gas grill knobs and high pressure?

[kcrucible]

I recently salvaged a broken down gas grill to use as a base on my forge/furnace when I realized that there were already two valves on the thing via the grill knobs. I can't image that the valves on that thing would have any problem taking 30 psi, right? Could be a convenient way to dial up and down without needing to go back to the regulator.

Obviously, I'd replace any hose on the thing with high-pressure propane hose to do this. I'm just wanting a little affirmation on the valves themselves.


And then if that works, it looks like it'd be rather easy to set up an idler circuit by using the two knob outputs...

[Ratel10mm]

Nice idea. The limiting factor will be the KW output of the burner(s). My local BBQ supplier told me that ordinary BBQ burners are rated too low to run a gas forge, but that the output from a single ring camping burner would do the trick.
It may be possible to bore out the jets in your burner if you need more output, but consult a licences gas technician so you don't make it unsafe.

[kcrucible]

Nice idea. The limiting factor will be the KW output of the burner(s). My local BBQ supplier told me that ordinary BBQ burners are rated too low to run a gas forge, but that the output from a single ring camping burner would do the trick.
It may be possible to bore out the jets in your burner if you need more output, but consult a licences gas technician so you don't make it unsafe.

Hehe. The burner is already taken care of.



Trials and tribulations on this other thread...


But you're right, using 1 or 2 high-volume burners (like they use on turkey fryers) would probably be a decent alternative, though you'd have to figure out how to make it work on your design.



The grill didn't come with the burners anyway... probably they rusted out and rather than replace them the owners junked the grill. But the knobs seem servicable for a more convenient heat management system (1 gas input, 2 outputs.. same as the front end of a gas idler circuit... mostly.. rather than on/off on the main gas input it'd be variable, but variable in the "I can adjust it back to the same point fast" way.)




But I'm liking the grill base idea... room for the furnace + spill area/sand casting table in one package + tools on the wings. Room underneath for the propane tank and hoses are protected from spillage, etc.

[edge9001]

I'm sure that I'm missing something. but the last picture, what is that setup?

[kcrucible]

I'm sure that I'm missing something. but the last picture, what is that setup?

It's a trick for what they call an "idler circuit" for a gas forge. Basically you take your gas input and split it between two different valves. The valve on the left is a ball-valve for macro on/off, and the valve on the right is a needle valve that allows fine adjustment.

Basically you get it set up so that both are open, but the needle valve side supplies just a little bit of gas. When you take your work out of the forge you can flip off the macro valve so that only the needle valve is supplying gas, but at a very reduced rate. This keeps the forge burning without using as much propane as maintaining forge-temp propane volume. After you re-insert your work, you flip the macro valve back on to heat your piece.


It's fairly clever. I'm not sure just HOW useful it is in practice.

[kcrucible]

It's a trick for what they call an "idler circuit" for a gas forge. Basically you take your gas input and split it between two different valves. The valve on the left is a ball-valve for macro on/off, and the valve on the right is a needle valve that allows fine adjustment.

Basically you get it set up so that both are open, but the needle valve side supplies just a little bit of gas. When you take your work out of the forge you can flip off the macro valve so that only the needle valve is supplying gas, but at a very reduced rate. This keeps the forge burning without using as much propane as maintaining forge-temp propane volume. After you re-insert your work, you flip the macro valve back on to heat your piece.


It's fairly clever. I'm not sure just HOW useful it is in practice.

Here's where I first read about it.

http://ronreil.abana.org/Forge1.shtml#Close

For a far more economical forge, you should use an "idle/full" valve arrangement so that you can instantly drop your forge to a quiet idle when you are at the anvil, or tending to some other chore, such as a phone call, etc. When you return to the forge, a simple quarter turn of the lower ball valve instantly brings the forge back up to full heat. You will discover that the forge will not lose its operating temperature when in idle mode either. The idle/full schematic diagram is self explanatory, and you can easily figure out how to adjust the upper and lower gas pressures by using the needle valve and regulator for your particular needs when starting your day at the forge. Although the schematic calls for 1/8" plumbing, you may want to use 3/8" for everything except the little bypass that has the needle valve in it. If you are using more then one burner, the larger diameter plumbing will provide a better fuel flow with less pressure drop. (Thanks goes to Rex Price of Hybridburners.com for the excellent Idle/Full schematic diagram.)

[pkrankow]

I was all gung ho about idle circuits for my first forge, I also built a forge too large to feed.

I rebuilt and have a tiny 1 burner without an idle circuit because heating more than one piece of metal at a time is more efficient.

My forge is now 150 cu inch, single 3/4 inch burner, mailbox shape, straight down in the center with the burner. A 3/4 inch burner should heat twice this volume to welding heat. I melt stuff easily and get 4+ hours on a grill bottle. I can throttle my burner down to idle by partially closing the ball valve. I will simply build another forge if I need a larger forge

If I start having forge sessions over 2 hours then I may change my mind about an idle circuit... It is better on paper, but not as helpful in practice.

Controlling loss of radiant heat is better for your efficiency. In other words: Doors are good, especially if they are functional and adjustable.

Phil

[kcrucible]

Thanks for the feedback, Phil.

I suspect that a lot has to do with how you use your forge If you fire it up, get the job done, then turn it off there's probably not a big benefit. If you leave it running all day for multiple pieces, break for phone calls, etc, more useful. Really the idle is nothing more than just turning down the fuel input, it's basically just a convenience to keep seetings, etc.

I could see it REALLY useful as a "warming torch" for glasswork to keep the boule and partially blown piece up to temp by periodically soaking it in high temp flame. Since you wouldn't have a lot of insulation to "save" the heat, you'd want to run it as low as possible when not actually using it and since your hands are kinda full, as easy as possible to operate.


I think I'll skip the drama for now and keep plugging away on the important stuff and skip the valve entirely for now, even though it may be somewhat more convenient than the regulator.