Since not all of us work with electronics all day every day I thought I would share a bit of what I do on the side.

Here is the multi fuel boiler system I have been working on for my brother over the last few months and just got the main boiler assy finished.

The dimensions are 42" wide by 60" long by ~96" high to the top of the stack.

The burner box is 28" square by 54" deep.

The overall working water capacity was designed to be around 250 gallons.

Total empty weight going by my forklifts lifting capacity is about one ton and its made entirely out of 5/32" 3/26" and 1/4" Hardox 450 high strength steel.
I figure I burned up about 45#'s of high strength E70 .035" welding wire putting it together.

He plans to put a fully insulated outer shell put on it and set it between the two buildings behind it the third picture with the intention to use it to heat the building on the left plus run lines up to his house and garage, that can be seen in the background of the fourth picture, next year.

 

Really nice boss...

 

My sister has been trying to get me to install one of those since 2001. Problem is, I couldn't weld two kitchen knives together if somebody handed me the right welding rod.

 

I do have to admit that making one like this is not an easy project. There is a load of calculating dimensions and marking steel sheets to get the most use out of the least amount of metal.

Hardox 450 is some pretty tough metal to work with as well. Plasma cutter and grinder are about the only way to cut and shape it.

Unless I am using carbide masonry drill bits that I have reground the carbide heads on for metal cutting any titanium cobalt or less grade of drill bit won't scratch it.

Most common off the shelf grades of mild steel are around 45,000 - 75,000 PSI tensile strength. Hardox 450 is somewhere around 205,000 - 225,000 PSI tensile strength.

Nice part is that for the most part the thing is physically and thermally indestructible and won't likely rust out during the rest of my lifetime.

 

The material you used seems pretty thin compared to most boilers I have seen, I had built mine from scratch also, and the thinnest I used was 3/16" for the water jacket. The burn chamber is out of 1/2" and the rest is 3/8" thick. http://forum.allaboutcircuits.com/showthread.php?t=70125

 

It's a open system so there is no pressure build up plus there is a considerable amount of internal bracing that balances out the internal hydrostatic forces on the sheets.

Then from there factor in the considerably higher rigidity and tensile strength of the Hardox 450 steel and structurally its similar to having been made out of material 3 - 4 times thicker.

This is the fourth boiler I have made of this box design and I can assure you they can really take a long term beating without issue.

My first one was made of 10 gauge mild steel and had been my primary heating system for around 12 years now and has never had issues due to the steel being too thin.
Granted age is taking it's toll and the base sheet needs to be replaced due to rust pinholing but the rest of the boiler is holding up just fine.

 

Too bad you are all the way in ND, I could use a good welder/fabricator at my shop.

 

Nice looking work, sir! That's one project I wouldn't want to take on. My layman's understanding of boilers is that they're scary, and their design and construction should not be done by the uninitiated (not insinuating you're uninitiated). I believe mechanical engineers must go an extra step and obtain extra certs and licenses to design them professionally, and I want to say that there might also be an additional license for welders who work on boilers. It is impressive you have done this yourself.

#12 I'm surprised you can't weld. You would have been one of my first guesses for which AAC regulars can weld. I'm a practitioner of what I call "practical welding" which is a glossed over way of saying "looks like pure ass, but it works"

 

....... I believe mechanical engineers must go an extra step and obtain extra certs and licenses to design them professionally, and I want to say that there might also be an additional license .....

For actual "boilers" that work off of steam ofcourse those require all kinds of degrees and licences, but these types of "boilers" that do not actually boil anything, these are open loop systems that do not build up any pressure, they are basically a wood burning stove that are set up outdoors and connected to buildings via water lines
. Dont get me wrong, people still have to know what they are doing to build these things and install them.

 

Exactly. Being an open system design that can not build up any pressure they fit under a different category and most anyone can build one if they have the metal working skills to put it together.

After I build one I do a what I call a full burn and boil test which is where I literally pile it as full of wood as I can get it and then let it run flat out with the door open until the fire burns out all while boiling like mad the whole time.

If I did my calculations right it will go from being at it's full water level to just above its minimum designed water level without doing any damage to the system.

I have not done it with this one yet. I wanted to do it yesterday but my brother was not sure his well has enough water to fill it in one shot plus he wanted to watch football anyways.

 

Surprised you use wood for the 'proof test'. Would have thought you would use old tires.

 

It's been a cold winter. I ran out.

I designed it to burn the typical assorted woods we can get for free around here so that is what is most fair to use for a burn and boil test but to be honest I would not be worried about running a good load of them mixed with hardwoods through it.

I made sure the reserve water capacity was well above what a single load of most anything can boil off and even if it did non of the actual firebox would get exposed.
To get that low would take about 100 gallons more water loss or about double over times what the reserve holds.
Boiling off 150 gallons of water takes a huge amount of wood to produce that much heat energy!

 

That is impressive, but then I am like #12...no welding skills. If I had the skills, I would like to build a tiny wood stove for a 180 square foot off-grid cabin. Even the smallest stoves I have found are too big, especially when the very coldest temps will be about 0°F, and anything below 20°F will be rare.

 

That sounds like a good excuse to buy a used mini MIG unit!

I wasn't born with a welding rod in my hand and had to learn it myself so I think you are more than capable of doing so yourself.

 

#12 I'm surprised you can't weld. You would have been one of my first guesses for which AAC regulars can weld.

Air conditioners don't need welding, but I can braze with the best of them.

 

My brother did a fill and low burn test Sunday and found three pinholes in my welds so today I brought it back home and patched them up.

After that I did the full burn and boil test. Everything passed at 100% output!

I also did the welding with my old Millermatic 35 welder I pieced together last week from old parts I had around the shop plus rewired it to work with a more modern Miller S21 type external wire feeder unit.

That too worked perfect!