Nabok Posted March 31, 2008 Share Posted March 31, 2008 I have been asked to look at natural gas forges. This is for a university art metals studio, mostly small scale stuff, a knifemakers or slightly larger would be about the right size. I know that I can make one, I made mine at home, but this is for work, I think at least partially for liability a commercial made forge is desired. I also suspect that for most users propane is the preferred fuel, again that’s what I use at home, but at the university we have access to natural gas, it runs the sculpture studios melting furnace, gas kilns in the ceramics studio, so I assume high pressure, but will check and we have a line in the art metals studio for a large annealing torch and a 2 burner set up. Besides natural gas is “free”, but propane would have to be bought. So the question is who makes a natural gas forge? All I’ve seen so far is Mankel and the too large for this application Johnson, any other candidates or words of wisdom? Thanks, Todd Quote Link to comment Share on other sites More sharing options...
Frosty Posted March 31, 2008 Share Posted March 31, 2008 The only problem with using natural gas is line pressure, most residential lines are low pressure. This isn't a deal killer even so; you just need a large line. A neutral burn for natural gas is around 1:10 gas:air ratio so the lower BTU/cu/ft is deceiving. Propane requires a 1:17.5 gas:air ratio so they're a lot closer to even up than most guys think. If the university has a commercial gas source you could even use naturally aspirated burners though you'd have to experiment with the jetting. Johnson, NC, Mankel, etc. any or all of them will probably jet a furnace for natural gas for you but you have to ask . . . Them. Frosty Quote Link to comment Share on other sites More sharing options...
Quenchcrack Posted March 31, 2008 Share Posted March 31, 2008 For use in a school, you may need extra safety furnishings like a thermocouple-controlled shut off valve. Check your local fire ordinances. Quote Link to comment Share on other sites More sharing options...
FredW Posted April 1, 2008 Share Posted April 1, 2008 A couple of years ago I bought a Johnson natural gas forge from the local school. It was in pretty good shape because the 2nd year they had it a student lost an eye from throwing hot iron in cold water. The bell just rang and he was ready to go. The board then decided to no longer offer the class. I bought the forge and a johnson melting furnace for $350 then sold them for about $750 a piece. Made over a thousand on the deal and got some nice tongs out of it. They also had a 75# and a 20# anvil but they would not throw them in. The school here saw fit to buy the Johnson but I checked out the price of that paticular model and new it is over $4,000. Surely there is something out there cheaper, however Johnson is very high quality. It had the safety features on it, just watch out no one loses an eye. I wish now I would have kept it with propane prices so high. Quote Link to comment Share on other sites More sharing options...
dablacksmith Posted April 1, 2008 Share Posted April 1, 2008 we use natural gas for a demo forge at a state fair I attend . I know thay had to increase line pressure so it would work but other than that its basically same as a propane forge (forced air type). The heat might be a little less but basically the same ...good luck ! Quote Link to comment Share on other sites More sharing options...
Jymm Hoffman Posted April 1, 2008 Share Posted April 1, 2008 Most forges/furnaces using natural gas (Johnson) use low pressure gas with blowers. While I have not tried one of my forges with nautral gas, it is built on a system similar to Johnsons, but a lot more effecient. The Johnson style furnace is very ineffecient and expensive to operate. While I do not build mine with thermocouples, they can be added for about $100.00 from NC Tool. My smaller 2 burner forges will do many projects. I have used 20lb. propane tanks and rolled steel of similar size for shells. Prperly lined with ceramic fiber blanket and ram refractory on the bottom, they hold up very well. I use them every day, along with a lot of forge welding. Quote Link to comment Share on other sites More sharing options...
skunkriv Posted April 1, 2008 Share Posted April 1, 2008 I have a two burner "double wide" Johnson (#122) and as Fred says they are top quality with all the safety features and run about $4300. I rarely use it because my home built atmospheric forge will do most of what I need and will work me right into the ground. Use the coal forge a lot also. In an institutional setting with liability considerations I think the Johnson would be my choice. They can adapt to a very wide range of configurations just by stacking firebrick. They can be used by multiple students at the same time working from two sides. Lucky for me I bought mine, which had only been fired six times, for $400 :D Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted April 1, 2008 Share Posted April 1, 2008 I bought a Johnson Heat treat furnace that is a cube shaped gas forge on a pedestal just about the right size for knife smithing. Not all of them are the massive trench forges they also make. Mine was from a Public School auction and cost me US$40 as none of the dealers were prepared that day. (Prices went way up the next auction as they had time to do the research on them). Unfortunately I don't have natural gas where I moved and so it's sitting in the corner. I could get it refribbed to use propane but my home built propane forges are working just fine. As a school you probably need to go for a new one with IR "flameout" detectors, etc. OTOH the local University's Fine Arts Metals program is building a propane tube forge to use for smithing. Quote Link to comment Share on other sites More sharing options...
Nabok Posted April 1, 2008 Author Share Posted April 1, 2008 Great, thanks for the input, I’ll contact Johnson and Mankel, and see if NC will change over to natural gas. All the Johnson forges I had seen were too big for our space, must have not looked the right place to find the smaller ones. I need to visit the Safety office to see what their requirements are, building one may not be entirely off the table, I know the sculpture department made a natural gas forge a few years ago, but there is a lot more attention to safety now. Thanks, Todd Quote Link to comment Share on other sites More sharing options...
Ice Czar Posted April 2, 2008 Share Posted April 2, 2008 Green Energy Park - Dillsboro, NC - Capturing Landfill MethaneJackson County Green Energy Park ? North Carolina ? Dillsboro, NC Methane Powered Forge (just related and interesting, Id say a blown forge over a naturally aspirated, and with the liability these days...) Quote Link to comment Share on other sites More sharing options...
Dragons lair Posted April 2, 2008 Share Posted April 2, 2008 The methane forges are blowen 3 burner mankels. Attended thier first class back in Sept They do get hot. Quote Link to comment Share on other sites More sharing options...
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