OWB Build

[hondaracer2oo4]

I am going to look at a 500 gallon Double walled 48 inch x 5 foot 1 inch fuel tank. I would like to know if anyone is familiar in how the double walled tanks are constructed and if there is any reason why one wouldn't work well as a water jacket? Thanks for any insight!

 

[cantoo]

It's a lot of work wasted if the fuel tank ends up being the weak point that leaks. I'm planning one someday and will likely go with 2 different sizes used propane tanks. I bought 2 used owbs and will be stealing ideas from them both to build a new one.

 

[hondaracer2oo4]

You too must be thinking that the tank thickness is not thick enough. I believe that plenty of boiler manufacturers are making their water jackets in similar thickness to what a fuel tank is. Also I think that if I add two Anode rods in the water jacket that it will help greatly with slowing down rust. Anybody cut one of these tanks open before?

 

[NSMaple1]

I have not built an OWB, and have no desire to.

But if I was going to try to do it, I would not use a fuel tank of any kind - I would go with propane tanks. A smaller one inside a bigger one.

But it's totally up to you on how you want to spend your time & money...

 

[Poston5]

We built an owb out of a 500 gallon propane tank as the water jacket and a 330 gallon for the firebox. To cut it we got a propane regulator and hooked it up with a 6 foot piece of copper tubing and released the propane from the tank while burning it off. Then we cracked the plugs and let it set for a week. Then plumbed the exhaust from a gas engine into it for 10 minutes then cut it with a partner saw. They will not explode as long as they are not under pressure.

It wasn't a difficult build just put a lot of thought into an adjustable door that seals tight.

The thing works great and he has about a grand in the enti setup including all controls and pumps.

Good luck and be safe.

 

[hondaracer2oo4]

Thanks for the tips so far. Ive got both tanks now, but haven't cut yet. I am looking for what to do for a flue pipe. My plan was to exit the rear of the firebox, head up about 6 inches and 90 degree and send the flue horizontal all the way to the front of the water jacket to maximize water contact and then T off at the front where the flue would continue up while I had a clean out on the front of the unit. I can't find any large steel schedule 40 6 inch fittings though for a 90 degree and a T. Do you guys have any suggestions? I was also thinking about contacting a well drilling company to see if they have any 6 inch well casing scrap that they would like to sell.

 

[comnrailpwr]

Any large plumbing supply house can get them although not cheap. Try mcmastercarr.com they have about anything. Your flu idea sounds good. My water jacket is 2' longer than the firebox so I recover heat from 2' flu pipe. I pull water from bottom and return to top. I have a 90 degree 6" elbow in the firebox to keep heat in. Works great. Get nearly 0 creosote, just a little black dust. It burns very hot.

 

[Mike from Maine]

Flue pipes

Here is how i'd build it.

 

[chaikwa]

You too must be thinking that the tank thickness is not thick enough. I believe that plenty of boiler manufacturers are making their water jackets in similar thickness to what a fuel tank is.

You asked and people are giving you reasonable and honest answers, but it seems like you're trying to talk yourself into believing that a thin-walled water jacket is sufficient. Manufacturers may well be using 12 gauge material for their water jackets, (12 gauge is what tanks are generally made of), but 'manufacturers' also made the Yugo and many other vehicles of similar quality, but that doesn't mean they were a good idea. I, like the others here, would not put my time into a project using questionable materials or methods. I wouldn't hesitate to BUY a product if it contained something of questionable design or quality as long as the rest of the product was sound and it had a warranty to fall back on. I'm about to purchase a Hawken product because I've run out of time to build one myself. The only thing I question about the product is the fact that they don't weld both sides of the seams. Would I weld both sides if I built it? YES. Is it necessary? NO. But either way, a bought unit will have a warranty that I will use without hesitation. If I build it, I AM the warranty!

They will not explode as long as they are not under pressure.

Not to be arrogant or sarcastic, but that is just a totally incorrect statement. Pressure has nothing to do with the flammability or explosiveness of propane or petroleum based flammable liquids. Either will ignite if the lower or upper explosive limits are reached, meaning if there's fuel and air in the correct proportions, you will have a fire. I just don't want people thinking if they release the pressure in a tank it won't explode.

 

[hondaracer2oo4]

Thanks comnrailpwr. That website does have what I am looking for. Looks like you didn't go with a grate system and ash clean out door. Any reason why not? I was planning to do one with mine.

 

[comnrailpwr]

Thanks comnrailpwr. That website does have what I am looking for. Looks like you didn't go with a grate system and ash clean out door. Any reason why not? I was planning to do one with mine.

at the time It was extra work and the space it would take up it would really limit door & firebox size. I create about a drum of ash a season. Shovel it out every 2-3 weeks. Its not the bad. When I build my next one I will Stand my tanks upright so I don't have to stack wood in it when loading. A taller firebox with fuel door at the top is better than a 4' deep one like I have now. I would be able to just throw wood in it and walk away if it was upright. It would also allow much more room for grates, ash clean out & make it easier to get the combustion air underneath the wood.

 

[hondaracer2oo4]

Yea I understand it is a bit more work. I just think that having a way to move the air under the fire is much more efficient than just blowing air at it from the door. My firebox is also going to be bigger since it is a 500 gallon, it is 37 inches across. I think I am going to put the fan on the front of the unit beside the ash door so it gets under the fire.

 

[hondaracer2oo4]

I was having some trouble finding 6 inch schedule 40 pipe 90 degree and T fittings but have found that the local fire protection company has them. Do you guys think these would be adequate to use for flue pipe fittings?