Boiler stays

[Bill DawesParticipant @billdawes]

Hi all, made a schoolboy error silver soldering stays inside firebox, hadn't noticed boiler was resting on stays already done and they popped up, still soldered in but rivet heads not flush against wall. Can they be left, just cutting off flush as you would do on the outside or is there some reason that escapes me that says you must have heads on the rivets. My logic is pressure is acting equally on inner and outer firebox and the outside will not have heads on, in fact would the force on the outer wall be slightly more as it will be a bigger area.

Another question, is it easy to remove glass on pressure gauge to put a max pressure mark on the actual gauge face.

And lastly, how do I stop the spring retainer on my safety valves unscrewing, Loctite ok? in fact any boiler fittings come to that, seem to remember reading somewhere that PTFE tape not a good idea, is that because it is not suitable or just the danger of loose bits floating around.

Thanks guys.

Bill D.

[Bill DawesParticipant @billdawes]

[Nigel Graham 2Participant @nigelgraham2]

The pressure-gauge question will be useful to me, too, for the same reason.

I've not heard of the retainers on safety-valves unscrewing. The spring tends to act as a friction-lock, so they shouldn't slacken back. At least they won't tighten.

I have heard the same advice about PTFE tape, actually from one of the speakers at a boiler-testing seminar. He advocates a thin fibre washer instead. The tape will lubricate and seal the threads in miniature boiler conditions, though should not be applied too thickly, but it does carries the risk of loose bits blocking fittings such as the gauge-glass.

Incidentally, a plumber and registered gas-fitter I know told me he uses barely half a roll of PTFE tape a year, and never in gas work. I don't know if that's for a similar reason, that of fragments choking small-diameter fittings.

[Henry WoodParticipant @henrywood50588]

Hi Bill

The idea behind using rivets for the stays, the head stops them from dropping through whilst silver soldering is carried out, if yours have just eased back a little as long as the soldering is good then I should leave them alone. However if they have moved back considerable, then if you can cut them back leave about 3/32" remaining. You mentioned cutting stays back flush on the outside, in my write up I did mention cutting back stays after a successful hydraulic test to 3/32"lg. with the exception of the bottom two rows which will need cutting back a little further to allow the boiler to sit down inside the frames.

H.Wood

[nigel jones 5Participant @nigeljones5]

If soldered correctly in the first place there is no problem in machining stays flat to the surface, the solder between the stay and the plate does all the work.

Whilst the regulations may require a permanent mark on the pressure gauge face plate, on smaller older gauges it is very unwise to attempt this as the retaining screws tend to corrode and snap off. New gauges come apart easily but must be handled with great care.

If your safety is unscrewing itself then something is badly wrong. As Nigel says, the spring should hold it plenty tight enough in place.

For most fittings I use fibre washers, but for brass plugs I use PTFE tape, and sometimes both if the direction of the fitting doesnt fall quire right. What a lot of people dont realise is that PTFE tape made for water pipes shouldnt be used for gas pipes. There are two types, one specifically for each application.

[noel shelleyParticipant @noelshelley55608]

PTFE Tape, white reel cover water, Yellow for gas ! I think. Noel

[Bill DawesParticipant @billdawes]

Thanks for that guys, as I said I couldn't see a problem but its nice to have confirmation.

Thanks Henry, I forgot to mention that it is your Emma Victoria that I am building, my first ever loco, just want to get this boiler done, Take your point about not taking them right back, bad choice of words on my part saying flush. it's been a love hate relationship, mostly due to my inexperience of course but I do remember in your build details you did mention silver soldering the boiler being a stressful and worrying time so I should take consolation from that I suppose.

My pressure gauge is, as yet, unused. I did have a tentative try at twisting off the the cover but it was too tight for me to risk wrecking it, no obvious sight of any retaining fixing, just a very tight machine press fit in manufacture I suppose.

Once again thank you all for the advice, sometimes on this forum you ask a question more or less knowing the answer but confirmation from others more experienced is a big help, other times it's because I haven't a clue.

Never have given up on any DIY type job but came very close to binning this boiler more than once, went away, deep breath, slept on it, few kind words from my wife and back to it.

Wouldn't say I am very close to finishing the loco, I'm not that naive but most of the million parts are made just? need all stripping down, cleaning, measuring, making things fit and work properly, remaking bits not happy with, painting, fitting, getting the whole thing to work……. Oh well maybe another 9 years.

Bill D.

[Bill DawesParticipant @billdawes]

PS see also my post on Oxy-Propane on this boiler subject

Bill D

[Phil H1Participant @philh196021]

Henry,

I am thinking forwards to my boiler (for Rob Roy) – so to help with my understanding, why is it acceptable to reduce the length of the lower stays but not the others? I understand the need to fit the boiler into the frames but do you expect the stress on the lower stays to be less than the others. Also, what is the thinking of 3/32" – is it to ensure you can see the edges of the solder fillet on the rivet?

Phil H

[Henry WoodParticipant @henrywood50588]

Phil

I agree with what as already been pointed out, if the soldering has been done correctly, then all should be O.K. taking them flush, but it is reassuring to see that small fillet, nothing to do with varying stresses. The figure of 3/32" is what I tend to use on the boilers I have made nothing special about it, with perhaps a little less where the boiler goes inside the frames.

Henry

[Phil H1Participant @philh196021]

Thanks for the clarification Henry.

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