PTFE Tape on Skin-Fitting & Seacock Threads??

To say that PTFE tape cannot be use as a thread sealant is nonsense. I regularly use PTFE tape as a thread sealant on Natural Gas pipelines operating at pressures up to 1000 PSI.......... if it seals that I am perfectly happy to use it on the threads on skin fittings.
Just to clarify on the number of wraps....... most PTFE tape now sold is of the 50% overlap variety. Quite simply this means that as you wrap the thread with tape you make a 50% overlap on the previous wrap and you only go along the thread once....... NO MORE THAN ONCE. The tape thickness is such that it won't enter the thread correctly if you do multiple passes.
All my seacocks are fitted with PTFE tape in this manner and I sleep very peacefully knowing I have a sound seal that will undo if required.
Oh, also most reels of PTFE have a little diagram on showing which wat to put it on the thread.

Hope that all makes sense,
Paul.
 
[ QUOTE ]
To say that PTFE tape cannot be use as a thread sealant is nonsense. I regularly use PTFE tape as a thread sealant on Natural Gas pipelines operating at pressures up to 1000 PSI.......... if it seals that I am perfectly happy to use it on the threads on skin fittings.
Just to clarify on the number of wraps....... most PTFE tape now sold is of the 50% overlap variety. Quite simply this means that as you wrap the thread with tape you make a 50% overlap on the previous wrap and you only go along the thread once....... NO MORE THAN ONCE. The tape thickness is such that it won't enter the thread correctly if you do multiple passes.
All my seacocks are fitted with PTFE tape in this manner and I sleep very peacefully knowing I have a sound seal that will undo if required.
Oh, also most reels of PTFE have a little diagram on showing which wat to put it on the thread.

Hope that all makes sense,
Paul.

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Thank you!
 
I agree with you here. With bells a whistles on. Altough PTFE tape may not , per se, create a seal, the threads on a male and female fitting will have been cut on different machines on different runs and possibly by different engineering firms in differerent workshops in different countries. So the tollerances in the threads may have built up to make the seal either efficient or very, very poor. The tape will fill the spaces and provide the seal.
Therefore there is no "correct" number or turns of tape, but merely "sufficient" to create the seal.

erm. That's an end to the discussion.
 
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erm. That's an end to the discussion.

[/ QUOTE ]Do you want to bet on that? /forums/images/graemlins/smirk.gif
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hammer.thumb.gif
"Artificial intelligence is no match for natural stupidity"
 
"Therefore there is no "correct" number or turns of tape, but merely "sufficient" to create the seal. "
...that's what I found also. One or two didn't quite fill the gap between the threads...needed a few more turns. My tape does seem very thin though...probably need some better stuff.
 
Re: PTFE Tape on Skin-Fitting & Seacock Threads??

Well How experienced are you?

I worked in the plumbing industry for a number of years and also have friends that are plumbers now.
One of the things that I learned was never take too much notice of the manufacturers who make the stuff! they don't use it in real live situations! The fact is that PTFE will disintigrate as a thread in wound on even if you only have wound it a couple of times or 10 times! I have had leaks doing a joint as you suggest and never when more is used, I know what I am talking about in practice.

Barry
 
Re: PTFE Tape on Skin-Fitting & Seacock Threads??

[ QUOTE ]
Well How experienced are you?

I worked in the plumbing industry for a number of years and also have friends that are plumbers now.
One of the things that I learned was never take too much notice of the manufacturers who make the stuff! they don't use it in real live situations! The fact is that PTFE will disintigrate as a thread in wound on even if you only have wound it a couple of times or 10 times! I have had leaks doing a joint as you suggest and never when more is used, I know what I am talking about in practice.

Barry

[/ QUOTE ]

Ergo, if you wind the entire spool ("The whole 9 yards", as some might say) onto the thread, it will NEVER ever leak. Correct?
 
Re: PTFE Tape on Skin-Fitting & Seacock Threads??

[ QUOTE ]
Thanks, all...

...sorry had intermittent www access of late...

[/ QUOTE ]

Bet you wish you'd never asked /forums/images/graemlins/smile.gif


Paul.
 
This thread fascinated me, so went on a hunt of the internet to see if the likes of Dupont or 3M had some authoritative advice. If there, with a quick search it wasn't obvious, so had a look at plumbing and DIY sites instead.

They seem to recommend 2 to 3 turns with the thread, some say to add a threading compound on top. This site is pretty representative of many many I looked at (scroll down to the bottom for the advice)

http://www.plumbingworld.com/tapes.html

NB I looked at about 40 sites and forums that actually covered the question, and skimmed several hundreds that didn't. That was off fairly general search terms, so most likely to turn up if you were looking for that info. If you wanted to find sites that recommend using more than that number of terms you can find them, but they are typically on forums rather than on technical sites.

I then went searching on sites that manufacture equipment, and had a look at their installation instructions. Those that did give specific instructions were largely those that had plastic in the fittings, and they all advised against excessive wrappings of ptfe as they could break the female plastic piece.

So, not very scientific, but a 15 minute search of probably thousands of sites, quickly changing search terms to get better results, all ended up in the same area of results, but none really authoritative. Might give it another go when I have more time

even using terms like best practice, interchanging ptfe with teflon, ignoring the word tape, etc etc provided little real information. However, this isn't my area of expertise, so I may well be using the wrong keywords. So if anyone can come up with some authoritative online info from a trusted source (rather than the many forums that have discussed it!) I'd be grateful
 
Can confirm this from servicing engine inlet yesterday! Without PTFE, the bronze filter was fully tight a 1/4 turn out of alignment; with 1.1/2 turns of PTFE, it was just enough to get that final 1/4 turn with the hose tail in perfect alignment and the fitting firmly and properly seated.
 
I think 'low leachability' is something to to do with the chemicals in the tape not contaminating the fluids or gasses passing through the joint, rather than anything to do with it's properties as a sealant.
 
Yes, clean threads thoroughly so you can assemble easily by hand. Then I use PTFE tape, 2-3 turns then trial assembly. If the final 1/4 to 1/2 turn by spanner makes the valve handle line up conveniently, then job done. If not, add or remove tape to achieve this.
 
Hi Folks,

Why would water ever make to the threads if the Thru Hull's mushroomed based if properly sealed with a good marine grade sealant?

The threads are only there to hold the thru hull tight against the hull so that seal remains. The tape in this case is only there to lubricate the threads.

If you have water penetrating to the threads, you have another problem... water infiltrating your core between the two fiberglass skins... and rotting it... well, to the core!

Claude
 
Hi Folks,

Why would water ever make to the threads if the Thru Hull's mushroomed base is properly sealed with a good marine grade sealant?

The threads are only there to hold the thru hull tight against the hull to protect that seal.
The tape in this case is only there to lubricate the threads.

If you have water penetrating to the threads, you have another problem... water infiltrating your core between the two fiberglass skins... and rotting it... well, to the core!

Claude
 
Hi Folks,

This is my 2 cents;

The thru hull seal is done at it's mushroom base with a proper marine sealant.
The Teflon tape in this case is just there to lubricate your threads.

If you have water even making it to the threads, you have a real problem. That means you hull core between the 2 fiberglass skins is being infiltrated and will rot. I would rather have a bit of water coming in through the threads warning me that the thru hull seal is compromised then having a dry bilge while my hull core is slowly rotting away...

Claude

Claude
 
Sorry Mr. (or mrs. Moderator... I thought this wasn't working so I sent a reply 2 or 3 times. Please only use my last reply.

Many thanks and sorry for the confusion... :)
 
I've supervised many industrial installations where screwed pipework (threads produced on manual pile threader) where ptfe tape was used as a lubricant/sealant always with success. I've also used it always on domestic plumbing so had no second thoughts when sealing joints on my boats. It's quick, clean and effective.
Some will recommend loctite thread locking products and/or backnuts to facilitate orientation of elbows and valve handles but I've never found these necessary and just use larger Stillsons. As for thread locking, I find it inconceivable that a fitting is going to unscrew itself on a boat. And as for Sikaflex, it's messy and makes subsequent dismantling difficult although no doubt it's a good sealant.
 
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