# Advice on Regulator Selection for Foundry Furnace



## vtcnc (Sep 30, 2022)

My father scored a free foundry furnace, blower and tube from a friend. Well, o.k., not free - he traded a couple of game skulls for it.

Anyhoo...the prior owner claims it was hooked up to a LNG line from his shop. I plan to fire on LP. I have the steel jacketed flex line that tees into the blower tube. There is no nozzle or regulator for the atomization and control of propane.

There is plenty out there on nozzles, blower tube, etc., but I'm having a hard time nailing down the type of regulator I should purchase. One thing I have learned is that a grill regulator will not work, the pressure is too low. Please correct me if I have drawn the wrong conclusion on that point.

I found this one from a link source on backyard foundry:






						Amazon.com : GasSaf 5FT 0-10PSI High Pressure Propane Adjustable Regulator with Hose or QCC1/Type1 Propane Tank Cylinder Fits for Turkey Fryer,BBQ Grill, Heater, Stove and More Appliances -Safety Certified … : Patio, Lawn & Garden
					

Amazon.com : GasSaf 5FT 0-10PSI High Pressure Propane Adjustable Regulator with Hose or QCC1/Type1 Propane Tank Cylinder Fits for Turkey Fryer,BBQ Grill, Heater, Stove and More Appliances -Safety Certified … : Patio, Lawn & Garden



					www.amazon.com
				




This claims to be high pressure, but as I inevitably shop around, I see other regulators for upto 20, 30 and 60! psi. 

So, the furnace will only be suitable for small crucibles, maybe no more than 3# of aluminum. Any advice on what size and type of regulator I should be looking at?

Thanks


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## jwmelvin (Sep 30, 2022)

With forced air, I don’t see why you’d need high propane pressure, because you can use as large a jet as you like. (In my naturally aspirated forge, the small jet creates a high-velocity propane stream to entrain air (Venturi effect).) So while a naturally aspirated burner may require up to about 20 psi, I see little chance for that with a blown burner. And a 0-10 psi regulator may give you better control in the range you need.


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## vtcnc (Sep 30, 2022)

jwmelvin said:


> With forced air, I don’t see why you’d need high propane pressure, because you can use as large a jet as you like. (In my naturally aspirated forge, the small jet creates a high-velocity propane stream to entrain air (Venturi effect).) So while a naturally aspirated burner may require up to about 20 psi, I see little chance for that with a blown burner. And a 0-10 psi regulator may give you better control in the range you need.


OK, just so I can confirm I understand, in the case of naturally aspirated burners, the regulator must supply enough gas at pressure to get to necessary heat?

And conversely, a forced air system will compensate for the low pressure regulator? Am I understanding correctly?

EDIT: it seems like the control then would have to be on the blower so as to achieve an adequate flame. Correct?


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## jwmelvin (Sep 30, 2022)

Looking on Amazon, it seems the 0-20 and 0-30 regulators are more plentiful. I’d just get one of those and go for it.


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## jwmelvin (Sep 30, 2022)

vtcnc said:


> OK, just so I can confirm I understand, in the case of naturally aspirated burners, the regulator must supply enough gas at pressure to get to necessary heat?
> 
> And conversely, a forced air system will compensate for the low pressure regulator? Am I understanding correctly?
> 
> EDIT: it seems like the control then would have to be on the blower so as to achieve an adequate flame. Correct?



With naturally aspirated, you need the pressure to drive a small stream of propane through the jet. With a blown system, you aren’t relying on the propane flow for your air flow (the blower does that) so the propane pressure does not need to be so high. 

In either case, it’s important to control the air:fuel ratio. For propane, that’s ~15.7:1 for optimum combustion (stoichiometric). You will control that with the blower speed, blower restriction, propane pressure, and propane restriction. Lots of ways to do it. Your overall heat power input will depend on propane flow and mix ratio. Since you want efficient combustion, let’s say you will tune for stoichiometric mix. 

To get the most power (highest rate of heat input), you will run the blower wide open. That delivers a certain amount of air. Now you need propane to match, so you will adjust the regulator pressure to deliver the right amount of propane. If your jet (restrictor on the end of the propane line) is too small, even with the regulator maxed out, you won’t get enough propane. But there’s no need for a small jet in your case, so by balancing the jet size against regulator pressure, you can achieve the propane flow necessary to get the stoichiometric mix you want with full blower output. That will be the maximum heating power for your forge. If you want less heating power, you will reduce airflow and propane flow proportionally (by blocking off the blower and reducing propane pressure).


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## vtcnc (Oct 2, 2022)

jwmelvin said:


> With naturally aspirated, you need the pressure to drive a small stream of propane through the jet. With a blown system, you aren’t relying on the propane flow for your air flow (the blower does that) so the propane pressure does not need to be so high.
> 
> In either case, it’s important to control the air:fuel ratio. For propane, that’s ~15.7:1 for optimum combustion (stoichiometric). You will control that with the blower speed, blower restriction, propane pressure, and propane restriction. Lots of ways to do it. Your overall heat power input will depend on propane flow and mix ratio. Since you want efficient combustion, let’s say you will tune for stoichiometric mix.
> 
> To get the most power (highest rate of heat input), you will run the blower wide open. That delivers a certain amount of air. Now you need propane to match, so you will adjust the regulator pressure to deliver the right amount of propane. If your jet (restrictor on the end of the propane line) is too small, even with the regulator maxed out, you won’t get enough propane. But there’s no need for a small jet in your case, so by balancing the jet size against regulator pressure, you can achieve the propane flow necessary to get the stoichiometric mix you want with full blower output. That will be the maximum heating power for your forge. If you want less heating power, you will reduce airflow and propane flow proportionally (by blocking off the blower and reducing propane pressure).


This all makes sense. Thanks. I'll post pics of what I have and what the results are once I piece it all together.


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## pontiac428 (Oct 2, 2022)

How many BTUs/hr will you need to melt 3 lbs of beer cans?  That seems like the key to me.  Gas volume can be throttled with a critical orifice after the regulator diaphragm valve.  Most of them are rated by max thermal capacity in BTU/hr.  That should be easy info to find to produce your melt.


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## ericc (Oct 11, 2022)

vtcnc said:


> OK, just so I can confirm I understand, in the case of naturally aspirated burners, the regulator must supply enough gas at pressure to get to necessary heat?
> 
> And conversely, a forced air system will compensate for the low pressure regulator? Am I understanding correctly?
> 
> EDIT: it seems like the control then would have to be on the blower so as to achieve an adequate flame. Correct?


Hi vtcnc.  Correct  on both points.  A blown burner will usually have just a simple tube for the gas.  These are typically fed at very low pressure, under a psi.  The natural gas line in a home runs at a similar low pressure.  The 0-10 psi or greater are for venturi (self aspirating) burners, like the Reil burner or Frosty burner.  The higher pressure propane regulators are often repurposed from turkey fryers and they are often color-coded red.  The silver colored BBQ regulators that you can get at a big box store should provide a decent pressure unless the furnace is really large.  For example, a Johnson forge eats gas and may draw too much for a BBQ tank.  Unless you have a large setup, it is more economical to have a smaller burner, since it can eat the cost of the unit in tank refill charges.


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## rwm (Oct 12, 2022)

I use a squirrel cage blower on a Reil type burner. I just switched from a 30 PSI to a 60 PSI regulator so I could get more BTUs. This makes a big difference when melting brass/bronze. For small aluminum melts a 30 PSI regulator is fine.
BTW there are people who just use the tank pressure and a needle valve and then adjust the flow to optimize combustion. That works too.


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## Cadillac (Oct 12, 2022)

I use a acetylene regulator I had and the line from a O/A setup. I had some old ones. Then at the business end I have another ball valve for volume control. Instead of a blower I use a airline from the compressor. The air line also has a regulator on it which if I remember I inject about 5-10 psi of air. I’m sure theirs better ways but it was all material on hand. Works good.


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## vtcnc (Oct 12, 2022)

I put a fan speed control on the blower. The 20psi regulator, hose and ball valve came in the other day. Was going to get a box store grill regulator but they were asking $39.99 and up and that seems like a steep price for zero flow control. I didn't want to get into dis-assembling to add the ball valve volume control so I ordered a complete assembly from Tejas Smokers out of Texas. The connector to the tank supposedly has a safety feature in it as well. We will see if that screws things up or not.

I'll post some photos in a  separate thread once I get things fired up. I think @pontiac428 had mentioned melting beer cans. Nope. Not interested in dinking around with that. I have lots of quality, clean, cast aluminum scrap and a source for more so I'm excited to learn how to make quality castings. I think at this stage my favorite channel on YouTube for learning about all of this is OlFoundryman.


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## pontiac428 (Oct 12, 2022)

The smelting beer cans thing was tongue-in-cheek, because we both know you're not that sort of shop bumpkin.   

I'm curious, why did you and @Cadillac choose ball valves for volume control?  Needle valves make a critical orifice which is insensitive to supply side pressure changes (withing a range), so pressure fluctuations (which may really happen using a regulator made for a different gas- acetylene goes up to 225 psi, vs propane which sits just above 100 psi) won't affect output volume.  Just asking.  A legitimate reason would be the ball valve gives more total volume than an equivalent pipe diameter needle valve, if you don't want to go up in piping size.


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## den-den (Oct 12, 2022)

If this was designed for natural gas, it likely has a large fuel orifice and runs with very low fuel pressure.  Many propane furnaces use higher fuel pressure to pull in enough air.  When a blower supplys the air, lower fuel pressure and a larger orifice gets similar results.


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## Cadillac (Oct 12, 2022)

I used ball valves because that’s what I had on hand and I figure it was better for the volume going through it. 
 I e been looking into changing over to a waste oil burner. I have endless amounts of used oil.


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## DevinSS (Oct 12, 2022)

Cadillac said:


> I use a acetylene regulator I had and the line from a O/A setup. I had some old ones. Then at the business end I have another ball valve for volume control. Instead of a blower I use a airline from the compressor. The air line also has a regulator on it which if I remember I inject about 5-10 psi of air. I’m sure theirs better ways but it was all material on hand. Works good.





vtcnc said:


> My father scored a free foundry furnace, blower and tube from a friend. Well, o.k., not free - he traded a couple of game skulls for it.
> 
> Anyhoo...the prior owner claims it was hooked up to a LNG line from his shop. I plan to fire on LP. I have the steel jacketed flex line that tees into the blower tube. There is no nozzle or regulator for the atomization and control of propane.
> 
> ...


I have a small furnace with out a blower and have run around 13 psi pressure on propane .
The burner was made from plans of the internet.I dont recall the actual hole size for the jet but remember volume through a orfice depends on pressure.


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## vtcnc (Oct 12, 2022)

pontiac428 said:


> The smelting beer cans thing was tongue-in-cheek, because we both know you're not that sort of shop bumpkin.
> 
> I'm curious, why did you and @Cadillac choose ball valves for volume control?  Needle valves make a critical orifice which is insensitive to supply side pressure changes (withing a range), so pressure fluctuations (which may really happen using a regulator made for a different gas- acetylene goes up to 225 psi, vs propane which sits just above 100 psi) won't affect output volume.  Just asking.  A legitimate reason would be the ball valve gives more total volume than an equivalent pipe diameter needle valve, if you don't want to go up in piping size.


LOL. Oh, I can bumpkin! I am from Vermont!

I went with the ball valve - mostly from the perspective of getting up and running quickly. I just want to get this thing running and not dink around with nozzles and orifices. So, I've got blower control from zero (ambient) to forced (some reasonable amount of CFM), then I have regulator control from 0-20psi and then ball valve control for gas volume. I figure between the three I should be able to dial into something reasonable with the gross controls I have in place. We will see.


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## vtcnc (Oct 12, 2022)

den-den said:


> If this was designed for natural gas, it likely has a large fuel orifice and runs with very low fuel pressure.  Many propane furnaces use higher fuel pressure to pull in enough air.  When a blower supplys the air, lower fuel pressure and a larger orifice gets similar results.


I think this was hooked up to NG. It came with a reinforced steel jacketed line which made me think NG. I'm hoping you are right about the blower + large orifice combination.


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## pontiac428 (Oct 12, 2022)

DevinSS said:


> I dont recall the actual hole size for the jet but remember volume through a orfice depends on pressure.


Not really, the relationship looks something like Q=diameter(^2) x sqrt(dP), so the diameter factor is far dominant and the pressure drop factor is minor.  That's what make critical orifices so useful in practice, the jet delivers the volume fairly consistently with fluctuating input pressure.

The reason I brought it up is we often optimize our projects to the Nth degree and strive for precision, whether it's necessary or not.  It's part of the shop fun, and none of us are strangers to waxing esoteric on the details around here!


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## rwm (Oct 26, 2022)

Did you try this yet?


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