Sealing BSP fittings

While I was fitting an adapter it came on and off a couple of times and I noticed small bits of ptfe tape had been torn off doing it up. Looking around on the web this seems to be a common problem and the tape can finish up blocking things.

The only pneumatics I have been near have all used push fit fittings so I wasn't sure about what to use to seal or if sealing is needed. The web suggests that BSP female switched to parallel at some point but still using a tapered male. So decided to use tape. Looks like that's a bad idea.

There are a number of different type of liquid ptfe pipe thread sealer about most are anaerobic and screwfix reviews suggest that once done up undoing is tricky - locked solid. I didn't look on their site initially. I have undone one fitting that had been sealed this way. Took heat, a lump hammer and 300mm wrench. They do sell a sealer called La Co. It's the only none setting one I can find.

so undo the ones I've done. clean up and re seal.

John

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John,

May I suggest "Boss White" ... It's cheap and readily available.

MichaelG.

With or without hemp?

PTFE Tape was banned on railway air brake systems due to the fact that loose strands could easily block small orifices. Loctite 572 was preferred alternative. Other cheaper alternatives available for less demanding applications - try Tru-Loc range

I assume we are talking fittings used for compressed air. BSP threads can be parallel or taper, they are basically the same thread, Whitworth form, but the taper one has a 1/16 in one inch taper. Taper threads generally seal without any further addition when fitted taper into taper. If you fit a taper male into a parallel female, which is incorrect, then tape can be fitted. BSP parallel fittings rely on other means to seal, the thread alone will not seal, bonded seals, o rings or a taper somewhere will be the seal. I have worked with both pneumatics and hydraulics in my working life and only used PTFE tape on pneumatic and water systems with no trouble. I would keep the Boss white and hemp for the lead toilet pipe!

Look further at some of pneumatic fitting manufacturers for fitting information, well worth reading.

Howard

Thinking about the boss white a bit more the oil in that may not be a good idea near some some of the gasses and oxygen that may be used for welding.

J

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Is that a technical choice, or a recreational one

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I fully accept that, Jason

... I was taking John's reference to 'pneumatic' as relating to an air line.

[probably an unreasonable assumption on my part]

MichaelG.

One post better note that taper into taper doesn't seem to be the standard any more. No idea when this happened but one comment on the web suggested that female went parallel on the basis than metric pipe was done this way. The general idea is that it should seal on a couple of threads via distorting the female part. I've bought fittings from 2 suppliers one major and they all use parallel female and taper male even on things like T's, reducing bushes or what ever. I want a female-female-male T and even that is the same. I've not really looked at them but did notice cone hydraulic fittings much the same as used for welding gas - spherical surface and a cone joints. Also some like my breakable joint with an o ring on the spherical part.

I should have thought more when I used the ptfe tape as it was difficult to use. Bits are bound to occur because it will only really be compressed over a short length.

There are plenty of comments around on not being able to undo bsp fittings that have been sealed with loctite this and that also other dedicated pipe thread sealers. I'd probably use tru blue if it wasn't for that. That one might be ok for undoing.

Cheap option - probably an automotive gasket glue such as red hermatite or even hylomar but the liquid ptfe one that set don't cost much.

I do have some hemp. It can be handy at times living in an old house.

Nope - going to use the none setting one I mentioned. The first review used it on 10 bar and it may well take a lot more than that.

Steam - i'd probably try hylomar and see what happens.

The compressor did have a way of using PTFE tape that could be used at times. Rather a lot of it so that it doesn't go into the female hole and finishes up as a sort of ptfe 0 ring.

I don't mind forking out for the screwfix one as from time to time I need to do water compression joints. I'm fed up of finding the boss green has gone hard. It's possible to wrap them with ptfe tape instead but this style of none setting sealer has been around for a long time and hopefully doesn't go off in the can.

John

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Edited By Ajohnw on 18/01/2017 13:37:11

Most of my plumbing nowadays is on stationary i/c engines,for permanent joints I still use boss white and hemp,it mass a good joint, for propane,kero,and petrol fuel lines I now use ptfe tape,though this can vary in thickness and quality, the cheap stuff from you know who is poor quality.The non hardening sealants do not work to very well and the more expensive sealants are ok if they are used up on one job as their shelf life is very limited ,a tin of boss white lasts for ages and hemp remains useable for ever, The best sealant I found for carbs and petrol fittings was Hermatite Golden which never hardened and was not affected by petrol,though of course as we all know anything that is any good disappears off the market due to commercial or legislation problems,have never found a good substitute. One of the best selants was reckoned to be white lead and hemp,though of course outlawed many decades ago it was very good in industrial applications on screwed steel pipework for oil,water, steam and compressed air,

A tip when using PTFE tape. Avoid winding it around the male start thread. If you wind it round and keep it off the start thread then, when you do up the joint, the tape does not 'contaminate' the inside of the pipe; it remains in the threaded portion out of harms way. Of course, when you undo the joint you have to carefully remove the PTFE residue from the internal thread, to avoid contamination on reassembly. If you wind the tape over the front of the start thread, then when you do it up, the tape gets pulled and maybe cut, and bits of the tape are left in the inside of the pipe ahead of the thread.

I have used the LaCo sealant on a few jobs recently. It is a 'gritty' and thick solution as it contains PTFE. I have used it on it's own without PTFE and it seals gas and water joints ok. If you put too much on then you can contaminate the inside of the pipe. As I say, keep it off the start thread.

I also use 'Rocol Gasseal'. It is a non setting gas seal solution. It is a bit like boss white, but it is much finer and it does not set. I generally use it on small gas threads on it's own without PTFE. I have also used it on compression fittings to consolidate the joint at the olive. It think it costs in the region of £30 nowadays. My tin have lasted me 20 years and it still works well.

When PTFE came out we stopped using Hemp. Hemp is good, if you need to pack a joint to get an elbow tight and facing in the right direction.

Steve

Edited By Steven Vine on 18/01/2017 15:00:30

This what they say about La Co

For threaded pipes carrying hot or cold water, gases, steam, air, petrol, oils and refrigerants. Solvent and water-free, contains teflon and PTFE. Brushes on oily, wet or cold threads. Disassembles easily. Will not dry out or harden.

It describes itself as heavy duty so I may find it too thick but some one has used it on a compressor.

I am tempted to use Hylomar. I've probably used that and moly grease for longer than most as one of my uncles was an aircraft fitter.

John

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Ajohnw. My wisdom seems to be lost on you.

Steve

Come to think of it ... my last purchase was Fernox Hawk White, not 'Boss White'.

Available here: **LINK**

https://www.bes.co.uk/products/213.asp

... and specified for non-medical air lines.

MichaelG.

Hi all

you could try jet blue its non setting can be used on gas, water & air

available from most plumbers merchants I know plumbcenter sell it ( usual disclaimer)

regards

Paul

Not really Steve. It suites me to buy the stuff I mentioned due to some pending pipe fitting to taps etc in the work I am doing on the kitchen. The last time I used my boss green was about 6 months ago and it wasn't in a very good state. Time before that probably several years. I do take care to seal them and position the polythene carefully. I also usually manage to restore the stuff for use but hard bits don't go away.

So I'm left with a choice. Use a recognised anaerobic one or something else. A review on screwfix suggests that the something else will be fine. Having undone a commercially made joint that use the other type I am not at all keen on using one of those unless I must. They'd applied enough to seal over a couple of threads. Even so it took several hefty hits on large spanner with a lump hammer to undo it. A blow torch also helped. As I am likely to need to change things around it just isn't suitable.

I used to run cars that I just couldn't afford to run without doing everything including rebuilds myself. I have never had a single problem with leaks after switching to hylomar and it also pays dividends if for some reason stuff has to be dismantled again. Not an uncommon thing to have to do on Lotus's.

One of the trade reviews might interest you

I assume the trade name has changed.

A truck mechanic mate gave me a bottle of liquid sealer used on truck air brakes. Like the railway comment above PTFE tape is now banned. If I can locate the bottle in the workshop I will post the name of it.

Liquid PTFE sealant is readily available.

Toolstation sell a PTFE enriched sealer called tru-blu,. a 50g tube is £2.63, I have recently used it on a Clarke compressor to cure leaking connections also replaced some central heating radiators using it with no problems...

HTH

Chris

I wondered about tru blu and use it but don't know if like liquid ptfe it comes with the undo problem as it does set.

I've never had to undo anything I've used tru blu on. I don't think it's anaerobic though. All ptfe liquids seem to be.

The Al Co stuff is a very thick ptfe paste.

John

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Edited By Ajohnw on 18/01/2017 20:25:42