Mastershake Posted August 4, 2012 Share Posted August 4, 2012 I have an idea to construct a 4 jet forced air propane forge. The blower would hook into a 1" pipe with the propane input centered a few inches down from there. The 1" pipe would spilt into 4 - 1/2" line and I would place them at angles into the forge clreating a fire swirl. Is this efficient? Please give any inputs. I am attaching a PDF file illustrating the idea.FORCED AIR FORGE.pdf Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted August 4, 2012 Share Posted August 4, 2012 There is a lot I do not know that may help me answer this: Have you used a gas forge? if so which kind? and was it lhome made and worked well or not so well? i ask as almost any of the usual store baoiught gassers and all of the ones I have seen or have been on here do not use youir design, ( i do expect someone has tried it) If you are new to this ,I think a good start woiuld be to visit someone with a gasser and give it a go! Youi may find the proven designs work really well. I am not sure wot size material yoiu plan on heating, but most on or two lburners gassers provide enough heat to do almost anything a homesmith wants to forge with a hand hammer. I did see a modified commercial forge used by a really good smith years back,,he added two more burners to a two burner forge. he used it for one forging contest and went back to less burners. If youi have been using a good gasser and want to heat larger stock and proven designs just come up short for you..make tis one and let usknow how it works. Take pics please, Quote Link to comment Share on other sites More sharing options...
Mastershake Posted August 5, 2012 Author Share Posted August 5, 2012 I have only used a homemade charcoal forge up until now. It's beat up and not that efficient so I decided to upgrade to a forced air propane forge instead of spending another $18.00 for a bag of charcoal. I have scrounged a blower and the sheet metal to construct the forge already. Quote Link to comment Share on other sites More sharing options...
quint Posted August 5, 2012 Share Posted August 5, 2012 Forgot what its called but there is a design for a burner that is basically a square box with a bunch of holes in it that the propane feeds to. They are suppose to work pretty good. May be something to look into as an alternative to make the build a little easier. It is in this forum somewhere. Quote Link to comment Share on other sites More sharing options...
pkrankow Posted August 5, 2012 Share Posted August 5, 2012 I am going to recommend you read what Jymm Hoffman has to say about forced air propane forges. Phil Quote Link to comment Share on other sites More sharing options...
Mastershake Posted August 5, 2012 Author Share Posted August 5, 2012 Thanks for all the great input. I will try to start messing with some pipes this week. Quote Link to comment Share on other sites More sharing options...
Sweany Posted August 5, 2012 Share Posted August 5, 2012 Lots of good info here too, if you want to design something new. Plus it covers some common mistakes builders makehttp://www.process-h...M100000f932a8c0____ Quote Link to comment Share on other sites More sharing options...
SoCal Dave Posted August 5, 2012 Share Posted August 5, 2012 You might want to look at Ribbon Burners. There are lots of posts out there on this subject and some knowledgeable people who have tried ribbon burners. As in anything, there are positive and negative issues with any burner. Good luck Quote Link to comment Share on other sites More sharing options...
dkunkler Posted August 5, 2012 Share Posted August 5, 2012 Here is a link for a good step by step on building a ribbon burner.http://blacksmith.or...gas-forge/page2 I think you will have problems getting equal pressure and flow on four 1/2" tubes split off of one 1". You may be in for a lot of experimenting, testing and tweaking. Quote Link to comment Share on other sites More sharing options...
quint Posted August 5, 2012 Share Posted August 5, 2012 Yeah ribbon burner, thats what I was trying to say. Quote Link to comment Share on other sites More sharing options...
timgunn1962 Posted August 5, 2012 Share Posted August 5, 2012 I don't want to seem overly negative, but the .pdf in the original post scares the wotsits out of me. I've only had dial-up speeds this week, so one of the links I've not followed may have mentioned this, but just in case: If I'm reading it correctly, the gas/air mixing is done prior to the plenum (big pipe) top right. The plenum and individual burner feeds are therefore, by design, filled with a flammable gas/air mixture during normal operation, with an ignition source (flame in the forge) at the end of the burner feeds. The only thing that can stop the mixture flashing back is the speed of the mixture down the burner feeds. As long as this is higher than the flame speed through the mixture, it should be safe, but as soon as the mixture speed drops, there will be a flashback into the plenum. The flame will start to move down the burner feed pipe, radiating heat into the mixture in front of it and generating pressure. As the pressure and heat build, the flame will accelerate, generating more pressure and radiating more heat, accelerating the flame and so on.This may or may not cause a major safety issue (eg, operator fatality). The pressure rise/flame front acceleration will stop either when the mixture runs out, or when the pressure has risen enough to overcome the forces constraining it (Translating from my native geek; the plenum explodes). It is certainly possible to engineer the plenum, burner feed pipe sizes, and so on to keep it safe, but the fact that you've asked the question on here tends to suggest that you aren't that familiar with the issues and that your time would be better spent on a design which eliminates the risk. It is the gas/air mixture that is the dangerous bit. Having it confined in the plenum is what gives rise to the explosion risk. If you just run air to the plenum and pipe gas to a separate nozzle near the outlet of each burner, there is only a gas/air mixture for the last bit of the burner feed pipe. Any flashback can only get as far as the gas nozzle, so it can't build the speed and pressure that would make it dangerous. I'll admit the chances of actually killing yourself with the original design are not particularly high, but assuming the plenum and pipework are built strong enough to contain things, the only route for the hot, high-pressure, gases to leave the plenum is via the burners. The risk of damage to the forge lining when this happens is quite high. Regards Tim Quote Link to comment Share on other sites More sharing options...
Mastershake Posted August 5, 2012 Author Share Posted August 5, 2012 I don't want to seem overly negative, but the .pdf in the original post scares the wotsits out of me. I've only had dial-up speeds this week, so one of the links I've not followed may have mentioned this, but just in case: If I'm reading it correctly, the gas/air mixing is done prior to the plenum (big pipe) top right. The plenum and individual burner feeds are therefore, by design, filled with a flammable gas/air mixture during normal operation, with an ignition source (flame in the forge) at the end of the burner feeds. The only thing that can stop the mixture flashing back is the speed of the mixture down the burner feeds. As long as this is higher than the flame speed through the mixture, it should be safe, but as soon as the mixture speed drops, there will be a flashback into the plenum. The flame will start to move down the burner feed pipe, radiating heat into the mixture in front of it and generating pressure. As the pressure and heat build, the flame will accelerate, generating more pressure and radiating more heat, accelerating the flame and so on.This may or may not cause a major safety issue (eg, operator fatality). The pressure rise/flame front acceleration will stop either when the mixture runs out, or when the pressure has risen enough to overcome the forces constraining it (Translating from my native geek; the plenum explodes). It is certainly possible to engineer the plenum, burner feed pipe sizes, and so on to keep it safe, but the fact that you've asked the question on here tends to suggest that you aren't that familiar with the issues and that your time would be better spent on a design which eliminates the risk. It is the gas/air mixture that is the dangerous bit. Having it confined in the plenum is what gives rise to the explosion risk. If you just run air to the plenum and pipe gas to a separate nozzle near the outlet of each burner, there is only a gas/air mixture for the last bit of the burner feed pipe. Any flashback can only get as far as the gas nozzle, so it can't build the speed and pressure that would make it dangerous. I'll admit the chances of actually killing yourself with the original design are not particularly high, but assuming the plenum and pipework are built strong enough to contain things, the only route for the hot, high-pressure, gases to leave the plenum is via the burners. The risk of damage to the forge lining when this happens is quite high. Regards Tim Holly monkeyballs! This is why I posted the question, to keep from blowing up myself and the back yard. I did not realize there was a risk of flashback into the tubes. The blower I have on hand isn't super powerfull so I defanitely need to redo my plans. I am going to look into the ribon burner design because of my flashback/explosion issue. I thank you, and my wife and kids thank you! Quote Link to comment Share on other sites More sharing options...
territorialmillworks Posted August 5, 2012 Share Posted August 5, 2012 Mastershake, there are endless burner designs, each with their own strengths and weakness..I've built hybrid-type burners plus 3 other venturi style burners and a blown ribbon burner. Why? Because I like to make tools as much as I like to blacksmith LOL. Since this is your first build, use the KISS principle while giving consideration to your own skills and abilities. Learn from the success/failures of others on Iforge. Here are some ideas for thought....First determine the size of the forge needed for the type of work you plan on doing so you can determine the burner requirements. Will you out grow this forge in a year. If so, you can always recycle the burners. Is your forge well insulated? You can have the 'best' burner made but it's useless if you don't have a well designed forge. There's info on the number of burners per cubic inches of forge volume and the size of the openings that need to be considered. For a naturally aspirated burners, check a Zoerller Forge. His burner design works and requires a limited amount of fabrication. Blown burners are going to be more expensive and complex. If you still want to go this route, I would encourage you to look at Pine Ridge ribbon burners. They are very affordable and have extensive engineering behind them. As a safety note, you MUST have a gas selenoid wired in-line with the blower in the the event that the blower stops working, you don't keep pumping propane into the the forge. Running my ribbon burner forge and my 3 burner forge side by side, they consumed nearly the same amount of propane. If I had only one, it be the ribbon burner. PM me if you have any questions or want to know how to build your own ribbon burner for the price of one fire brick..Keith Quote Link to comment Share on other sites More sharing options...
timgunn1962 Posted August 5, 2012 Share Posted August 5, 2012 Ribbon burners are harder to get right than their apparent simplicity would suggest (in fact this is true of pretty much any type of burner). If you are going this route, it's probably best to copy, very faithfully, a proven design. Whatever type of burner you use, for safety, always bear in mind that keeping the volume of gas/air mixture that is in the system at any time as small as possible, minimizes the energy released if/when things go wrong. Also, minimizing the distance between the start of gas/air mixing and the ignition source (forge in this case), means that there is not much of a run-up over which the flamefront can accelerate to damaging speeds/pressures. To be honest, I'd not actually spotted the 1" and 1/2" line sizes mentioned in the text of your first post (I was too busy panicking and assuming the not-to-scale .pdf was something like to-scale, for which I apologize). They are probably small enough to keep the volume down to acceptable levels. Putting separate gas jets on each burner a few inches before the forge would be a fairly simple modification to the design and would certainly make it safer. Quote Link to comment Share on other sites More sharing options...
pkrankow Posted August 5, 2012 Share Posted August 5, 2012 Flashback is always a problem in any burner design, atmospheric, venturi, blown. Because your gas is regulated, and propane will not ignite in the absence of oxygen flashback is usually an annoyance and not destructive. The flame will not travel up the propane fuel feed (unlike acetylene, which can ignite without oxygen under certain conditions) If a typical blown burner looses power, the flame enters the burner, rapidly consumes the available oxygen, and the excess propane spills out forming a soft flame...sometimes from both ends. Separate fuel feeds for each nozzle is not necessary for a blown burner. Fuel was frequently introduced upstream from the fan so the fan would mechanically mix the air and fuel. There are a number of reasons to not do this. Phil Quote Link to comment Share on other sites More sharing options...
Mastershake Posted August 5, 2012 Author Share Posted August 5, 2012 Once again, thank you all for your input. This is an awesome and informative forum. I started forging with my little charcoal burner after retiring from the Air Force after 24 years and I was quickly hooked. I beat the crap out of that little forge just practicing hammering and drawing out techniques. I am ready to upgrade to propane and thank you all for your help! Quote Link to comment Share on other sites More sharing options...
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