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[monarch]

Hi All
I have some threaded joints to seal on a boiler, whats the best way to achieve a sound joint that will be OK with superheaded steam.

Lionel

[benjaml1]

Tapered or parallel threads ?

[derekwarner]

Monarch.......annealed copper washer or washers if you have an axial alignment consideration PLUS Loctite liquid Teflon paste ....the latter from memory is rated to 200 degrees C......Derek

[monarch]

Hi
It's a parallel thread.
Lionel

[Underpressure]

Loctite lock'n'seal - 243

I use this on all boiler applications. It sets quite quickly and will fill a slight gap.

[Bunkerbarge]

I use PTFE thread tape.  I lay our a few inches then cut it into thin strips with a scalpel and then bind the thread exactly as you would with any other plumbing joint.

The tape fills threads extreemly well and is good up to 260-300 degrees C.  It is also easy to remove afterwards and redo without having the task of cleaning a threadloc type product out of the threads.

[benjaml1]

Technically, parallel threads are used with a flat face mating gasket. This could be soft copper ( annealed as said before) or a composite. However, these guys know a darn sight more about modelling than I do. I'm just a retired instrumentation engineer, as so often the real world doesn't apply...

[HS93 (RIP)]

some of you have some really crap pipe joints if you need to use all the different ways to seal them locktite do a soft seal in a tube you get a tube with most cheddar engines the stuff Underpressure uses, I have made up lots of pipes and as long as the right bits are used together and you don't go made with the silver solder or the FILE they seal with a spot of goo. on boilers I uses copper washers on some  boiler fittings,  BUT they must be annealed to make them soft if re used .

Peter

[monarch]

Hi All
Some great advise, because I need to seal a threaded joint with no shoulder it appears that either Lock-seal 243 or ptfe tape cut to strips is the answer.
It's great to learn form others  that have vast practical experience in the fascinating world of steam.
Thanks again  Lionel   

[Brooks]

With tape, it can be important to leave the first 1 or 2 threads unwrapped with the tape. As the threads cut into the tape upon assembly of the joint, they make tiny whiskers of tape. If the whiskers break off, they can foul the small passages in the engine or boiler (say the safety valve, making it weep). This precaution is Particularly germain to joints of gas lines, if you fire with gas. The whiskers will play hob with the jet.

The same precaution is appropriate for liquid ptfe pipe goop, too.

Not much you can do to control the flow of Loctite, but since it solidifies upon cure, less chance of bits coming free to fall into the boiler or elsewhere.

[monarch]

Hi Brooks
That sounds like really good advise, I had not given to much thought to the process but having read that it seems obvious ( Why don't I think about things like that).   

Lionel

[Perkasaman2]

If using ptfe tape it's more important to pull/stretch the tape as you lay it in the thread....... build tape up in layers if necessary and finally  rotate the taped fitting  in tight nipped fingers to compress/polish the tape into the  threads before assembly. Poorer quality ptfe tape snaps too easily and  does'nt allow the vital tensioning  which ensures the seal and prevents slippage/displacement of the tape. I wish I had a penny for every joint I've ............   

[Bunkerbarge]

.....and make sure that you wind it the correct way according to the thread otherwise it will be pushed out as you tighten the fitting.

[gondolier88]

Just don't use PTFE tape or PTFE based compounds on any joints on the gas pipe near the burner- above a certain temperature it produces Flourine gas- what Germany used to send across no-mans land to the trenches of the allies- not nice stuff at all!

Personally I use a little bit of Rocol pipe jointing compound for water, steam, oil and gas- black goo that hardens but doesn't set- never had a leak with it and you only need the smallest amount.

Greg

[red_noir]

I use PTFE thread tape.  I lay our a few inches then cut it into thin strips with a scalpel and then bind the thread exactly as you would with any other plumbing joint.

The tape fills threads extreemly well and is good up to 260-300 degrees C.  It is also easy to remove afterwards and redo without having the task of cleaning a threadloc type product out of the threads.

I do the exact same thing works very well ! and very easy to clean off the threads !!

[monarch]

Hi All
The Rocol product is it the Foliac Manganese or Foliac Graphite both appear to be used on steam which is best to use please.   

Lionel

[HS93 (RIP)]

Just don't use PTFE tape or PTFE based compounds on any joints on the gas pipe near the burner- above a certain temperature it produces Flourine gas- what Germany used to send across no-mans land to the trenches of the allies- not nice stuff at all!

Personally I use a little bit of Rocol pipe jointing compound for water, steam, oil and gas- black goo that hardens but doesn't set- never had a leak with it and you only need the smallest amount.

Greg

 Rocol pipe jointing compound


do you use it on full size or model steam boats

Peter

[HS93 (RIP)]

remember the joint to the gas tank needs to have a rubber O ring to seal or a way to break the line and re seal without any, tape/gunk /goo etc as you will be removing the tank to fill each time you sail.

Peter

[Perkasaman2]

The popular version of rocol is sold primarily for sealing gas unions/fittings but being sticky it does attract/hold  debris. Sealing tape intended for gas is sold alongside rolls of 'white ptfe' and is easily recognised since it is always retailed on a YELLOW (ocre) coloured reel. Yellow tape is softer and snaps far more easily than white ptfe and needs a lot more care in use.
Rocol is relatively expensive and there is a danger that excess paste will be pushed into fitting/union when they are tightened up, especially on mini model fittings/pipework and cause blockage. Traditional sealing compounds such as stag  types A &/B are available together with a multitude of exotic and very expensive hi tec specials over and above the old faithful 'hemp n' paste' which old hands swear by.
(Providing the wrapping technique I outlined above is followed then the direction of tape wrapping makes no difference in my experience.) Testing the integrity of joints under working pressure occasionally with a little soap solution (check for bubbles forming ) may be a good idea for peace of mind. Minimal joints on gas supply to burner and silver solder joints if unavoidable other than the screw joints at the connection points.