Home brew fire tube boiler design

[JoeBlob]

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.

Oh man that is fantastic info to have! If I can find one with a bad pump engine that would be an excellent starting point

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.

Well that is handy, I will have to check that. I know Washington has a law on hobby boilers that was reduced in scope a couple years ago but i havent found a definitive list of the limitations. Need to find someone from the area with the regulations book or something. The websites for WA are dang near useless 30+ pages just explaining who the board members are and the fines for non compliance but I cant find the actual regulations yet

 

[RJSakowski]

Many years ago, I made a high efficiency wood furnace by running about forty 1-1/2" pipes through a hot air plenum, the idea to extract as much heat as posswible. Not a good idea for wood as the cooler exhaust temperatures favored the condensation of creosote which plugged up the pipes and eventually rotted them out.

 

[JoeBlob]

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.

I did want to ask, is that a modern standard to be 1/2" thick even at low pressures or is that the older cast style? I would hope modern metallurgy is better than it used to be.

And a smaller tank with less surface area at the same pressure say 15psi, (so let's say 2 gallons) could theoretically be made thinner than one with a huge capacity (say 100 gallons) right?
Not looking to push any limits just trying to understand the physics from someone with experience

At this point the monotube flash style boiler is looking promising since they're fairly simple, can be more precisely controlled with a burner and have a lot smaller capacity of hot water inside so theoretically safer.. and since I can source proven components from a hot pressure washer

 

[john.k]

The monotube washers arent cheap to buy,and the tubing is normally what fails......I do know a diesel washer unit cost me $1500 to have a new tube coil wound up for it may years ago......There is a lot of tube in one,and they are quite heavy........You would also want to run one on diesel or light oil,certainly not any kind of tarry wood.......if you must use wood,charcoal would be necessary.

 

[JoeBlob]

Yeah I used to be a pressure washer/roof and gutter cleaner. Even a standard washer of decent quality is well into the 4 digits.
Ideally Id be looking for one with an engine someone didnt maintain and siezed up but I think I will end up going the DIY route using their setup as a design template.

Definitely no wood or coal fuel that and takes away the ability for a fast shut down. Regardless of style I am thinking I would need a propane burner. Cheap reliable and adjustable. For something like this the venturi style burners they use for small forge furnaces would probably be perfect and they're easy to build yourself i made one a few years back to melt pop cans out of black iron pipe and an adjustable regulator.

 

[john.k]

Nevertheless,fire tube boilers do have the proper steam allure,and shortly Ill be building the biggest one Ive ever done,14" diameter and something like 6' long.....for a steam tractor.......Ive already salvaged several sets of big gears from old crawler cranes ,some large air tanks for wheel rims,and much scrap metal for bits and pieces.....All I need now is for my new big workshop to be built......concrete slab is there ,steel is there,contract builders arent there .....anytime soon.......Anything to do with builders is promises,promises,and no action.