have a dripless shaft seal on my boat. It is the type which has a raw water feed from the main engine.

I hope that this configuration cannot flow back and flood the engine and even sink the boat? I also hope that this configuration does not depend on an anti-siphon valve for its integrity and that there is an isolating valve, between the dripless shaft seal and the feed from the main engine, which is frequently used or tested.

Originally Posted by S/V Alchemy

Other than that, keep the relief hose above the WL and double-clamped and you are good.

Originally Posted by Randyonr3

Reason being, I've had problems with mine.. whenever I've put it in reverse, the prop blows water back up the log and the spring isnt enough to keep it from blowing water into the boat..

This is common it is why the mechanical seal should be installed with a vent, relief hose as indicated above. In some instance when the hose discharge this give an indication that the mechanical seal is properly lubricated, cooled, and that the raw water supply pump is supplying raw water to the seal.

Originally Posted by eyschulman

Why? If the units need so much care and are make or break(sink your boat) why spend the money when the new school packing can be drip-less or as dry as a drip-less. My drip-less was not 100% dry. Now on my new boat I have standard box with new school packing and it is dryer than drip-less and easier to maintain. Duramax Ultra X packing

Why? Because a mechanical seal will not wear the shaft and there is far less maintenance. 12 years quote the OP. My experience with stuffing boxes is that they require daily inspection and very frequent adjustment by an experienced person. This is expensive and it is why mechanical seals, more expensive to purchase than stuffing boxes still become far more economical in the long term. I will never hesitate to convert a pump with a stuffing box to one with a mechanical seal. In any case if stuffing boxes where so good it would have been no requirement for producing mechanical seals.

[neilpride]

My previous boat come fited with the old fashion bronze stufing box, packing, packing packing!! and now i live with this stuff for the past 5 years.. Lip seal by tides marine, the water cooling hose is fited to the end of the heat exchanger cap, above the waterline and with a small valve to open or close the flow of water ... i will say honestly we dont see any major failure of weird thing with this seal, even a drop in normal circunstances , only a momentary leak after haul out due shaft removal and fix it by moving the seal few mm forward, not a drop for the past 3 years...Dry bilges for us is a priority....
Tides Marine SureSeal Shaft Seal - Lip Seal Change - YouTube

[foolishsailor]

Originally Posted by chala

I hope that this configuration cannot flow back and flood the engine and even sink the boat? I also hope that this configuration does not depend on an anti-siphon valve for its integrity and that there is an isolating valve, between the dripless shaft seal and the feed from the main engine, which is frequently used or tested.
.

I also have this system.

Consider idling that the ID of the hose that sends engine water is less than 1/4" and is also a fully self contained system - I can't imagine it sinking a boat. With the engine off and the impeller not running, at best it would be a drip leak and less that any stuffing box would produce. The siphon issue would not be at play for this.

[chala]

Originally Posted by foolishsailor

I also have this system.

Consider idling that the ID of the hose that sends engine water is less than 1/4" and is also a fully self contained system - I can't imagine it sinking a boat. With the engine off and the impeller not running, at best it would be a drip leak and less that any stuffing box would produce. The siphon issue would not be at play for this.

I have a PSS and I have dry bilge. Getting on the boat 2 days before departing for a month and half cruise I found water in the bilge, checked all the trough hulls could not find a leak, checked the oil level in the main, bad way to high, checked the air cleaner, sea water dripping from the air cleaner. With an engine flooded this got me busy for the next 6 hours. By midnight I had new oil and the engine running now I had the time to think about from where the seawater did come from. I did suspect a leaky services valves so I closed the main main inlet and outlet valves. The engines onboard are both fitted with exhaust riser. On each riser a bleed valve is fitted for the purpose of preventing, when required, seawater entering the engine. For good purpose I opened the bleed valve on the main and went to rest. After few hours sleep I went to check the bilge and found water again I checked the bleed valve and a flow of sea water accentuated by the roll of the boat was coming from the bleed valve. Lucky I had that bleed valve open or the engine would have filled again with seawater. Then come to my mind that the seawater may come from the feed line to the stern tube. That feed is equipped with a ball valve that I closed and the flow of seawater from the bleed valve stopped. At daylight I inspected the anti-siphon valve and found that the 20 cents seal had swollen and jammed shut allowing seawater to siphon into the boat via the engine. After this we become more concerned about shutting services valves and even more concerned of not forgetting to reopen these services valves before operating the engines.

[chrisjs]

I do not understand this post. Our PSS has a water feed line that is fed from the engine seawater cooling just prior to the exhaust riser. I do not see how water could flow out of this tube when the main engine seawater pump is stationary. We always close seawater inlets when we leave the boat. Are you suggesting that water entered the engine by flowing from the shaft seal back into the engine?

[Wotname]

OK, what am I missing here...

Surely only high speed vessels (>12 Kts) have a water injection connected to the PSS barb. Vessels operating essentially below 12 kts only need a vent line connected to the PSS barb and then taken to a point high above the waterline and left open. This of course should be somewhere the centreline of the keel and not off to one side.

Perhaps you all have high speed boats?

[chala]

Originally Posted by chrisjs

Are you suggesting that water entered the engine by flowing from the shaft seal back into the engine?

Yes

Originally Posted by chrisjs

We always close seawater inlets when we leave the boat.

A PSS is normally considered to be an outlet but it can also become an inlet and for this reasons it would be prudent to install a ball valve in the line and close it when the engine is not in use.

Originally Posted by chrisjs

Our PSS has a water feed line that is fed from the engine seawater cooling just prior to the exhaust riser.

Not clear to me what you mean, an exhaust riser exhaust gas.

Originally Posted by chrisjs

I do not see how water could flow out of this tube when the main engine seawater pump is stationary.

Water will flow out of this tube if the water due to a failure of the anti-siphon valve is siphoned into the water lock. The water lock will fill up and so will the mixing elbow and the connecting pipe then if an exhaust valve in the engine is open when stationary and because an engine crankcase is vented to air, water coming from the tube, not from the stationary main engine seawater pump, will feed into the combustion chamber and fill up the engine.

Originally Posted by chrisjs

I do not understand this post.

I hope that the above may help.

Note: Not to panic every motor owner but the above is in regard of an engine installed below the LWL.

[foolishsailor]

I have a water line as described above and high speed for me would be 8kts under motor.

[noelex 77]

Originally Posted by Wotname

Perhaps you all have high speed boats?

A lot of yachts seem to to be fitted with an active water feed from the engine cooling system instead of the much simpler vent. I have often puzzled why.

[Wotname]

Originally Posted by noelex 77

A lot of yachts seem to to be fitted with an active water feed from the engine cooling system instead of the much simpler vent. I have often puzzled why.

Me too

[foolishsailor]

Mine actually works well as a purpose but only because of the pecularities of my propellor shaft - it is 1.7m long and the inside of the top cutlass bearing does not get adequate flow.

[chala]

Originally Posted by Wotname

Me too

May be because it is possible for the mechanical seal to run dry if the cutlass bearing get blocked by some fouling, I had one blocked for 2 years. 3 psi would not unblock it and one day it cleared it-self. The possibility to supply cooling water to the seal is needed so is the necessity of relieving excessive pressure on the seal and the removal of any entrapped air.

[delmarrey]

Originally Posted by chala

May be because it is possible for the mechanical seal to run dry if the cutlass bearing get blocked by some fouling, I had one blocked for 2 years. 3 psi would not unblock it and one day it cleared it-self. The possibility to supply cooling water to the seal is needed so is the necessity of relieving excessive pressure on the seal and the removal of any entrapped air.

As well, the clearance between the stern tube and shaft maybe very small not allowing water to circulate enough to keep the seal cool.

[noelex 77]

I have a simple vent on my PSS seal. The tube runs up to deck level.
I still get a few drops of water out of the tube when setting the anchor in full reverse.
The backwash from the propellor is obviously enough to raise the water head well above the waterline.
I have installed a small overflow container so its not a problem.

However if the water head is about 1.2m above the engine surely if it was a direct injection system it enough to force seawater into the engine!!!

The anti syphon valve won't help because its not a syphon. I must be missing something ( perhaps the exhaust pressure is enough to stop this happening) otherwise all the engines with direct injection of seawater are at risk of some seawater damage.

[Sailmonkey]

I ran the engine water to ours to keep the bearing clean.....I figure the more silt I can keep from accumulating in the bearing the better.