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GFO packing

I'm thinking about it . But I read Mainsails' thoughts on it and now I'm not sure it's worth it . Re-Packing A Traditional Stuffing Box Photo Gallery by Compass Marine How To at pbase.com
I mean the galvanic thing . We have a SS prop shaft , but I'm thinking we also have a bronze box . Any thoughts ?
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Re: GFO packing

The 'teflon' (TetraFluoroEthylene, etc.) in GFO is an inert dialectric solid - no galvanic contribution.

However, as with all packing made from fibers there will be 'some' water interspersed between the fibers (although GFO/teflon does not become 'wetted' as its a hydrophobic), etc. .... water is the electrolytic 'conductor' of galvanic action. The usual shaft/prop zinc anode will protect the shaft. You can run an electric bonding 'jumper' from the bronze stuffing box to an anode; but, most dont.
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Re: GFO packing

Quote:
Originally Posted by Markwesti View Post
I'm thinking about it . But I read Mainsails' thoughts on it and now I'm not sure it's worth it . Re-Packing A Traditional Stuffing Box Photo Gallery by Compass Marine How To at pbase.com
I mean the galvanic thing . We have a SS prop shaft , but I'm thinking we also have a bronze box . Any thoughts ?
I also have a SS shaft and bronze stuffing box (don't we all?). I chose Ultra X which is also mentioned in the article.

Duramax Shaft Sealing Systems

Available from Hamilton Marine.
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Re: GFO packing

Quote:
Originally Posted by RichH View Post
The 'teflon' (TetraFluoroEthylene, etc.) in GFO is an inert dialectric solid - no galvanic contribution.

However, as with all packing made from fibers there will be 'some' water interspersed between the fibers (although GFO/teflon does not become 'wetted' as its a hydrophobic), etc. .... water is the electrolytic 'conductor' of galvanic action. The usual shaft/prop zinc anode will protect the shaft. You can run an electric bonding 'jumper' from the bronze stuffing box to an anode; but, most dont.

Rich,

It is not the Teflon that creates the issues it is the graphite they use for added lubricity that makes it galvanically active... A teflon non-graphite impregnated packing is galvanically inert but a graphite impregnated teflon packing is not.
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Re: GFO packing

Quote:
Originally Posted by SVTatia View Post
I also have a SS shaft and bronze stuffing box (don't we all?). I chose Ultra X which is also mentioned in the article.

Duramax Shaft Sealing Systems

Available from Hamilton Marine.
How long have you had it on there ? And when was the last time you checked it ? I ask humble .
My good buddy with a Cat. 32 yr. 95', has a bronze prop shaft .

Last edited by Markwesti; 1 Week Ago at 12:41 AM.
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Re: GFO packing

Maine-
Its the water that is the electrolyte of 'galvanic action'. Even without packing, the close proximity of a wetted stainless propshaft and a wetted bronze stuffing box, will have an electro-potential for galvanic attack, the same in similar fashion of a bronze prop affixed to a stainless, etc. shaft. Simple electro-chemistry.

Flax and other 'botanic cellulosics' used in typical packing are also carbon based, and their electropotential is also based on metallic contamination inherent in the fibers, or on the surface formed 'carbon black' on flax, etc. packing due to the point to point heating caused by shaft friction. The electro-potential of graphites is also probably due to metallic impurities, more than the graphite by itself.
If 'carbon' in such applications was a 'real' problem, then dripless shaft seals with their stationary carbon flanges would also be rapidly attacked by galvanic action.
Dont forget that 316 stainless can have up to ≤0.7% carbon in its chemical composition.
The rubber hose of bellows on dripless seals and the hose used on shaft logs are all 'carbon filled' rubber.
;-)

The usage of anodes in all dissimilar electro-potential situations is the 'answer' ... such as a prop or shaft mounted anode, etc. This applies to ALL types of (dripless) seals and stuffing boxes used on boats and other water wetted installations.

The usage of GFO is OK for stuffing boxes. Its rapidly becoming the choice packing in industrial applications involving stuffing boxes. If 'carbon' is a perceived problem, then one must consider to remove all dripless seals, carbon filled rubber bellows and that reinforced carbon filled rubber hose that connects between the stuffing box and the outlet tube .... as they too all contain 'carbon', in a form quite similar to, or as a 'graphite'.

BTW - PTFE has one the lowest coefficients of friction of all solids 0.04, one cant get a lower lubricity than that with any solid. The graphite is used to seal up 'intersticies' in the PTFE yarn braid, plus helps to hold the PTFE yarns together as a structure.

Anodes !!!!!!

regards
;-)
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Last edited by RichH; 1 Week Ago at 01:31 AM.
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Re: GFO packing

Quote:
Originally Posted by RichH
The usage of GFO is OK for stuffing boxes.
ABYC Standards:
"6.7.4 Graphite impregnated packing material shall not be used because of the possibility of galvanic incompatibility with the shaft material."


Not me, that is the ABYC saying these packings shall not be used .....


I disagree to some extent, because in many cases, with properly installed anodic protection, and AQ 19-22 shafting this can work but you should check your shaft/gland/prop at least yearly. The key is properly installed anodic protection. Many yards and boaters fall down on how to properly install anodes.


You can do this experiment yourself with an Ag/AgCL reference cell and it takes two seconds... Throw in a rubber shaft log hose too. Never seen one that is galvanically active.

https://youtu.be/RfbD7cFfY70

Graphite is the highest element on the galvanic scale for things we use on boats. As such everything becomes anodic to it.

Zinc is: -980 to -1050
Naval / Tobin Bronze is: -300 to -400 (what most bronze shafting was made of)
Marine Stainless Shafting variants range from: -150 to +130
Graphite is: +200 - +300


Quote:
Originally Posted by RichH View Post
Maine-
Its the water that is the electrolyte of 'galvanic action'. Even without packing, the close proximity of a wetted stainless propshaft and a wetted bronze stuffing box, will have an electro-potential for galvanic attack, the same in similar fashion of a bronze prop affixed to a stainless, etc. shaft. Simple electro-chemistry.

Flax and other 'botanic cellulosics' used in typical packing are also carbon based, and their electropotential is also based on metallic contamination inherent in the fibers, or on the surface formed 'carbon black' on flax, etc. packing due to the point to point heating caused by shaft friction. The electro-potential of graphites is also probably due to metallic impurities, more than the graphite by itself.
If 'carbon' in such applications was a 'real' problem, then dripless shaft seals with their stationary carbon flanges would also be rapidly attacked by galvanic action.
Dont forget that 316 stainless can have up to ≤0.7% carbon in its chemical composition.
The rubber hose of bellows on dripless seals and the hose used on shaft logs are all 'carbon filled' rubber.
;-)

The usage of anodes in all dissimilar electro-potential situations is the 'answer' ... such as a prop or shaft mounted anode, etc. This applies to ALL types of (dripless) seals and stuffing boxes used on boats and other water wetted installations.

The usage of GFO is OK for stuffing boxes. Its rapidly becoming the choice packing in industrial applications involving stuffing boxes. If 'carbon' is a perceived problem, then one must consider to remove all dripless seals, carbon filled rubber bellows and that reinforced carbon filled rubber hose that connects between the stuffing box and the outlet tube .... as they too all contain 'carbon', in a form quite similar to, or as a 'graphite'.

BTW - PTFE has one the lowest coefficients of friction of all solids 0.04, one cant get a lower lubricity than that with any solid. The graphite is used to seal up 'intersticies' in the PTFE yarn braid, plus helps to hold the PTFE yarns together as a structure.

Anodes !!!!!!

regards
;-)
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Last edited by Maine Sail; 1 Week Ago at 07:35 AM.
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Re: GFO packing

Unfortunately for the ABYC graphite/carbon can be of either +4 or -4 electronic valence - meaning the net potential of any form of carbon can be positive, negative or (balanced as a 'net' potential) neutral. The usage of anodes is the 'protection' for all underwater electronic / galvanic incompatibilities.

As a physical chemist ... my view is that the ABYC is quite 'obviously faulty' (I'm being kind here) as the exact same carbon species as found in most underwater rubber hosing/seals as a 'filler', is specified by ABYC; so, under ABYC 'mindset'/opinion should also be banned due to its electro potential; and, only non-filled (weaker) polymers should be used for hosing - of course not.
Even the 'newer' low friction marine packings - probably ECTFE, FEP or PFA - ... and of the same approximate frictional coefficients as PTFE but are 'better' vs. frictional heating are graphite impregnated/coated.

Anodes are what provides the protection versus all dissimilar galvanic potentials. ABYC should know and recognize this in the case of 'graphite'.

Will ABYC become 'apoplectic' with the change over from copper based to zinc based bottom paints?

;-)
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Last edited by RichH; 1 Week Ago at 09:01 AM.
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Re: GFO packing

Quote:
Originally Posted by RichH View Post
Unfortunately for the ABYC graphite/carbon can be of either +4 or -4 electronic valence - meaning the net potential of any form of carbon can be positive, negative or (balanced as a 'net' potential) neutral. The usage of anodes is the 'protection' for all underwater electronic / galvanic incompatibilities.

As a physical chemist ... my view is that the ABYC is quite 'obviously faulty' (I'm being kind here) as the exact same carbon species as found in most underwater rubber hosing/seals as a 'filler', is specified by ABYC; so, under ABYC 'mindset'/opinion should also be banned due to its electro potential; and, only non-filled (weaker) polymers should be used for hosing - of course not.
Even the 'newer' low friction marine packings - probably ECTFE, FEP or PFA - ... and of the same approximate frictional coefficients as PTFE but are 'better' vs. frictional heating are graphite impregnated/coated.

Anodes are what provides the protection versus all dissimilar galvanic potentials. ABYC should know and recognize this in the case of 'graphite'.

Will ABYC become 'apoplectic' with the change over from copper based to zinc based bottom paints?

;-)
And we all know how boaters always maintain their anodes. Anodes do disappear, fall off etc.. You be shocked at the number of boats I measure mid season with zero or near zero anodic protection...

Please understand that my site only suggests CAUTION using these packings and suggests to check it periodically. I won't personally use it on bronze shafts, to much of a voltage spread for me, but still do install it with AQ 22 shafts for customers who are good about keeping up with anodic protection.

I know you think the ABYC are wrong so how do you feel about Western Branch Metals, the largest distributor of stainless shafting in the world. They actually manufacture the shafting. Are they wrong advising against it too?


Western Branch Metals - Manufacturer of Aqualoy Marine Shafting:

"The use of graphite-impregnated packing is not recommended because of the possibility of galvanic corrosion of the shaft material. FEP fluorocarbon (Teflon***) - impregnated asbestos braid, the fibers of which are impregnated with the plastic prior to braiding, is considered to be excellent for shaft seals. Wax impregnated flax packing may also be used."


Edit:

Just took a few measurements (Fluke 179 NIST Calibrated using Ag/AgCL reference cell):

Casco Bay Sea Water - Temp 46F:

Zinc -1.049
GTU Graphite Packing +0.136
Bronze Shaft -0.404
PSS Bellows (used) 0.000 to -0.008
Standard Packing Box Hose (used) 0.000 to -0.002
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Last edited by Maine Sail; 1 Week Ago at 02:04 PM.
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Re: GFO packing

Ive been using Aqualloy shafting for many years with GFO .... perfect and no hint of galvanic action.
PTFE and its analogues are notorious for the generation of static electricity when in high friction or high liquid flow application. This 'may' be the cause of the perceived 'alarm' by ABYC. Internal (to the flow, etc.) grounding wires, discharge probes are the usual solution to such electrical discharge by 'teflonics' in liquid and gaseous flow. Just a passing thought and perhaps a Ag/AgCl cell test with and without grounding of an operating stuffing box would help to clear up the 'misperceptions'. ;-)

More/most importantly - Casco Bay @ 46° .... the stripped bass should soon be arriving to spawn. You New Englanders and Down Easters usually get what spawned in the Ches. and sounds behind the NC Outer Bank about 2 years later.
The Mid-Atlantic autumn striper crop last year was dismal, so next year you can expect slim pickings.

;-)
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