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[shane g]

all right guys  i have run into a problem getting my steel the we are having quality issues with our steel supplier so i am not going to buy any from them until they get that straight i can get my hands on the same stuff i am building my water jacket it is between 3/16 and 1/4 " 50 grade do you guys think this would be suitible if not i will just wait but if so i can aquire that and get started sooner
give me your opinions please
thanks

[kjw58]

Welcome Shane
 There is so much info on this website it is almost mind boggling!! I will ad my two cents . If I where you I would not start a build without a firm plan or design.  You really need to look at the design of different manufacturers and take the things that make sense and incoporate them into your design. Changes you make along the way can have a way of getting expensive.  You can check out some of the features on manufactureres wesites but there is nothing like seeing a stove in operation, and talking to the owner. 
If you check out Jackels built on this site, he combined a Natures Comfort gassifier with some features from portage and main and some of his own ideas to build a one of a kind gassifier.  I have never seen Jackels stove personally, but I have seen P&M's Optimizer 250 gassifier and I own a Natures Comfort GT-220 and both are very impessive stoves.  Good luck with whatever you decide to build and always remember if there are no pictures posted here it never happened!!!!

[Bull]

That should be fine for your water jacket.

[shane g]

i did not clarify myself woud this steel be ok to use in my firebox or is it too thin its between 3/16 and 1/4 50grade sorry for the incomplete post

[martyinmi]

Shane,
   I've never built one with less than 1/4" for the burn chamber. The 3/16" should be fine for the boiler vessel.

[peacmar]

7ga (3/16" thick) grade 50 will work fine in your burn box. Most grades of "boiler plate" is nothing more than A36 steel with a few alloys added to reduce thermal expansion rates. But from a structural standpoint is still only A36. Your grade 50, aka A50 7 ga sheet steel has superior mechanical properties. As the grade number denotes the tensile strength in psi times 1000. A few strength calculations based on the modulous of elasticity show us that 7Ga A50 has a higher strength value than 1/4" A36. So your steel will be plenty strong enough, and also the alloys added for extra tensile strength also happen to reduce thermal expansion. The only loss you will have is a very slight chance that it might rust through a couple years earlier, but with proper maintenance this should never be a problem. Keep in mind also that the high end wood gas boilers like the orlan and the froling use material with less than 3/16" thickness and some of those units have been in use for better than 20 years. In the end its all about water care and maintenance. Monitoring your ph, nitrate, keeping it full of water and never below 140 degrees. Water gives up its absorbed oxygen at 180 and doesn't absorb it again till it drops to 140.140 degrees is also the magic number when water vapor in flue gas starts to condense in the fire box. So another reason to keep it above that temp. your fire box will be plenty solid with that material. If it where me, I would use it. Because I built my fire box out of 3/16 thick A70 and know that ill cut this thing apart to recycle the steel far long before anything fails.

[Ridgekid]

 

Great information. I hope others will read between the lines concerning operating temps! Makes more sense now why CB defaults their controls to 185 off / 175 on.

Thanks! 

[peacmar]

I also want to add quick that its my opinion that The use of "boiler plate" in an outdoor wood burner is nothing more than a sales gimic that appeals to the uninformed. Asme rated plate is graded by its pressure and temperature capability. Even the lowest grade of asme cert steel is capable of far more than a owb can ever produce. Asme Temperature ratings state that SA36 is more than sufficient, and thickness is determined by operating pressure. Which I hope is atmospheric for anything home made. So necessary thickness is actually minimal. The only application where boiler grade steel should probably be used is in a gasifier, where temps call for at least SA 285-x but SA 516-xx would be best. Just my $.02 but something I wanted to throw out there because I see it over emphasized way to often.

[jackel440]

peacmar,  great info there!
I also agree that the "boiler Plate" is an over used sales gimmick to persuade uninformed consumers.

[peacmar]

Thanks for the thumbs up guys, I've decided that that info will be a part of my informational thread. And not trying to jack your thread shane g just doing my best to help you make informed decisions. To elaborate a little on my previous response, and something tying consider when you get yours up and running. It may work to your favor to run your boiler all the way up to 200 degrees the first time you fire it. Then back the temp down to around 160-170 depending on what your controller differential is. I use a PID controller with thermocouple and have an adjustable differential but have found that if I run from 150 to 170 I get far better mpg so to speak out of my wood usage. I didn't notice my air handler running any more often even in the middle of January last winter when it was -25 and we also have a constant 15-45 mile per hour wind up on top of our hill with no wind breaks grown in yet. But lowering the temp range down from 180-190 I used about a third of a cord less of wood in Jan than I did in the 40 degrees warmer month of December. I know this is out there a ways yet but something to keep in mind for when the time comes. I wouldn't suggest any lower than 150 though, especially if you happen to have forced air, as your return water temps will be below 130 if your exchangers is sized right and you will need sufficient heat stored in the boiler to keep the overall temp from never going below 140.

[shane g]

wow great info just the info i need looks like i am going with that steel then
ok when i put the pipes in for the forced air in the fire box some body on here said i should only have 20% of my air going under the fire and 80%blowing on the top side?? was planning on running 2" pipe
2 of them out of my blower motor box any idea on how to reduce the cfm in the pipe maybe manual butterfly valves
thanks again for thi info main goal in life this week is to cut and bend firebox and hopefully weld this weekend and get pics of this on here

[peacmar]

I will draw up a sketch and take a picture to put up here. It's very simple though, fan blows into a box and box has two pipes going into the burn box. One high one low. The end of the pipe in the fan box has a round plate welded to the head of a bolt that goes through the fan box to the outside. The fan box is threaded so when you screw the bolt in it brings the plate closer to the end of the pipe until its closed, loosen the bolt and it backs aware from the pipe end and let's more air through. Very linear and very precise and easier to fine tune than a butterfly. jamb nut to lock it in place and both of your air pipes can be metered the same way. I too also believe that 20% under and 80% over is good. Ideal is 1/5 ratio so that's about right percentage wise.

[jackel440]

I will draw up a sketch and take a picture to put up here. It's very simple though, fan blows into a box and box has two pipes going into the burn box. One high one low. The end of the pipe in the fan box has a round plate welded to the head of a bolt that goes through the fan box to the outside. The fan box is threaded so when you screw the bolt in it brings the plate closer to the end of the pipe until its closed, loosen the bolt and it backs aware from the pipe end and let's more air through. Very linear and very precise and easier to fine tune than a butterfly. jamb nut to lock it in place and both of your air pipes can be metered the same way. I too also believe that 20% under and 80% over is good. Ideal is 1/5 ratio so that's about right percentage wise.

if you go and look at my build thread this is exactly how I built my air box.I can precisely control. Air flow in each chamber.works excellent.although I suggest to apply antisieze to the threaded rods due to creasote in the box that gets on the  threads.
I would like to advise you to perhaps up size your air tube to something bigger than 2".I am running a 2x3" tube into mine.I sometimes wonder if a little bigger feed tube would improve performance any.

[peacmar]

Great suggestion jackel440, a picture is so much better than a sketch. And when you purchase or find your fan, use the outlet as a guideline for the air tube sizing. They are designed for optimal flow and if you figure out the surface area of the fan, you will know how large to.make your air tubes. The air tubes must all add up to be equal to or greater than the area of the fan. 2"x3" outlet is in the ball park of 170 cfm for a typical squirrel cage blower at no load air flow. One rule with blowers is the air velocity exiting cannot be faster than the tip speed of the blower wheel, as the wheel just can't push air any faster than its spinning. But 170 cfm is still a massive amount of air through a gasifier. One particular company only uses a pair of 50 cfm fans, on their 200,000 btu hr model. So 170 is quite a bit. Although, if you have a place to store it then let the heat roll out.

[shane g]

  our laser been down and ops are catching up on production so my little project got put on the back burner hope to start soon but here in VA its 70 degrees so thats helping my fuel bill but sucks that opening day of gun season starts sat and its  freakin hot