Getting a good seal on BSP fittings

[TerryE]

I've got quite a few BSP fittings in my system. Getting my head around these isn't straight forward.  Hence this topic just to have a sanity check with @Nickfromwales et all, and for others new to this confusion.

 

In Europe BSP junctions have two flavours:

• Tapered or BSPT (also known as "Iron" fittings since these are commonly used on iron pipework). Here the taper allows the seal to be made on the threaded section.
• Parallel or BSPP.. Here the threads do not be themselves seal the joint but instead pull the male and female parts together. The seal is by a washer or O ring at one end of the fitting.

Most if not all of my fittings use BSPP and therefore need washers or O rings.

 

Even so it is still not simple as on any fitting there is an inner male and outer female part and BSPP fittings do not have a consistent approach to whether the seal is at the female end or the male one.

 

Taps have the seal at the end of the male end and the female is also male in that it has an inner guide that slots inside the male.

 

Fittings like my Hep2O manifolds have the seal at the female end and in fact the male end doesn't even have a decent face to put an O ring against it you wanted to.

 

Fittings like my PHE and TMV have the seal at the end of the male end, but the inside diameter won't accept a tap connector, so I need a female fitting with a flat plate inner face and matching washer.  Tap washers will fit but the seem unnecessarily narrow.  

 

In the case of my PHE for example, I want to turn a 22 mm pipe into a ½" BSPP male. I originally planned to use a ½" to 15mm tap elbow with a 15 to 22 EF convertor, but this involves (1) cutting off the inner flange and filing flat, and (2) having a 12mm inner diameter on the turn. A better solution is a straight ½" to 22mm coupler and a 22 EF street bend, as this preserves the inner diameter of the PHE fitting as the narrowest restriction.

 

So any words of wisdom on this mess? Any advice on best place to approach this, get fittings / washers / o rings? 

 

One last comment here is that I came across a recommendation to use liquid PTFE if you want a good seal. Is this a good idea?

[Onoff]

I'm hooked on this stuff tbh:

 

http://sespipeline.co.uk/Jet-blue-jointing-compound-steam-water-oil-gas-bss-wolseley

 

A revelation on threaded fittings. Lubes and seals. No more squeaky brass compressions or weeps.

 

Think @Nickfromwales favourite is "Gasseal". The Jet Blue is labelled specifically for potable water, is why I went for that instead.

 

Perhaps some of this and a box of assorted fibre washers? LIDL btw we're doing BIG assorted boxes of O rings and washers for a fiver each.

Edited March 8, 2017 by Onoff
typos

[PeterW]

Rectorseal every time - it's both a lubricant and contains PTfe fibres so works as a mix of fill and seal too

[Barney12]

I was taught to use pipe cord on BSP threads and I have to say I have never had one leak when using it:

 

https://www.cromwell.co.uk/shop/adhesives-and-sealants/pipe-sealants/55-pipe-sealing-cord-50mtr/p/LOC7255800A?

 

 

[MikeSharp01]

I have never been confident of compounds as it seems to me that most fittings should have well designed / engineered seals. If it won't seal at the design pressure without such compounds then perhaps you might want to wonder if a better design might not be available or has it been put together correctly. In the world of parallel threads I have a box of Dowty bonded seals (1380 bar max - see here!) I use in face sealing otherwise the olive has to do the work. In the tapered thread world it does get a bit more complex but for most things I think good old PTFE tape is the way forward (There are places this is not appropriate) and in petrochemical applications some compounds are available.

 

I guess we need to await Nicks views though - obviously Wales is not awake yet!

[Onoff]

Thinking about it, the last BSP joint I did was the garden tap. Following @Nickfromwales instructions to the letter I think I wound on "25-28 turns" of PTFE tape. I was still thinking it was far too much as I was tightening it up but the advice was bang on.

[Gone West]

22 minutes ago, Onoff said:

Thinking about it, the last BSP joint I did was the garden tap. Following @Nickfromwales instructions to the letter I think I wound on "25-28 turns" of PTFE tape. I was still thinking it was far too much as I was tightening it up but the advice was bang on.

 

I use the thicker 'gas' type PTFE tape so I don't have to put as many turns on.

[Vijay]

I always use a wipe of Fernox LS-X on pipes that are a pain or in an awkward position and I don't want to touch again. It's brilliant stuff

[Nickfromwales]

Wales had to wave his boy off from school today as he's off for an 3 day outdoors jolly. Coach going at 09:30. Yay ?

You shouldn't really be coming across tapered fittings in a domestic plumbing install TBH as they're typically only found in true iron fittings, but some weird and wonderful bits of equipment come as such, now and then, but rare. 

For BSPP the humble roll of PTFE tape is the weapon of choice. 

You can use fibre washers and wind the fitting right home, but I find the rotational force combined with compression of the two meeting ( washer and opposing mating surface ) chews the washer unless your absolutely spot on with the number of turns and torque applied. 

With PTFE you don't have to turn the fitting completely home, and you have to be pretty hard done by not to get a reliable joint. 

13-18 turns of tape for rad valves

Everything else needs a minimum of 21 turns, but if the dry fit is slack then don't be afraid to shove a good 26-28 turns on. What the fittings doesn't want will get displaced anyhoo but the number one thing to do, after applying the tape but prior to assembly, is to grab the taped fitting in a clenched hand and squeeze the tape down whilst giving a slight clockwise rotation ( turning the tape on in the correct direction is paramount of course otherwise it'll twist off as you do the fitting up   ).