Segmental Thin Plastic Refractory/Wool Furnace Build 14" Dia Bore

Denis, thanks for the initial write-ups and follow-ups on your setup. It must have been satisfying to see the reduction in fuel use and skin temperature from the last rebuild.
-Did you ever discuss the burner setup on this one? Oil-fired stuff is new to me, I am used to 'cooking with gas' so to speak. If you had a link or two that would be awesome.
-Between the plinth and hemispherical lid, is the crucible pretty well centered in the cavity vertically?
-Would you recommend 3000F service refractories for this? My local supply recommended a 2500F product, I don't remember us discussing 'ferrous foundry' as the application during the phone call.
Thanks!

 

Tops,

The general design of the burner is important, for sure. But equally important is how it is tuned to burn efficiently. Finding that tuning sweet spot has been a journey for me:
http://forums.thehomefoundry.org/in...with-a-pelton-sensor-and-digital-readout.811/

Here is a post that shows the burner deign I used. I do not think the "fancy" mount I made for the nozzle is required. A simpler design that keeps the nozzle more or less near the center could be used. Also, It would be easier to simply run the supply tubes for the nozzle right down the main tube rather than bring it in from the side. Attaching the combustion air to the side tube would be easier and just as good ---in retrospect. But, I have used that burner ever since and it has worked well.

http://forums.thehomefoundry.org/in...-diesel-fired-furnace-break-in.235/#post-3914

Denis

 

Thanks Denis. The phrase "Hago .75 gal/hr siphon burner" out at Duck-Duck-Go brought me back to here:
https://forums.thehomefoundry.org/index.php?threads/hago-siphon-0-75-gph-nozzle-burner-design.85/
Which got me to videos from SVSeeker and MyFordBoy.
Are you still doing some PSI air over oil in the tank and an electric fuel pump?

 

-I use a Holley automotive fuel pump. Black model 12V. No tank pressurization---not needed with pump.
-I use 40 PSI (I upped it in the last couple months) atomizing air
-I use a flow meter and run .19L/min
-I blow combustion air with a throttled down 20V leaf blower.

Denis

 

Thanks Denis, very appreciated!

 

It is so important to know how to tune a burner, even more so when melting cast iron, so I don't need a constant readout of oil flow to my burner to get the hottest temperature in my furnace. Experience is the most important factor here. I use WMO which is far cheaper than diesel and can use more than needed but the burner still has to be tuned right so I can get hot iron. It would be interesting to know how many here measure the flow of propane to their furnaces when they tune their burners? I think everyone would use the pressure reading on their regulator to get an approximate idea of how much propane is flowing into their burner.

 

With only 5 years of melting experience, knowing my fuel flow rate and being able to set it the same +/- 2% every time is a beautiful thing. Not only does it help me get set right on the money from the first minute of a burn, but it will detect any anomaly in fuel flow due to any problem from the fuel supply tank to the nozzle as it occurs. It keeps this one factor constant against which combustion air flow can be be adjusted as atomization is also measured and kept constant. It has allowed me to keep a consistent ratio of fuel per pound of iron melted and melt time duration within 5 minutes from one melt to the next. I plan to use the flow meter for the next 15 years until I have enough experience to get along without it. (I was born in '48---you do math.) ;-)

Denis

 

so i have zero experience, but my plan is to set the oil flow rate and then dial in the air to set the mixture. high pressure constant flow rate is the plan.

 

Thanks Everyone. Can a burner be test run outside of the furnace to see if it is basically too rich, too, lean, or just about right? Or does it need to be in the furnace with a plinth and loaded crucible for that? What would be signs (sight, sound, smell) related to rich, lean, about right?

 

The whole thing needs to be assembled to run properly, an easy method is to have a K type thermocouple (good to 1350 deg C) inside the chamber beside the crucible and run at a given fuel setting, then vary the airflow to keep the temperature climbing. As the furnace warms up and fuel gets hotter, the settings need to tuned on the fly to keep temps rising and surprisingly small adjustments can make a difference. There are quite rugged ceramic insulated thermocouples avaliable quite cheaply.

 

Thanks Mark. I have one of Mifco ones that has been mentioned by others on the forum and the Harbor Freight multi-meter with the K-type inputs. I also have an inexpensive one from Amazon that my work helped me make a graphite sleeve for so I can use it in aluminum.

 

Tops, There is little correlation to how a burner runs in open air vs in YOUR furnace. Back pressure, environmental temperature, swirling flame, reflected heat, and who-knows-what-else play significant roles in performance. Running in open air can let you see how well fuel is atomizing.

For iron, you want to run a slightly reducing flame. One way to confirm a flame is reducing is to hold a piece of clean metal in the exhaust for a few moments. If it soots up a bit, then the flame is reducing.

Also: http://forums.thehomefoundry.org/index.php?threads/melt-time.2006/#post-42527

Beware of the extremely common error of blowing too much air and fuel through the furnace but not giving enough time to fully combust in the furnace.

Denis

 

Thanks Denis. I was thinking about how I used to tune a cutting torch and if there was a correlation.

 

I would think you can adjust it in air and then you're like within an order of magnitude of the right settings for when you put it into the furnace. The back pressure will make a big difference etc but I'd think doing it where you can see it will help your sanity for the first light off

 

FWIW, here is the method I use to light the furnace. It works well. Trying to light with full atomization pressure, full combustion air, and full fuel flow is problematic. But, beginning with gentle flow is easy.

http://forums.thehomefoundry.org/in...ner-for-larger-furnace.1043/page-2#post-25357

Denis

 

Denis, are you running an A20 crucible or something different/bigger? Thanks!

 

A25 most of the time. I also have an A20 that I use for smaller melts. I wish I had an A30, but they seem to be uncommon.

Denis

 

A couple of notes on my furnace.

I converted the blower from the leaf blower motor I hadc been using to a common bucket vac as the leaf blower gave up the ghost. I made a somple adaptor for the exhaustof the vacuum that provides a good suport for a blast gate that connects to the combustion air supply. The Vac provides plenty of air---I kept it throttle to about 1/3 to 1/2 open and could see that my flame at the chimney was nearly identical to the leaf blower at almost full throttle.

This adaptor goes on the vac exhaust.




THis is taken mid-melt so that is the running position.

It is also quieter than the leaf blower motor.

On a less happy note, part of my lid gave way near the end of the melt. It had been on borrowed time and I new I'd need to replace it soon. Well, soon is now. Dang. I wanted to keep on melting. Now decisions need to be made concerning the new lid and its design.

Denis

 

Sorry to hear about the lid Denis. I have this picture in my mind (and on my 55 gallon thread) of it sitting proudly upon your furnace looking like a double-stuffed Oreo cookie.



PS that gate valve and adaptor look really nice, thanks for posting. Would you say that is more trouble-free than a router speed control?

 

For me it surely is as simple a solution as I can imagine. For one thing, I do not have to worry about damaging the motor by having the motor all throttled down electronically at the start of the melt. I just star out with the valve almost closed. But, I believe that does not hurt the motor as it actually is under less load (you can hear it spin up) as it is moving less air and yet motor cooling is still OK as the cooling air is provided by a little fan blowing air through the motor. If this info is incorrect, I hope someone will say so. Once the flame is established, I just turn up the compressed air and then open up the gate in steps to prevent blowing out the flame. The whole process probably takes 30 seconds. At that point I know my fuel flow rate is right based on the flow meter. I know the compressed air is right based on its pressure meter. And I can hit a tick mark for the combustion air and know I am all set except for some very fine tuning of the combustion air which I do from time to time as the furnace gets hotter. I've noticed that after the furnace runs for maybe 10 to 15 mins I can add maybe 5%c ombustion air and towards the last 20 mins or so as the furnace is at max heat, I add just a bit more. I imagine those additions are the result of improved combination of O2 and fuel at higher temps.

I do know I liked the fact that I felt like I had the all the combustion air I needed at only 1/3 to 1/2 blast gate opening whereas with the prior blower srtup, I was getting to a 95% gate opening witih little more air available should I need it and occasionally wished I had just a bit more combustion air. She ran nice and hot yesterday with 65 pounds melted to 2580 in 95 mins and 17 liters of fuel.

Denis