Firebox/Arch Temperature

[csteves]

Hello everyone,

I'm a new member here at Maple trader and I've got a question about evaporator temperatures. Can anyone tell me approximately what the temperature of the firebox in the average evaporator is? I think I've seen anywhere from 1300-1600 degrees Fahrenheit tossed around before, but I was hoping for some more concrete numbers.

Any ideas?

[325abn]

HOT!!!!!!!!!!

Good question!

[csteves]

I've seen guys with pyrometers mounted to their rigs, but I'd just like to know. Actually, I'm curious because I'm working on a project with some of the professors in the mechanical engineering department (I'm a college student) and as far as we know there aren't many places to get data like this out there, so unless we get our own evaporator and try it, then the next best thing is to ask the folks who're out there using them the most.

So, if anyone's got any input, I'd be more than happy to hear it!

[Fred Henderson]

In 3 years of use with the mild steel that is in the arch, the metal(unprotected by fire brick) will be totally void of its carbon element and starting to burn away.

[csteves]

Fred,

Is this why cast iron is prevalent as the material of choice for the front of the arch and the firing doors? Also, what's the difference between the interior of an oil fired arch and a conventionally fired wood arch. I ask because by visual inspection it doesn't look like there's a bit of cast iron on todays modern oil fired rigs. I'm assuming that's because they can be mostly constructed of steel but there interiors are probably heavily clad with fire blanket I'd guess.

Does the fire blanket and brick really make such a noticeable difference in evaporators in general that it greatly extends the life of the arch? Why don't we see such deterioration in steel wood stoves? Do you think it's because they just don't get as hot?

[Bucket Head]

I've got a chart here that list's the color's of steel with their corresponding temperature's.

Faintest dull red- 900F
Dull red- 1200F
Cherry red- 1400F
Orange red- 1500F
Bright salmon orange- 1600F
Brilliant orange- 1640F

I speak from experience here, I would say an arch with a blower and good dry wood top's out between 1600 and 1700. The first year I ran the arch I have now, I had the door and a small part of the firebox on each side orange. It was only noticable after dark, so I "backed her down a bit" after that. It is fully insulated now, but the first year I did not have enough brick's to cover it completely.

Steve

[802maple]

Wood stoves don't burn as hot.

There has been tests done with forced draft evaporators that show temperatures at times that are above 1800 degrees but mostly in the 1600 to 1700 range. Oil fired are protected with more insulation then woood fired as they get hotter, although I am not sure what the temperature is. I remember in one of my oilfired evaporators from GH Grimm that it had a long fire box and under heat it would warp and the pans would want to fall in. I thought I could solve the problem by putting a 3/4 steel rod across and hold it together, well after 12 or so hours of boiling I discovered my pans almost falling in again and I looked inside the evaporator and the rod was totally gone except where it went thru the insulation.

[csteves]

Thanks for all the replies everyone!

[Sugarmaker]

This is good info. I like the color indicators and can only relate this story.
We were boiling real hard one night and the stailness stack got to glowing red orange and looked like you could have poked a shapr object throught it. We closed the power draft and let it cool down. So the 1600 to 1700 degs was probably where we were at.
Since then we run the blower on low speed a lot.
Good luck with your project. Let us know the results. Can you go to some sugarhouses and get data?
Chris

[WESTVIRGINIAMAPLER]

Chris,

You were a lot hotter than that. I was running mine at 1500+ stack temps and the stainless stack was not even slightly red.

[csteves]

Yes, I'll keep everyone posted, we might get in contact with some of the good folks at UVM's Proctor Maple Research Center. They're doing some awesome stuff there and I'm thinking they might have some great data on arch temperature and such. You can all check out their website:

http://www.uvm.edu/~pmrc/

It's pretty neat, I think they're doing a lot for introducing younger folks like myself to the maple industry and advancing the technology too.

[mikeb]

I built a drum style evaporator this year and painted it (and the stack) with 1200 degree wood stove paint. Was it a mistake to paint it? Will a rig like this get over 1200 degrees? If it does, what will happen? I'll attach a picture of what it looked like before the paint job. Thanks. Mike

[Maple Restoration]

Hi Mike I paint my rig and stack every year and never had a problem even when we had the temp up to and over that point it work fine.
Check out my photos

[csteves]

Speaking of temperature in the firebox, I have a related question to go along. Does anyone know what type of steel is usually used for parts of the arch? Is regular A36 structural angle usually used for the arch rails? How about the exterior sheet metal, is that usually something like 18-22 gauge stainless or galvanized sheet metal? Are there advantages to using hot or cold rolled steel for any of the thicker materials (for example an airtight arch front made of steel)? I'm curious just because I'm not sure how the metals used for each of these parts reacts to the high temperatures.

[Sugarmaker]

MikeB,
Nice arch and set up. Thats what I should be using:) I am serious!
Chris

[RileySugarbush]

Normal structural steel is fine if you insulate adequately. The only steel exposed to high temp gasses would be the inside edges of the rails, and they are partially cooled by the outside surfaces and the relatively cool bottom of the pan. I made my arch of pretty small stuff, 1.25 x .125 angle forms the frame, and 16ga carbon steel sheets for the panels. I used self tapping screws and high temp caulk to seal it up. So far, no problems at all. It is strong and no distortion when hot.

[csteves]

OK, great. You guys are awesome, thanks for the info!

[mikeb]

Sugarmaker,
thanks for the complement... but with 400 taps, you should stick with your 3x10. This has been a fun project for my family. This is our first year making maple. We are sizing the project for 12 taps, with the goal of 3 gallons of finished syrup. The entire project has cost us $300... which includes everything from spiles to firebrick to canning jars. It's more than we expected, but it's been worth it. Thanks to everyone here for your advice and inspiration. We may be tapping as early as next week! Mike

[Sugarmaker]

Mike,
This is like most hobbies you get out what you put in, and it is good clean fun and a lot of hard work mixed in with a little dollars. But the results on pancakes. PRICELESS!!:)

Chris