Stuffing Box Q: Drip Rate vs. Nut Temperature

RichH · Jul 12, 2010

YES - operating temperature is THE most important.
Best indication is that the packing nut is cool to touch or 'just slightly warm' ... it means regardless of the packing installed that there is sufficient cooling water. From your description it is 'probable' that GFO has been installed, and that shaft was properly 'faced/dressed' with precision surface finish. Consider yourself VERY lucky that the PO was 'fastidious'.

BEST is to monitor the ACTUAL temperature with an infra-red optical thermomenter - cheap from Amazon.com, etc. .... and you can use the IR Thermo to 'profile' the entire engine for reference to check against 'future' engine/alternator/cooling system, etc. problems.

Bill Roosa · Jul 12, 2010

Answer is in the name

Id say that a slow drip is exactly what "dripless" packing is all about. A cool nut sounds like it is doing its job the way I'd expect.

Ralph Johnstone · Jul 12, 2010

The Biggest Old Wive's Tale ..................

........... on this site is the need for a packing gland to drip in order to "lubricate" and cool the packing. The shaft surface speed is just plain too slow to cause any amount of heating as long as the packing isn't too tight. The shaft is more than capable of removing all the heat formed by the shaft rubbing on the packing.

The second biggest "old wives tales" is that the packing will "score" the shaft if the gland doesn't leak or the gland is too tight. That's why they make packing from flax and other soft materials like GFO fibre so that they don't score.

At the low shaft surface speeds we see on sailboats, there is no reason for there to be any leakage on a well maintained packing gland.

There ..................... that should get the pot boiling. Been too quiet around here for the last while. :stirthepot:

Chuckbear · Jul 12, 2010

Ralph Johnstone said:
........... on this site is the need for a packing gland to drip in order to "lubricate" and cool the packing. The shaft surface speed is just plain too slow to cause any amount of heating as long as the packing isn't too tight. The shaft is more than capable of removing all the heat formed by the shaft rubbing on the packing.

The second biggest "old wives tales" is that the packing will "score" the shaft if the gland doesn't leak or the gland is too tight. That's why they make packing from flax and other soft materials like GFO fibre so that they don't score.

At the low shaft surface speeds we see on sailboats, there is no reason for there to be any leakage on a well maintained packing gland.

There ..................... that should get the pot boiling. Been too quiet around here for the last while. :stirthepot:

Pretty much all of that is incorrect. Chuck

zeehag · Jul 12, 2010

i use teflon packing.....works well.....i never obsessed over the temp of my packing gland--i have at least 2 of them--packing for rudder and for shaft.....seems the only time the gland would heat and retain heat would be under adverse conditions --like the stuffing is shot......only makes sense.....many boats, in order to get to tha stuffing box, need to hire a neonatal monkey trained in utero to do the work--so i dont go there---that is for the monkey--

RichH · Jul 12, 2010

Sorry Ralph -
any time salt or other carbonate laden water goes beyond about ~154°F the carbonates (principally calcium carbonates) precipitate out of solution, become trapped, additively accumulate and become an abrasive which will polish or gall the shafting. Sure the shafting may transfer heat, but the shaft certainly cant do a mass transfer of accumulating calcium, etc. carbonate.

Stu Jackson · Jul 12, 2010

And, Ralph, if you read the instructions for the gore packing, it says ALMOST (virtually) drip free. Google emarine packing

Maine Sail · Jul 12, 2010

I don't think Ralph was being serious just stirring the pot, which apparently he did..

BTW thought you guys should know that 5 minutes ago it was sunny and nice and I am now sitting in 50 foot vis. The upside is that I no longer have to stare at the Carver (read powered CONDO) that is new to the anchorage this year.... Talk about pollution, sight pollution..

Deadline · Jul 12, 2010

Blowoff

Chuckbear blowing off Ralph as "pretty much incorrect" does nothing to refute his assertions. I'm no metalurgist, but my experience of 15 years in this debate coincides exactly with Ralph's points.

My contribution is that one should back off the packing nut just enough that it gets water between the packing nut and the locking nut. This is reflected in the greening up of the seam over time, which comes from water dripping ever so slowly -- but adequately.

Ralph Johnstone · Jul 12, 2010

Nope .............................

.............. sorry, still going to stand by every word in my original post.

1. The shaft has plenty of cross sectional area to conduct away all heat formed from friction.

2. No worry about carbonates precipitating at elevated temperatures because the shaft always runs cold.

3. Buddy of mine (with money) uses GFO packing and runs his stuffing box dry as dust and stone cold. Gortex is just playing it super safe with their "almost" drip free statement.

4. I can only afford (read as cheap) teflon impregnated flax and I've never had a drop of water in my bilge from the gland.

5. I do have a light salt fuzz which forms (after a full season) where the shaft enters the gland nut which shows any microscopic leakage is evaporating before it can drip. I keep the gland and shaft covered in silicone grease and all wipes clean in a second at the end of the season. There is never a drop of water below the shaft.

Looks like Old Wive's Tales really die hard around here.

Sort of reminds me of Maine's expose on whether a prop has more resistance to drag when rotating or when locked in place. There's one old wive's tale that died a sudden death. Please offer solid facts if you intend to argue this point.

Speaking of old wive's tales like these two, does anyone out there have anymore gems they'd like to post here or perhaps start a new post.

I can't make it out sailing on a beautiful windy day like today so thought I'd add a little more fuel to the fire. Fair winds to the smart people who are out there today.

zeehag · Jul 12, 2010

Ralph Johnstone said:
.............. sorry, still going to stand by every word in my original post.

1. The shaft has plenty of cross sectional area to conduct away all heat formed from friction.

2. No worry about carbonates precipitating at elevated temperatures because the shaft always runs cold.

3. Buddy of mine (with money) uses GFO packing and runs his stuffing box dry as dust and stone cold. Gortex is just playing it super safe with their "almost" drip free statement.

4. I can only afford (read as cheap) teflon impregnated flax and I've never had a drop of water in my bilge from the gland.

5. I do have a light salt fuzz which forms (after a full season) where the shaft enters the gland nut which shows any microscopic leakage is evaporating before it can drip. I keep the gland and shaft covered in silicone grease and all wipes clean in a second at the end of the season. There is never a drop of water below the shaft.

Looks like Old Wive's Tales really die hard around here. Sort of reminds me of Maine's expose on whether a prop has more resistance to drag when rotating or when locked in place. There's one old wive's tale that died a sudden death. Please offer solid facts if you intend to argue this point.

Speaking of old wive's tales like these two, does anyone out there have anymore gems they'd like to post here or perhaps start a new post.

I can't make it out sailing on a beautiful windy day like today so thought I'd add a little more fuel to the fire. Fair winds to the smart people who are out there today.

thankyou---is good to hear--was and is my exact plan for exact same reasoning..LOL...thank goodness i am not an old wife nor have ability/desire to have old wife ...LOL

Bill Roosa · Jul 13, 2010

Don't have an experience but...

I have seen prop shafts scored by something. The location would indicate that it had to be the stuffing. Don't know the type of "flax" but clearly something was a rubbin.
RichH's salt sandpaper idea makes sense if the gland drips while turning but does not when stopped. The flax would be wet and dry between uses which would allow crystals to form from evaporation. Course they could just as easily be almost immediately dissolved once the gland begins to leak while in operation so......

Maine Sail · Jul 13, 2010

Just so folks can make up their own minds on this "old wives tale" the conversation below was within the last few weeks with Buck Algonquin the largest manufacture of standard stuffing boxes.

It is YOUR boat and YOUR prop shaft and I would caution you heed some of the advice given above VERY carefully..

From Buck Algonquin in response to a query about GFO packing that was out of spec size wise:

Buck Algonquin said:
We have seen the variations in the packing sizes that you have described. 95% of my packing box questions revolve around the goretex graphite based packing. It is good packing. However, most people misinterpret the instructions and believe it is drip free. All three materials (graphite, teflon, and flax) have there drawbacks.

Flax. low cost. temperarture tolerance minimum. abrasive. Does require water for cooling and lubrication.

Teflon. medium cost. High temperature tolearance (packing only). mildly abrasive. Does require water for cooling and lubrication.

Graphite. higher cost. High temperature tolerance. least abrasive. Does require water for cooling and lubrication.

The common theme here is they all require water for cooling. I do not believe you will get a much better setup than the goretex. The temperature will vary with the amount of water drip through the packing and the shaft speed.

The abrasion factor would be the other consideration. Since the goretex has the least abrasion impact, it would be the better choice.

I hope this helps.

Best Regards.
Steve

Please remember that this information is striaght from the largest manufacturer of stuffing boxes in the US...

If still in doubt I have lots of photos and insight to share from when I used to be the bilge grunt who did all the re-packs and shaft work, cause I was the small guy and the yard grunt. When you've done as many re-packs and shaft replacements as I have, and hung around shafting and prop shops as much as I have, you'd then realize quickly that the info about water lubrication is not an old wives tale. An N=1 does not negate years of industry, not just marine, or the knowledge of the largest manufacturer of traditional stuffing boxes. Take the advice you get on the net with a grain of salt, including mine.

Was just at my buddy's prop shop this morning and snapped a few more pictures to add to the collection. If I get a chance I will post some.

P.S. I guess a "slow" shaft speed depends on what you consider slow. Our prop shaft spins, at cruise RPM, is turning 19 revolutions per SECOND or 1143 revolutions per minute.

To put the speed into an odd perspective the tires on my SUV turn at 111 RPM at 70 MPH...

Here is a video to put the speed of some shaft / prop speed into perspective. I aimed my digital tachometer at my Vornado fan and set it to 1187 RPM, which is about as close as I could get to the 1143 my prop shaft spins at. Slow?

RPM Video (LINK)

tommays · Jul 13, 2010

A 1" shaft at the 1150 is 3600" a minute of movement my poor A4 at 2000 rpm will be at 6200" a minute so it better drip a bit and surface speed is what tends to set most sealing rules/guidelines

Maine Sail · Jul 13, 2010

Of course...

Ralph Johnstone said:
The second biggest "old wives tales" is that the packing will "score" the shaft if the gland doesn't leak or the gland is too tight. That's why they make packing from flax and other soft materials like GFO fibre so that they don't score.

At the low shaft surface speeds we see on sailboats, there is no reason for there to be any leakage on a well maintained packing gland.

Of course we all know packing can't score a shaft..

Next four pics taken this morning..

This shaft out of a single screw down east style boat one had worn .05" when the owner adjusted the "drip-less" packing to be drip-free packing..

More...

Oh and one more..

Warren Milberg · Jul 13, 2010

While I, too, believe that packing material may score a shaft, I tend to believe that the reason this happens is leaving packing material in service too long and continuing to tighten it down as it ages and hardens. In the excellent pics posted by MaineSail, I would wonder if if the real culprit really was new or newish Gore GFO packing that was overtightened, or whether it was old packing overtightened rather than replaced? Do you know the circumstances Maine?

Maine Sail · Jul 13, 2010

Warren Milberg said:
While I, too, believe that packing material may score a shaft, I tend to believe that the reason this happens is leaving packing material in service too long and continuing to tighten it down as it ages and hardens. In the excellent pics posted by MaineSail, I would wonder if if the real culprit really was new or newish Gore GFO packing that was overtightened, or whether it was old packing overtightened rather than replaced? Do you know the circumstances Maine?

The only one I know the circumstances of are the ones with the calipers. That was traditional flax impregnated with white PTFE. Shaft was three years old.

Those were in reference to the statement that packings can't score a shaft because they are too soft. I have personally seen and worked on many scored shafts..

The others were just in the junk pile which is slim this time of season... I have a couple other shafts in my barn that I'll have to dig out too...

RichH · Jul 13, 2010

"I would wonder if if the real culprit really was new or newish Gore GFO packing that was overtightened, or whether it was old packing overtightened rather than replaced?"

Its almost totally impossible to score a shaft with Gore-tex or other 100% PTFE packing .... it turns to a gas when above ~650 deg F. !!!!

Its quite easy to score a shaft with flax packing by over tightening, happens a LOT in the Chemical Process, etc. industries even in applications where the stuffing box is submerged. Flax is a 'botanic' and therefore doesnt have 'constant' moisture absorbency, etc. rates, etc., its a quite a 'variable' product in most applications - thats why the change over the years to Ramey, Asbestos, synthetics, and now Gore-Tex. Gore-tex packings are the 'wonder drug' for industrial pump, etc. packing glands, they are reliable, adjustable if needed. One problem is that they can 'transpire' gases through the porosity of the micro-fractured PTFE, so not used in hazardous or lethal applications.