Repacking a gland

[Warren Milberg]

So, I've started spring maintenance early by opening and picking out the old packing from my packing gland. In thinking about repacking this conventional bronze gland, I know it is recommended that the new packing be cut on a bias and the rings installed separately with the cuts offset in each ring. The question is why? In helping a friend repack a similar gland in this boat I noticed that the old packing material was installed with 4 loops on a single strand. I asked my friend about this and he said that it was easier to get the old stuff out as one single strand and that his old packing material worked well in keeping the drips to a minimum. In short, he was pretty satisfied. So, what do you all think the advantages are of cutting the new packing material into separate rings, or just wrapping one long piece around the shaft, push it into the compression nut, and be done with it?

 

[SamLust]

A single long spiral will provide a nice pathway for water to follow. There will be open gaps where the second turn passes the first. Ever repack a hydraulic ram from something like a bulldozer? done the same way except split formed resiliant rings in stead of flax. Only place I would use a single strand multiple turn is on the stem bonnet of a hose bib outside the house. Just because your buddy is OK with it does not mean it is OK.

 

[Ed Schenck]

I think it sounds like a great idea. Trying to imagine what could go wrong.

Got interrupted and I see Sam jumped in. Still don't see a problem. You set up for a drip anyway. You are suggesting the water will somehow go through the middle and thus not lubricate the shaft?

I use dripless GFO. When I pull it out it is one coagulated lump. I don't think water is going to transit through the material. But you create enough doubt so that I will continue the old fashioned way. God knows I am no hydraulic expert.

 

[Bill1565]

I never had problems with single strand spiral would packing over 25+years and 3 different boats. It may be conceptually true that there could be a path along the gap but there is verry little hydraulic pressure to force water in and around at the depth of the packing gland.

 

[sailingdog]

I'd point out that the rings will be compressed more evenly if there are four different separate rings of packing, rather than having two hard points...

 

[Dan Johnson]

Warren...

the only thing that strikes me is that, in spiraling the packing you would not get flat facings at the fixed and moveable faces of the gland. Tapering the ends might help.

Compressing enough spirals would minimize the water through-flow and get the required drip volume needed.

Let us know how this works out--it's on my to-do list this Spring!

 

[Maine Sail]

So, what do you all think the advantages are of cutting the new packing material into separate rings, or just wrapping one long piece around the shaft, push it into the compression nut, and be done with it?

Warren,

The only advantage is a time savings of perhaps 60 seconds, the rest are all disadvantages...

Please don't do this. There is a good reason for cutting individual rings and that is because the stuffing boxes are designed for flat rings.

"Hey guys gas currently costs less than diesel, what do think are the advantages if I just mix a little diesel & gas?"

For illustrations sake I see your question the same way you'd probably see the one above..

The two "tail ends" will create un-even har spots or compression spots where there will be more contact on the shaft in one spot and less in another, thus potential for creating hot spots, or leak paths, that have uneven sealing potential. This can lead to incorrect adjustments, cocked packing and/or ruining of the shaft. The nut end and the log end are smooth and are designed to except a single flat ring. It takes under a minute to cut three rings with a sharp razor blade.

I think the stuffing box manufacturers like Buck Algonquin and packing makers such as Gore, marine authors such as, Calder, Casey et. al know what they are talking about. Marine installations are NOT the only industry to use packing. The major use of this is in industrial pumps, they cut rings just as the packing boxes are designed for.

Trying to reinvent the wheel, with the potential to sink your vessel or ruin your shaft is probably not the best choice for an experiment. Mixing two brands of varnish to get a desired color or patina? Well ok, that's a relatively safe experiment. Messing with a hole in your boat that is supposed to keep water out, when there is plenty of sage industry advice all pointing to the same installation technique, for a reason, strikes me a a bit, well, un-wise..

Have I pulled DIY installed single line flaxes out before? Sure, and they were always problematic, hence why they were pulled in the first place. Most of these shafts were badly worn and scored and the packing to drip rates were problematic. Could you get lucky? Maybe, but why do this when the labor to do it right takes about 60 seconds?

 

[Chris Burti]

Hydraulic ram = 10 - xxx tons per square inch = rings

High pressure steam, over 3000 psi = rings
http://www.valv.com/app_common/118/110/library/3/iom_choke_050907_r1.pdf

Residential water system 40 -100 pounds per square inch (hose bib) = string

Low pressure steam, 4 - 10 psi = string http://www.thisoldhouse.com/toh/video/0,,1638785,00.html

Marine shaft gland = What? Maybe 5 psi ?

IMHO - pick your poison, it is your boat.

Stray thought though...If I were doing the job for someone else, I would likely use rings and in fact do so on my own boats...but that has more to do with past experience in working with live steam systems than any concern that they are required.

 

[Ron20324]

Though familar with the packing, I've never done it. Is Warren confusing the string packing with the different (fiber?) rings? The 'different" ones being somewhat square-ish in shape and firmer, and those are the ones cut on the bias and the cuts stagger around the shaft. Or Warren, is your post talking string in both cases? .

 

[Maine Sail]

Low pressure steam, 4 - 10 psi = string http://www.thisoldhouse.com/toh/video/0,,1638785,00.html

Marine shaft gland = What? Maybe 5 psi ?

IMHO - pick your poison, it is your boat.

Stray thought though...If I were doing the job for someone else, I would likely use rings and in fact do so on my own boats...but that has more to do with past experience in working with live steam systems than any concern that they are required.

That's funny, I actually know Rich. He used to be a direct competitor when I was a manufacturers rep in the hydronics industry. He's also a sailor and I can guarantee you he has rings on his boat...

Steam radiators don't have spinning shafts, and I too have packed them with a single wrap, as that is really all that's needed. You just jam the nut down and it works because you don't have the constant friction of a shaft spinning and no worry of ruining the shaft..

 

[Deadline]

Off-center myth

I love the gas/diesel analogy!

As to the off-center rings, it's hard to execute. After carefully marking the rings, your hand will rub off the markings in the event of all the turning to repack. Suffice it to say that the three or four rings will be pretty well packed to preclude any problem if by random chance all three cuts lined up perfectly. In that event, I have an old combination lock that needs opening.

I just repacked with the black JCR or whatever it's called. Very messy, especially with the lube that you buy separately. But I'm assured it will outlast the Obama administration.

 

[Warren Milberg]

Thanks for all your helpful comments. I do plan to cut and install 3 or 4 separate rings, using virtually dripless GFO fiber packing (+/- $20 from eMarine).

I did note, however, that the single strand of packing removed from my friend's boat was MUCH easier to remove than all my other experiences teasing out 3 or 4 separate rings with picks, needle-nosed pliers, and flax removal tools. Yet the potential disadvantages, real or imagined, seem to far outweigh this one advantage.

I kept that single strand and am posting a few pics of it, wound on a mandrel and alone, for those interested. It worked flawlessly on my friend's boat for around 500 engine hours and was replaced as part of routine maintenance, not failure.

 

[Chris Burti]

MaineSail

While I am in the "rings" camp, I do a lot of things that I either consider or know to be overkill for vsarious reasons.

However, packing doesn't wear a shaft unless it is run dry and becomes burned hard. Dirt, sand and other contaminants trapped in the packing is what normally wears the shaft and are why packing should be changed on regular maintenance intervals.

I do not understand how the lateral compression of a stuffing box on static packing will create wear on its faces. Nor do I understand how that compression will harden non tapered ends and make them more abrasive than any other part of the compressed mass.

While I am not questioning that you have observed excessive wear on shafts with spiral wrapped packing, I do question your conclusions as to causation. If you can point me to any quantitative studies addressing the issue, I am willing to be educated.

Note that I am not advocating the use of spiral winding, I just want to be clear on the facts.

 

[Sam Salter]

You guys are messing with 200 years of tradition here!
sam

 

[Nik]

Sooo many opinions here, so I'll add one more to the mix. I do have a background in rebuilding valves, shaft packing's and hydraulic cylinders (different kind of packing's). Is one piece spiral packing a good idea? IMHO, No, Nay, Never. Does it have to be be cut on an angle / bias, and perfectly sized? Depends on the installation; 3000PSI steam, YES, 20 - 50" WC, no. Wrap the packing around your shaft and with a razor knife / blade make a clean straight cut. Repack your rings alternating the cuts 12/6/12/6, some opt for 12/6/9/3 etc. on the clock. This gives you separation of layers / joints and no gaps at the front and back. Easy and simple. 27.71 inches of water equals 1 PSI, do your math. Even at these low pressures it amazes me how a 1 or 2 inch hole can sink a boat so fast. YMMV

 

[kloudie1]

Many years in machinery engineering experience taught me that spiral wound packing on low pressure on a linear sliding shaft is OK..like Nik says. But spiral wound on a rotating shaft is a no-no.. We had packed pumps that ran continuously on water for 8000 to 9000 hours without repacking.. those always had straight cut or in some cases bias cut rings.. but always separate rings as is industry practice.. Spiral wound rotating shaft packing can “catch” on the shaft and spin in the packing box if operated intermittently and allowed to dry between run times.. Remember how Mercury used a spiral wound spring as a clutch in some of their outboard motors? It grabs in one direction, and slips in the other..