Dripless shaft seal flow meter. Good or bad idea?

ancora said:

I'm also an advocate of K.I.S.S., packing shaft seals work just fine on my twin Volvos, and my 34 year old ferro-resonant battery charger still charges the batteries, without the hassles of an inverter. No Xantex horror stories on this boat.

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I wasn't aware that dripless shaft seals or inverters were complicated for the benefits derived. Of course I've only been boating since the late 50s.

Not that have or would have a dripless shaft seal aboard; but I think your PO added unnecessary complication and two or more pinch points to each feed and perhaps yellow brass or plastic fittings and improper hose below the W/L. KISS

An exhaust temp alarm tells you if there is water reaching the exhaust. That may be a surrogate for the shaft seal, but it isn't a perfect one. Much depends on the points of failure in the rest of the system. I do not have a flow sensor, but intend to install one as I've had an issue with the forward cutlass bearing seizing up, perhaps from lack of flow. There are many flow sensor types, it would be important to pick one that cannot block the flow as a failure mode, and these are certainly available.

I also intend to install a temp sensor on the cutlass bearing housing which is very near the Tides seal. Since on my boat the water comes from the exit of the transmission cooler, and is therefore somewhat warm, either a rise in temp or a drop in temp would indicate a problem.

DDW said:

An exhaust temp alarm tells you if there is water reaching the exhaust. That may be a surrogate for the shaft seal, but it isn't a perfect one. Much depends on the points of failure in the rest of the system. I do not have a flow sensor, but intend to install one as I've had an issue with the forward cutlass bearing seizing up, perhaps from lack of flow. There are many flow sensor types, it would be important to pick one that cannot block the flow as a failure mode, and these are certainly available.

I also intend to install a temp sensor on the cutlass bearing housing which is very near the Tides seal. Since on my boat the water comes from the exit of the transmission cooler, and is therefore somewhat warm, either a rise in temp or a drop in temp would indicate a problem.

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Wouldn't it make sense to install a regular packing gland that you don't even have to think about from one decade to the next? If you insist on a dry bilge put a pan w/ a small pump under it?

MapisM said:

Interesting. In other words, the water flow is reversed, i.e. with water picked from the wet side of the shaft seal, and contributing to feed the engine cooling through the pipe connected to the main pick up?
I never heard of such setup, and I suspect that its capacity to draw water from the hull entry of a rotating shaft might be the opposite of what logically necessary, i.e. progressively lower as speed increases.
What sort of speed can the boat reach?

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Yes that is the situation. Reason why I asked for your views as at times it worries me. However at higher rpm the sea water pump would be sucking up larger amounts of water.
The seal is PSS and boat cruises at 15 and max 19 knt.
At times I`ve checked by hand at various speeds warm but never hot, though it takes me 30-50 sec till I put in neutral and do the check.

Yup, I appreciate that the higher pump rotation demands a higher flow.
But I'm puzzled by what must happen on the external side of the shaft seal, for two reasons:
1) the shaft rotation, that "shuffles" the water flow, and
2) the backward direction of the water flow, which is the opposite of the path that the water should take to enter the shaft seal.

Now, on paper, I would think that both these effects should "resist" the pump suction, to some extent. And even more so as speed increases.
In this respect, 15+ kts is a respectable speed, in the ballpark of water coming out under pressure from an irrigation hose.
So, it's as if your boat would try to suck water from such hose, but with the pickup oriented in the same direction as the flow, if you see what I mean.

Have you ever had a chance to see if in some other Belliure boats there is the same setup?
I've never been on one, but I've seen boats of many other builders, and I'm pretty sure to have never come across such solution.

We put PSS logs in a previous boat. They were ok. This boat has the traditional logs. It had GFO packing in it and it did not leak at all anytime. So I am sticking with them and just rebuilt one and again used GFO packing. It isn’t nearly as tight as it was with the old packing but it isn’t leaking now. So I see no advantage to going to dripless shaft logs.

Unfortunately no I have not seen any other Belliures.
A while ago I had another boat with a similar shaft seal but in this one, instead of the small pipe being connected to the engine intake, it was connected to an underwater through hull seacock. Boat cruised at 22knt, had it for 10y with no issues

I had my dripless shaft seal hose partially plug at the hose barb on shaft seal. A piece of shell caught on the hose barb edge and other bits collected on top of it. Not a total blockage. When I serviced the freshwater cooling system, I pulled the heat exchanger tube bundle out. The hose is connected to the front end cap. When I went to reassemble everything, I tried to blow through it and had very little flow, which led to the investigation.

My solution is to put a small strainer in the hose to catch trash and add a floating piece of plastic in the strainer on the up stream side. The idea is to see the plastic dance in the flow. I'll post some pics when I get done over engineering it.

Ted

Comodave said:

We put PSS logs in a previous boat. They were ok. This boat has the traditional logs. It had GFO packing in it and it did not leak at all anytime. So I am sticking with them and just rebuilt one and again used GFO packing. It isn’t nearly as tight as it was with the old packing but it isn’t leaking now. So I see no advantage to going to dripless shaft logs.

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I concur...how many feet (yards) of packing could I buy for the price of two dripless seals?

I've little experience with modern packing materials, I gave up on the old packing glands with the advent of dripless seals. It seams like they would have the same issue with heat and needing lubrication as a dripless seal? On my boat, there are two cutlass bearings, separated by about 4'. Both are in the keel. Duramax requires 2 gallons/minute water minimum through the bearings. This can only occur with a pressure water feed from somewhere - it isn't going to backup from the aft one to the forward one on a lark. So how and why in this situation would a packing gland work better than a lip seal? Why are they really very different? Don't both press a flexible material against the shaft to seal the water out?

For my upper bearing my boat has a clamshell that feeds water into the chamber ahead of the bearing. Seems like a better idea than trying to use the excess from a packing gland.

My prior two boats I had early PSS seals and liked them. For the last 14 years I’ve run gore packing in a traditional gland. Dripless seals don’t make sense for me anymore, now that the gore packing has become so well proven and comes without the added failure points of the dripless.

"I concur...how many feet (yards) of packing could I buy for the price of two dripless seals?"

Not that many,

The Goretex or Duramax are fairly expensive , but cheap as insurance against sinking.

ismar1 said:

A while ago I had another boat with a similar shaft seal but in this one, instead of the small pipe being connected to the engine intake, it was connected to an underwater through hull seacock. Boat cruised at 22knt, had it for 10y with no issues

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Happy to hear that, because it's exactly the same setup that I've got in my current boat, which I've only had for two seasons, but is by now 16yo and never had a problem with her Fluiten seals.

The advantage which I see in dedicated seacocks, on top of not "stealing" water from the main circuit (which is also true in your setup of course, as opposed to more typical solutions where the pickup is downstream of the raw water pump), is that the dynamic pressure on the pickup point increases with speed, while I suspect that in your setup it's the opposite, at least to some extent.

Then again, if your system worked so far without any trouble, as the old saying goes, if it ain't broke...

ancora said:

No Xantex horror stories on this boat.

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Therein lies your problem. Magnum all the way when it comes to inverters!!!

ghost said:

For my upper bearing my boat has a clamshell that feeds water into the chamber ahead of the bearing.

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The chamber ahead of my forward bearing is the bilge, so not possible.

Baker said:

Therein lies your problem. Magnum all the way when it comes to inverters!!!

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There are Magnum inverter horror stories aplenty. I'm quite sorry I bought the one in my RV.

DDW said:

There are Magnum inverter horror stories aplenty. I'm quite sorry I bought the one in my RV.

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Ok they all suck...you happy? Magnum is the best out there...IMO and experience. None are perfect.

My Taiwan built trawler has a sump in the forward part of the engine room where all bilge liquids collect, including shower water, thence pumped overboard, thus, we always have a dry bilge.

Far better off with a temp sensor/alarm on the seal. Tides sells a kit.

My boat is keeled cooled and dry exhaust, so I don't have any sea water being pumped by the engine. I use an electric pump that supplies Sea water to the two shaft seals, and the refrigerator/freezer condensers, whenever any of them is switched on. I went through a period of pumps that were overheating and tripping off unexpectedly, and I would loose cooling to the dripless seals. Despite the boat operating at slow speeds that the dripless seal literature implied I shouldn't even need cooling, fairly quickly they would start making a loud groaning sound when underway. At this point the outside of the seals was warm to the touch, but not hot. I would shut down the engines and mess with the pump till I got it running again, or changed out for a spare, which I got very fast at. When I started back up with cooling, the seals would leak a tiny bit for the next few hours. Just enough to fling around a fine mist of salt water all over everything. The noise was very obvious long before they catastrophically burned up. I think I finally got my problems solved by switching to a magnetically coupled centrifugal pump that is designed for continuous duty. Just in case, the old pump is still installed as a backup, that can be quickly put in service by open/closing a couple valves, and switching the Deutsch connector on the power feeds.

Edit- My boat also has temperature alarms that sense on the aluminum shaft tubes just behind the seals. Never in these in multiple incidences did the temperature get anywhere near high enough to trip the alarms. I think at least in the beginning the problem starts right at the face of the carbon and stainless surfaces. When they were dripping afterwards I pulled them back and felt the surfaces with my finger and they felt completely smooth. Whatever scarring they had must have been very small. They always seem to fix themselves after a few hours. It really freaked me out the first couple times it happened.

Snapdragon III said:

snip.... Despite the boat operating at slow speeds that the dripless seal literature implied I shouldn't even need cooling, fairly quickly they would start making a loud groaning sound when underway. At this point the outside of the seals was warm to the touch, but not hot.....

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If you are using PSS seals then my read of the installation instructions say if you're not supplying water to the seal then the water line from the seal needs to be vented above the boat's waterline. With a failed pump in the water line yours wasn't vented but blocked.

The failure I experienced, which started this thread, was a blockage in the PO installed flow meter. So I had similar conditions to yours, no flow, no venting. The seal got uncomfortably hot, probably hot enough to set off an alarm if installed. Alarms will be installed because the seals and shaft logs are aft of the engine room under the aft cabin decking. To access the port seal for inspection I need to move furniture and pull up carpet. The starboard seal is under the head decking, easy to get to.

Comodave said:

Look at Borel Manufacturing. I have their alarms on the exhaust, high water and water in fuel. Easy install and draws no power unless there is an alarm. No affiliation just a very satisfied customer.

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Question regarding the Borel or similar alarms:
Each of my engines has 2 exhaust elbows. Do you just put an alarm band on one of the 2 exhausts of each engine assuming that failure would likely be upstream and affect both?

ORIF said:

Question regarding the Borel or similar alarms:
Each of my engines has 2 exhaust elbows. Do you just put an alarm band on one of the 2 exhausts of each engine assuming that failure would likely be upstream and affect both?

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Since exhaust elbows can also become clogged, it is best to have them both monitored.

FF said:

I understand how why the dripless seals solved a problem decades ago , but wonder why folks put up with the risk and maint required today?

A modern packing in an ancient designed stuffing box can frequently go years with out requiring an adjustment.

With no danger from sinking from a not replaced on sked rubber bellows or tiny plastic tubing.

Why bother when better is OTS. ?

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I'm not sure what risk and maintenance you are talking about. I've had both over my lifetime, and they both work. But, it is a stuffing box that needs maintenance with periodic tightening. A shaft seal basically needs no maintenance, but you may change them out at factory prescribed intervals if desired. I've known many folks that didn't even do that and went on longer.
The newer PYI seals have even longer replacement intervals. Bilges stay dry. I never even thought to monitor the water flow. I'll add that to my list. I don't think I'll go for more electronics/monitoring, other than hand touch and maybe IR gun.

People. They both work if installed correctly, and inspected from time to time. I think this is being over-argued.