Non hardening sealant to 400psi

[picclock]

I think the subject says most of it. I am trying to get hold of a non hardening thread sealant that will be good for up to 400 psi and resistant to oils and petrochemicals. Only used at temperatures up to 50C tops. At the moment I use Rocol foliac threadseal XS, which works well but you have to wait at least an hour after assembly to test, then if there is a problem another hour etc. So I'm trying to speed things up and make disassembly easier.

I'm in the UK so although I'm pretty sure such stuff exists in the states, I haven't had a lot of luck finding something suitable over here.

Many thanks for your time

Best Regards

picclock

[Lew_Merrick_PE]

Picclock,

ND Industries (US) makes a product called Vibra-Tite.  It comes in two forms: solvent vehicle and water vehicle.  The water vehicle version works quite well in firearm gasnut applications (i.e. up into the 1400 psi & 370°C range) and is used extensively in racing engine applications.  The recommended application is as a patch (like a nylock insert), but I have used it in dip to cover xx% of threads to 100% coverage applications.  Normal (i.e. non-rushed) cure is 24 hours at room temperature.  Rushed cure (not recommended, but it works) involves heating the entire fastener to 100°C until the water evaporates.

I am not sure what pertrochemicals it is fully resistant to in practice.  Normal machine oils & greases have never caused a problem in my experience.  I doubt that it would survive anything that causes urethane to degrade.

I have used it several times when dealing with gasnuts in firearms.  McCann Industries (now in hiatus after the death of the owner) used it in a number of custom firearms used by Special Operations troops since 1996.  The adjustment screw in these gets relocated according to the user's preference and load of ammunition used -- call it twice a month on average.  As of late-2010, there were no failures in any of the firearms.

Does this help?

[John Rudd]

Picco....Isnt PTFE any good?

I work in the gas industry where we have pressures over 3500 psi, we use various sealants  Liquid PTFE, BossWhite and hemp....

I'll see what else we use...

[Stilldrillin]

I use Blue Hylomar. So, I can dismantle easily, when necessary.

Works for me! 

David D

[chipenter]

I use Stag type B red for instant seal up to 650 C .

[John Rudd]

I use Stag type B red for instant seal up to 650 C .

Yup, We used to use Stag all the time when I was an apprentice...

[Stilldrillin]

I use Stag type B red for instant seal up to 650 C .

Yup, We used to use Stag all the time when I was an apprentice...

Yep! Same here. 

This is the first I knew it was still being manufactured! 

Never forgotten the smell, from 50+ years ago........   

David D

[chipenter]

Yep you can still get Stag not the cheapest http://www.buckandhickman.com/find/product-is-316205 mine is old and I have to put meths in now and again to thin it .

[picclock]

Thanks for the replies. I used to use Hylomar, but they reformulated it and the new stuff is nowhere near as good. If subject to pressure you can see it bubble out of the joint.

Amazing description by Buck and Hickman :

'Stag 'B' is a thick non jointing compound

right next to a tin of Stag B Jointing compound 

This does sound like the right stuff though so I'll get some and give it a try.

Many Thanks for your help

Best Regards

picclock

[picclock]

OK, so Buck and hickman have supplied the Stag red. It seems very runny. There is no info on how long you have to leave it for a high pressure test, just that it creates a low pressure seal immediately. Unable to find any application data other than apply it with a brush. Tin says suitable for joints in 1/2" pipe upwards - Why not use with smaller ? How long should I leave it for a 400psi 1/2" bsp joint ?

Amazing smell though - sort of smokey.

Also ordered some BLACK SWAN SWAN SEAL PTFE JOINTING COMPOUND, no idea if it will be better or worse but worth a try.

Best Regards

picclock

[chipenter]

You have to stir it well the black always comes to the top , i would leave it overnight or until the smell goes away .

[doubleboost]

Blue hylomar is now classed as cancer causing (this is why the new stuff is no good)
I still use "stag wellseal" on face to face joints
http://www.hutsonprecision.co.uk/wellseal-jounting-compound/
John

[picclock]

Just had a failed 1/2" BSP threaded joint fail with Stag Red. Most disappointing. Pressure only 150psi. Stag red applied copiously to fitting and allowed to set overnight. Threads of mating parts are good though dissimilar metals, brass/aluminium. Temperature ambient.

Clearly something is wrong here but without further application info I'm not sure what. Threads were cleaned and degreased prior to assembly.  Around 7 threads engaged as far as I remember. Also found that when leak checking with paraffin, that the paraffin appears to dissolve the stag red, not impressive for a sealant supposedly resistant to petrol and oil (so it says on the tin).



Hopefully the alternate PTFE sealant I purchased will arrive today and I can see how that fares.

Best Regards

picclock

[John Rudd]

Is this thread a tapered bsp thread or parallel?

I would not expect a tapered thread to leak with 7 threads engaged and sealed with a decent sealer...

When I was an apprentice we had to do a test piece for pipe fitting, threads were cut using appropriate dies and then 1 and a half turns of PTFE tape applied and then hydraulic pressure tested to check the quality of the threading and assembly. Pass or Fail...

[picclock]

@ John

Its a parallel threaded fitting. On disassembly I found that the male thread was evenly coated to the end with the sealant. However only the top two female threads had sealant, although it looked like an even coating. I had only applied sealant to the male part as per instructions, and it would appear that because the threads were so good excess got scraped off after the first two threads. It may have been a different story if I had coated male and female threads.

However the real killer is that the sealant clearly dissolves with paraffin. And I'm betting it would with any other oily bits, despite the tin saying that its resistant to petrol and oil. I suppose it depends on how you define resistance, but I would say the performance is poor against these petrochemicals.

I am about to remake the joint with Swan Seal, a ptfe compound (it says on the tin).

Best Regards

picclock 

[vtsteam]

Doesn't a parallel thread usually require a shoulder and washer/gasket/o-ring?

[Rob.Wilson]

Doesn't a parallel thread usually require a shoulder and washer/gasket/o-ring?

It dose 

Hi picclock

Personally ,I would not go for tape or any other sealant on a parallel thread as the tread is not designed to seal , tapered threads are , what you need is a face sealing fitting , using a copper /fibber washer , O ring or dowty seal .

From what I can see/read   1/2" BSP too 1/4" BSPT  is what you require .



Dowty seal





Good to thousands of PSI       If you want I can pick one up for you and wack it in the post .


Rob
   

[picclock]

@ vsteam / robwilson

The 1/2" to 1/4" bsp adapters I'm using don't have rim or facility for that. The thread on the adapter is just inside the flat so no shoulder to speak of (22.6mm AF so with thread OD @21mm <1mm either side).

However this Swan Seal stuff (no affiliation) seems amazing . You just apply it and tighten. No setting off time needed (I emailed them and they said immediate seal). Took me about 10 mins to get the part back but it works and seems to make a very good non leaky seal. Also being being ptfe is not likely to dissolve with hydrocarbons. I think its game over unless I find some other issue.

I'm quite blown away by the fact that something that has the same sort of consistency as stag red and the new Hylomar can behave in such a different way. No special treatment, just cleaned the threads and slapped it on - job done. Because of the immediacy of the seal I can easily test and check parts under pressure with no delays wondering if the sealant has cured. 

So far so good .. .

Best Regards

picclock

[Rob.Wilson]

Good you got it sorted 

I would have sent the fitting as well as a few seal , offer still stands if thing dont work out ,just PM me

Rob

[picclock]

@RobWilson

Many thanks for your kind and generous offer. For most of this sort of stuff I do use tapered fittings, but I don't have the tooling to cut tapered threads so where I have to make stuff its into a parallel thread. Most of the time, where disassembly is not required I can use Rocol foliac XS, which is hard setting and seems to work well under all sorts of conditions. The downside is it takes an hour or two to cure. Other alternative is low grade epoxy (Lidl £2 per pop) which gives a very good seal but can be removed by heating above 200C (Oven - but she who must be obeyed must never know  ).  But this job I needed to be able to remove and replace easily to service a valve behind the fitting. Hence the need for a soft sealant. If this stuff is as good as it seems to be I may use it exclusively simply because of the speed with which an effective high pressure seal may be made, and its chemical resistances.

Many Thanks

Best Regards

picclock

[David Jupp]

Hmm - though some of my experience is to much higher pressures than you are using (and with flammable gases), I would never expect a parallel thread to seal against pressure.   Tapered/Parallel combinations, though designed to seal (with compound or tape) are enough of a 'bodge'.

If it works for you then fine, but I'd keep a careful eye on it and always be a little suspicious...

[picclock]

@ DavidJupp

OK, you've convinced me. I've just changed it for a male 1/2" to 1/4" tapered thread fitting.  With this new sealant its a snap as its pressure tight straight away so no curing times.

Best Regards

picclock

[Lew_Merrick_PE]

Hmm - though some of my experience is to much higher pressures than you are using (and with flammable gases), I would never expect a parallel thread to seal against pressure.   Tapered/Parallel combinations, though designed to seal (with compound or tape) are enough of a 'bodge'.

O-ring seal (JIC type or MIL-SPEC type) provide much better sealing.  Silicone o-rings of the proper compound can work up to nearly 600°F.  At that or higher temperatures, a crush-type copper face seal works quite well.  Tapered threads with any flurocarbon seals tend to die once the pressure gets much above 15,000 psi.

[awemawson]

I used some allegedly 'non hardening' sealing compound to seal the joint between the head casing of my J&S 540 surface grinder and the Optidress wheel forming attachment. It had to seal yet be easy to remove. You guessed it - several months later when I came to remove it it was stuck utterly solid. I rang the makers help desk and their only solution was to heat it to 150 deg C - remember this is precision equipment - I wasn't best pleased! Sadly I cannot remember the make.