Model boiler safety calculations

[Phil H1Participant @philh196021]

Nick,

I think you have demonstrated my point regarding small model boiler calculations. The author talks about a safety factor of 6 or maybe 10. Then you say that the a letter suggested 5000 rather than 7000 be used in the equation – so why bother at all?

I think that small copper boilers are quite well established regarding plate and tube sizes and that is all based on many years of successful use. There is absolutely nothing wrong with successful historical information being used because it works.

I think we should avoid trying to suggest some kind of design engineering in taking place by throwing some equations about when there s clearly no sound basis.

Phil H

[JasonBModerator @jasonb]

Posted by Andrew Johnston on 24/01/2021 09:18:53:

That's odd, there was a following post made that simply said "deleted", presumably by the poster. But it now seems to have disappeared. Is it policy to remove posts where the poster has thought better of it and deleted the text?

Andrew

I tend to delete them if I see them to keep the thread tidy just as I also delete double posts. Poster could have thought twice, or simply poste din the wrong thread

[Benedict WhiteParticipant @benedictwhite51126]

Posted by Dave Smith 14 on 18/01/2021 20:13:00:

Andrew

I have a copy of the Aussie code if you want a copy. It details how a person without the necessary engineering expertise can demonstrate a boiler design is structurally sound.

Does the Australian code contain the calculations for end plate thickness? It seems to me that I would need to establish that then go on to stay calculations for my project.

Many thanks in advance.

[duncan webster 1Participant @duncanwebster1]

You cannot divorce the two, thicker end plates need fewer stays, but if it has firetube(s) running end to end you need to allow some flexibility for differential expansion. This latter isn't usually a problem.

[Dave Smith 14Participant @davesmith14]

Benedict

Tube and plate thickness is established using the working pressure and tabulated data, no calculation required for any of it. Stays size/pitch etc are also tabulated although there are formula for you to use if you need to go off-piste.

Dave

[Benedict WhiteParticipant @benedictwhite51126]

Many thanks Duncan and Dave. The barrel thickness is "off-piste" but at 2.54" diameter and 0.040" shell thickness should be safe at 5PSI but I was hoping to get a calculation on the plates.

[Paul KempParticipant @paulkemp46892]

Some raw formulae you can use here for guidance. As the intro suggests if you want greater accuracy refer to Rourke. Obviously you have to adjust for copper not steel (assuming you are using copper). For a tube plate it can be complicated!

https://roymech.org/Useful_Tables/Mechanics/Plates.html

Paul.

[Benedict WhiteParticipant @benedictwhite51126]

Many thanks Paul.

[Author]

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