Optimal number of boiler tubes.

[ajoeiam]

Looks like there is quite a lot we agree on HMEL. I have never worked with the ASME code, but I know it runs to several volumes and needs a barrow to carry it around. So REALLY knowing your way around it is a lifetime's work.
snip

Hmmmmmmmmmm - - - - several - - - I see listed ( ASME Boiler and Pressure Vessel Code - Wikipedia ) some 13 sections some of which would be several, if not more, volumes in themselves.
Last I saw a set it was a number of library shelves full of books.
Even for welding there are some 4 different sections involved.

Dunno if any one person would know their way around even with a lifetime of working with it.
Remember sitting in a coffee room listening to a guy with some 50 years experience in the industry.
His stack of certifications was over 12" tall with each level being some 4 pieces.
The stories were very very interesting. (Lots to be learnt just by listening!)

 

[Steamchick]

Thanks HMEL, Martin, I find it helps when I feel I am talking to people "with the knowledge and expertise".... who can tell me what I am doing wrong...
e.g. "Tubes with pressure on the outside have to be treated differently because hoop stress can not help."
So should I be looking at "buckling load" - and applying factors for degradation of UTS of copper for temperature, "FOS of >8" commonly used for model copper boilers, Stress concentrations due to penetrations, distortion factors due to tube actual shape, compressive stress instead of tensile (I think not as this formula uses E), etc. ?
I can see Buckling load as:
"delta"Pmax (pressure difference) = 2E/3 x (t/D)cubed.......

I note that ASME use a "Table factor A" derived from:
A = 1/8 x 1/(Ro/t), where Ro = outside radius of tube, and t = min thickness of wall. (1/8 = FOS).
- which is then used with a material chart (NFC7), to determine the stress from the factor A.
Then using: B = A x E /2, where E – modulus of elasticity = 16,000,000psi.

So in effect the Buckling load factor "(t/D)cubed" is "managed" by the "1/(Ro/t)" and use of a material chart.... then used to manage the "2E/3" factor by using "B = A x E /2"..

But I have no idea how they have done their "Magic"! - Or even if I have interpreted it all correctly?
Hence I feel completely "bamboozled", as in my simple world as an engineer, I figured there would be a Regulation with a straight-forward method of calculating things... as sums are pretty reliable at giving the same answers to everyone.
But I must be in cloud cuckoo land as usual...
Please have a laugh at my stupidity/culpability, then tell me what I should do? - with simple maths if that is possible?
K2

 

[Steamchick]

Maybe I have missed a few volumes (steel boilers... etc.) But found what I needed very quickly.... just didn't understand all the "Engineering" as I trained in other stuff (not pressure vessels). But I have studied the Japanese book of vehicle certification and the European stuff, and been audited by Middle Eastern, Korean, Japanese, Ukraines, Russians.... et al. Just not the Fed's, Canadians and Australians. So maybe I am just not fazed by Regs? I learnt to use these sorts of documents on Power Station electrical equipment to UK National standards.... 40 years ago..
I like National standards. They work for me...
Call me an odd-ball?
K2

 

[user 52078]

Hi Steamchick,
Like you I was in design engineering, but not specifically pressure vessels. Also like you I am well used to ploughing through standards and specs. - just not ASME ones.
Fundamentally, the firebox / external pressure problem is of buckling - analagous to a strut, but not quite the same.
I revisited the calcs. I did to BS2790 last night. That has a completely separate section for fireboxes and reverse chambers in compression. I notice that the BS method involves looking at how far apart the end supports are (firebox tubeplate and foundation ring in this case) in addition to the transverse I value (remember that strut analogy) so hoops and corrugations are a big help in preventing the buckling. If you look at the rail tank wagon implosion video, you can see at mid span it nearly flattens, but the ends stand up relatively well - so that makes sense. However, BS2790 does not do copper. I also had a trawl through the text books, but there was very little of practical use there. So it comes down to slavishly following the appropriate bit of whichever code happens to suit your geographic location. Yes, there will be theory and experience that underpin that code, but untangling just what it might be is going to be one hell of a problem. I sat on a few steering groups for such things over the years and even the steering groups couldn't always remember how we had got to where we were!
I will also p.m. you with some more bumf.
Have to dash now.
Martin

 

[Steamchick]

Thanks Martin. Very interesting!
I did ask the Southern Federation of Model Engineers for a contact who could advise/ teach me what I should be doing to size materials and rate existing old refurbished boilers. Unfortunately, they suggested it was "outside their remit" to offer such advice.... but their Safety man did look at a calculation I had prepared and told me "I was wrong" - as his equivalent calculation (that he would not show) said the design was better than I predicted... But he suggested that stress concentration factors, stress variations for temperature, shape, etc. were encompassed in the Factor of Safety of "8" or whatever...? And he said they did not need to consider ASME Regs in the UK. Basically, he thought I should ask "the experts at my local club" (but that seems to be me!) Or use proven standard designs....
He was the Health and Safety regulation expert for the Federation, not a "boiler designer", so I stopped bothering him after that.
K2

 

[BillHowcroft]

The original ASME Boiler & Pressure Vessel Code for steam locomotives was ASME section III.
As the manufacture of steamers disappeared, Admiral Hyman Rickover kidnapped the section III section title to use for the (then) new-fangled civil nuclear industry; copying across chunks of the military reactor design philosophy for civil industry use.
Does anyone have access to this scan which may direct attention to specific design features:
http://www.rypn.org/forums/viewtopic.php?f=1&t=2994

 

[user 52078]

Interesting, Bill. Is that why steamchick comes up with seemingly conservative answers when trying to apply ASME Section 3?
I followed your link and the second link within that link seems to be the poster's email address. Have you tried e-mailing him?
Martin

 

[Steamchick]

Hmmm. Been searching the web... got lost, but it appears there was a new ASME Locomotive Boiler code in 2015?
I did pick-up an excellent comment "ASME are not writing a text book on boiler design for Dummies" - I think that is exactly the right thing. They are writing Regulations by which the best and most competent designers all agree is best practice for the MINIMUM requirements that must be achieved, not "the norm". Good designers exceed requirements for many reasons, but ensure they never drop below minimum requirements.
I wish someone had written the book for Dummies though... I would buy it as I am a Dummy trying to learn...
K2

 

[Steamchick]

Martin, the ASME Section 3 thread I saw was from 2002...
K2

 

[HMEL]

Hmmm. Been searching the web... got lost, but it appears there was a new ASME Locomotive Boiler code in 2015?
I did pick-up an excellent comment "ASME are not writing a text book on boiler design for Dummies" - I think that is exactly the right thing. They are writing Regulations by which the best and most competent designers all agree is best practice for the MINIMUM requirements that must be achieved, not "the norm". Good designers exceed requirements for many reasons, but ensure they never drop below minimum requirements.
I wish someone had written the book for Dummies though... I would buy it as I am a Dummy trying to learn...
K2

Here is the book I like to use:
The ASME Code Simplified
Power Boilers
Dyer E. Carroll & Dyer Carroll, JR
Mc Graw Hill 1997 copywrite

Its about 300 pages long maybe an inch thick and about 6 x 8 inches nice size for reference. Has several tables for reference. Its not a substitute for the code but it is nice to reference what has to be looked at. And of course there is the caveat that things can change over time. I have found it to be very useful.

 

[Raygers]

I have heard back from one of my local model railway contacts. According to him, although he will deny it in a court of law, boilers below a certain size 10" and pressure 100psi do not need to follow any regulations. As Steamchick put it, "you are free to build your own bomb".

I'm still following this thread, even if it sometimes make me cross my eyes, But I'm going to start another one about the actual build, I'm sure I'm going to need help on that, in fact I already have a question.

 

[Steamchick]

Hi Raygers. I too have seen references to some States of the USA and perhaps regions of Canada where the "Authorities" do not mandate for boilers "for home use" below a certain size. But sometimes it simply comes down to common sense - that rarest of all things created by humans - and "what could happen that can hurt"? - type of risk assessment.
Considering most boilers fail at a joint between to components ( often at a tube into plate joint) from the few boilers I have repaired.. and failures I have seen., then this causes a jet of steam - often inside a firebox - that cannot directly impinge on flesh... So the operator (I hesitate to class them all as "capable firemen" as in proper trained locomotive firemen) sees a boiler that cannot develop the steam he thinks he should have, usually both pressure and volume, and cannot think "Why?". An Hydraulic test or air under water test usually shows where there is a hole and that is where the steam is going... I have never actually heard of an explosion of a model boiler, but I am sure there are some if you search the web!
Meanwhile, I suggest you do not silver solder anything for a week or 3, as I am still pondering the good and questionable sizes of parts of your boiler.
Of course, my advice is freely given and not subject to "absolutes" - just suggestions where I think you may improve the boiler, or areas where I think better advice is needed.
K2.

 

[Jonathan Coates]

I just found this thread yesterday afternoon and, having read through it, found it to be very enlightening indeed. I'd never come across the analogy between compressive failure in tubes and Euler's slenderness ratio, but it opened my eyes a bit. Now I'm thinking of strengthening hoops as guy ropes on a slender strut and stuff is making sense.
It's the first time I've seen these kinds of discussions since doing thermodynamics in college forty years ago, as the insights are very nuanced and well discussed. Thanks for the entertainment and education.

 

[Steamchick]

Stupid me... just started doing my own style of analysis on Raygers boiler.... just proved I don't know enough really to even bother having a go. But I am glad your are entertained by it all Jonathan. Just read the text books and do it properly, and not believe what I write as being correct!
I did Quantum mechanics in Uni, not Euyler buckling.... and failed to understand QM. So I have no chance now with EB!
(Are we related? My Grandmother was born Coates - From Sunderland?).
K2

 

[Jonathan Coates]

Stupid me... just started doing my own style of analysis on Raygers boiler.... just proved I don't know enough really to even bother having a go. But I am glad your are entertained by it all Jonathan. Just read the text books and do it properly, and not believe what I write as being correct!
I did Quantum mechanics in Uni, not Euyler buckling.... and failed to understand QM. So I have no chance now with EB!
(Are we related? My Grandmother was born Coates - From Sunderland?).
K2

The Feynman quotation? “If you think you understand quantum mechanics, you don't understand quantum mechanics.”

The family link is possible, I visited family in Darlington in the 60's, but have no recollection of it. The family harks back to a village near Grimsby, Great Coates, from what my late father discovered, perhaps your family also.

 

[Richard Hed]

The Feynman quotation? “If you think you understand quantum mechanics, you don't understand quantum mechanics.”

The family link is possible, I visited family in Darlington in the 60's, but have no recollection of it. The family harks back to a village near Grimsby, Great Coates, from what my late father discovered, perhaps your family also.

So I don't understand QM, does that mean I do?

 

[Steamchick]

It's the quantum probability problem, explained by Schrodinger. (The Schrodinger cat matter, or wave particle duality, or something I don't understand...).
To put it simply.
What you understand is either a "Yes, I understand it", or "No, I don't understand it", You cannot be part way between the two. So if it is a "No", it absolutely must be a "no" until you investigate that state, and by investigating there may be some "yes" there.... So If you think there is some "yes", it absolutely must all be a "yes", as you can't have a "Yes" and a "no" existing in the same place. What has happened is that by trying to see if there is a "yes" or "no" to your understanding, you have changed your understanding from a "no" to a "Yes".
Then when you investigate the "Yes" state further, your investigation determines that there is something you don't understand, so as you cannot have a "No" and "yes" existing together, it becomes an absolute "no" and you don't understand anything...
Do you Understand? - Be ready for this, because if you do understand it you Don't, but if the Don't understand it you Do.... Because by imply investigating whether you Do or Don't understand it you change the state of understanding, or not understanding, to the other state.
If you comprehend Wave-particle duality you are a part way there, but by not understanding that fully, you cannot be in an understanding state, yet to understand some of it you cannot be in a not-understanding state, so being neither understanding, or not understanding, you cannot exist.
So that means I am typing to myself, and this is all a figment of some Cosmic imagination. So I don't exist. If that is the case, what is this thought? - so I must exist...
An now I shall give up, because I don't understand what I understand, so have no place typing into this chat site...
Understand? - Just say "no" and I'll stop.

Let's just say it is a joke among those who understand, because they "understand they don't understand it"?
And this has nothing to do with the Optimal number of Boiler tubes, because they don't exist. Or do they? - Over to you Raygers!
K2?

 

[Richard Hed]

It's the quantum probability problem, explained by Schrodinger. (The Schrodinger cat matter, or wave particle duality, or something I don't understand...).
To put it simply.
What you understand is either a "Yes, I understand it", or "No, I don't understand it", You cannot be part way between the two. So if it is a "No", it absolutely must be a "no" until you investigate that state, and by investigating there may be some "yes" there.... So If you think there is some "yes", it absolutely must all be a "yes", as you can't have a "Yes" and a "no" existing in the same place. What has happened is that by trying to see if there is a "yes" or "no" to your understanding, you have changed your understanding from a "no" to a "Yes".
Then when you investigate the "Yes" state further, your investigation determines that there is something you don't understand, so as you cannot have a "No" and "yes" existing together, it becomes an absolute "no" and you don't understand anything...
Do you Understand? - Be ready for this, because if you do understand it you Don't, but if the Don't understand it you Do.... Because by imply investigating whether you Do or Don't understand it you change the state of understanding, or not understanding, to the other state.
If you comprehend Wave-particle duality you are a part way there, but by not understanding that fully, you cannot be in an understanding state, yet to understand some of it you cannot be in a not-understanding state, so being neither understanding, or not understanding, you cannot exist.
So that means I am typing to myself, and this is all a figment of some Cosmic imagination. So I don't exist. If that is the case, what is this thought? - so I must exist...
An now I shall give up, because I don't understand what I understand, so have no place typing into this chat site...
Understand? - Just say "no" and I'll stop.

Let's just say it is a joke among those who understand, because they "understand they don't understand it"?
And this has nothing to do with the Optimal number of Boiler tubes, because they don't exist. Or do they? - Over to you Raygers!
K2?

as for schroedingers cat, the cat is BOTH dead AND alive until you open the box, then it's one or the other. So me thimpfks it follows that since I don't know if I understand QM, then as long as no-one informs me either that I do understand it or not, then I BOTH understand it and don't! Don't start me on the properties of light.

 

[Jonathan Coates]

And don't mention the Heisenberg disaster, nobody can be certain how that happened.

 

[Steamchick]

Too clever for me Richard... I can follow your train of thought, but you simply pose better questions and answers than my brain! - Thanks!
Back to the number and size of Flues in Rayger's Boiler.
is it still to be 55 off 7/16" flues?
Or the scheme Martin proposed?
Maybe I missed something along the way, when I wasn't here....?
K2