Making a simple boiler.

[Brian HParticipant @brianh50089]

Hello Peter and others who may be thinking about boiler making. I would suggest a look at the Tubal Cain book mentioned earlier and also the K.N.Harris book called Model Boilers and Boilermaking.

It would also be an idea to check on the insurance and boiler testing procedure, especially if one is hoping to steam up in public.

Whichever way you choose, all the best with it and you know where to come to gain more information.

[JasonBModerator @jasonb]

You don't need a vast number of fixings to resist the loads, the closeness of the rivits was to close the joint in the plates.

Think of a steam chest cover for instance, six or eight small studs and nuts and that is at full pressure from the boiler, or the water pump on the side of the Minnie in my avitar, 4 bronze bolts and I don't seem to hear of them poping off the side of engines.

J

[Gas_mantle.Participant @gas_mantle]

Hi,

Thanks for everyones help, I'm glad I asked the question, the answers have shed a lot of light on the problem.

As Jason says my reasoning for having a lot of bolts regularly spaced around the tube wall was to help get a good seal and not so much to do with bearing the load. Lets face it bolts are cheap and I can drill and tap as many holes as necessary. I mentioned the figure of 12 bolts per end plate as an example but if more are needed I'd use more.

I'm obviously missing something here but surely with a good sealant, O ring or whatever and enough bolts closely spaced I'd get good seal.

My original idea with the end plates was to use fairly thick plates and cut a very shallow taper to mate with a similar taper cut into the tube, then if I add a few stay rods through the entire tube with decent sized nuts at each end surely I'd be able to pull the plates into the taper before then adding the ring of bolts.

Presumably years ago before welding or modern sealants boilers were made by relying on lots of closely spaced bolts or rivets ?

I can see this boiler being able to stand a nuclear attack the way I'll built it

Peter

 

Edited By Peter Nichols on 29/07/2015 21:20:50

[Anonymous]

I very much doubt that the pressure in the steam chest of any traction engine is particularly close to boiler pressure. There are too many opportunities for pressure loss on the way.

The strength and number of bolts isn't really the problem when it comes to being steam tight. The issue is one of the plate distorting slightly between the fixings. Similarly with an O-ring seal the problem is the O-ring not sealing properly due to the plate distorting between bolts, due to the resistance of the O-ring to compression. I can say from experience that simply clamping two plates together with a bolt is not likely to result in a water (or steam) tight seal.

Peter: Indeed boilers of old were riveted, although the boilers often needed a lot a caulking to get rid of small leaks. If you care to analyse the riveted boilers you will find that they are designed so that the rivets holding the plates together are generally in shear, not tension. And of course the rivets were formed hot, so they really clamp the plates as they cool. Stays of course are different.

Andrew

[JasonBModerator @jasonb]

You got me thinking Andrew and I did a bit of looking, seems Julia can get 150psi in her steam chest when the boiler presure is 180psi so quite close. Hopefully we are talking about a much lower pressure boiler in this instance.

Do you think there would be much distortion between screws with say a 6mm plate with screws say 1" apart around a 4" OD tube, would be similar proportions to a cylinder end cover or reguilator/valve chest cover on a 4" TE?

J

Edited By JasonB on 30/07/2015 17:08:12

[Gas_mantle.Participant @gas_mantle]

I mentioned earlier I tried making a boiler out of an old thermos flask just as a quick experiment to see if I could improve on the Kelly kettle.

Here are a few photos, I'd be lying if I said it doesn't leak a bit but nothing like as much as you'd expect.

All that is holding the end cap on is molten lead poured in, I drilled a few holes in the flask wall so the lead flows through them an gives a better seal but there are no bolts other than the hollow steam outlet bolt you can see.

Even the steam outlet has no sealant other than a piece of rubber on the inside trapped behind a nut and a washer and it doesn't leak at all.

If something as crazy as that works surely 4" dia tube with 10mm thick walls holding 10mm thick plate held by at least 12 bolts and a sealant / gasket is going to work.

Peter.

Edited By Peter Nichols on 30/07/2015 17:59:49

Edited By Peter Nichols on 30/07/2015 18:00:35

[AjohnwParticipant @ajohnw51620]

One thing that interested me concerning model boilers was early attempts at super heating. They simply ran the steam pipe through the area that contained the fire. It causes all sort of corrosion problems but probably wouldn't with more gentle heating techniques.

John

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[Mike BrettParticipant @mikebrett89695]

A short while ago I purchased a short length of stainless steel pipe about 4 inches diameter that I needed for a piston cylinder. It was thick walled with welded seam and at the time I thought this would make a very strong boiler.You could use stainless steel for the ends and get these welded on plus fittings for inlets . Not sure where you live but I get my supplies from Mill Steel in Wisbech Cambs. They only charged me about £14 for the pipe and you could get the end discs of ebay. Not easy to work with but stainless would last a very long time and it would make a cheap boiler. I found a local trailer making firm who where willing to do a small welding job for £10.

Mike

[AjohnwParticipant @ajohnw51620]

I've never bought any of these people but it might not be welded tube as I don't think that would fit in with their business.

**LINK**

It's where I usually go for my none ferrous.

John

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[Boiler BriParticipant @boilerbri]

Bloody hell have you all gone mad? This guy needs to read a lot of books and take advice from a boiler inspector before venturing into boiler making, at the least he will hurt himself, at the worst others. Please get a grip!

Even in our world of modelling there are strict rules on this subject. Have we all forgotten Flixborough which brought about the pressure systems regulations?

Bri

[JasonBModerator @jasonb]

If he is just using it at home to run a small stationary engine he has no need to consult a boiler inspector or follow any rules

It would however be prudent to at least read a few book on the subject.

As I said earlier stick a low rated safety valve on it and it won't even be within the 3bar/lts rule. Just like Brian John has been doing with his little copper boilers.

Edited By JasonB on 31/07/2015 20:02:43

Edited By JasonB on 31/07/2015 20:06:01

[Gas_mantle.Participant @gas_mantle]

I really do think it needs to be kept in context, I'm not building something to power the Titanic here!

A boiler made from 10mm thick steel tubing with similarly thick end plates held on by at least 12 bolts, with a safety valve and pressure gauge isn't going to hurt me nor anyone else.

A couple of weeks ago I made a small stationary engine that was originally featured in a magazine article, their boiler was far less substantial than the one I'm proposing.

[Brian HParticipant @brianh50089]

I could well be several years out of date here but, my understanding is that amateur made copper boilers do not require mill certs if they have been silver soldered but steel boilers need the mill certs, especially if welded and then only by a certified welder.

[SteambuffParticipant @steambuff]

and Stainless Steel boilers are a no-no

[AndyPParticipant @andyp13730]

Don't forget you will have to heat the boiler shell as well as the water in it, a 10mm thick steel boiler is going to need a hell of a lot of heat to get steam up.

Can I recommend Stan Bray's book Making Simple Model Steam Engines ? Easy to follow and the simplest boiler is just a "pot boiler" of 100mm long 50mm dia 1mm wall copper tube with flanged 1.5mm thick end plates and the minimum 2 bushes.

Andy

[AjohnwParticipant @ajohnw51620]

Some how I think people are getting a little carried away. The "regs" used by model engineers are here

**LINK**

It doesn't rule out steel boiler or people welding them up themselves. It is also basically aimed at people who run trains about in clubs etc or run boilers where some one might wish to inspect any type of model steam boiler It's self policing not law.

If this is needed then builder will have to provide calculations that show that the boiler is capable of taking 2x it's working pressure. Testing is to 1.5x. If welded the inspector may wish to see examples of the persons welding or even joints before they are welded – that sounds a little like "well I have known Jack for years and he's ok" to me. Everybody makes mistakes at times even Jack. That's what the testing is intended to cover. It doesn't specify that they must be certified welders only competent. Personally I wouldn't trust some one who welds trailers up to do the job but that is a different issue.

There do not appear to be any verboten materials and quite rightly there shouldn't be. The only requirement is that it is designed to take 2x the working pressure. Having done some safety critical structural design I'm surprised that there isn't a bit more detail in that area and there probably is for commercial items that are sold to contain all sorts of things at pressure and come under true HSE legislation. In that case all sorts of materials will be used.

John

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[Simon CollierParticipant @simoncollier74340]

Posted by Steambuff on 31/07/2015 22:27:34:

and Stainless Steel boilers are a no-no

The AMBSC allows, and has a specific code for, Duplex boilers.

[JasonBModerator @jasonb]

And they have no problem with stainless boilers in mainland europe, you may even be able to get them commercially tested here, its just that a club inspector can't test stainless that people say its not allowed.

Nice stainless boiler being featured on another website this week. Is that an "O" ring and ring of bolt holes I see also tested to 500psi

Edited By JasonB on 01/08/2015 07:32:37

Edited By JasonB on 01/08/2015 07:33:43

[Gas_mantle.Participant @gas_mantle]

That ring of bolt holes is exactly the sort of thing I had in mind.

It's difficult to tell in the picture but I'm I'm guessing the ring is of a similar size to the one I'm proposing (possibly a bit smaller) and it's held by 16 bolts.

I just can't see how an arrangement like is going to leak.

[JasonBModerator @jasonb]

From the other Photos it looks to be about a 150mm boiler so the bolting face is within the size you are thinking of. Close off with something like a 6mm plate. Not etwo safety valves oon top "A"

[Boiler BriParticipant @boilerbri]

291524685062

That above is for a boiler on auction on eBay. Go and buy that or try to to stop yourself harming yourself.

Bri

[JasonBModerator @jasonb]

No sign of any CE marking on it, as its being sold "new" and commercially made then surly it should have CE marking? No mention of what it was tested to so could hurt yourself it you used it at a higher pressure.

[nigel jones 5Participant @nigeljones5]

if you look at my boiler making thread i used the exact same o ring set up – they work brilliantly, but you wont be able to flange and machine like this in copper

[JasonBModerator @jasonb]

Fizzy Nick intends to use 10mm wall steel tube so shoulkd be able to fit a 1/8" nominal section O ring.

Could be done with thinner wall copper tube if you soldered a "washer" on the ends, quite a few Trevithick Dredging Engines about that work well with just a gasket and ring of bolts..

Edited By JasonB on 01/08/2015 10:29:04

[Gas_mantle.Participant @gas_mantle]

Hi Fizzy,

Could you put a link up to your boiler making thread please ?

I intend to make mine entirely from steel.

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