I'm trying to get some sales/technical/installation info on Drip-Free Packing, the blue Teflon/grease that was the subject of a thread on this list a month or


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NameI'm trying to get some sales/technical/installation info on Drip-Free Packing, the blue Teflon/grease that was the subject of a thread on this list a month or
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Stuffing Boxes

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Sailnet Tayana List


I'm trying to get some sales/technical/installation info on Drip-Free Packing, the blue Teflon/grease that was the subject of a thread on this list a month or so ago. I've contacted the company several times and the info was promised, but nothing has shown up. Does anyone know if the company is having problems or what might be going on?


Second, since this packing seems to stop circulation along the shaft, does this place the shaft in an anaerobic environment that could lead to wastage?


Thanks, Coleman S/V Traveler February 2000

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WEST MARINE sells this packing under their own label, you might contact them for info. I just repacked my stuffing box with it and so far it has worked great; no drips and the shaft is not heating up.


Jim S/V SMILES (T37 Hull 407) February 2000

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Subject: Shaft and stuffing box


After rebuilding my 4-108 and dropping it back in with only removing, not changing the old rusty coupling. I have been able to move back the shaft sufficiently to install the new coupling. I want to get the engine aligned so I can test all is working well under load. The problem is now to get the shaft and the coupling to slide back toward the motor. I tried diving the boat and working it over with a four-pound hammer and a block of wood but it did not budge.


Question: if I remove/replace the packing in the stuffing box will the shaft loosen up enough to be moved fairly easily? (not sure how old the packing is and should probably be replaced anyway). Has anyone tried the dripless packing I have been reading about, and how well does it work? How difficult is it to replace the packing in the water?


Phill T 37 #101 October 2001

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Phill,

Sorry for the misunderstanding. I think I wrote out a overly long description of repacking the stuffing box a few years ago, and at risk of excess redundancy, it's pretty straightforward. It is easy to replace the stuffing. But you are raising two different issues. One is how to get the coupling back to the engine, and the other is how to replace the stuffing. Although they are possibly related, as you indicate, I would not completely remove the stuffing until you get the shaft back to where it can be re-connected to the transmission.


Thus, you can "loosen" the stuffing box collar, but do it very carefully, making sure that your bilge pumps are working reliably. Applying equal pressure on both side of the flange (i.e. on port and starboard sides) with a small jack, you should be able to gradually push the flange towards the engine. This is the point at which you should now carefully re-align your engine mounts. (I assume that you replaced the old mounts with new ones when you re-installed the rebuilt engine.)


Prepare to spend a few hours doing this the first time. Best to get someone who has done it to help, to avoid the possible disconcerted reaction some people have when they suddenly see large quantities of water pouring into your beloved boat.


Make sure that you have adequate electric bilge pump capacity, and that the bilge pumps are all working. Test them repeatedly to give you confidence in their performance.


Based on the age of your boat, I suspect that the stuffing box is built in a manner similar to ours. There are two bolts coming forward from the fixed part of the stuffing box. There is a collar with two ears that slide on the two bolts. The collar has a tube that extends aft into the main part of the stuffing box. The shaft should be 1.25 inches in diameter. The opening in the stuffing box is approximately 1.75 inches in diameter. The tube on the collar is slightly less than 1.75 inches in diameter. Thus you have a space between the shaft the inside of the stuffing box that is about 0.5 inches, or 0.25 inches all around the shaft when centered. This might lead you to assume that the proper wax laden flax should be 0.25 inches so that is will form a snug collar around the shaft. However, you may find it advisable to have two sizes of flax on hand: a roll of 1/4 inch (0.25) and a roll of 3/16 inch. The small size may prove necessary to allow you to fit the material around the shaft and still push in the collar. The 1/4 inch material may make such a tight packing that you will have trouble getting it into place, and will have water pouring in as you find the sweat on your brow turning to a flood with your increasing anxiety. When you push the collar back into the stuffing box, it will compress the flax, and the 3/16 material will be just fine most of the time.


Read Nigel Calder or any other good maintenance manual on how to re-stuff a stuffing box. You will cut a series of pieces of flax so that it exactly completes a single ring around the shaft. Cut the ends on a bias so that it forms a good seal. The length of the flax pieces should not be too long or too short. Cut at least 4-6 pieces and make sure that they are the correct length for a snug fit around the shaft. Buy a good quality spiral tool for removing stuffing at any good chandlery.


Have several tools at hand, particularly a few 14-mm deep sockets to loosen and tighten the nuts on the stuffing box.


Make sure that you have lots of light down below.


Put several drops cloths under the prop shaft forward of the stuffing box. This will trap any tools or nuts that you may drop, and prevent them from sliding all the way down into the bilge. But keep the cloths loose enough to allow water to drain down into the bilge.


Test your bilge pumps again. The boat won't sink, but you will think things will get out of control as you are deep in the bilge and have fantasies of drowning in the lazarette as your boat sinks. Relax. Don't take a drink at this time. You will need all your faculties.


NOW:
Carefully lay out your various tools.


Loosen the nuts on the stuffing box. Place them in a very secure location. Do not drop them into the trough leading to the bilge. But if you do, remember, I suggested that you put some drop cloths in there to catch them.
Carefully slide the collar forward on the shaft. You may find there is an increasing drip of water.
Relax, take a deep breath, and let it drip. If all the bilge pumps are working, you are in good control of the situation.


Before you remove any of the stuffing, check to see if the flax you previously cut in careful lengths really will fit. Put a piece around the shaft and push it into the stuffing box with the collar.


Take the spiral tool (looks like a miniature corkscrew) and carefully slide it into the stuffing box. Turn it to snare the piece of stuffing. Pull out the stuffing. You now know how to proceed. Now reach in and using the spiral tool, remove one of the older pieces of stuffing. The rate of flow of water will increase. Take comfort in the operation of your bilge pump. Probe for any additional material. Take a deep breath. No rush.


Now put flax into the stuffing box one ring at a time. After each insertion, tamp it in with the tube extending aft from the collar. Each ring should form a nice snug complete circle. Each circle should start at a different point on the shaft so that the ends are not all at the same point on the shaft to avoid leakage. When you have put in about 3 or 4 rings, make sure that you can still slide the collar on far enough to be able to secure it on the bolts.


Now tighten down the collar, and it should be about 3/4-inch gap between the collar and the fixed portion. If you have to add more rings of flax, do so. If you can't get even three rings in, then you didn't remove all the old flax.


Lean back and relax.

Check engine alignment. This is critical. Secure the coupling flange with the four bolts.


Start the engine and let it warm up. Leave it in neutral. Make sure you are securely tied to the dock.

Have a second person in the cockpit.
You should now go back into the lazarette. Have them put the tranny in gear. Be very careful that you don't have any clothing that could be caught in the rotating shaft before you do that.
Watch the shaft and stuffing box. There should be a slow dripping from the stuffing box. If there is none, the stuffing box may be too tight. Put the tranny in neutral.
Loosen the nuts on the stuffing box ever so slightly. Put the boat in gear and check for dripping. As the flax settles in, it will increase the rate of drip. Now carefully tighten the nuts. It should drip about 2-8 drops per minute.


Do not rush.

Now climb out of the bilge.

Now you have that beer.


regards, Harvey October 2001

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Just at the local boat show. The Shelter Island Boat Yard people had a large booth where they were displaying the PYI PSS dripless stuffing box. The exhibitor then suggested that rather than spending several hundred on the PSS and its installation, I should try out the GFO Gore-Tex and Teflon stuffing material. About $20 worth of material would be enough for the T-37. Very interesting material. I mentioned it to a friend with a big ocean fishing boat, and he said that he had been using it for 4 years, and it ended the Too-Loose/Too-Tight sequence of repeated adjustments immediately. He received a free sample directly from the manufacturer and ended years of fiddling with the stuffing box.
Anybody else had any experience with this material? As with many of the Gore products, they are based on very clever design and application of materials sciences to deal with the various aspects of a problem.
regards, Harvey January 2002

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Bob,

Just managed to find more info on the GFO at the webpage for E.F. Gore, Co.

http://www.gore.com/en_xx/products/sealants/packing/gore-tex_valve_stem_packing.html
I also include a quote from their page on packings.


"Packings"

W. L. Gore & Associates manufactures a full line of high-performance compression packings. These materials are chemically inert, highly abrasion resistant, and able to withstand temperatures up to 550°F (228°C). Our packings can be used in virtually any static or dynamic application requiring compression packing in your facility.


GFO® Packing - Unexpected packing failures are a thing of the past. Reduce downtime and cut maintenance costs with compression packing made from long-lasting non-asbestos GFO® fiber. Chemically inert, with few exceptions, over the entire 0-14 pH range. Withstands temperatures from -400°F to +550°F (-240°C to +288°C). For any type of pump - centrifugal, rotary, turbine,
reciprocating. For valves, agitators, mixers, dryers, and refiners.


GFO® Marine Service Packing - Ideal for use in stern tubes and rudder posts. It runs virtually leak free and does not damage expensive propeller shafts. Helps keep bilges dry and lasts longer than flax. GFO® marine service packing cuts easily and is easy to install. When it is time for haul out, GFO® marine service packing is easy to remove from the stuffing box. Used by the U.S. Coast Guard, specified by the U.S. Navy, and approved by the American Bureau of Shipping. "


Harvey J. Karten January 2002

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I found a place in Ft. Lauderdale that sells the GFO. Emarine.

$17-$56 depending on shaft size, etc.

http://www.e-marine-inc.com/products/gfopacking/packing.html
John Reynolds January 2002

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Alan,


We had persistent problems with our stuffing box, with continuous leaking, etc. I was planning to put a PSS seal on our shaft, but the shop that installs them on Shelter Island suggested that I first try using the GFO Teflon braid from Gore-Tex. This is completely different product from the Teflon Stuffing material sold at West Marine and most other places. I've now had it in place for about 1.5 months, and it has finally controlled the leakage, while keeping the shaft cool. The cost of the GFO packing was a total of about $20. The mechanic could have sold me the more expensive PSS plus the installation charges, so this was a trivial cost for a successful (so far!) experiment. You can track down the Gore Company website and find their web page about their GFO packing.


You might try that route. The other advantage of GFO is that this can be repaired even at sea, if it did start leaking. The concern about the PSS expressed by several mechanics is that you have to haul the boat to install it, and if it blows out, you are in real trouble. The PSS/PYI people clearly state that the PSS has to be put in place with the boat on the hard. On the positive side of things, I have not personally heard of any reports of it blowing out. But I did wonder what is wrong with the PSS on Charles Freeman's T37?


regards, Harvey J. Karten February 2002

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Can you provide the dimension on the Gor-Tex packing that you used? I understand that 1/4 is recommended but I understand that others have found 3/16 more user friendly.
Sid Rubin February 2002

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Alan and Sid,

The dimension I used was the 3/16". I had to go to the slightly smaller size as our shaft is somewhat eccentrically placed within the stuffing box. The 1/4" couldn't fit fully around. That meant that I had to use an excess of 3/16" to compensate for the greater gap on one side, but it fit perfectly on the other side. The company says that you should be able to restuff using a single small pack of material. But since I had to use one size smaller, I needed two packs. So far - it works well.


Alan - as far as the vibration is concerned, check several things:

  1. Condition of motor mounts. If they are more than 10 years old, they should probably be replaced.

  1. Remove all the material from the stuffing box and replace it completely with the GFO Teflon/graphite braid stuffing.

  1. Very carefully align the motor relative to the shaft and stuffing box. If you haven't done this before, I suggest that you hire a friendly and skilled mechanic who will show you how to do it properly.

  1. After the initial alignment, install a PYI isolation coupler. This serves two purposes - it reduces the prospect of shaft damage in the even that your prop snares an object, and it helps reduce vibration.

  1. Check your shaft to make sure that it is true, check the cutlass bearing for wobble

  1. Check the prop for imbalance. Once you have the vibration under control, I would also check the accuracy of your Tachometer. We found that after replacing our alternator with a new unit, that our tachometer is reading 20% lower than the actual value.

  2. At that point, depending upon the present material used, consider replacing the sound insulation material. Our engine box was "insulated" with cheap acoustic tiles made of some sort of wood particles. The wood fragments dropped into the bilge, and were a source of potential problems for the bilge pump. We replaced it with a modern sound insulation material with foam, weighted middle layer and aluminum reflective foil. I still don't like to motor, but at least it no longer jars my teeth nor deafens me. Engine efficiency has improved.


regards, Harvey February 2002

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I bought from: http://www.e-marine-inc.com/


Jim (SMILES) February 2002

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http://164.109.56.82/english/ipd/sealants/packing_GFO_Marine.cfm

Alan Jett Alliance Studios February 2002

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Hi Rich

Thanks for the information but my shaft does not have a nut on it at the flange end. There is a keyway that I managed to get out yesterday but the flange still eludes me. I am getting to the point that I will probably cut the shaft and have the flange pressed off. After 18 years it's unlikely it will come off any other way.


Andy Windy Blue April 2002

Andy
The shaft is secured to the coupling with a set screw and a key. The coupling is in two parts. One side is secured to the shaft and the second part is secured to the transmission. he two halves bolt together. I have a 4-108 and the flange has 4 bolts that hold the two halves together. These four bolts are the ones being described for removal. Slide the shaft aft with the coupling attached and place a 1/2-inch nut between the two halves of the flange. Using longer bolts, tighten the 2 halves of the flange together. The shaft will move, providing the set screw is removed. Repeat the process with a socket next (a little longer than the nut), then possibly the socket and a nut. The process is tried and it works. It will save a few hundred dollars for a shaft.


Joe Sprouse Sojourn Deltaville, VA April 2002

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We have now had the GFO Teflon packing in place for a few months. Continues to perform well. Shaft remains cool, and almost no moisture comes in through the stuffing box. (Of course the stanchions, chain plates, hawse pipes, and ports left open are another matter!).


After the first week or two as the stuffing was settling into place, I have only had to occasionally touch the adjustment nuts on the stuffing box by less than 1/8th of a turn. The bilge pump rarely goes on any longer. All that money wasted on bilge pumps! (Ha! That's challenging fate!) On a more serious note - assuming that the shaft is OK, I have decided against installing a PSS dripless seal. The problems associated with removing the flange from the shaft, and the recommendation that the PSS only be put on when the boat is on the hard, combined with the uncertainty about difficulties of emergency repairs in the event the bellows leaks when offshore, prompt me to decide in favor of the GFO. The PSS is not Fail-Safe, though it is highly reliable. But if it goes, there is big trouble. The worst that could happen with GFO is that I might have to add some more material. In addition, the price differential is substantial ($20 versus $400 - including parts and labor, but not the cost of hauling the boat). I can recommend GFO highly to those of you who are still considering installing a PSS to avoid the perpetual problem of a leaking stuffing box.


Harvey April 2002

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There was a thread on this bulletin board about a location in Florida that sells it for a reasonable price. About $20 buys enough to do the whole stuffing. I bought it at one of the small shops on Shelter Island. It is made by the Gore Company (of Gore-Tex fame).


I used the 3/16" wide material. Get a diver to pack some wax around the cutlass bearing. Make sure your bilge pump works well. Remove the stuffing box flange, and slide it up the shaft. Remove all the old stuffing. This might test the reliability of your bilge pump.


Put in several rings of the GFO. Push the flange back in, and tighten. If it goes too far in to the point that the flange is almost all the way in, remove the flange and add more stuffing.


Follow the directions about adjusting the stuffing box. After the initial settling in period when you may get a bit of leakage, you can eventually completely stop all leakage, but adjust it so that there is no overheating of the shaft.


That's all that there is to it.
regards, Harvey April 2002

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By the way, I am only referring to the GFO Teflon material from Gore-Tex people. There are other brands of Teflon stuffing material. I found that they were not very good, leaked after a short period of time, were very expensive, and finally had to be pulled out and completely replaced with ordinary flax stuffing.

The Teflon stuffing at West Marine and at Boat/US is not recommended - the GFO is a very intelligent combination of materials and design.
Harvey April 2002

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To buy:

http://www.e-marine-inc.com/products/gfopacking/packing.html

To Install:

ftp://ftp.sailnet.com/tayana/cutlass/GFOpack.pdf

I'm switching from the blue Teflon stuff to GFO


Ray Slaninka Red Bank, NJ April 2002

John:

I guess I'll go with 3/16. I think I could squeeze 1/4 but it might be too tight and I don't want to risk scoring the shaft. I think 3/16 is what most people use. And it is what the spec reads.
Ray Slaninka April 2002

I also noted that the manual says that you should use 3/16" stuffing, not 1/4". If the stuffing box were perfectly aligned to the shaft, 1/4" might be preferred.


The problem with sizing is exaggerated if there is any eccentricity in the centration of the shaft within the stuffing box. And there definitely is in our boat. Thus, the space available on the top of the shaft is slightly more than on the bottom. I can easily fit 1/4" above, but barely 3/16" below. I have had the engine realigned, and have checked the alignment on several occasions. The cutlass bearing is in good shape, and was carefully checked during our recent haul out. The conclusion was that the original installation of the stuffing box was not done with sufficient care and accuracy, so it is slightly eccentric.

I suspect that leaking stuffing box on our boat has been a problem since its original construction. That was also a reason I was considering shifting to PSS, as it provides greater freedom to align the shaft between only two points - the transmission coupling and the cutlass bearing. The stuffing box intrudes into this straight line if it is in any way not only eccentric, but if it is even slightly "off-angle" (i.e. - not perfectly parallel to the shaft, when the shaft is properly balanced between the transmission coupling and the cutlass bearing. Of course this assumes that the cutlass bearing is properly aligned!).
The great virtue of the PSS is that the shaft basically "floats" at that point, so the stuffing box does not have to be as accurately aligned. A great concern would also be that the stuffing box flange scrapes against the shaft, scoring it. The only saving grace might be that the flange is made of softer material than the stainless steel shaft, so that the flange will wear more that the shaft. But not a happy situation.


Packing the stuffing box with traditional flax with wax is a problem as the flax is relatively incompressible and hard, and takes more time to seat properly. It also doesn't conform well to the available space, and permits water to leak past it. The GFO material is apparently made of a fiber material that is far more adaptable, and includes both graphite and Teflon. The combination both lubes the surface of the shaft, and the Teflon apparently seals around it.


By using 3/16" material, you can more easily pack in and compress enough material to halt the leakage. While I felt that I should only use complete rings of material, I found that there was still a gap on the top of the shaft because of the eccentric stuffing box. I therefore added a bit of extra material on the top before putting in the last of the rings of stuffing. I compressed the collar to seat it all, removed the collar and then added a few more rings of GFO. Had I been able to use the 1/4", then a single package of GFO would have been sufficient. But since the 3/16" had to be used, I used two packs of 3/16" GFO. (Each pack is about 24" of material). Just to play is safe, I ended up buying 3 packages. I still have one unopened package, as a backup. The place in Florida sells them for about $9 a package. The place here in San Diego charges about $12 a package (for the 3/16").


regards, Harvey April 2002

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http://www.e-marine-inc.com/
order GFO packing on line. 2 day delivery in Richmond, Va.
Joe Sprouse April 2002

Subject: Rusting Propeller shaft
I have just replaced the propeller shaft and cutlass bearing because the shaft had started to rust in the area of the stuffing gland. The rusted area was about 5" long and extended from just out side the gland to the end of the stuffing material. I noticed last season that there was a leak from the gland and a build-up of a rusty colored paste around the gland. I decided that I would re-pack the gland with GFO after I read about it on this site.


Has anyone else experienced rusting of the shaft. Why should a SS shaft rust especially where it is exposed to air? It has been speculated that it could be electrically induced as followings. The shaft in my case was not bonded since both the flexible coupling to the gear box and the cutlass bearing are both insulating. I have also noticed that when it rains that water leaking into the stern of the boat eventually runs down over the stuffing gland. I have now bonded the shaft with a copper strap across the flexible coupling.


Greg Barnicoat KISH April 2002

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Greg,

Did the rusting begin only after you installed the GFO? Or did you install the GFO after the start of the rust?


regards, Harvey Karten April 2002

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Subject: Rusting Propeller shaft
I replaced my shaft three years ago when I got my boat..... It probably was a 304 0R 302 series stainless and had lots of 'rust bloom' all over the in the bilge exposed area near the stuffing box. Seeing the exterior corrosion, pitting, etc. I removed the shaft for inspection and found the area of the stuffing box packing was severely galled, pitted and corroded (in the section that is between the stuffing box and the cutlass).


At this time, I have the subject old shaft / worthless paperweight in front of me at the moment and report to you that I do have a 'rust bloom' on the area exposed in front of the stuffing box. Testing the rusted areas shows slight magnetic attraction whereas the rest of the shaft does not. Visually the 'rust' looks like a typical chlorine/halide attack on stainless - as would be similarly found vs. deaerated salt water; and, also exhibits surface cratering (chipping/stress corrosion) under the rusted area. It was the 'chipping' that led me to pull the shaft out and inspect it and to ultimately replace it. Fully exposed, I found massive catastrophic surface damage.


My *hunch* (based on long, long past engineering / chemistry experience in the foundry business, etc.) is that the salt water enters the packing area and with poor flow of lubricating water to keep up the needed oxygenation of the stainless surface, the fluid deoxygenates into the surrounding fiberglass, packing material, shaft log, etc. .... and begins fretting, etc. corrosion on the shaft. ...... and that why I prefer to use PTFE coated FLAX packing ... because it leaks a little and such 'sweep' volume of seawater through the packing keeps the shaft oxygenated to maintain the proper oxide coat on the stainless, etc. I currently work with various forms of Gore-Tex, etc. and am quite suspicious that the perfusion of oxygen through the PTFE packing onto the shaft is quite limited - typical gaseous intrusion pressures of such a wetted hydrophobic material are typically 25-75 psi, etc. (Sorry to again run against the crowd on this one).


Note: If I DID install pure Gore-Tex in future, I'd first soak the packing material in isopropyl alcohol to allow the material to wet-out so that the necessary (I believe) perfusion of gases would occur, .....of course it would then leak like regular packing and I would only benefit from the low frictional characteristics of the Gore-Tex but NOT the hydrophobicity.


Anyway it cost me over US$600 for a new shaft .... and it all started by seeing the rust zone on the shaft directly in front of the stuffing box.


BTW... I only use 3 rings of PTFE coated flax packing - 1 drip per 1-2 minutes not running (0,25 - 0,5 Liter/day), 5 drips per minute running..


If you'd like pics of the galling/corrosion I'd be glad to send.....


Rich Hampel April 2002

Hi Rich,

After reading the response from Sandra Blake I am even more convinced of the galvanic corrosion theory. In Dublin I had a swing mooring in the middle of Dun Laoughie Harbour and thus no stray currents. In Stockholm, I have a mooring in a marina with electrical outlets and hence the possibility of stray currents.


I also want to get some clarifications from your description below. In the stuffing gland, I had imagined that seepage of water in the stuffing gland was essentially a boundary effect, i.e. lack of perfect seal between the flax and shaft etc; and not the diffusion of water through the flax.


As for GFO if you believe their literature it has the following advantages over other packing material:
a. high thermal conductivity

b. low expansion

c. low friction, due to PTFE

d. soft/pliable material, hence easily molds into the gland cavity


All of which combine to give the gland a very low seepage rate.


I expect that the Gore-Tex fiber gives the material the high thermal conductivity, but I have not heard of this property before. Can you comment on this.


Greg Kish, Stockholm May 2002

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I just installed GFO packing. I used one package of 1/4" material and I got 4 rings out of it. Yesterday I launched the boat and 4 rings is barely enough as I almost ran out of adjustment before I stopped the flood. Luckily I got 2 packages and I will add more. Then I was reading an old TOG #26 and ran across a warning from a 1984 letter not to use graphite packing. I wonder what they meant back in 1984 by the term graphite packing? GFO has graphite in it. Also does anyone have a copy of the ABYC standards? If so, can you look up P6-6d and look for a warning about graphite corrosion. Derek, are you still reading these?


Back in January 2002, I posted this about graphite:


As far as the graphite in the packing, maybe I'm a little out there on this one, but I was concerned about it because of possible galvanic reactions. Graphite is a conductor. There is a pretty big spread between Silicone Bronze and Graphite in the Galvanic Series, although it is close enough to 316 stainless, it is pretty far from bronze. Graphite is the most noble metal, which means that you could start losing some of your stuffing box and even, to a lesser degree, your shaft. But even as I write this, I have to question how much metal would actually be lost and if it is worth worrying about.


Here's the rub, the 1984 letter warns about the shaft and the packing. Graphite and stainless are closer on the galvanic series than bronze and graphite. Go figure!


Ray Slaninka Tayana 37 May 2002

__________________________________________________________________________________________________


We just put new GFO packing in last week also. One thing we discovered on our first roll of GFO was that, because that type of packing has considerable stretch to it, we cut the first batch of rings too short because we apparently pulled the packing a little too snug on the shaft when cutting it. (This was evidenced by the rings not completely joining end-to-end when installed.) We wrapped a little duct tape around the shaft when forming our second batch of rings, and they came out perfect. You might want to check this out before you add more rings.
Regarding your question about galvanic corrosion, I seem to recall reading somewhere, perhaps Calder's book, that ABYC does proscribe the use of graphite packing. I don't think GFO packing has anywhere near as much graphite as the true graphite tape packing that caused all the problems in the past, but I don't know for sure. This is definitely worth checking out. The Gore Company that makes the stuff has an 800 number. I'll see if I can dredge it up and will give them a call.


Dayton Eckerson T-37 #215 May 2002

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Dayton, Ray, and others

The concern about the graphite is probably something that Gore Company can answer. They claim that the U.S. Navy now uses GFO in their stuffing boxes. I would hope that this concern was addressed in the formulation of the MilSpecs on this material. I would hate to think that a Destroyer would suddenly lose its prop shaft while in the midst of a move to avoid a submarine!


Yet another month has gone by and the stuffing box continues to work well without excessive leakage and no heat buildup.


regards, Harvey May 2002

__________________________________________________________________________________________________
Protection is provided by the proper zinc mounted on the shaft or prop.


Rich Hampel May 2002

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