Home brew fire tube boiler design

Cool project ! Are you planning on reusing the spent steam or just blow to waste ?
 
As a guy who burnt 83% of his body and spend 16 weeks in a burn unit, along with about 40 yrs of serious related health issues since, a boiler accident. Remember the engineering of a boiler is extremely complex. I currently have 45+ yrs in the industrial boiler business.

While the propane tank has a high pressure rating, but at what temperature?? Even low pressure steam boilers (less than 15 psi) have shell thickness of about 1/2”, way more than a propane tank. Be very careful of unapproved homemade designs, building and property can be replaced, but human flesh is very unforgiving and the after effects can be extremely life altering.
 
Alcap said:
Cool project ! Are you planning on reusing the spent steam or just blow to waste ?
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First iteration would just be wasted to atmosphere to bring down complexity
Buffalo21 said:
As a guy who burnt 83% of his body and spend 16 weeks in a burn unit, along with about 40 yrs of serious related health issues since, a boiler accident. Remember the engineering of a boiler is extremely complex. I currently have 45+ yrs in the industrial boiler business.

While the propane tank has a high pressure rating, but at what temperature?? Even low pressure steam boilers (less than 15 psi) have shell thickness of about 1/2”, way more than a propane tank. Be very careful of unapproved homemade designs, building and property can be replaced, but human flesh is very unforgiving and the after effects can be extremely life altering.
Click to expand...
Yeah that sounds like a hell of a bad time. I had thought 40psi left ample headroom at the low boiling temps I had in mind but being scalded by 10 gallons of boiling water doesnt sound real enjoyable...
May need to scale down and make something smaller first and see how it goes. I have seen all sorts of random crap people have made and used from a soup can (terrible idea all around) and 1lb propane tanks, band wrapped barrels etc.
Been having a hell of a time finding the specific regulations around boilers in WA state, I know we have some sort of deal to do with hobby non commercial boilers but I cant find the specifics for size and pressure so far. Absolutely not wanting to hop on the "this is my boiler horror story" bandwagon
 
Stanley's used a vertical fire tube boiler. I believe you are thinking of Doble steam cars, they did use a flash boiler, which started producing pressure almost immediately.

Stanley's had a butt load of fire tubes and a low water volume to raise steam quickly, and could be under way in 10 minutes or so.

San Francisco used White steam cars as ambulances and just left the boilers fired at an "idle" temperature requiring only to turn up the burner and be ready to roll as soon as the crew was aboard.
 
You're in the realms of it being quite a large boom if something lets go. Lotta energy in there at 10psi with that size tank, let alone 50 or so. Remember also that it's not only over-pressure events that makes boilers fail. Safety valve or not, you're sitting on a large amount of contained energy in a medium that will expand rapidly it suddenly not contained. Maybe have a look around for an existing design if you're interested in building something? Model clubs can point you in the right direction in design, construction, testing and legal.

For the sake of discussion and some comments on your design: Boilers of that size or larger tend to have a water jacket around the entire firebox for two reasons: the water surrounding the firebox keeps the plate temperature under control, but just as importantly, the firebox is where most heat is actually transferred - far more than in the tubes in the case of full size loco boilers. It'll be heinously inefficient without any of the firebox itself being used as heating area.
Anything that runs through a pressure vessel should do so orthogonal to the plates it pierces. Otherwise expansion stresses tend to play havoc with the joints. I mention this as you'd shown the tubes running at an angle.
Welding something like this, if that's what you're intending, should not be taken lightly. An imperfection leading to a crack, or simply a poor joint that fails could have deadly consequences, particularly around that dome.

I've spent a lot of time around and working on full size loco boilers in preservation. I'm by no means an expert on their design, but knowing what I do, I know that I don't know enough to design a sizeable one from scratch. Lean on the knowledge of live steam modellers to make something safe and reliable. It's entirely possible, but there's lots of engineering involved, so you might as not reinvent the proverbial wheel!
 
I really appreciate everyone chiming in on this.
Obviously I am a bit in over my head with that idea.

That monotube boiler that was mentioned in the first page may be the way to go for something small to mess with. No large mass of boiling water to contain and the heat insulating layer/container around the coil would shield a little bit from a release from a rupture. Gives easier temp control with a propane burner under the coil as well.

I am by no means dead set on a setup I came here to figure out what may and definitely wont work. Will have to see what there is local for a hobby steam community
 
do a search for gassifier as a means of fueling it, worth a looksie.
 
Say, I looked at monotube flash steam boiler plan posted above. That is exactly how a hot high pressure washer is built. Mine does 4000 psi. Its got everything done for you, just remove the gas engine and pump. Get a feed water pump and you are good to go.

Start shopping Craig's list for an old broke one.
 
A possible advantage of monotube boilers is they are nearly always exempt from state laws governing the testing ,maintenance ,operation and qualification of tube boilers.......however most jurisdictions do have a "model boiler" code ,which generally means you can build a tube boiler to say 12" or 14" shell dia,and be within the model code.
 
It's worth also mentioning that you can make a lot of steam from quite a small boiler if it's well designed! With a boiler, the smaller it is, the safer it is.
Gasifier fireboxes** have been tried and turned out to be very successful, though sadly arrived too late in steam loco development to have been widely adopted. Loads of interesting avenues to go down with steam.

**Look up gas producer combustion systems by Andre Chapelon, David Wardale and L. D. Porta if interested.
 
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