Author Topic: Model steam boiler questions  (Read 456 times)

Offline Chuck in E. TN

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Model steam boiler questions
« on: July 25, 2018, 11:14:32 AM »
As my interest in model steam engines grows, the thought of a boiler to run them is nagging me. I have never seen, owned, or operated a model scale boiler. This thread will be used to ask questions and gather resources for a first boiler build.
 I am reading everything I can find on model boilers, from 100+ year old books to more recent writings like Stan Bray's book(ordered but not received yet). I have found a lot of reading material online.
 If you have built, and operated your own model boiler, I ask you to post at least the name/style of boiler, where you got the plans, and where you got the materials. I'm in Tennessee, USA, so especially looking for resources near me, but all are encouraged to post. Recommendations on simple, home built, favorite designs are welcome.
 I am also looking for plans and information on safety valves, pressure testing pumps, gauges, burners, and any other accessories needed.
 I prefer a design I can build, but if there is an affordable kit available, info on that would be nice. By affordable, I mean I'm on a limited OAP budget... an I've not won the lottery, ...yet!
Chuck in E. TN
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Offline David Jupp

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Re: Model steam boiler questions
« Reply #1 on: July 26, 2018, 03:02:03 AM »
I suggest you spend a bit of time checking out the legal / insurance position, just to make sure you don't accidentally put yourself in an awkward situation.

If ASME codes are compulsory (or even advisory) in your State, bear in mind that these tend to be conservative compared to some other codes.  A boiler design from elsewhere in the world may not meet ASME requirements.

Hopefully there'll be members who are familiar with the issues, who can give more detailed advice.

Offline John Rudd

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Re: Model steam boiler questions
« Reply #2 on: July 26, 2018, 04:45:35 AM »
Chuck, Irrespective of design codes etc. ( this will come later...)
The size of boiler is going to be dictated somewhat by the size of engine you want to run from it......

Burner sizes again, dictated by boiler size, what thpe of fuel? Gas, spirit, coal?
Safety valves, again back to boiler sizing, working pressure of boiler will dictate the release pressure, and the size of sv, needs to be big enough to reduce the steam pressure quickly....
Can you quantify?
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Offline Chuck in E. TN

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Re: Model steam boiler questions
« Reply #3 on: July 26, 2018, 03:56:10 PM »
Chuck, Irrespective of design codes etc. ( this will come later...)
The size of boiler is going to be dictated somewhat by the size of engine you want to run from it......

Burner sizes again, dictated by boiler size, what thpe of fuel? Gas, spirit, coal?
Safety valves, again back to boiler sizing, working pressure of boiler will dictate the release pressure, and the size of sv, needs to be big enough to reduce the steam pressure quickly....
Can you quantify?

I have various sizes of engines, from 3/8" bore x 1/2" stroke, to 1" bore x 1 1/4" stroke. None will be operated at high speed. Fuel, probably propane or spirit. From what I have read(obviously not enough reading), I only need about 45-50 lbs. steam pressure. I haven't started a boiler yet. I'm trying to ask the correct questions as my knowledge increases.
Any references to determining the requirements based on my given(though uneducated) parameters would be most appreciated.
I will not be exhibiting my engines publicly, just running them for myself or family/friends.
If necessary, I'll have any observers sign a release prior to firing it up...
Chuck in E. TN
Famous TN last words: "Hey ya'll, watch this..."
MicroMark 7x14, HF X2 mill, Green 4x6 saw. Harbor Freight 170A mig

Offline Will_D

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Re: Model steam boiler questions
« Reply #4 on: July 26, 2018, 04:55:56 PM »
The first consideration would be: Where will it be used?

If its going to a public place/meet/society etc then a steam boiler (or ANY pressure vessel) will need to be certified by a qualifies boiler inspector.

If this is your aim, first find an inspector. ME societys and the like usually have access to the qualified people.

The inspector can help in the basic initial design and also detailed construction details. (After all these details are what he will be inspecting - its not just about the hydraulic test).

Construction of said boiler usually involves the following base material options:

1. Silver solder copper (The old ME way)
2. TIG welded copper
3. Welded mild steel (Prone to corrosion)
4. Welded Stainless  (Cheaper than welded copper)

HTH

Will
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Offline Ironhorse57

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Re: Model steam boiler questions
« Reply #5 on: July 26, 2018, 05:42:25 PM »
How do you run your engines at present?  Reason for asking - I bought an engine a bit larger than my usual 'toy' size some years ago and whilst awaiting delivery I started to ask the same sort of questions about boiler building.  When it arrived I ran it via my airbrush compressor and was surprised to find it needed a much lower pressure than anticipated, enough that I was able to just build a basic horizontal pot boiler using brass tube with a commercial 15 psi safety valve.  It is quite basic but tested to 60 psi with no leaks and I was able to use soft solder throughout - the end caps are though reinforced with a central stay for additional safety.
If you are looking at anything with a higher operating pressure then Will's advice is recommended - even if you don't plan to fire it up anywhere else than your own place.

Dave   

Offline vtsteam

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Re: Model steam boiler questions
« Reply #6 on: July 26, 2018, 05:50:28 PM »
good luck  :beer:

ps. the information highway is a two way street.
I love it when a Plan B comes together!
Steve
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Offline Chuck in E. TN

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Re: Model steam boiler questions
« Reply #7 on: July 26, 2018, 09:20:37 PM »
I run, or have run, my engines on compressed air only.

No public/meet or society gatherings. No ME Societies local to me, that I am aware of. I would only run the boiler on my private property, but I still want to be as safe as I can make it.

No model boiler inspectors near me that I know of.
Chuck in E. TN
Famous TN last words: "Hey ya'll, watch this..."
MicroMark 7x14, HF X2 mill, Green 4x6 saw. Harbor Freight 170A mig