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Rocketman
02-23-2008, 12:04 AM
I have a bit of a problem.

I was given an small commercial/educational furnace over the summer. You see them on ebay fairly often - its a McEnglvan / Speedy Melt model B16 furnace.

The original equipment burner was a forced air natural gas burner with a UV sensing safety shutoff system. It was rated around 150,000 BTU's.

The gentleman who gave this furnace to me scrapped the burner assembly many years ago. You really cant find these around anymore.

So I have a bit of a problem. I'm more of a liquid fuel type of person, kerosene/heating oil is my preference. Its really easy to get around here (24hr pump at the local gas station) and I have a burner built from a reddy heater that works quite well in my 5gal pail furnace. I would like to convert this Speedy Melt into a liquid fuel furnace, however its tuyere inlet is very small, on the order of 1 1/4" ID. This really doesnt lend itself to any sort of kero burner.

I guess what I'm asking for is a solid design for a forced air propane burner. I have a wide array of blowers, and two choices of variacs to control said burners, so airflow is not a problem.

What kind of nozzle should I use? Propane regulator? Should I have some sort of mixing area in the burner? Will I need a flame holder of sorts? There arent any provisions for a flare.

I'm not really keen on buying tanks and regulators and hoses and shit, and having to get them refilled.

My other option is to get ahold of a cutting torch somehow and cut out a larger tuyere, and I'd probably stick a residential gun burner in there.

Heres a pic of the B16, with the crucible, next to my now defunct 5gal pail furnace.

Any ideas?

http://www.werbatfik.com/uplimg/foundry/speedymelt.jpg

HAVEHEATWILLCAST1
02-23-2008, 12:22 AM
Why not go with a Reil type burner ?
Or if you like kerosene/heating oil use a burner like Lio's.


Maybe you can make a fireclay funnel for what you got.
( That furnace looks too neat to cut on and may throw off your center. )

rocco
02-23-2008, 12:22 AM
My first burner was a forced air propane burner, it was an ULTRA simple design, a 1" steel pipe about 2 feet long, a hair dryer as a blower, the blower was plugged into a variac for air flow control, the propane was introduced through a short piece of 1/4 tubing brazed into a hole about 6" from the blower end of the steel pipe, the regulator was "borrowed" from a barbeque.

I found that with a low pressure regulator like a barbeque regulator, no nozzle was required. A low pressure regulator has another advantage, when you're using propane at a fast rate, the tank cools off considerably dramatically dropping the pressure in the tank, with my atmospheric Reil type burner operating at 30 psi, this was a problem, I had to put the tank inside a bucket of warm water to keep the pressure up, that wasn't an issue with the forced air low pressure burner.

Anon
02-23-2008, 03:40 AM
Low pressure won't work if you need to fit 150,000 BTU's into a 1 1/4" hole. A 1" Reil burner will run fine, using the tuyere as a flare, at about 50 PSI. You'll need a high-pressure regulator (http://www.cajunshoppe.com/regulator.htm), available there for about $35. You'll also need a tank and hose, but I presume you knew about that part.

Jammer
02-25-2008, 05:11 PM
I just bought a high pressure, adjustable regulator from Tractor Supply. $19.95, no gauge, I have one. May still be Quality Farm and Fleet for some people.

Matt22191
02-25-2008, 08:28 PM
You don't need a jet with forced air. All you need are a few chunks of pipe fitting. The first propane burner I made was forced air, and it was essentially this design:

http://anvilfire.com/21centbs/forges/gasburn1.htm

No tiny holes to drill or align, no screwing around with MIG tips . . . it lit the first time, and every time since. The only real problem is that my blower doesn't like to turn at lower than about 1/3 of full speed, so there's a limit to how far I can turn the burner down. A simple air gate would solve that problem.

einstein
02-25-2008, 08:52 PM
I wouldn't try to convert that over to liquid fuel even if it did accept a larger tuyere- oil needs larger vents too and you would ruin the refractory of the lid trying to make that modification.

Pretty much, propane and Natural Gas both you just dump your fuel straight pipe into the center of your air stream, with a good 12" mixing distance between the fuel inlet and the furnace. Outside the furnace you will want a Reil-like flare, but in a furnace it shouldn't need one.

Also, 150000 BTUs seems rather high for a gas furnace, that sounds like a figure used for an iron melter. My oil burner only puts out 109,000 BTU with the curent nozzle set up, to make 150,000 BTU an hour I would have to go to a 1.0 or 1.25 GPH nozzle.

HAVEHEATWILLCAST1
02-26-2008, 03:14 AM
Maybe a kerosene/heating oil "hot box" burner ?
Make it will a removeable lid for vent/start-up and use a outlet pipe size that fits the furnace. (put a thin clay liner in the pipe)

V8 BUG
02-28-2008, 05:15 PM
You don't need a jet with forced air. All you need are a few chunks of pipe fitting. The first propane burner I made was forced air, and it was essentially this design:

http://anvilfire.com/21centbs/forges/gasburn1.htm

No tiny holes to drill or align, no screwing around with MIG tips . . . it lit the first time, and every time since. The only real problem is that my blower doesn't like to turn at lower than about 1/3 of full speed, so there's a limit to how far I can turn the burner down. A simple air gate would solve that problem.

Do you think that design would be a good start to use with NG? I am trying to start with something.
Thanks

Kevin

Matt22191
02-28-2008, 05:38 PM
It'd work fine with NG if you can get enough fuel flow. If you're using low pressure you need a fairly big orifice to pump the necessary BTUs. I don't know how much gas a typical residential line can supply, so I don't know the practicalities.

Call the gas company and ask them what peak draw (in cubic feet per unit of time) your gas main will support. Cubic feet of natural gas x 1000 gives you the approximate maximum BTUs your line can supply.

Bobnova
02-28-2008, 07:39 PM
Considering the flame size i've seen gas driers put out, i think there is probably plenty of flow available. They have a good foot of thick flame.

rocco
02-28-2008, 07:42 PM
I'd think a household NG supply would be able to support a fairly large burner. I don't have NG at my home so this is somewhat speculative but I say that after considering the size of many of the common household gas appliances, a home heating furnace is around 100,000 btu/hr, water heater 35-50,000 btu/hr, a gas range 40,000, a gas grill about the same and so on. Based on that, a 200,000 btu/hr burner seems within reason especially if one is able to ration other gas use while the burner is operating.

Matt22191
02-28-2008, 08:17 PM
I suspect you're both right -- but the easiest way to know for sure is to call the gas company!

Bobnova
02-28-2008, 08:45 PM
I suspect you're both right -- but the easiest way to know for sure is to call the gas company!
Dudes got a point, really :P

rocco
02-28-2008, 11:20 PM
I suspect you're both right -- but the easiest way to know for sure is to call the gas company!
Dudes got a point, really :P

Indeed he does.

Adam Ziegler
02-29-2008, 01:09 AM
I am a big fan of forced air propane. If you need help sizing your fan: http://adamziegler.net/foundry/propaneorifice.php

Unless you know what you are doing, leave the default values as is. Fill in everything else. If you dont know a run time, just make one up... it does not effect the blower calc.

Anon
02-29-2008, 03:35 AM
Here are my views on the pros and cons of naturally aspirated versus forced-air, seen in this thread (http://www.backyardmetalcasting.com/forums/viewtopic.php?t=2191).

(If you couldn't tell, I'm a big fan of naturally aspirated burners.)

HAVEHEATWILLCAST1
02-29-2008, 06:26 PM
Ok, if I take this old cutting torch head and pumb propane at 20psi down the center hole and compressed air at 20psi down the preheat holes and run it as an aspirated burner ; Would you two be Happy :?:

ToddW_00
02-29-2008, 06:34 PM
Where do you put the oil? :P

Bobnova
02-29-2008, 08:40 PM
Ok, if I take this old cutting torch head and pumb propane at 20psi down the center hole and compressed air at 20psi down the preheat holes and run it as an aspirated burner ; Would you two be Happy :?:

Thats an interesting idea.
Specially because i have a oxy-acet welding torch head around here somewhere.

HAVEHEATWILLCAST1
02-29-2008, 11:44 PM
Well I had first thought of shooting oil down the center hole and propane in the preheat holes. The idea was that the oil would be heated by the propane flame around it. DK how it would work but I have a feeling that you would need 2 air inputs. Maybe like a naturally aspirated Reil burner stuck inside a bigger (like an up-wind) pipe that could be blown or it's back-end open too if it would suck air at/with the propane burning.

Talk about your jet placement. :!:

Rocketman
03-01-2008, 01:49 AM
The problem with the B16 furnace is that it generate a LOT of backpressure - when I was exeprimenting with it I had a tons of problems with it blowing flame out the bottom vent, and burner stability with the lid closed.

A naturally aspirated burner would have a hell of a time with it.

HAVEHEATWILLCAST1
03-02-2008, 02:39 AM
Can you set the lid on some 1/4 rods or something ?
Make a new lid with a bigger vent - it looks like you could change it easy.

Matt22191
03-07-2008, 03:11 PM
Adam,

According to your propane orifice calculator, if I wanted to build a little 25,000 BTU/hr. propane forge I'd need about 0.2 CFM of propane and only about 4.8 CFM of air.

Is that really right? A 10 CFM blower would be far more than adequate?

Anon
03-07-2008, 08:48 PM
It sounds right to me. Hence why naturally aspirated burners work so well--you don't need a hurricane. Also, that's a pretty little burner.

Matt22191
03-07-2008, 09:33 PM
This explains why I had such a hard time turning my blower down enough to satisfactorily run my forced-air burner (and why the only way to really make it work was to turn the propane up so much that the tank froze far too soon). It's a 200 CFM blower. Apparently it wants to be paired with a 1 million BTU/hr. propane burner.

If only I had a propane tank that big. :)

Bobnova
03-08-2008, 02:23 AM
Heh, that would tend to explain it.

Matt22191
03-11-2008, 06:02 PM
This weekend I built my first Reil burner, and I have to admit that it was awfully simple and it works well.

My only complaint is that no matter how I tune it it seems to burn somewhat rich. I have a 1.5" reducing coupling on a 0.75" burner tube (with a 1" bushing, since I couldn't find a 1.5" x 0.75" coupling). Does the coupling need to be even bigger? Should I add a hole or two upwind?

Anon
03-11-2008, 09:53 PM
http://www.backyardmetalcasting.com/forums/viewtopic.php?t=2207

A 1" x 0.75" reducer should be fine. That bushing may be interfering with the airflow. (I'm not entirely sure how you have it set up; a picture might be nice there.)

What jet size are you using? Is it properly aligned? What pressure(s) are you running at?

Matt22191
03-12-2008, 12:49 AM
#57 orifice. It's as properly aligned as I know how to get it. I've been running it at 10-15 p.s.i. in the forge.

I'll try to get a pic a little later.

Anon
03-12-2008, 03:52 AM
You need a smaller hole. #57 is .043", and you want more like .030", or #68.

rocco
03-12-2008, 03:36 PM
For my orifice, I used a mig tip 0.035" in my 1" burner, it works great and if some reason I want to go bigger or smaller, it's very easy to change.

Matt22191
03-12-2008, 04:11 PM
D'oh!

You know I never even looked up the diameter of the #57. Reil recommended it on his page, so I went with it. But yeah, that explains it. From experience, 0.035" is too big for a 3/4" tube (gives a rich mix), so 0.043" certainly is.

HAVEHEATWILLCAST1
03-13-2008, 07:25 AM
D'oh!Get out the old 200CFM blower. :!:

HAVEHEATWILLCAST1
03-22-2008, 02:48 PM
Ron's blown propane burner. (Next to the bottom.)
http://backyardmetalcasting.com/forums/viewtopic.php?t=1177&start=0&postdays=0&postorder=asc&highlight=&sid=f0420e982fd323e1235530eeb0b07e75

machinemaker
03-29-2008, 07:09 PM
I appologize for going back to an old thread, but I'm new here. If you still need a burner here is my suggestion. Go to McEnglevan's site www.mifco.com and look up the specs for that furnace, find the motor and blower cfm and the gas line size. then find someone you know that has a grainger account (www.grainger.com) or ebay or where ever and buy a radia vaned blower that has the same cfm. When you get the blower make a closeable damper from a piece of sheet metal so you can close down the air intake if you ever want to, (for holding) and weld a pipe fitting beside the air intake on the blower. feed the gas, either NG or propane directly into the blower and control it with either a needle valve or ball valve. Now you have nearly what was origanal equipment, but with out the spark starter and the electronics to keep the gas from flowing when the flame isn't there. If you really want the starter look for some old oil burners to take parts from or a step up transformer and make an electrode.
kent