Derek Melton Posted October 3, 2016 Share Posted October 3, 2016 I have a small, one burner propane forge that I've been using off and on for about 15 years. Lately, as I've gotten deeper into blacksmithing work I've been perturbed by the amount of propane I believe I'm wasting. I've started to turn the gas off as I reach to take the work out. Once the forge is up to heat, it will easily re-light itself with a quick turn on the tank knob and it doesn't seem that I lose too much heat. I'm curious, does anyone else forge in this manner? I know traditional coal forges conserve coal by simply lowering the air flow into the fire. I was tired of just burning propane while hammering and walking away from the forge. Quote Link to comment Share on other sites More sharing options...
Brazer Posted October 3, 2016 Share Posted October 3, 2016 Turning off gas and letting it relight itself is not a safe practice. Years ago a man did the same thing on a gas appliance, and the flame started up and shot out of the appliance and he had no eyebrows for quite some time. I would suggest just turning the burner down if need be, but the keep fire going to conserve fuel, for safety's sake. Work safe. Quote Link to comment Share on other sites More sharing options...
Yuppiejr Posted October 3, 2016 Share Posted October 3, 2016 Not sure if this works for every style of smithing, but I had it drilled into me early that having the forge running without metal in it is a waste of fuel. I usually start with 2 pieces in the fire and then alternate between them as I work... though I probably burn through more metal stock as a result so there's still a cost (though if I get the work done right at least I have another to sell/gift/use). Quote Link to comment Share on other sites More sharing options...
Frosty Posted October 3, 2016 Share Posted October 3, 2016 You can find diagrams for "Idle circuits" for the propane so you don't run your burner full blast all the time, the idle level flame helps keep it at forging temperature. You don't really want to use the tank valve for this kind of thing, they're also slow if you have a propane fire where you don't want it. I put my burners on 1/4 turn ball valves, they shut off instantly and it's EASY to see in one is on or off when you open the tank valve. While I've shut my burner(s) down when at the anvil I don't recommend it. It's too easy to spend a little too much tie at the anvil or fiddling with something and have the forge cool off enough it doesn't relight instantly. This can seriously POOOF you, resulting in a cartoon face painting and hair do. At the very least follow the basic precaution of NOT standing in front of your forge when you light it no matter how. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
olfart Posted October 3, 2016 Share Posted October 3, 2016 1 hour ago, Frosty said: While I've shut my burner(s) down when at the anvil I don't recommend it. It's too easy to spend a little too much tie at the anvil or fiddling with something and have the forge cool off enough it doesn't relight instantly. This can seriously POOOF you, resulting in a cartoon face painting and hair do. At the very least follow the basic precaution of NOT standing in front of your forge when you light it no matter how. Frosty The Lucky. I recently invested in one of those bendy-snout propane lighters. Bent at a 90 degree angle, it lets me relight my forge while safely standing to the side and keeping my hand out of harm's way in the process. Quote Link to comment Share on other sites More sharing options...
Andy98 Posted October 12, 2016 Share Posted October 12, 2016 On 10/2/2016 at 11:22 PM, olfart said: I recently invested in one of those bendy-snout propane lighters. Bent at a 90 degree angle, it lets me relight my forge while safely standing to the side and keeping my hand out of harm's way in the process. FWIW, I find that I can generally light my forge by putting a flame to the air intake of the burner. Quote Link to comment Share on other sites More sharing options...
Frosty Posted October 12, 2016 Share Posted October 12, 2016 12 hours ago, Andy98 said: FWIW, I find that I can generally light my forge by putting a flame to the air intake of the burner. What it's worth is NOTHING doing it wrong is NOT WORTH A THING, ZIP, ZERO ZILCH. NOTHING. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Buzzkill Posted October 13, 2016 Share Posted October 13, 2016 Could you elaborate a little, Frosty? I agree that the preferred or "right" method is to introduce a flame to the forge interior, but I'm wondering what the drawback is to lighting the burner that way. Is this a safety concern or do you see it as a practice that will somehow damage the burner? As long as the flame doesn't continue to burn in the tube after ignition I'm just not sure I understand the problem. Quote Link to comment Share on other sites More sharing options...
Frosty Posted October 13, 2016 Share Posted October 13, 2016 I suppose if you're operating burners that aren't working to capacity it'd work. If you're running them near where they should run then the jet in inducing the correct amount of air without blasting through at 60mph. that means a burner with a jet at the correct diameter to produce heat a 3/4" tube is capable of will burn back if you let it. Lighting one at the air intake causes a flame front in a position to form a standing wave and burn there instead of in the forge where the fire is supposed to be. A burner that can be successfully lit at the air intake without burning in the tube is a poorly made burner. A typical sign is a burner than needs the choke closed most of the way to operate It's like owning Cessna or other light aircraft. Sure you can prop start them but it's a waste of time when there's a starter in the cabin and in some cases dangerous. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Andy98 Posted October 25, 2016 Share Posted October 25, 2016 On 10/13/2016 at 0:54 AM, Frosty said: a jet at the correct diameter to produce heat a 3/4" tube is capable of will burn back if you let it As usual, I think I'm confused. You're saying that if the jet orifice is the right size, the air/gas velocity in the mixing tube is roughly at the flame-propagation speed so lighting it inside the burner creates the risk that the flame stays right there. A burner with too-small a jet orifice will have a higher air/gas velocity in the mixing tube and will basically blow the flame into the forge, but will be logically injecting less fuel making the burner net lean and needing choking. Did I come close on that explanation? I'm surprised that the air/gas velocity inside the mixing tube is that close to the flame-propagation speed. I always assumed it would be faster because the air/gas is considerably cooler in the mixing tube, plus I thought part of the roll of the forge-body/flare was to allow the gas to slow down to balance with the flame-speed. I believe I did read a comment you made that the point of the flare isn't to "hold the flame" but instead to improve air induction, which confused me, but I guess that's because of the same misconception on my part here. Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted October 28, 2016 Share Posted October 28, 2016 Ideally, the flow speed of an air/gas mixture is a considerably faster than propagation speed, and is modified down to that speed, either by a flame nozzle, or in the heating chamber, in the lack of a nozzle. A properly designed flame nozzle varies flame speed quite a bit by the amount of over- hang past the end of the mixing tube, which they are positioned at. Quote Link to comment Share on other sites More sharing options...
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