oil tank evap bricking/archboard help

[sugarnut]

howdy folks. it's been quite a while since i have posted on this site as i have many irons in many seasonal fires. i am looking forward to another maple run. i hope everyone is getting ready.

i am getting ready to build an arch/evaporator, on a very, very tight budget, out of either blocks, gravel and fire brick or to have an old fuel oil tank cut and welded and lined with fire brick and arch board. i have seen lots and lots of designs and posts on this site and basically have the "jist" of what i need to do, but i do have a few questions on insulating certain areas. the amount of posts on this site is immense. i have viewed many threads and pictures, but i have not found any close up pictures of the bricking or use of arch board. the points that puzzle me are the areas of transition from the firebox to the pan and the pan to the rear or flue area.

my tank is 67 inches long. i plan to set a 2 x 3 flat pan on top of gasket placed on a 2 inch angle iron frame welded to the tank. that leaves 11 inches in the rear for a flue and 20 inches in the front for a firebox. i am leaning towards mounting the flue collar on top of the tank behind the pan. i will brick the firebox and the bottom of the arch under the pan, and the sides under the pan, but i am lost as to how to insulate the top of the firebox or the transitions from firebox to pan and pan to flue area. i wish to protect the angle iron from warping.my thoughts are to weld angle iron in the firebox so i could drop in arch board and have it directly under the angle iron. should i try to do the same for the flue area?

i was thinking of running gasket and angle iron along the entire top of the tank and finding a way to bolt a metal plate with a flue collar on the top of the gasket. my thoughts are that doing so will give me access to maintain the board and bricks if i need to, or to eventually move the flue collar to the rear side of the tank if i need to expand the top for a larger pan or preheater.

i suppose that if i did that, i could weld angle iron under the flue plate and cut the board to allow a circular hole for the flue. hopefully this would allow me to insulate the angle iron and keep it from warping so bad.

another thought is that my original thought was to have the angle iron pointing down into the tank, leaving the top totally flat. perhaps it would be better to have the angle point upwards. that would make it easier to run the board just under it.

i would appreciate any thoughts, and especially pictures, that could help with my project.

sugarnut

[Gary R]

First, how tight of a budget? It will cost at least $175 if you have to buy brick and blanket because of the round bottom. Your pan should sit on top of the firebox. I would move the pan all the way to the front. Then I'd block off the back and bring your smoke stack out right behind the pan. This way you won't have excess heat radiating out into the room.

[sugarnut]

i plan to weld in metal of some sort...cut out tank material or plate of some kind, so the amount of brick should be just enough to cover the surface area exposed. i have a fair number of firebrick already. i will be boiling outside. i may even be able to salvage a few rounded firebricks from an OLD hot air furnace for the bottom of the firebox. there will be a grate in the firebox with a cleanout/draft located under the door.

[Pete S]

Check out what I did in the post "Cutting a 275 gallon tank" as I just put some photos on there.

Not the best way proably, but it was purty easy!

Pete

[sugarnut]

First, how tight of a budget? It will cost at least $175 if you have to buy brick and blanket because of the round bottom. Your pan should sit on top of the firebox. I would move the pan all the way to the front. Then I'd block off the back and bring your smoke stack out right behind the pan. This way you won't have excess heat radiating out into the room.

so you think i should move the pan all the way forward? i think i should have some sort of setback. perhaps not the entire way back as i have initially described, but far enough back so as to get the full flame as it is drawn back by the draft.

[C.Wilcox]

sugarnut-

I think there will be plenty of heat under the pan even if you pull it all the way to the front. I could be wrong, but I believe almost all evaporators have the pans all the way to the front. That's how mine is going to be set up as well. The excess length of the tank will be behind the pan. If you're using a 2X3 pan you could just cover the excess area behind the pan with a piece of sheet steel that will get hot and then put a pan/pot on it to preheat your sap in. Kind of like having your own griddle. :)

I attached a photo of my tank showing how the angle supporting the pan is attached. If you look close you can see the line where the ramp and flue area will be. Is this how you were planning on building your firebox or were you thinking of something different?

[sugarnut]

that's basically what i had in mind. i haven't decided on a "ramp" or straight step, though. i am thinking that it will be simpler in the time i have left to make a straight step up.

i noticed on basically every evaporator i have seen, here and in catalogs, that all of the top surface is used (the pan is all the way forward). i assumed that is to make use of all the space. i have never seen a setup where the pan is much smaller than the available space. from what i have seen from firing woodstoves for 30 years and the masonry woodstove i boil on outside for the last 5 years is that the flame follows the airflow. there always seems to be a spot up front devoid of flame unless the air flow is restricted and the draft is slow. i doubt a slow draft will be my goal, lol, although i may incorporate a damper and shut the draft back a little if i have flames shooting 1 or 2 feet out the top of my stack like the stove outside. :)

my plan is to weld angle, like you have, around the entire tank after i cut the top off. my goal is to use gasket around the entire thing and bolt down a plate with the flue collar and any plate, to the front or rear, to seal the rest. that way i can expand with an additional pan when i can afford it. i guess what i will have to do is weld plate or angle facing down as a crossmember to support the pan where needed. perhaps i could weld a plate under the the flue plate to mount gasket to so it is all flush with the sides and my pan will sit true.

i am most concerned about any metal exposed to the flame. i don't want it to warp so bad that i cannot get the pan to sit right. every steel refracting/recirculation plate i have seen in every fireplace insert or wood furnace has warped. cast iron would be best, but that is tough to come by.

maybe i'll forget about steel for crossmembers and find a way to use firebrick between the flue plate and the pan.

[thenewguy]

not to step on anyones toes, but I have a oil tank evaporator and my pan is back a foot from the door. first year I used it I could never get enough heat under the front of the pan, so second year I moved it back and it works fantastic. Although my door is just cut out of the oil tank and leaks alot of cold air I'm sure. I've had enough of the oil tank arch and will be buying a new one next year...

[Pete S]

Hey "the new guy",.............yer scarrin' me! I'm just wingin' my build and hope to test fire in a week or so.

I hope I don't experience the same issue, as I stepped up the back portion of mine.

Did you squeeze the heat with a tight "arch"?

Thanks!

[jrobida]

I have my pan all the way to the front on my oil tank arch and it works great.

[C.Wilcox]

i am most concerned about any metal exposed to the flame. i don't want it to warp so bad that i cannot get the pan to sit right. every steel refracting/recirculation plate i have seen in every fireplace insert or wood furnace has warped. cast iron would be best, but that is tough to come by.

maybe i'll forget about steel for crossmembers and find a way to use firebrick between the flue plate and the pan.

sugarnut- As you said, your plan is going to force you to have steel supports exposed to the heat on the front and the back of the pan which you are right to be nervous about. Maybe you could bolt ceramic blanket on underneath the crossmembers to shield them from the heat? The guys that put in over the fire air injection wrap the nozzles with blanket to keep them from over heating. I would guess you could do the same with your set up. The blanket will eventually break down, but can be replaced fairly easily. If you moved your pan all the way to the front and built your ramp as a vertical wall I would think the heat would be forced up against it pretty well, but that's just me guessing. It would also mean that you'd only have one cross member, the back one, to wrap in blanket instead of two.

thenewguy- did you build a firebox and ramp into your tank or did you use it "as is"?