Johnson furnace, uses how much fuel per session?

[Harold_V]

Given a choice, I'd certainly pursue the used oil burner, assuming you have a reliable source of oil. That's particularly true considering you'll be operating the furnace outside.

I have yet to build a melting furnace for my current shop. I have, however, made provisions for firing with oil. I heat with #2 oil, but the decision was made when I could buy it for 72¢/gal, plus sales tax, delivered. Those days are now long gone. I expect I will still fire with oil (no natural gas here), and I am not about to pay the asking price for propane, which is actually more expensive than heating oil due to the lower heat yield per gallon.

Thumbs up on the used oil idea. Please share anything you may learn where burners are concerned, and I'll try to return the favor, should I uncover anything that may be useful.

Harold

[PapaLion]

Well the other site has pages of info on various burners including Waste Oil. Mostly it is three or four hobbyists who are sorting thru 10-15 variables (on at least 3 types of burners .. all at the same time) to try to achieve some improvements and sharing the info piecemeal over and again with a pack of followers.

It appears from gleaning this long tedious section with 100s of similar threads that there is a REIL (designer I guess) burner which might work for me because it does not require preheating the furnace (If i read it correctly). It seems easy to build and would burn about a gallon an hour of oil or heavy fuels like diesels, heating oil etc.

A concern for me is the health ramifications? Burning oil is definitely carcinogenic and at least marginal for respiratory safety. If I can find some evidence that it can be done safely then I'd pursue it. I need to read more I guess. I'm moving from that bulletin board with anecdotal evidence to some more serious organized approach. It drives me crazy that they don't as a group design an experiment with a given ? and then go test the variable, return, share evidence and do the next variable. Not trained in the scientific methods at all obviously. Even a blind mouse finds a kernel of corn once in awhile...

[PapaLion]

? how hot will the outside of this thing get? I'm looking at various Rustoleum High Temp paints... I'd like to go with the 500 degree stuff, more selection... enough? or should I use the 2000 degree one. I'm gonna' use the 2000 degree primer anyway.

[Harold_V]

A great deal depends on how it is insulated, and how long it might operate. If you intend to paint, select paint with the highest possible heat tolerance. The small furance (#8 crucible) I built when processing precious metals ran quite hot on the exterior if it operated for a prolonged period. It was never painted for fear it would burn off.

Harold

[Too_Many_Tools]

Just from my experience I have used the 100# tank for my feed. It is portable enough to chuck in the truck and drive up to a supply just blocks from home and buy any amount of Propane up to a full fill, and take it home to wrestle back inot the shop.

The 100# tank wont freeze or loose pressure until it gets run hard down to the last coupla gallons, then it will how frosting at the base. Teh fact that the tank is so big it is a pretty good radiater and maintains good pressure, even at my rediculous firing rates for a furnace.

This particular tank, does double duty, as it is the core of my Oxy-fuelgas rig for the low pressure industrial torch in the garage. It will blast 1 inch plate without a nod. ( NO, the LP mark on the torch, does not stand for Liquid propane. It stands for Low Pressure.) I can hook it to the house supply of natural gas and do the same thing. The low feed on the house will not adequately run my furnace.

So how long would a #100 tank run a Johnson furnace?

I ask because I am considering a number of FREE #100 tanks that I want to build a foundry setup around.

Thanks
TMT

[steamin10]

Truly I cannot give you an hour meter count, as I fired hot and heavy on my homebuilt and Johnson furnaces. I would run several hours, until I got my parts count, ran out of material, or got tired and quit. Usually fuel level was not a problem. I would take the 100lb-er to the trailer sales outlet, and top er off, they were used to me, and charged by (gallon) weight anyway. So, as I think about it, a coupla sessions could total about 8 hours, and not run out, but this is a very rough statement. Your true mileage may vary.

[PapaLion]

I have been studying on the Waste Oil Burners and this seems a good way to go. They are simple some require a preburner to warm up the Furncae (Propane) for 5 minutes or so... all good. But here is an interesting twist.

a Johnson Furnace like I have has a ~1" pipe main entry~ which enters below the furnace at the bottom, (Via an ~outside "T"~ the blower goes into this pipe also) and via an ~underneath "T" ~ under the furnace it routes the gas eventually to two different furnace entrances. One is low and the other is midway up the wall. The objective is to swirl the flame inside and not destroy the crucible by cooking it. Good idea, but the fuel (Natural gas or Propane) travels about 3-4 FEET in the pipes before it enters the furnace openings. I believe it is ignited by a spark system as it enters the chamber. Meanwhile, I am figuring to go with a Waste oil burner.

As I understand Waste oil burners they atomize the oil at the entrance to the Furnace and IF there is adequate heat from a preburner then it ignites.
Choice 1: Traveling 3-4 feet as "atomized" oil clear to the furnace entrances which doesn't seem feasible, Or
Choice 2: it ignites early at the point before the ~underneath T~ then you have hot oil burning in the pipes for 4 feet. Also not good.

So, I believe a solution might be to to place a fitting in the 1" pipe line just before each entrance and run a short pipe in for the fuel. What you would end up with is a dual Waste oil Burner setup, one burner for each entrance.

Thoughts?

[Too_Many_Tools]

Truly I cannot give you an hour meter count, as I fired hot and heavy on my homebuilt and Johnson furnaces. I would run several hours, until I got my parts count, ran out of material, or got tired and quit. Usually fuel level was not a problem. I would take the 100lb-er to the trailer sales outlet, and top er off, they were used to me, and charged by (gallon) weight anyway. So, as I think about it, a coupla sessions could total about 8 hours, and not run out, but this is a very rough statement. Your true mileage may vary.

Thanks for the info.

Do you think a coulpe of #100 tanks with a couple in reserve would work well?

Anyone else?

TMT

[Harold_V]

So, I believe a solution might be to to place a fitting in the 1" pipe line just before each entrance and run a short pipe in for the fuel. What you would end up with is a dual Waste oil Burner setup, one burner for each entrance.

Thoughts?

Because I have no experience with oil fired furnaces, I'm likely not the right person to respond, but if my experience with natural gas fired furnaces counts, I think I'd eliminate the upper and use only the lower port. By sizing the blower and providing an adequate amount of fuel, it should be more than adequate to melt anything you desire, maybe even cast iron (which I would not recommend).

As you alluded, the flame should not impinge on the crucible, but swirl around it, instead.

If you are not familiar with oil burners for furnaces and boilers, it might be a good idea to explore how they work. I seem to recall, in the distant past, someone using just such a burner for a melting furnace, with good results. Dealers that sell and install such heating systems are likely to have one that has been removed, possibly free for the hauling. With the high price of heating oil now, I can't help but think that many are switching to other heat sources.

If you pre-filter waste oil (not an easy task, but it can be done. I've done it successfully for years), you can use waste oil in a heating oil burner. It would have to be heated, or you would have to change the nozzle to one that might be better suited to the application. There's also a waste oil burner on the market, but I am not familiar with how it works.

Do keep posting on your progress.

Harold

[Wanna-Be]

My question goes back to the original post regarding the propane supply/demand.

My recently aquired McEnglevan MP36 furnace is NG or propane and rated at 128,000 BTU/hr and has a burner inlet of 3/4" ips and that is what the manual recommended for either supply connection. Propane pressure to be 8 oz Max for L.P.. I am using the 100# cylinder and I ask the suppler for a high flow rate reducer for this tank. I told him of my need for the 128k BTU and pressure as well as the inlet size. He provided a hose that seems large enough but the tank reducing valve is only 1/2" IPS with a bell reducer up to 3/4" for the hose connection.

When I was test firing and drying out the brick lining, I gradually increased the firing rate until the blower was up to about half speed. From that point on the heat didn't seem to increase, even with the fuel valve wide open.

I think the burner is being starved for fuel. I don't have a pyrometer yet so I can't speak to temp. yet. I do know the I could observe the fire bricks getting read. I think I should check the actual temp. before I complain to the propane dealer.

Should they have a tank pressure reducer with at least 3/4" IPS outlet??

Thanks, Steve

[steamin10]

In my home built furnace, my entry pipe is 3" that is served by a oxweld torch tip #10, that serves as a readymade orafice, and blows though a cut bell reducer of cast iron that has been cleaned up and thinned in a lathe. I use a conventional torch regualtor for the LP gas bottle. By running the line pressure up and down I can regulate the flame from just a pilot on the bell, to a full blow roar that fills the the firetube into the furnace. Without a blower. The small holes that are the torch tip limits the volume and velocity of the gas, so it is not like a full open pipe, but draws a large amount of air for a nice burn. I just got lucky and there is a sweet spot here that I have not seen in many furnaces. In ten minutes of run time, the bottom walls are emmiting a LOT of UV with orange -yellow color. Bottoming the gauge gives me about 30psi in a 3/8 welding hose line to the burner, barb fittings.. You must use a fuel gas rated hose, if you do any fabbing on your own, as it will eat right through most rubber hoses. (Ask me how I know).

My furnace shell is a 55 gallon drum lined with radially laid 1' ladle brick, fireclay and silica mix for mortar. This frunace has an overlarge chamber, and a flat brick in the middle to rest a pot on. It has a nasty tendancy to destroy the top from heat shock, and is without a top right now. Without a top to control the heat flow, you are way off the mark for efficiency, but I can melt anyway, I have done it. I have no reasonable guess as to the BTU output of this burner.

In your case, adding blower air MUST be balanced with fuel, or your temperature goes down. Overblowing will add nothing to the process, only giving you more Nitrogen that does not support flame. Oxy not burned is just more that will bleed heat from the sytem. You have to judge the flame as lean, and mean blue, with a healthy roar, or you aren't getting there. Normal LP regulators for a gas grill will not give enough gas to pass for a good flame. Too much restriction in the internals.

The one furnace I dont use yet is plumbed for City Natural gas of high pressure and has a regulator built into the supply of the furnace. It is designed to run on high pressure. Well that is something like 11 lb instead of 7, but represents a near doubling of gas volume in a small pipe.

[PapaLion]

Harold, that is a good idea, clear thinkin', and starting point. So for now, I'll block off the upper midway entrance and just start with one burner at the lower entrance and see how it goes. I'm focused on cleaning it up/painting with 2000 degree paint still and then reinstall the blower assy and get air moving first... Next, I'll work in a propane system at the regular orifice entrance...for preheating... and finally add a WO burner.
Clear as mud:)