hot seals

recently my mechanic repacked my stuffing box with graphite. I had teflon before He told me the graphite packing should not drip at all even underway. I've read that graphite disperses heat much better than teflon and drips less but I still had concerns. We left the marina -idiling for ten minutes then slowly got to 1600rpm( 12mph). 5-10 minutes the temps on both seals was over 200F . After drifting for 30 minutes - temps down to 130F. Any increase above idle drove it higher.There was some black fluid bubbling out -? liquifying graphite. I'm assuming he overtightened the stuffing boxes.I want to go back to dripping seals. Appreciate thoughts. OB

Does your shaft tube have a water supply coming from the engine?

Ted

Even with Teflon, my stuufung boxes properly tightened only get warm and don't really drip. More of an ooze that will barely wet the tip of my finger.

Back them off till they drip. Run them. Then take a small turn on them until the drip almost stops. Then check them for temp.

If they got hot enough to bubble the packing, there's a chance they'll have to be re-packed. The heat glazes the packing and sometimes it just won't recover. It's not a terribly difficult job, and it can be done in the water. Then again, if you paid someone to do it, I suppose you'd expect they'd do it right the 1st time rather than do it over. for free.....

True graphite packing won't melt. It's what is used in superheated steam valves.

What you probably have is a graphite impregnated material if some type.

GFO is a common shaft packing used in marine applications. It is graphite in a Goretex fiber. It is dull grey and will turn your fingers shiny. True GFO has GFO stamped on in in white letters every inch or so..

It sounds like the gland was loaded too much on start up. Common mistake. It needs to be run in, over a period of hours, until it is consolidated properly.

Repack it. And start with hand tight gland (or finger tight gland nuts). Run it and tighten it up slowly every hour. In 2-4 hours it will be good for many many years.

Thanks for the help. The graphite was put in without cutting strips. Does it need to be cut in sections like teflon?

obenton said:

Thanks for the help. The graphite was put in without cutting strips. Does it need to be cut in sections like teflon?

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I've used the GFO, IIRC the instructions recommend cutting strips to fit the circumference of the shaft, cutting on a 45 degree so the ends overlap, not butt. The joints should be offset for each successive ring so the lap is covered by a solid section.

There's a handy removal tool, like a mini-corkscrew and a flex spring on a t-handle. Sized for the packing dimension. Makes removing the old packing a snap.

Yes, as Maerin wrote.

Frankly, any "mechanic" that spiral wound packing on a shaft, must not have any formal training in marine or industrial mechanics.

C'mon guys take a step forward and save yourself all that hassle, fit a PSS seal fit it and apart from periodic checks forget it. k.i.s.s
I've had one for over15 years with thousands of miles cruising with no trouble at all.
If your handy with the spanners you can even fit it yourself while the boats in the water if your not nervous.

At this point in time I think the GFO will do away with complex seals .

KISS always works , tho even with GFO a tiny bit of knowledge is required to install the packing properly.

The yard guy needs to go back to,,,

"will that be paper or plastic bags madam"

FF said:

At this point in time I think the GFO will do away with complex seals .

KISS always works , tho even with GFO a tiny bit of knowledge is required to install the packing properly.

The yard guy needs to go back to,,,

"will that be paper or plastic bags madam"

Click to expand...

And THAT'S how they earn the unflattering title of "yard monkey".

I've always repacked my own stuffing boxes and I've repacked the packing on hundreds of valves in heavy industry. never once have I seen the packing put in in one piece

Sometimes if the packing is running hot, loosening it does not really relieve the pressure. You have to loosen the gland then whack on the side of the gland to get a little water gap to open up. Once it is dribbling, get someone to drive the boat and snug just a tiny bit at a time til drip rate goes down and temps stay cool.

Some glands once re-packed take a lot of running time to "break in" or whatever, and like to run hot. This happened on my ride. Then one magic day it decided it wanted to run cool. It has stayed running cool for the last few thousand miles!! And only a drip now and then.

Irish Rambler said:

C'mon guys take a step forward and save yourself all that hassle, fit a PSS seal fit it and apart from periodic checks forget it. k.i.s.s
I've had one for over15 years with thousands of miles cruising with no trouble at all.
If your handy with the spanners you can even fit it yourself while the boats in the water if your not nervous.

Click to expand...

I've been formally trained and working with mechanical seals and packing on rotating shafts and valve stems for 34 years.

They both have their pros and cons.

But, for the simple, low shaft speed, clean liquid, non-toxic fluid application of a boat shaft, I'll stick with my packing, thanks. [emoji4]

I agree. Keep it simple S.......

I would not use graphite packing with a stainless steel shaft due to galvanic corrosion issues.

Teflon is the way to go. In the millwright trade packing material was always cut as individual rings on a 45 degree angle and the cuts staggered to prevent blowby. This is generally more of an issue with high pressures like you find on steam turbines, high pressure pumps and the like but it's still good practice.

Another reason to use individual rings is so that if a leak develops you can pull one or two rings and put in new ones to control the leak till later. You can't do that with a single spiral bound piece.

Graphite impregnated packing will not cause your shafts to corrode any more than other types of packing or dripless seals.
The key to keeping corrosion at bay in the packing is the regular use of a fresh water flush.
I’ve seen fierce corrosion occur in all types of packing when it’s left steeping in salt water for extended periods.

I disagree completely.

Here's just one link to data regarding graphite and stainless. Why even take the risk when there are other materials available. Packing is cheap compared to a getting a drive shaft coated and machined.

https://www.materials.sandvik/en/materials-center/corrosion/wet-corrosion/galvanic-corrosion/

packing woes

hi all,
ok I bought my boat in march. drove it from just above ft. myers to Carrabelle. once docked I noticed the bilge running every 10 minutes or so. since this is my first inboard boat I am unfamiliar with packing stuffing boxes etc. the marina recommended martin marine, a local boat mechanic. he came by, checked the boat , said it needed stuffing after trying to tighten the nut. he did not have any with him. in retrospect, since this is a common , simple repair I guess I should have been suspicious. in any event, he packed it the following day, I headed out the next day to panama city. as soon as I anchored the bilge fired off. I checked and had a steady stream of water running. I tightened it a bit and had a regular drip. I had read and watched some posts so I felt comfortable I had it under control. headed out in the morning , that evening , same thing. tightened again but still flowing. day after day til I got to mobile bay where the mechanics checked it, said I had the wrong size packing, thanks, Martin Marine ( I would never use him again ) . anyway it stopped leaking, they used Teflon, told me to run it an hour so next day I headed north up through mobile. checked it in an hour, running water, tightened, it stopped so I continued my trip. that evening, anchored out, same darn thing. tightened some more, stopped leak. finally at bobby's fish camp I could not get it any tighter but a local guy put a pipe wrench to it and it stopped. now the boat is in demopolis. they are going to check it it out. boat will be there on the hard after tomorrow and they will investigate. wondering what they are going to find. bad shaft, bad cutlass bearing, I don't know. any ideas folks ?

If the packing was installed correctly, there shouldn’t be any leaks after run in and retightening.
The shaft could be scored or abraded, that can happen when packing gets overtightened, overheated, or if corrosion damage has already occurred.
This may be one of those jobs where in order to be sure it’s done correctly, you must do it yourself.
It’s really quite straightforward, and there’s lots of tutorials available on google or you tube.

Red flags are having to tighten after it stopped and then do it again. Further, having to go to a pipe wrench, massive red flag. You should never aggressively tighten packing like this. If you are having trouble with standard packing and it has been put in correctly to start with, that’s a pretty strong indicator that the shaft is wobbling in the shaft log, which means issues with part or all of your running gear. You can’t ask packing to work if the shaft is not running true to begin with. If you tightened it with a pipe wrench, pretty high chance to have a scored shaft now.

obenton said:

recently my mechanic repacked my stuffing box with graphite. I had teflon before He told me the graphite packing should not drip at all even underway. I've read that graphite disperses heat much better than teflon and drips less but I still had concerns. We left the marina -idiling for ten minutes then slowly got to 1600rpm( 12mph). 5-10 minutes the temps on both seals was over 200F . After drifting for 30 minutes - temps down to 130F. Any increase above idle drove it higher.There was some black fluid bubbling out -? liquifying graphite. I'm assuming he overtightened the stuffing boxes.I want to go back to dripping seals. Appreciate thoughts. OB

Click to expand...

I realize there is a company that sells it, and I've contacted them a few times to pose questions with no response, however, graphite should not be used for marine shaft packing. Graphite is thee most noble metal, place it in contact with almost any other metal, in the presence of an electrolyte (seawater in this case) and it will cause the other metal to corrode.

There are a range of other packing materials, from conventional flax to Teflon, Goretex and others, from which to choose, there's no good reason to use graphite based packing, and at least one good reason to not use it.

As far as temperature goes, my rule of thumb is the stuffing box should not be more than 30-40F above ambient water temp at wide open throttle. Temperature is far more important than drip rate, if the box is not overheating that's what matters. Based on your description it sounds as if yours is running hot.

I occasionally find a small pyramid of wax under an overheating conventional stuffing box, that's what happens when it runs too hot, the wax melts out of the packing, as it drips onto the hull beneath it cools and builds a small mound.

More on the subject, including on graphite, here: https://stevedmarineconsulting.com/conventional-wisdom-for-conventional-stuffing-boxes/

(In Taiwan conducting a new build inspection)

This is a "new to you" boat, what it was doing before is unknown. On my boat, I had both glands repacked after purchase. One was good for 8 years, the other would leak after about a year and need adjusting > repacking. After a while I figured something was wrong, turned out it was a bent shaft.
Something is wearing out your packing prematurely, or preventing the gland tightening up normally. It needs dismantling and a good inspection, and you`re having that done. Maybe it was repacked before sale and survey to help get it sold.

Kscviour nailed it!

Graphite is at the very end of the galvanic scale, use it and do profound damage to your shaft. Anodes won’t help you here, the corrosion will eat the stainless. Graphite packing is for factory pumps and is not intended for salt environments. Flushing with fresh water will just slow the destruction.

Get it out and fire the yard guy.

Oops didn’t see Steve’s post - great minds...

5 bucks says it's not graphite, but PTFE or ePTFE with graphite powder.

Is that $5 US or Canadian?
Either way I know which side to bet with...