first time firebricking, need help

[Stamford sugarmaker]

Just bought a new 2 X 4 with a flat pan and realized how little I knew about firebricking. The guy who made it said I needed 75 half bricks. As I was buying them today from a Leader dealer in Rutland, VT, they told me that the full bricks were only twenty cents more than the halves and provided twice the heat retention value.

With the words of the builder sticking in my head "get half bricks", I bought the halves. Since then I've been wondering if I did the right thing. I hesitate to call the builder again because I've already called him a couple of times with questions.

Your thoughts?

Peter

update- I just looked at the Mason website showing how to brick a 2 X 4 and noticed he didn't have a 45 degree diverter going towards the stack. Mine is a flat pan and is designed the same way. However, on another post a diagram shows a 45 degree diverter on their design.

Should I make one for mine, or is it OK to have the flame path just hit that 90 degree wall on the way out?

[C.Wilcox]

If the builder called for half bricks you did the right thing by getting half bricks. The next question is, are you planning on adding insulation behind the bricks?

Not sure what you mean by "diverter". Are you talking about the ramp at the back of the firebox or some other structure right below the stack?

[Stamford sugarmaker]

I will add insulation behind the bricks if that's the way to go. I thought I was supposed to cement the bricks to the sides of the firebox, so I'm not sure where the insulation would be placed.

Yes, "ramp" probably is a better descriptor of what I mean. It would be placed at the back of the firebox.

Peter

[Brent]

You do NOT want to retain heat. When you finish boiling you want the rig to cool down fast.
Full bricks will retain more heat.

What you do want is insulation. First for safety. An inch of mineral wool type arch board will still leave the outside walls so hot that syrup will scorch on it. If a kid or you ever slipped and put a hand on it, you'd have a serious burn. A 2 x 4 will get so hot that it will melt your nylon snow jacket if it touches it. Secondly, poor insulation means a lot, an awful lot of heat lost = more wood.

The bricks have a near zero insulating value. But you need the bricks to protect whatever you do use for insulation.

Ceramic boards are best but expensive, ceramic blankets are next best, mineral wool arch boards are better than nothing.

[Stamford sugarmaker]

Thanks, Brent. I think I'm beginning to understand how this is supposed to work.

Can I buy ceramic boards in the amount I actually need instead of a huge quantity? Who sells it? Do I cement it to the vertical walls of the arch and then cement the firebrick to it? I believe Leader sells ceramic blankets in sizes that I need, so maybe that's the way to go?

Should I fabricate a ramp?

As is the case in many things, the more you learn the more questions you have!

thanks, Peter

[Brent]

Peter

Here is where I got the 2" board that I used on my rig.
http://www.unifrax.com/web/UnifraxHome3.nsf/AllDocuments/8AAA501C5FD37B0585256C3E00601654?OpenDocument
The prices are posted there. They don't seem to have local distributors.
I really like this stuff. You'll see on other posts here that I can put my hand
on the outside of the arch during a long boiling session. Safer, more heat efficient.

The blanket from Leader is also a good choice, almost as good an insulator when it's new, easy to ship, but not stable
for the backing of the bricks.

Go to the Leader site and download the instructions for their Half Pint evaporator for some ideas and how they tell you to built a wall to force the flame path up under the pan. You have to trade off between the size of the fire area at the front on the desire to force the flames up to travel real close to the pan at the back.

I'd make a vertical wall on a rig that size, fill the void behind it with vermiculite and lay some bricks or ceramic board on top of the vermiculite to make a smooth top about 1 to 1-1/4" below the bottom of the pans. If you put it too close you'll choke the flow.

If you leave your evaporator warm, or in a warm sugar shack, you are likely to get a bacteria growing that causes the sap and syrup to go ropey. Foul stuff. Does not taste good. You pretty much have to dump it, clean everything and start over in order to get rig of it. So when you finish boiling you want to cool down and stay cold until the next boil. I've done this two years in a row because I tried to keep the whole sugar shack warm for the RO membranes. Not smart and very costly, not to mention that too many people saw a grown man near tears when we had to dump the junk.

The Leader Half Pint instructions just say to build a vertical wall/ramp by stacking the bricks... use full bricks for the stack. You can't make bricks stick to the ceramic blanket so if you use thin bricks it will be like trying to stack dominoes on the thin edges. So I would tend to use full bricks on the sides just to help keep it stable. Cement it in because you, or the people helping you will tend to toss firewood in and this will run the risk of knoking bricks loose. This is a disadvantage of the ceramic cloth ... there's nothing rigid behind the bricks, and with the board it is very rigid and you can cement to it.

45 degree ramp ? On a flat bottom rig I would not bother. The 45 degree slopes on bigger rigs also serves to get a good flow up between the flues. You just want the flow close to the bottom as the hot air moves back.

If you use the 1" green mineral wool arch board you'll scorch anthing that touches the sides. In fact you won't even want to stand withing 3' of it for very long. It will melt your nylon shells or ski jackets it they happen to touch it. I think the maple equipment dealers should start offering the ceramic board like Unifrax makes.

I had a Leader Half Pint for 2 seaons with green mineral wool green boards, then a 2 x 6 drop flue that I did the same way. Now have a 2-1/2 x 8 that we did with the ceramic boards last year.

All this is just one guys perspective. Other's mileage may differ. Good luck.

[Stamford sugarmaker]

Thanks for all that great info, Brent. I hope to be able to get started on doing it soon.

Peter

[Stamford sugarmaker]

Brent,

I have done some research and have more questions. The 2" Duraboard would cost about $450, no can do. They have something called Durablanket which has 2' thickness for about $100. The prices are supposed to be emailed to me soon.

The blanket is obviously more difficult to work with but I'm thinking I would just put it on the sides of the firebox where it would be damaged by loading the wood.

I'm also confused by the firebrick. Is it advisable to use full bricks on the bottom of the firebox and tunnel? I still don't get why half bricks are better than full bricks in some applications.

Peter

[Brent]

The only reason I can think of is that half bricks retain less heat and therefore would cool faster at the end of a boil. To me this is a desirable thing because a long slow cool down will allow for more bacterial action and ropy syrup, especially if you have feed tanks in the sugar shack that will also stay warm, and don't methodically clean them out every night after boiling ( sheepish grin ).

The blankets do not offer any support. They are like heavy cotton batten. A carelessly tossed in log will hit on the bricks pretty firmly and over time almost certainly crack the cement between the bricks. They then stand up only because of the way they are stacked and that will mean that full bricks will stand better than half bricks. Part of the reason I like the boards is that they are very stiff, quite a bit strong than pink styrofoam insulation, and will make a good backing for the bricks.

Lots of people use ceramic blanket. Most only use 1" from what I've seen and the insulation value of new, uncompressed blanket is lower than the boards.

Like far too many things in life, .... compromises.

[Stamford sugarmaker]

Brent,

I clean the pan after each boiling so a slow cool down is not an issue. Bascom's has arch board rated for 1,900 degrees. Is that sufficient? I don't know if it's the green mineral arch board you had mentioned in a different thread.

By the way, in talking to a guy at Unifrax, he believed that wood-fired fireboxes don't reach 3,000 degrees and that the 3,000 degree fireboard is overkill for that application. You seem to have first hand experience which would be in conflict with that opinion, is that correct?

Peter

[Brent]

When I sold the 2x6 that had the mineral wool insulation, and had used it 2 seasons, the insulation was in "fair" condition. I have not found many publications or info here telling what real temps we get in the firebox, but Leader recommend 3000 deg firebricks. I have however ordered and will get next week a pair of pyrometers, one for the stack and one for the firebox, so when I get them mounted I will finally have some real numbers. My guess is that was get in the 2200 degree range ... but it's only a guess. If you look at various pictures of used evaporators, they all seem to have scorched syrup on the sides, so I would guess that most evaporators have not been well enough insulated. Mine got warm on the sides last year. Never hot. Only the rails under the syrup pan and the top of Leader's door were too hot to touch. Needless to say I'm very happy with the result. I might have saved a bit of cash if I had gone with 1-1/2" board, but as I've said before ... I don't think I'd take the chance at saving $200 and having it run too hot.
Just one guy's experience, for what it's worth.

[Stamford sugarmaker]

Is the stuff they sell at Bascom's

https://www.bascommaple.com/item/abin/arch_installation_supp/

the same stuff you said you didn't like, the mineral wool insulation? I certainly wouldn't want to buy it if you felt it was a waste of money.

I will be interested to learn the actual temps you record.

Peter

[Brent]

I wouldn't say it's a waste of money. It will certainly keep your sides cooler than nothing but bricks and it's
less expensive than ceramic blankets or boards.

I hope to install the pyrometers in the next week or so and do a final boil to clean the pans before freeze up.