Sans Bateau
Well-known member
Is PTFE tape the best product for sealing threaded joints? Seacock to skin fitting etc. Or is there something better I should use?
PTFE tape
- Thread starter Sans Bateau
- Start date
DavidGrieves
Member
PTFE
Hi
Not sure if there is anything better, I have always used PTFE on my seacocks and never had a problem. Just get plenty of it on and wrap in in a clockwise direction. For bigger threads I have used "gas PTFE" tape. I think it's the same stuff but just a bit thicker. Worked OK for me.
http://www.screwfix.com/p/ptfe-gas-...g & plumbing&gclid=CM3mos6s460CFUVTfAodlkRD9Q
Hi
Not sure if there is anything better, I have always used PTFE on my seacocks and never had a problem. Just get plenty of it on and wrap in in a clockwise direction. For bigger threads I have used "gas PTFE" tape. I think it's the same stuff but just a bit thicker. Worked OK for me.
http://www.screwfix.com/p/ptfe-gas-...g & plumbing&gclid=CM3mos6s460CFUVTfAodlkRD9Q
Martin_J
Well-known member
Hi..
and for what it's worth.. I've always used 'Jet-Lube V2 Plus' as well.. It's designed to seal threaded joints and copes with up to 10,000 psi.
http://www.jet-lube.co.uk/03 thread sealants.html
It's half way down the page (and it actually contains PFTE!) Suitable for use on potable water, fuels and gas as well so I find many uses for it.
If you're at the boat later I can bring a pot of it round for you to see..
Rgsd Martin.
and for what it's worth.. I've always used 'Jet-Lube V2 Plus' as well.. It's designed to seal threaded joints and copes with up to 10,000 psi.
http://www.jet-lube.co.uk/03 thread sealants.html
It's half way down the page (and it actually contains PFTE!) Suitable for use on potable water, fuels and gas as well so I find many uses for it.
If you're at the boat later I can bring a pot of it round for you to see..
Rgsd Martin.
Sans Bateau
Well-known member
Martin, I wont be back at the boat until next Sat, your welcome to visit then if you like.
Martin_J
Well-known member
Sounds good.. The other thing about the Jet Lube is that it's not messy.. so you can use a few wraps of PTFE tape with it and tighten the joint.. If doesn't line up correctly then just undo, put a few more (or less) wraps of tape around and then re-tighten.
I like the fact it can be used on diesel and gas threaded connections as well... and can be immediately pressurised.
I like the fact it can be used on diesel and gas threaded connections as well... and can be immediately pressurised.
VicS
Well-known member
Yes PTFE tape is excellent
BUT It is intended for use on tapered threads.
Joints with parallel threads should ideally be tightened down onto a joint washer, or possibly an O ring, although this is unlikely to be possible with a seacock to skin,fitting joint.
For a seacock to skin fitting joint I would use a back nut or nut to fix the seacock in the orientation required together with a sealant on the threads.
ASAP have the lock nuts http://www.asap-supplies.com/search/locknuts/lock-nuts-brass-standard
You could of course do as most people do ... fudge it up with PTFE tape
BUT It is intended for use on tapered threads.
Joints with parallel threads should ideally be tightened down onto a joint washer, or possibly an O ring, although this is unlikely to be possible with a seacock to skin,fitting joint.
For a seacock to skin fitting joint I would use a back nut or nut to fix the seacock in the orientation required together with a sealant on the threads.
ASAP have the lock nuts http://www.asap-supplies.com/search/locknuts/lock-nuts-brass-standard
You could of course do as most people do ... fudge it up with PTFE tape
Martin_J
Well-known member
Just checked..
and yes, I do have backnuts as well to lock the fittings onto the through hulls....
The gas joints that I did (as well as the diesel ones) were tapered threads.
and yes, I do have backnuts as well to lock the fittings onto the through hulls....
The gas joints that I did (as well as the diesel ones) were tapered threads.
rob2
Active member
Some considerable time ago, when PTFE tape was "new" I was told to consider it as a lubricant, not a sealant (it doesn't actually set or do anything to make a seal) but that as a secondary effect of its lubricant properties the thread will tighten more until the tape fills it so completely that it seals - but basically the thread form is the sealing face. Although this supports the doubt as to whether it will seal a parralel thread, we all know that in practice it will. The backing nut is a damned good idea though, or the lubricant properties may also allow it to unscrew!
I'd like to hear what is different about "gas" tape. If it is just thicker then it makes no difference whether it is gas you are trying to seal. Surely if the thickness is optimized for a domestic gaspipe sized joint it would make it useless going on dangerous to try to seal a much smaller bottled gas line?
Rob.
I'd like to hear what is different about "gas" tape. If it is just thicker then it makes no difference whether it is gas you are trying to seal. Surely if the thickness is optimized for a domestic gaspipe sized joint it would make it useless going on dangerous to try to seal a much smaller bottled gas line?
Rob.
VicS
Well-known member
alteredoutlook
New member
Someone once recomended to me rather than use pfte tape one should use superglue.
I am sceptical - has anyone got any thoughts?
I am sceptical - has anyone got any thoughts?
savageseadog
Well-known member
I've always used Sikaflex on skin fittings threads. Never leaks and does undo.
D
Deleted member 36384
Guest
I don't think its the best thing for sealing threaded connections. Jet Lube has been mentioned, I use Liquid O Ring, which is an American product used in the Oil Industry. It's a thick green paste and works well.
PTFE tape is quite adequate for the job so use it if required. One issue with PTFE tape is that one can over do it and this leads to two problems: yielding of the female fitting and insufficient thread engagement of the male fitting. Both are easy to avoid just don't over wrap in the extreme. It has been known for some fitters to wrap about a 1mm band of PTFE tape and tightened up the fitting to effect a seal but not realising that only a few threads had engaged and the female part had yielded. It does happen and in my industry fatalities have resulted as fittings become lethal projectiles under pressure.
My employer has a standard for applying PTFE tape which is quite simple: start at the nose of the male fitting, do not over lap the nose. Make one full wrap, make the next wrap overlap by half the tape width and continue to the last 3 threads overlapping by one half. When wrapping apply sufficient pressure to just indent the tape around the thread profile, no need to stretch the tape right into the profile.
The above keeps gas fittings for instrument connections pressure tight on hydrocarbon systems operating up to 10,000 psi. However, I would say that in in this application it is nearly redundant and local plants have banned its use based on availability of better products such as those available from Loctite http://www.loctite.co.uk/cps/rde/xchg/henkel_uke/hs.xsl/thread-sealing-4477.htm
With regards to diesel fittings. I have found that PTFE tape became quite slimy after 2 years leading to diesel leaks. The fittings were on a Vetus dual filter assembly. The device was dismantled and rebuilt with Liquid O Ring and so far it is OK. It could have been assembled wrongly for all I know with insufficient tape as not a lot came out when rebuilding.
VicS
Well-known member
I think you are not alone!
bedouin
Well-known member
Can you still get "Boss White". I always used to use it for domestic plumbing (until I discovered compression joints don't need a sealant 
.
PTFE is fine but only as a lubricant, not a sealant itself
.PTFE is fine but only as a lubricant, not a sealant itself
Vara
Active member
In a domestic setting I've used this stuff very successfully ,
http://www.fernox.com/products/traditional+plumbing+products/jointing+compounds/ls-x
Will give it a whirl when doing waste cock renewal next week.
http://www.fernox.com/products/traditional+plumbing+products/jointing+compounds/ls-x
Will give it a whirl when doing waste cock renewal next week.
VicS
Well-known member
Can you still get "Boss White". I always used to use it for domestic plumbing (until I discovered compression joints don't need a sealant
PTFE is fine but only as a lubricant, not a sealant itself
Yes and I think there is a grade for potable water systems as well as the standard stuff.
Traditionally used with hemp though on threaded joints
pampas
New member
Stag "A" or "B" has served the world well
MarTer
Member
PTFE Tape
I was told by a marine engineer never to use PTFE tape on skin fittings. He recommended Loctite 577 I think it was. They do a range of thread sealents so do check the number as this was a few years ago. The parts do not need to be tightened so allowing the parts to be positioned exactly as required. Expensive but worth it.
I was told by a marine engineer never to use PTFE tape on skin fittings. He recommended Loctite 577 I think it was. They do a range of thread sealents so do check the number as this was a few years ago. The parts do not need to be tightened so allowing the parts to be positioned exactly as required. Expensive but worth it.
dje67
Active member
I'm going through exactly the same thought-process as Galadriel as I'm replacing all 8 seacocks and associated connections (except through-hulls as they are bronze; all other bits were brass on my 1998 Bene).
Most of the fittings comprise of a skin fitting followed immediately by a right-angled elbow, followed by the seacock followed by the hose-tail. All are BSP parallel except the hose-tail into the valve which is tapered.
I was intending to use PTFE for the hose-tail but decided that all the others would potentially slip in the future if I used PTFE tape. I aslo felt that some of the elbows would be absolutely impossible to fit if they needed to be screwed on very tightly over PTFE tape. (lack of working space being the problem here).
A final consideration was that since the seacocks would be mounted above the elbow then closing/opening the valve would exert a nice turning moment on the elbow.
Rightly or wrongly, I decided to use Loctite 577 for all the joints having rumaged around the forum. This seemed to allow me to assemble the whole lot easily, in the knowledge that it would "set" into position. Not sure whether I'll ever be able to get it all undone again, but since the existing brass fittings have done 14 years, I'm hopeful the ASAP-supplied DZR fittings will be good enought that I don't need to do the job again for a couple of decades!
I also bought back/lock nuts to help hold the elbow securely onto the skin fitting. I'm going to get stuck into all this work next week, so any last-minute suggestions from others on this approach would be welcome (without wishing to hi-jack Galadriels thread...!)
Photo of what I'm doing attached.
Photo of why I'm doing it also attached
Most of the fittings comprise of a skin fitting followed immediately by a right-angled elbow, followed by the seacock followed by the hose-tail. All are BSP parallel except the hose-tail into the valve which is tapered.
I was intending to use PTFE for the hose-tail but decided that all the others would potentially slip in the future if I used PTFE tape. I aslo felt that some of the elbows would be absolutely impossible to fit if they needed to be screwed on very tightly over PTFE tape. (lack of working space being the problem here).
A final consideration was that since the seacocks would be mounted above the elbow then closing/opening the valve would exert a nice turning moment on the elbow.
Rightly or wrongly, I decided to use Loctite 577 for all the joints having rumaged around the forum. This seemed to allow me to assemble the whole lot easily, in the knowledge that it would "set" into position. Not sure whether I'll ever be able to get it all undone again, but since the existing brass fittings have done 14 years, I'm hopeful the ASAP-supplied DZR fittings will be good enought that I don't need to do the job again for a couple of decades!
I also bought back/lock nuts to help hold the elbow securely onto the skin fitting. I'm going to get stuck into all this work next week, so any last-minute suggestions from others on this approach would be welcome (without wishing to hi-jack Galadriels thread...!)
Photo of what I'm doing attached.
Photo of why I'm doing it also attached
Sans Bateau
Well-known member
No dje67, you have not hi jacked the thread at all (are we using PTFE to secure this 'thread'!).
Your concerns over removal of fittings in the future, the only reason you are likely to be removing is for replacement. To do this when the fittings are so tight you cannot get a turn on them, you can always use the adjustable spanner that always works, a disc cutter in the angle grinder.
For my own installation, I'm going to be looking at the liquid sealer's like the Loctite 577 mentioned. Alternatively, and I need to think of a good reason why not, savageseadog's suggestion of Sikaflex, I have enough of that left before it goes off.
).Your concerns over removal of fittings in the future, the only reason you are likely to be removing is for replacement. To do this when the fittings are so tight you cannot get a turn on them, you can always use the adjustable spanner that always works, a disc cutter in the angle grinder.
For my own installation, I'm going to be looking at the liquid sealer's like the Loctite 577 mentioned. Alternatively, and I need to think of a good reason why not, savageseadog's suggestion of Sikaflex, I have enough of that left before it goes off.
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