what thread type for gas tight threads?

[BrokenBiker]

nice short one from me for a change, what threads to use on an air/gas tight thread?

more out of curiosity if im honest, but i always assumed BSP was self sealing, until i realised earlier all my 1/4BSP air fittings leak like no tomorrow without an o-ring or ptfe

 

[Dozzer]

BSPP or BSPT?
there is a difference
BSPT is tapered and designed to seal at low pressures with the likes of thread sealant.
BSPP (parallel) is designed for a dowety or similar internal or external face seal for higher pressure applications.
Have used BSPP up to 2200bar with stainless steel nitrogen filled o rings

 

[BrokenBiker]

BSPP or BSPT?
there is a difference
BSPT is tapered and designed to seal at low pressures with the likes of thread sealant.
BSPP (parallel) is designed for a dowety or similar internal or external face seal for higher pressure applications.
Have used BSPP up to 2200bar with stainless steel nitrogen filled o rings

so, taper threads with ptfe would do for air fittings and the likes, but high pressure needs parrallel threads with a seal for anything major?

or i assume, something like a bullnose fitting that is just clamped with the threads would be a better option for something like a gas connection?

 

[Turbo]

so, taper threads with ptfe would do for air fittings and the likes, but high pressure needs parrallel threads with a seal for anything major?

or i assume, something like a bullnose fitting that is just clamped with the threads would be a better option for something like a gas connection?

I have used both taper and parallel threads with 3000 psi hot pressure washer systems but neither is self sealing. Ptfe tape will sometimes work for sealing but a suitable loctite product is more reliable.

For self sealing you will need a taper cone type fitting something like the bullnose on your regulator and gas bottle.

 

[gaz1]

you should try the old ways

hemp and thread seal set harder than a rock and was a git to remove

ptfe and paint and yes on the net it says dont use it but guess what it still seals

those are the old methods of sealing gas and air old style

 

[BrokenBiker]

I have used both taper and parallel threads with 3000 psi hot pressure washer systems but neither is self sealing. Ptfe tape will sometimes work for sealing but a suitable loctite product is more reliable.

For self sealing you will need a taper cone type fitting something like the bullnose on your regulator and gas bottle.

thanks,

for any application i would ever need i think ptfe would be sufficient on taper threads...i was asked to make a removable adapter to plumb propane into a small pulse jet, but that was always going to be a bullnose type fitting anyway.

did do a little bit of googling but as usual you get a differen answer on every link...som say tapered male and parallel female, some say both tapered are a perfect seal, some say you should never use tape on either and others say tape is mandatory...

asking on here has got much clearer answers that i know i can trust

 

[BrokenBiker]

you should try the old ways

hemp and thread seal set harder than a rock and was a git to remove

ptfe and paint and yes on the net it says dont use it but guess what it still seals

those are the old methods of sealing gas and air old style

i will admit i have been using 'water' ptfe on my air fittings since before i can remember...its how my father does it, and how my grandfather did it...

 

[Dozzer]

i will admit i have been using 'water' ptfe on my air fittings since before i can remember...its how my father does it, and how my grandfather did it...

there is nothing wrong with using the liquid PTFE on fittings, probably better than tape, you can swell a joint on softer fittings like brass with to much tape.

ideally you should use taper with taper, and parallel with parallel, the amount of thread engagement gets a bit sketchy, but think many have been in the "bugger only got" situation.

As @Turbo says. On any of the hydraulic stuff i always use Lock & Seal, our local hose shop has their own brand, most are OK
If you fancy a trip to the dark side you can look at automotive/hydraulic fittings, there are LOTS of standards!!

 

[BrokenBiker]

there is nothing wrong with using the liquid PTFE on fittings, probably better than tape, you can swell a joint on softer fittings like brass with to much tape.

ideally you should use taper with taper, and parallel with parallel, the amount of thread engagement gets a bit sketchy, but think many have been in the "bugger only got" situation.

As @Turbo says. On any of the hydraulic stuff i always use Lock & Seal, our local hose shop has their own brand, most are OK
If you fancy a trip to the dark side you can look at automotive/hydraulic fittings, there are LOTS of standards!!

automotive stuff can bugger off, those bits are already available to buy as it happens, i need to make a little brass adapter to connect a hose to the coolant pipe stand on the lathe, looks suspiciously like 1/4bspt

 

[brightspark]

you should try the old ways

hemp and thread seal set harder than a rock and was a git to remove

ptfe and paint and yes on the net it says dont use it but guess what it still seals

those are the old methods of sealing gas and air old style

using hemp and boss white paste worked real well . hemp swells up when it gets wet so if it did weep it self sealed

 

[BrokenBiker]

using hemp and boss white paste worked real well . hemp swells up when it gets wet so if it did weep it self sealed

can you still get that?

 

[brightspark]

yes https://www.google.com/search?q=boss+white+plumbing+paste&sca_esv=a5f19cfa0813df82&sxsrf=AE3TifPWCYI2fOxfde_VZUFFJ3PfCkb9sg:1749492261498&source=hp&ei=JSJHaPigHL6ihbIPqrOkmAI&iflsig=AOw8s4IAAAAAaEcwNfWR-M_pdHy8h-rU_LVV5-Gz_d78&oq=boss+white+paste+&gs_lp=Egdnd3Mtd2l6IhFib3NzIHdoaXRlIHBhc3RlICoCCAIyBhAAGBYYHjIGEAAYFhgeMgYQABgWGB4yBhAAGBYYHjIGEAAYFhgeMgsQABiABBiGAxiKBTIIEAAYgAQYogQyCBAAGIAEGKIEMggQABiABBiiBDIIEAAYgAQYogRImF5Q2QZY0TtwAXgAkAEAmAGGAaABvAuqAQQxNC4zuAEByAEA-AEBmAISoAKwDKgCCsICBxAjGCcY6gLCAg0QLhjHARgnGOoCGK8BwgIKECMYgAQYJxiKBcICCxAAGIAEGLEDGIMBwgIREC4YgAQYsQMY0QMYgwEYxwHCAggQABiABBixA8ICDhAuGIAEGLEDGNEDGMcBwgIEECMYJ8ICBRAAGIAEwgIFEC4YgATCAggQLhiABBixA8ICCxAuGIAEGLEDGIMBwgIOEC4YgAQYsQMYgwEYigXCAgsQLhiABBixAxjUApgDFfEFGOYpldlFsDKSBwQxMy41oAflgAGyBwQxMi41uAebDMIHBjItMTYuMsgHaA&sclient=gws-wiz

 

[BrokenBiker]

yes https://www.google.com/search?q=boss+white+plumbing+paste&sca_esv=a5f19cfa0813df82&sxsrf=AE3TifPWCYI2fOxfde_VZUFFJ3PfCkb9sg:1749492261498&source=hp&ei=JSJHaPigHL6ihbIPqrOkmAI&iflsig=AOw8s4IAAAAAaEcwNfWR-M_pdHy8h-rU_LVV5-Gz_d78&oq=boss+white+paste+&gs_lp=Egdnd3Mtd2l6IhFib3NzIHdoaXRlIHBhc3RlICoCCAIyBhAAGBYYHjIGEAAYFhgeMgYQABgWGB4yBhAAGBYYHjIGEAAYFhgeMgsQABiABBiGAxiKBTIIEAAYgAQYogQyCBAAGIAEGKIEMggQABiABBiiBDIIEAAYgAQYogRImF5Q2QZY0TtwAXgAkAEAmAGGAaABvAuqAQQxNC4zuAEByAEA-AEBmAISoAKwDKgCCsICBxAjGCcY6gLCAg0QLhjHARgnGOoCGK8BwgIKECMYgAQYJxiKBcICCxAAGIAEGLEDGIMBwgIREC4YgAQYsQMY0QMYgwEYxwHCAggQABiABBixA8ICDhAuGIAEGLEDGNEDGMcBwgIEECMYJ8ICBRAAGIAEwgIFEC4YgATCAggQLhiABBixA8ICCxAuGIAEGLEDGIMBwgIOEC4YgAQYsQMYgwEYigXCAgsQLhiABBixAxjUApgDFfEFGOYpldlFsDKSBwQxMy41oAflgAGyBwQxMi41uAebDMIHBjItMTYuMsgHaA&sclient=gws-wiz

ta, always like to have a source for stuff that just works, im assuming wrap the hemp around the threads like ptfe tape, then paint the paste on?

 

[gaz1]

no wipe on then wrap then paste again then screw your fitting on

most dont the internet says wrap hemp and then paste thats wrong, what you should do as it get the paste on both threads

 

[brightspark]

used to watch the heating engineers use it mainly on steel pipes with malleable iron fittings many moons ago

 

[Turbo]

Another classic sealant is stag, a fuel resistant used by heating engineers, similar to red hermatite.

Really messy stuff that usually ended up on everything you touched like tools, overalls, tool box, door handles, etc.

 

[RWD3M]

so, taper threads with ptfe would do for air fittings and the likes, but high pressure needs parrallel threads with a seal for anything major?

or i assume, something like a bullnose fitting that is just clamped with the threads would be a better option for something like a gas connection?

Loctite 55. It's like industrial dental floss. As recommended here, works a treat!

 

[brightspark]

Another classic sealant is stag, a fuel resistant used by heating engineers, similar to red hermatite.

Really messy stuff that usually ended up on everything you touched like tools, overalls, tool box, door handles, etc.

once put some on my norton chaincase gasket and couldnt get it off without using a few pry bars bars

 

[Turbo]

Taper to taper joints should in theory self seal, the ptfe tape is to let the threads slide past each other until it is tight enough to seal.

Problem is that the threads and tapers on mass produced fittings are less than perfect so you will never get them tight enough to self seal.

Stainless fittings will gall long before they are tight if you don't use a liquid sealant.

If you want to get an elbow or tee to point a certain direction once assembled that might not be the same position where the joint is tight. That's where a solid setting liquid sealant is essential to hold the joint in the right position.

 

[gaz1]

and if your curious hemp and paste was used on sink taps, sink waste, traps and many other stuff

some have seen it used for that square to round on the old sinks

sink taps it was used in place of a rubber washer under the taps
it filled the square to round making a solid connection to the sink it was that solid it stopped the taps spinning when you used the round taps with no square at the bottom of them